Helena Jäntti
Cardiopulmonary
Resuscitation (CPR)
Quality and Education
Publications of the University of Eastern Finland
Dissertations in Health Sciences
HELENA JÄNTTI
Cardiopulmonary
Resuscitation (CPR)
Quality and Education
To be presented by permission of the Faculty of Health Sciences, University of Eastern Finland
for public examination in the Mediteknia Auditorium , Kuopio University Campus, on Friday
15th, October 2010, at 12 noon
Publications of the University of Eastern Finland
Dissertations in Health Sciences
28
Department of Anaesthesiology and Intensive Care, Institute of Clinical Medicine
School of Medicine, Faculty of Health Sciences
University of Eastern Finland
Kuopio University Hospital
Kuopio
2010
ii
Kopijyvä Oy
Kuopio, 2010
Editors:
Professor Veli-Matti Kosma, M.D., Ph.D.
Department of Pathology, Institute of Clinical Medicine
School of Medicine, Faculty of Heath Sciences
Professor Hannele Turunen, Ph.D.
Department of Nursing Science
Faculty of Health Sciences
Distribution:
Eastern Finland University Library / Sales of publications
P.O.Box 1627, FI-70211 Kuopio, Finland
http://www.uef.fi/kirjasto
ISBN: 978-952-61-0205-4 (print)
ISBN: 978-952-61-0206-1 (PDF)
ISSN: 1798-5706 (print)
ISSN: 1798-5714 (PDF)
ISSNL: 1798-5706
iii
Author’s address:
Department of Intensive Care
Kuopio University Hospital
P.O.Box 1777
FIN-70211 KUOPIO
Finland
Supervisors:
Docent Ari Uusaro M.D., Ph.D.
Department of Intensive Care
Kuopio University Hospital
University of Eastern Finland
Kuopio, Finland
Docent Tom Sillfvast, MD., Ph.D
Department of Intensive Care
Helsinki University Hospital
University of Helsinki
Helsinki, Finland
Reviewers:
Docent Leila Niemi-Murola M.D., Ph.D.
Department of Anaesthesiology
Helsinki University Hospital
University of Helsinki
Helsinki, Finland
Markus Skrifvars M.D., Ph.D.
Liverpool Hospital
NSW
Sydney, Australia
Opponent:
Professor Maaret Castren, M.D., Ph.D.
Department of Clinical Science and Education
Karolinska Institutet
Stockholm, Sweden
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Jäntti, Helena. Cardiopulmonary resuscitation (CPR) quality and education. Publications of the University of Eastern
Finland. Dissertations in Health Sciences 28. 2010. 92 p.
ABSTRACT
The quality of cardiopulmonary resuscitation (CPR) affects survival. Good CPR quality essentially means that chest
compressions are performed to produce the best perfusion possible in a cardiac arrest (CA). Achieving this goal
requires that chest compressions are sufficiently deep, performed at the right rate, and done with complete release
between compressions and minimal pauses in compressions. Teaching these fundamentals of CPR primes students’
primary emergency care skills.
The aim of this study was to evaluate the current status of CPR quality in Finland and to evaluate effect of external
factors; the most recent change in resuscitation guidelines, the usage of rate guidance and surface characteristics
underneath the manikin, on CPR quality and rescuer fatigue in simulated CA studies. The current status of CPR
education was evaluated via an anonymous Internet survey delivered through Finnish institutions educating CPR to
emergency medicine providers.
The resuscitation guideline change from a three- to one-shock protocol with a longer CPR period between shocks
halved the no-flow time but did not affect chest compression depth or rate. Use of a metronome to guide the chest
compression rate during CPR corrected the rate for each compression cycle to within resuscitation guideline
recommendations, but did not affect chest compression depth or rescuer fatigue. The surface underneath the manikin
did not affect chest compression depth, rate, or rescuer fatigue in simulated CA. The amount of CPR education varied
widely among the institutes. In one third of these, the instructor’s visual estimation was the sole method used to teach
correct chest compression rate and depth.
The current resuscitation guidelines themselves require minimal interruptions for rhythm analysis and defibrillation. If
we aim to reduce no-flow time even further, attention should focus on defibrillation properties (rhythm analysis and
charging during CPR) and airway control to enable continuous CPR. A metronome is a simple and effective method to
guide chest compression rate during CPR, and it should be routinely used in the clinical setting. Possible applications
include metronome guidance during dispatcher-assisted bystander CPR, a metronome within a defibrillator, or a
separate metronome in CPR equipment. The effect of the surface underneath the manikin requires further evaluation,
although experienced nurses perform CPR effectively regardless of the surface. Objective tools in CPR education
should be used to evaluate CPR performance during training. Nationally or internationally uniform instructions for
CPR education in different institutions might be useful.
National Library of Medicine Classification: QY 35, WG 205, WX 215
Medical Subject Headings (MeSH): Cardiopulmonary Resuscitation; Defibrillators; Education; Electric Countershock;
Emergencies; Emergency Medical Services; Heart Arrest; Heart Massage; Manikins; Pulmonary Ventilation;
Resuscitation Orders; Ventricular Fibrillation
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Jäntti, Helena. Peruselvytyksen laatu ja opetus. Itä-Suomen yliopiston julkaisusarja. Terveystieteiden tiedekunnan
väitöskirjat 28. 2010. 92 s.
TIIVISTELMÄ
Peruselvytyksen laatu vaikuttaa elvytystilanteesta selviytymiseen. Pohjimmiltaan hyvänlaatuinen peruselvytys
tarkoittaa
elvytyksen
toteuttamista
tavalla,
joka
tuottaa
mahdollisimman
hyvän
verenkierron
sydänpysähdystilanteessa. Tällöin paineluelvytys on toteutettava mahdollisimman yhtäjaksoisesti, oikean syvyisenä,
oikealla tahdilla ja rintakehän on annettava palautua painelujen välillä. Elvytystaidot perusteet opetellaan jo
opiskeluaikana.
Tämän tutkimuksen tarkoituksena oli selvittää miten peruselvytyksen laatuun vaikuttaa simuloidussa
elvytystilanteessa elvytysohjeiden muutos, metronomin käyttö painelutahdin säätämiseen ja potilaan alla oleva alusta.
Lisäksi selvitettiin miten peruselvytyksen laatua opetetaan eri asteen oppilaitoksissa ensihoidon toimijoille.
Elvytysohjeiden muutos kolmen iskun defibrillointisarjoista yhden iskun sarjaan puolitti painelemattoman ajan, mutta
ei muutoin vaikuttanut painelun laatuun. Metronomin käyttö painelutahdin ohjaukseen korjasi painelutahdin, mutta ei
muutoin vaikuttanut painelun laatuun eikä elvyttäjien väsymiseen. Painelualusta elvytysnuken alla ei vaikuttanut
painelun laatuun eikä elvyttäjien väsymiseen. Elvytysopetuksen määrä vaihtelee huomattavasti eri oppilaitoksen
välillä. Kolmasosassa oppilaitoksissa kouluttajan silmämääräinen arvio on ainoa tapa arvioida painelun laatua
pienryhmäkoulutuksissa.
Nykyisten elvytysohjeet sinänsä vaativat minimimäärän taukoja paineluun rytmin analysointia ja defibrillointia varten.
Jos painelutaukoja halutaan vielä vähentää, vaihtoehdot ovat defibrillaattorin ominaisuuksien kehittäminen (rytmin
analysointi ja lataus painelun aikana) tai ilmatien varmistaminen jatkuvan painelun mahdollistamiseksi. Metronomi on
yksinkertainen ja tehokas tapa kontrolloida painelutahtia ja sen rutiinikäyttö elvytystilanteessa olisi suositeltavaa.
Käytännön mahdollisuuksina on maallikko-puhelinelvytysohjeiden tahditus metronomilla, defibrillaattorin kiinteästi
kuuluva tai elvytysvälineissä oleva erillinen metronomi. Painelualustan merkitys tarvitsee lisäselvittelyjä, vaikka
kokeneet hoitajat suoriutuvat simuloidusta elvytystilanteesta yhtä tehokkaasti alustasta riippumatta.
Elvytysopetuksessa tulisi käyttää objektiivisia mittareita peruselvytyksen laadun opettamiseen. Tarvetta on myös
kansallisille tai kansainvälisille eri tason ensihoidon toimijoiden peruskoulutuksen aikaista elvytysopetusta koskeville
suosituksille.
Luokitus:
Yleinen suomalainen asiasanasto: akuuttihoito; elvytys – opetus; ensihoito; sydämenpysähdys – akuuttihoito;
sairaankuljetus; sydämenhieronta; ; tekohengitys
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To Ronja, Otso and Oula
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Acknowledgements
I express my deepest gratitude to my principal supervisor, Docent Ari Uusaro, for intelligent guidance throughout the
study. He modified my curiosity into scientific questions and specific aims. His calm and warm encouragement helped
me in many ways during these studies.
Docent Tom Silfvast was my second study supervisor. I appreciate his positive and comprehensive attitude toward
scientific work and encouragement during various phases before these final steps.
I am grateful to Professor Esko Ruokonen, Head of the Department of Intensive Care, for support during these studies.
I admire his endless enthusiasm for scientific research. His positive attitude about linking scientific work and education
led to my having available the facilities to complete this thesis.
For indispensable help throughout the work, I am deeply grateful to Vesa Kiviniemi, Ph Lic, for rapid and positive
responses to all manner of questions and for the specific talent of making statistics simple and suitable for clinical
problems. Also, I thank my other co-authors, Docent Markku Kuisma and Rn, PhD Heikki Paakkonen, for their
valuable and constructive comments during these studies. Co-writer Anu Turpeinen, PhD, provided an important
cardiological perspective on these studies, but most of all I am grateful for her friendship, which has lasted for more
than 20 years.
I owe my sincere thanks to the official reviewers of this study, Docent Leila Niemi-Murola and Markus Skrifvars, PhD.
Their comments were valuable and constructive and improved the thesis considerably.
My appreciation also goes to the critical care nurses of the intensive care unit (ICU) of Kuopio University Hospital,
paramedics of Northern Savo, and paramedic students of Savonia, who voluntarily participated in this study and made
this work possible. Also, I thank medical students Anna Govenius, Sini Sievänen, Timo Kontula, Jukka-Pekka
Kervinen, and Heikki Alanen for valuable help with data manual calculation and storage.
I owe my warmest gratitude to ICU head nurses Anneli Kasanen and Ulla Kesti and educational nurses Virpi Tauru
and Hannele Virnes for their valuable help with the practical aspects of this work. With their assistance, this study was
organized effectively, and scenarios were performed rapidly. Also, I am very grateful to my nearest workmate, clinical
teacher Kirsikka Metsävainio, for giving me the opportunity to focus on this work. She helped to filter out disruptions
and thanks to her, I have been able to concentrate solely on this study and the enjoyable parts of education.
I owe my sincere thanks to the whole group of paramedics, doctors, and pilots of Ilmari-HEMS for teaching me their
‘just do it’ attitude. The base of Ilmari, wherever it is, is my second home. Crew: thank you.
Also, I wish to thank all my anaesthesiology colleagues at the Kuopio University Hospital for their supportive attitude
and good working relationships. My special thanks to Sinikka Purhonen, PhD, for superlatively positive
encouragement during these years. In addition, I am grateful to the doctors overseeing the clinical work, Docent Minna
Niskanen, MD, Pekka Pölönen, and MD Esko Tyrväinen, for arranging my clinical duties to serve scientific work in
many ways.
This study has been a part of my life for four years. I am grateful to my friends, relatives, and loved ones for sharing
the most important things and moments of my life outside of this work. Especially, I thank Maarit Lång, Tiina Jussila,
Minna Hälinen, Tuija and Pertti Kilpeläinen, Jaana Leinonen, Timo and Julia Bengtsson, Pentti and Soile Aaltonen,
Eeva-Liisa Aaltonen, Heikki Hämäläinen, and Emma Rautiainen for their precious company and support. Also, I thank
Hertta Aaltonen for support during the early years of this study and want to say that most of all, I am forever grateful
to her for the young ones.
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I owe my deep gratitude and love to my father Antero Jäntti, for his never failing support during all stages and aspects
of my life. I admire his passion for life and his energy and impatience as a positive force. He has been a great source of
inspiration for my work on this thesis.
During the final stages of this thesis, life presented me with a great opportunity. Merja Kuusela has infused me with
the courage and love that have helped me to finally finish this work lightly and with joy. I am grateful and deeply in
love.
Finally and most of all, I wish to express my deepest love for my amazing children, Ronja, Otso, and Oula. You are my
determinants of a good quality of life. With you, every day runs without pauses, at a just right rate and to the perfect
depth of feeling at each moment. I am proud and privileged to be your mother. 'Kääpiöt': I love you and dedicate this
thesis to you.
This work was financially supported by the Foundation of Emergency Medicine.
Kuopio, September, 2010
Helena Jäntti
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List of original publications
This thesis is based on the following original articles, which are referred to in the text by their Roman numerals:
I
Jäntti H, Kuisma M, Uusaro A: The effects of changes to the ERC resuscitation guidelines on no flow time
and cardiopulmonary resuscitation quality: a randomised controlled study on manikins. Resuscitation.
2007;75(2):338-44.
II
Jäntti H, Silfvast T, Turpeinen A, Kiviniemi V, Uusaro A: Quality of cardiopulmonary resuscitation on
manikins: on the floor and in the bed. Acta Anaesthesiol Scand. 2009;53(9):1131-7.
III
Jäntti H, Silfvast T, Turpeinen A, Kiviniemi V, Uusaro A: Influence of chest compression rate guidance
on the quality of cardiopulmonary resuscitation performed on manikins. Resuscitation. 2009;80(4):453-7.
IV
Jäntti H, Silfvast T, Turpeinen A, Paakkonen H, Uusaro A: Nationwide survey of resuscitation education
in Finland. Resuscitation. 2009;80(9):1043-6.
The publishers of the original publications have kindly granted permission to reprint the articles in this dissertation.
xiv
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Contents
1. INTRODUCTION
1
2. REVIEW OF THE LITERATURE
2
2.1. Cardiac arrest
3
2.1.1. Epidemiology
3
2.1.2. Chain of survival
4
2.1.3. Outcome
2.2. Cardiopulmonary resuscitation (CPR)
4
6
2.2.1. A short history of CPR and CPR guidelines
6
2.2.2. Chest compression
7
2.2.3. Ventilation
8
2.3.4. Defibrillation
2.3. Quality of CPR
9
9
2.3.1. Significance of CPR quality
9
2.3.2. Determinants of CPR quality
10
2.3.2.1. Pauses in chest compression
11
2.3.2.2. Optimal chest compression depth
12
2.3.2.3. Optimal chest compression rate
12
2.3.2.4. Rescuer fatigue
13
2.3.3. Monitoring CPR quality
14
2.3.4. Current status of CPR quality in clinical situations
15
2.4. CPR education
15
2.4.1. A short history of manikins and CPR education
16
2.4.2. Significance of CPR education
16
2.4.3. Problems with CPR education and retention of skills
17
3. AIM OF THE STUDY
19
4. PARTICIPANTS AND METHODS
20
4.1. Participants
20
4.2. Institutions
21
4.3. Study design
21
xvi
4.3.1. Current status on CPR quality and educational methods to facilitate this in Finland 21
4.3.2. Effect of external factors on CPR quality
22
4.4. Quality of CPR
24
4.5. Time factors
25
4.6. Rescuer’s fatigue and ‘signature’
27
4.7. Participants’ opinions
28
4.8. Sample size
28
4.9. Statistical methods
29
5. RESULTS
30
5.1. The participants
5.2. Current status of CPR quality and educational methods to facilitate this in Finland
30
5.3. The effect of external factors on CPR quality
33
5.3.1. The effect of resuscitation guidelines change
33
5.3.1.1. No-flow time with different resuscitation guidelines
33
5.3.1.2. Chest compression quality with different resuscitation guidelines
34
5.3.2. The effect of the surface underneath the manikin
35
5.3.2.1. The quality of CPR on different surfaces
35
5.3.2.2. Rescuer’s fatigue: the effect of surface on CPR quality
36
5.3.2.3. Rescuer’s fatigue: opinions
39
5.3.2.4. Rescuer’s ‘signature’
39
5.3.3 The effect of metronome use
42
5.3.3.1. The quality of CPR with and without metronome
42
5.3.3.2. Rescuer’s fatigue: the effect of metronome guidance on CPR quality
43
5.3.3.3. Rescuer’s fatigue: opinions
46
5.3.3.4. Rescuer’s ‘signature’: effect on chest compression rate and rescuer’s fatigue
46
5.4. Undergraduate CPR education in Finland
6. DISCUSSION
47
49
6.1. Current status of CPR quality and educational methods to facilitate this in Finland
49
6.2. The effect of external factors on CPR quality
50
6.2.1. The effect of resuscitation guideline changes
50
6.2.2. The effect of the surface underneath the manikin
52
6.2.3. The effect of metronome guidance
55
6.2.4. CPR education
56
7. LIMITATIONS OF THE STUDY
59
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8. CONCLUSIONS
62
9. FUTURE IMPLICATIONS
63
10. REFERENCES
64
11. APPENDIX:
75
Survey Questionnaire
Original publications I-IV
xviii
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Abbreviations
ACD
Active compression–decompression
AED
Automated external defibrillator
AHA
American Heart Association
ALS
Advanced life support
BLS
Basic life support
CA
Cardiac Arrest
CPR
Cardiopulmonary Resuscitation
ECC
Emergency cardiac care
EMS
Emergency Medical Service
ERC
European Resuscitation Council
EtCO2
End-tidal carbon dioxide
ILCOR
International Liaison Committee on Resuscitation
PEA
Pulseless Electrical Activity
ROSC
Return of Spontaneous Circulation
SCD
Sudden Cardiac Death
VAS
Visual Analogue Scale
VF
Ventricular Fibrillation
VT
Ventricular Tachycardia
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Definitions
CPR quality
For the purposes of these theses, determinants of CPR quality were chest
compression rate, compression depth, complete release between compressions, and
pauses in chest compressions (no flow time). Adequacy of ventilation was not
considered a determinant of CPR quality.
No flow time
No flow time was defined as the time without chest compressions during the
resuscitation episode regardless of the reason, i.e. delay in starting chest
compressions, pause for ventilation/rhythm analysis, automated external
defibrillator charging and defibrillation, or change of the rescuer.
xxii
2
1. INTRODUCTION
Cardiovascular disease is a leading cause of death in Western countries, and approximately half of these
deaths are sudden (Lloyd-Jones et al. 2009, Chugh et al. 2008, Gillum 1990). About 4 to 5 million sudden
cardiac deaths occur annually worldwide (Chugh et al. 2008), with about 3000 occurring in Finland. The
only hope for victims of sudden cardiac death is cardiopulmonary resuscitation (CPR). The modern version
of CPR was developed ~50 years ago (Kouwenhove, Jude, Knickerbocker 1960, Zoll et al. 1956, Safar,
Escarraga, Chang 1959). CPR is currently performed according to the International Guidelines for CPR,
which are published every five years; the most recent guidelines were published in 2005 (ECC Committee,
Subcommittees and Task Forces of the American Heart Association 2005, Handley et al. 2005).
Since chest compressions generate only about 25% of normal perfusion (Weil et al. 1985), it is vital to
perform CPR correctly. The quality of CPR was highlighted in the latest resuscitation guidelines. The main
elements of CPR quality are correct chest compression depth and rate and minimal pauses in compressions
(Kramer-Johansen et al. 2007). The quality of CPR is often poor in the clinical setting when performed by
professionals (Wik et al. 2005, Abella et al. 2005), although the survival benefit is clear. In studies of
bystander CPR, approximately half of the patients received good-quality bystander CPR, and good-quality
CPR was associated with a four times higher survival to hospital discharge compared to poor-quality CPR
(Wik, Steen & Bircher 1994, Gallagher, Lombardi & Gennis 1995, Van Hoeyweghen et al. 1993).
When CPR is not performed correctly, i.e. when the CPR quality is poor, survival is negatively affected.
Pauses in chest compression are common; at worst, patients receive chest compressions only half of the time
(Wik et al. 2005). Interruptions in chest compressions decrease coronary perfusion (Berg et al. 2001) and
worsen the outcome of CPR (Yu et al. 2002b, Edelson et al. 2006a). Compression depth is often too shallow
during CPR (Wik et al. 2005, Abella et al. 2005). Deeper chest compressions have been shown to correlate
with better perfusion (Babbs et al. 1983, Bellamy, DeGuzman & Pedersen 1984, Ristagno et al. 2007) and to
3
increase survival to hospital admission (Edelson et al. 2006a, Kramer-Johansen et al. 2006). The compression
rate is often not optimal during CPR (Wik et al. 2005, Abella et al. 2005). However, higher chest compression
rates are associated with improved haemodynamics (Wolfe et al. 1988, Sunde et al. 1998, Kern et al. 1992,
Berg et al. 1994) and better primary survival (Feneley et al. 1988).
Not surprisingly, the quality of CPR education affects CPR quality. The International Liaison Committee on
Resuscitation (ILCOR) stated that the overall outcome after cardiac arrest depends equally on the quality of
the resuscitation guidelines, the local ‘chain of survival’, and the quality of education for CPR providers that
enables them to put the theory into practise (Chamberlain et al. 2003). CPR skills diminish rapidly after
instruction (Weaver et al. 1979, Kaye et al. 1991), and without objective tools during CPR training, the skills
cannot be reliable analysed and, perhaps, learned correctly (Weaver et al. 1979, Kaye et al. 1991, Ramirez et
al. 1977, Lynch et al. 2008).
Several external factors, such as the resuscitation guidelines, chest compression rate guidance, surface
underneath the patient, and rescuer fatigue during a long CPR episode, can affect other elements of CPR
quality. The aims of this study were to describe the current quality of chest compressions in CPR in Finland
and to evaluate the effect of the following external factors on CPR quality: changes in the resuscitation
guidelines, metronome usage, and the surface underneath the patient. The amount (length of instruction
time) and methods of CPR education in Finland institutes that teach students of emergency medicine at
different levels was also evaluated.
4
2.
Review of the literature
2.1.
CARDIAC ARREST
2.1.1.
Epidemiology
Cardiovascular disease is a leading cause of death and premature mortality in western countries (LloydJones et al. 2009, Chugh et al. 2008). Sudden cardiac death (SCD) is defined as sudden and unexpected death
within an hour of symptom onset without any obvious non-cardiac cause, such as trauma (Myerburg,
Castellanos 2005). Approximately half of all cardiac heart disease deaths are sudden (Gillum 1990), and only
half of the victims had a prior history of cardiac disease (Gorgels et al. 2003).
In Utstein recommendations for uniform reporting system cardiac arrest was defined as the cessation of
cardiac mechanical activity, confirmed by the absence of a detectable pulse, by unresponsiveness, and by
apnoea (Anonymous 1992). The annual incidence of sudden out-of-hospital cardiac arrests (CAs) depends
on the methodology used to identify cases of SCD (Chugh et al. 2008). Studies that have used retrospective
death certificate–based methodology to identify cases of SCD may overestimate SCD incidence (Arking et
al. 2004). In prospective studies using data collected by first responders, the annual incidence of treated
primary CA ranged between 97–121/100000 (de Vreede-Swagemakers et al. 1997, Cobb et al. 2002). The
limitation of this methodology is that patients with a non-cardiac cause of CA cannot be excluded.
The Oregon Sudden Unexpected Death Study is an ongoing community-wide evaluation of SCD intended
to avoid the problems that arose with the previous studies. It is prospective, so overestimation problem
should be avoided. This study is population-based and multiple sources are used to collect information, so
all CA cases should be included. Cases are reported by first responders (70%), the State Medical Examiner
(25%), and from the hospitals (approximately 5%). In the first year of this study, the annual incidence of
SCD was 53 per 100 000 residents and accounted for 5.6% of overall deaths (Chugh et al. 2004). An almost
identical annual incidence of SCD (51.2/100 000) has been reported from Ireland (Byrne et al. 2008) and
5
Canada (Vaillancourt, Stiell & Canadian Cardiovascular Outcomes Research Team 2004). For the world
(total population approximately 6 540 000 000), the estimated annual burden of SCD would be in the range
of 4 to 5 million cases per year (Chugh et al. 2008). If similar estimations are done within the Finnish
population (approximately 5 326 000), the number of SCD cases would be around 3000 annually.
2.1.2.
Chain of survival
The actions that link the victim of sudden CA with survival are called the ‘chain of survival’. The ‘chain of
survival’ concept was first introduced in 1991 (Cummins et al. 1991c), and this chain remains a symbol of
resuscitation services in many parts of the world. The original four links and the aim of the chain of survival
were as follows: (1) early access to activate the emergency medical services (EMS); (2) early basic life
support (BLS) to keep some circulation to the brain and heart and to buy time to enable defibrillation; (3)
early defibrillation to restore a perfusing rhythm; and (4) early advanced life support (ALS) to stabilise the
patient. For in hospital CA the chain of survival is a bit different and not so famous. It extends the chain
into CA prevention and post-resuscitation care (Perkins and Soar 2005).
In 2005, significant changes were made to the resuscitation guidelines. Also the chain of survival was
modified by changing the meaning of the links. The first link indicates the importance of recognising those
at risk of CA, while the second and third links remain the same with the importance of BLS highlighted. The
fourth link has been modified to address effective post-resuscitation care, targeted at preserving function
particularly of the brain and heart, and recognises the importance of restoring quality of life to the CA
survivor (Nolan, European Resuscitation Council 2005). The background of this change were studies
documenting the inadequate quality of CPR in both in-hospital and out-of-hospital settings (Wik et al. 2005,
Abella et al. 2005). Also, it has become established that the quality of CPR affects survival (Wik, Steen &
Bircher 1994, Gallagher, Lombardi & Gennis 1995, Van Hoeyweghen et al. 1993). Also as therapeutic
hypothermia was shown to improve neurological outcome after cardiac arrest (Bernand 2002, HACA 2002),
renewed focus and attention has been applied to the post resuscitation phase of care.
6
2.1.3.
Outcome
Before development of modern cardiopulmonary resuscitation in the 1960s, there have been only a few case
reports from survivors of CA in the in-hospital and out-of-hospital settings (Cooper, Cooper & Cooper
2006). After that time, the total survival rates for all out-of-hospitals CA has varied in different studies
between 3.5–31%, indicating the need for a uniform reporting system (Eisenberg, Bergner & Hearne 1980).
In 1991, the Utstein style for uniform reporting of data from out-of-hospital CA was published (Cummins et
al. 1991a), and a similar uniform reporting system for in-hospital CA was published in 1997 (Cummins et al.
1997).
Survival of out-of-hospital CA depends on the sequence of interventions in ‘the chain of survival’, all of
which have to be optimised to maximise survival (Cummins et al. 1991b). The most important factor
affecting survival from CA is time from collapse to onset of resuscitation efforts (Eisenberg, Bergner &
Hallstrom 1979). Each passing minute of untreated ventricular fibrillation (VF) reduces the likelihood of
survival by 7% to 10% (Cummins et al. 1991b).
CA is associated with four first documented electrocardiographic rhythms: pulseless ventricular
tachycardia (VT), ventricular fibrillation (VF), pulseless electrical activity (PEA), and asystole. VF as the
initial rhythm is associated with a more favourable outcome than other rhythms (Cummins et al. 1991b).
This true also for in hospital CA; in a recent large multi centre in-hospital study with over 50 000 CA the
first documented rhythm was asystole in 39%( survival to hospital discharge was 10.8%), PEA in 37%
(survival to hospital discharge was 11.9%), Pulseless VT in 7% (survival 36,9%) and VF in 17% (survival
37.3%) (Meaney et al. 2010).
The primary cause of CA is also important. Cardiac causes have better prognosis than non-cardiac causes
(Pell et al. 2003). Whereas VF is strongly associated with coronary heart disease (Baum et al 1974), the
conditions that cause PEA as initial cardiac rhythm often reflect a non-coronary aetiology like pulmonary
embolism or cardiovascular rupture (Comess et al 2000, Virkkunen et al 2008).
Almost all survivors
experienced witnessed arrests (Spaite et al. 1990), and bystander CPR improves the probability of survival
(Wik, Steen & Bircher 1994, Gallagher, Lombardi & Gennis 1995, Lund, Skulberg 1976, Cobb et al. 1980,
Skrifvars et al. 2007b).
7
The best probability of survival is from witnessed CA that can be reached rapidly in VF. So far, the best
reported results are from casinos, where the majority of VF events were treated in less than 3 minutes and
survival was 74% (Valenzuela et al. 2000). Otherwise, in out-of-hospital settings, the time to reach the
patient is usually longer and survival is poorer; for witnessed VF, survival is reported at 22% in North
America and Canada (the first rhythm analysis 9 minutes) (Nichol et al. 2008), 21% in Europe (Atwood et al.
2005), and 29% in Tampere, Finland (the first rhythm analysis 10 minutes) (Kämärainen et al. 2007).
For in-hospital resuscitation, survival depends on the same elements as that influencing out-of-hospital
resuscitation (Kaye, Mancini 1996), but also on other elements such as level of the hospital influences
survival (Skrifvars et al. 2007a). In Göteborg, Herlitz compared in-hospital CA to out-of-hospital CA. More
patients were discharged alive following in-hospital CA (37.5% vs. 8.7%) (Herlitz et al. 2000). In other
studies, discharge from in-hospital CA has been poorer than in Göteborg, ranging from 17%–20% (Peberdy
et al. 2003, Tunstall-Pedoe et al. 1992).
2.2.
2.2.1.
CARDIOPULMONARY RESUSCITATION (CPR)
A short history of CPR and guidelines
The roots of resuscitation extend back centuries, with some of the earliest mentions of ventilation efforts for
resuscitation occurring in the Bible (Cooper, Cooper & Cooper 2006). In the 1950s, investigators developed a
marked improvement with ventilation: Peter Safar, working with paralyzed volunteers, found that the
airway can be held open when the neck is extended or an oropharyngeal tube used and mouth-to-mouth
undertaken (Safar et al 1959). Danish anaesthesiologist Bjørn Ibsen introduced manual bag ventilation
during the poliomyelitis epidemic in the early 1950s (West 2005).
The first cardiac compressions were performed in the open thorax in animal models in the 18th century, and
the first successful open-chest cardiac massage on a patient was performed in 1901. In 1958, William
Kouwenhoven introduced external cardiac massage, today known as chest compression, to patient care
(Kouwenhoven et al 1960b). Closed-chest CPR produces about one quarter of the normal cardiac output
8
(Delguercio et al 1963, Weil et al. 1985). The goal of CPR is to generate sufficient oxygen delivery to the
coronary and cerebral circulation during the resuscitation period.
Claude Beck in 1947 performed the first successful (open) human defibrillation (Cooper et al 2006), and Paul
Zoll performed the first successful closed-chest human defibrillation in 1955 (Zoll et al. 1956). Portable
defibrillators were developed in the late 1960s. Development of semi-automatic/automatic defibrillators
enables their use with minimal training, offering the possibility of out-of-hospital defibrillation.
In 1966, the first guidelines for CPR and emergency cardiac care (ECC) were published (Anonymous 1966).
Since that time, national conferences have been held regularly, lately taking place every five years. The
focus on dissemination of international guidelines has led to a goal of regularly collating the scientific
evidence and updating the resuscitation guidelines.
The main emphasis of guidelines in the 1970s and 1980s was proper BLS. Defibrillation and drug
administration were only in the hands of special teams in out-of-hospital settings. From the 1980s,
defibrillation became the most important link in the ‘chain of survival’. Many different early defibrillation
programmes were built up in different EMS contexts in different countries (Eisenberg et al. 1990). In 1979,
the first portable automatic external defibrillator was developed (Cooper et al 2006). In the 1980s
development of fully or semi-automated defibrillators enabled their widespread use by minimally trained
personnel with very good results (Stiell et al. 1999, Valenzuela et al. 2000, Caffrey et al. 2002).
The latest international guidelines for CPR published in 2005 emphasised good quality and minimally
interrupted BLS (ECC Committee, Subcommittees and Task Forces of the American Heart Association 2005,
Handley et al. 2005). Essentially, guidelines went ‘back to basics’ as first emphasised in the 1960s, when
basic CPR was developed. The bases of this change were studies documenting the inadequate quality of
CPR in both in-hospital and out-of-hospital settings (Wik et al. 2005, Abella et al. 2005). Also, it has become
established that the quality of CPR is critical to patient survival and that poor-quality CPR has been
associated with poor outcome in animal studies (Babbs et al. 1983, Bellamy, DeGuzman & Pedersen 1984,
Ristagno et al. 2007) and in the clinical setting (Edelson et al. 2006b).
9
2.2.2.
Chest compression
Two competing theories have emerged regarding the mechanism of blood flow during CPR. According to
the cardiac pump theory, the mechanism of blood flow during external chest compression is the result of
direct compression of the heart between the sternum and the vertebrae, which squeezes the blood from the
heart (Kouwenhoven et al 1960a, Redberg et al. 1993). According to the thoracic pump theory, external chest
compression causes an increase in the intrathoracic pressure. This increase generates a pressure gradient
between the intrathoracic and extrathoracic vascular compartments, and blood flows from the intrathoracic
arteries to the extrathoracic arteries as venous valves prevent retrograde flow from the right heart to
systemic veins (Rudikoff et al. 1980). In a recent study, Kim et al. (2002) performed left ventricular contrast
echocardiography during clinical CPR. They showed that during the compression phase blood flows into
two different directions: antegrade from the left ventricle to the aorta and retrograde from the left ventricle
to the left atrium. These findings support the cardiac pump theory (Kim et al. 2008). The basic principle is
to generate sufficient oxygen delivery to the coronary and cerebral circulation during the resuscitation
period.
Ideal chest compressions are performed from the right place (the centre of the chest) with the rate of 100 per
minute. Compressions must be deep enough (4-5 centimetres), compression and decompression phase
should last equally time and the chest must be completed released between compressions to fill the heart.
The pauses in compressions should be minimal.
2.2.3.
Ventilation
Ventilation during CPR can be performed in many ways, and the method of choice depends on where the
CA happens, the rescuer’s experience, available equipment, and international and local guidelines.
Healthcare professionals have many choices for performing ventilation. Intubation is still the ‘gold
standard’, but it is not easily performed by inexperienced responders (Katz, Falk 2001, Jemmett et al. 2003),
10
and intubation efforts take time. The mean duration of intubation-associated CPR interruptions has been
reported to be 46.7 seconds with paramedics (Wang et al. 2009), and serious, even fatal problems are
associated with intubation (Timmermann et al. 2007). Hyperventilation via the intubation tube is common
in the clinical setting and decreases survival in animal models (Aufderheide et al. 2004). Use of a
supraglottic airway device is an alternative method for intubation (Gabrielli et al. 2002). Bag-mask
ventilation is also still a common strategy for ventilating the patient. When ventilations are performed via
intubation tube or supraglottic airway devices, there is no need to pause chest compression for ventilation,
but if ventilation is performed with a bag and mask or mouth-to-mouth, pauses in chest compression must
be made to allow for ventilation.
The role of ventilation, particularly in bystander CPR, has recently been widely discussed. If a bystander
performs mouth-to-mouth ventilation, the most difficult part can be the long period for performing two
rescue breaths, 11–14 seconds (Heidenreich et al. 2004, Higdon et al. 2006). Also bystander mouth-to-mouth
ventilation is associated with a significantly increased risk of regurgitation (Virkkunen et al. 2006),
bystanders and even professionals are unwilling to perform mouth-to-mouth ventilation (Holmberg,
Holmberg & Herlitz 2000, Ornato et al. 1990, Brenner, Kauffman 1993). Recent studies showed that chest
compression-only CRR by bystanders was equivalent to conventional CPR in adult patients with out-ofhospital cardiac arrest (Bohm et al. 2007, SOS-KANTO study group 2007, Iwami et al. 2007). The American
Heart Association (AHA) has recommended that chest compression only is a preferable approach to
resuscitation for adults who suddenly collapse (Sayre et al. 2008). For children who have out-of-hospital
cardiac arrests from non-cardiac causes, conventional CPR (with rescue breathing) by bystander is still the
preferable approach to resuscitation (Kitamura et al. 2010).
2.2.4.
Defibrillation
Nonsynchronized electric countershock, defibrillation terminates VT and VF into asystole. Proper chest
compressions produces coronary flow and enables restart of organized rhythm. Claude Beck in 1947
performed the first successful (open) human defibrillation (Cooper et al 2006), and Paul Zoll performed the
11
first successful closed-chest human defibrillation in 1955 (Zoll et al. 1956). Portable defibrillators were
developed in the late 1960s. Development of semi-automatic/automatic defibrillators in 1980s enables their
use with minimal training, offering the possibility of out-of-hospital defibrillation. This progress toward
early defibrillation is vital; since the time from the onset of ventricular fibrillation/ventricular tachycardia to
shock delivery is critical, each passing minute of untreated ventricular fibrillation (VF) reduces the
likelihood of survival by 7% to 10% (Cummins et al. 1991b). Resuscitation guidelines determine the number
of defibrillations and the period of CPR between them.
2.3.
QUALITY OF CPR
2.3.1.
Significance of CPR quality
There is no specific definition for CPR quality in literature. Basically good CPR quality means that chest
compressions are performed in a way that produces as good perfusion as possible in a CA circumstances.
This requires that chest compressions are deep enough, performed with right rate and complete release
between compressions and minimal pauses are held in compressions during resuscitation attempt.
The first concerns about the quality of CPR trace to the mid-1990s. Three studies with similar ideas and
results were published regarding bystander CPR (Wik et al 1994, Gallagher et al 1995, Van Hoeyweghen et
al. 1993). In brief, the studies concluded that approximately half the patients received good-quality
bystander CPR with a four times higher survival to hospital discharge vs. poor-quality CPR. In detail, in
Gallagher’s study, trained prehospital personnel assessed the quality of bystander CPR on arrival at the
scene by simple observation. Of the subset of 662 individuals (32% of all) who received bystander CPR, 305
(46%) had it performed effectively. Of these, 4.6% (14/305) survived versus 1.4% (5/357) of those with
ineffective CPR (OR = 3.4; 95% CI, 1.1 to 12.1; P<0.02). Similar findings were documented from a study out
of Norway, which found that good bystander CPR, defined as a palpable carotid or femoral pulse,
improved hospital discharge rate as compared to not-good-bystander CPR or no-bystander CPR at all (Wik
et al 1994).
12
After these findings, the issue of CPR quality was almost ignored for a decade because development of
automatic or semi-automatic defibrillators enabled less-trained personnel to perform early defibrillation. It
was the primary message in the 1992 guidelines, and development of different early defibrillation
programmes dominated the next few years in the area of resuscitation (Anonymous 1992, Cummins 1993).
In addition, active compression–decompression (ACD) techniques drew great attention in the 1990s. Active
compression-decompression CPR (ACD CPR) is performed with a handheld suction device applied to the
chest wall. Chest compression is unchanged, but suction applied by withdrawal of the device during the
diastolic phase of CPR creates negative intrathoracic pressure which is postulated to promote forward
blood flow. Finally, active compression–decompression techniques were ultimately discarded after no
benefit was identified in large, randomised studies (Schwab et al. 1995, Stiell et al. 1996).
2.3.2.
Determinants of CPR quality
Determinants of quality CPR were defined in an international collaborative meeting of CPR quality
researchers, and a uniform reporting system of measured quality of CPR was published in 2007 (KramerJohansen et al. 2007b). Specific CPR quality variables are time without chest compressions (no-flow time),
compression depth, compression rate, compression duty-cycle, compression with incomplete release,
compression delivered per minute, and ventilation rate.
2.3.2.1.
Pauses in chest compression
Single pauses in chest compressions during resuscitation attempts occur for multiple reasons, including
rhythm analysis and defibrillation, airway manoeuvres, rescuer change, and chest compression/ventilation
ratio. To assess CPR pauses, we need to know when a resuscitation episode begins and ends. The start of a
resuscitation attempt is typically recorded when the defibrillator is turned on, and the end of the
resuscitation attempt is marked by a return of spontaneous circulation or death, operationally defined as
the last chest compression (Kramer-Johansen et al. 2007b).
When all single pauses are added up during a resuscitation attempt, time without compressions is called no
flow time. Outside that period rescuers are using chest compression in an attempt to achieve blood flow
13
during CA. So during the pause time blood does not flow (no flow time). This total no-flow time can be
described as the cumulative time without chest compressions in the absence of pulse from the first
therapeutic effort to the end of the resuscitation attempt (Kramer-Johansen et al. 2007a). The no flow ratio is
the fraction of the total no flow time relative to the total time of the resuscitation attempt. The minimal
single pause duration which is regarded as no-flow time ahs been defined as 1.5 seconds (Kramer-Johansen
et al. 2007).
Pauses in chest compression are common; patients receive chest compressions in out-of-hospital settings
only half of the time (Wik et al. 2005) and in-hospital 76% of the time (Abella et al. 2005). The importance of
time without chest compression is clear: In animal models, interruptions in chest compressions for
ventilation decrease coronary perfusion (Berg et al. 2001), and interruptions exceeding 15 seconds for
rhythm analysis prior to defibrillation worsen the outcome of CPR (Yu et al. 2002). Also, in the clinical
setting, the pre-shock pause has been shown to affect shock success (Edelson et al. 2006a).
Rhythm analysis and defibrillation add the no-flow time, especially when automated external defibrillators
(AED) are used (Berg et al. 2003). It takes more time to analyze rhythm, charge and defibrillate with AED
than with manual defibrillator (Pytte et al. 2007). Also airway manoeuvres, rescuer change, and chest
compression ventilation ratios influence no-flow values. In fact, resuscitation guidelines determine
application of all of these factors (ECC Committee, Subcommittees and Task Forces of the American Heart
Association 2005, Handley et al. 2005), so the guidelines themselves significantly affect no-flow-time.
2.3.2.2.
Optimal chest compression depth
Compression depth is defined as the maximum posterior deflection of the sternum prior to chest recoil. In
the resuscitation guidelines, target compression depth is 4–5 cm (ECC Committee, Subcommittees and Task
Forces of the American Heart Association 2005, Handley et al. 2005); however, too-shallow chest
compressions are common during CPR in both the in-hospital and out-of-hospital settings (Wik et al. 2005,
Abella et al. 2005). Deeper chest compressions have been shown to correlate with increased cardiac output
in animal models of CA (Babbs et al. 1983, Bellamy et al 1984, Ristagno et al. 2007). Also, in humans,
14
increasing compression depth has been associated with increased defibrillation success and survival to
hospital admission (Edelson et al. 2006a, Kramer-Johansen et al. 2006).
Some factors can affect chest compression depth, including the surface underneath the patient, rescuer
fatigue during a long CPR episode, rescuer’s weight or height and stiffness of the patient thorax. In the
clinical setting, resuscitation is generally performed on the floor in an out-of-hospital setting and in the bed
with various mattresses in the in-hospital setting. Therefore, the surface underneath the patient is worthy of
focus. In manikin studies, chest compression depth has been documented to be deeper on the floor (Tweed
et al 2001, Perkins et al. 2003), but participants in these studies were few and the populations
heterogeneous. Resuscitation guidelines recommend using a backboard, but clinically they are not routinely
used, at least in Finnish hospitals. In addition, data concerning the efficacy of backboard use in terms of the
quality of CPR in the bed is conflicting (Perkins et al. 2006, Andersen et al 2007). Results about rescuer’s
weight or height correlation on chest compression depth are also conflicting (Perkins et al 2004, Jones et al
2008).
2.3.2.3.
Optimal chest compression rate
Compression rate, defined as the frequency of chest compressions during a compression series, is easy to
measure and modify. In resuscitation guidelines prior to 1986, the recommended chest compression rate
was 60/minute. This recommendation later changed to 80–100/minute (National Conference on
Cardiopulmonary Resuscitation (CPR) and Emergency Cardiac Care (ECC) 1986), and in the last few
guidelines issued, including current guidelines, the recommended rate is 100/minute (ECC Committee,
Subcommittees and Task Forces of the American Heart Association 2005, Handley et al. 2005).
In animal studies, higher chest compression rates are associated with improved haemodynamics (Wolfe et
al. 1988, Sunde et al. 1998) and better primary survival (Feneley et al. 1988). Feneley compared chest
compression rates of 120/min and 60/min and found that higher rates resulted in better 24-hour survival. In
two human studies, a higher chest compression rate produced an increased exhaled end-tidal carbon
dioxide (EtCO2) concentration, reflecting better tissue perfusion (Kern et al. 1992, Berg et al. 1994). In these
15
two studies, the chest compression rates compared were 80/minute and 120/minute (Kern et al. 1992) and
100/minute and 140/minute (Berg et al. 1994), and a metronome was used to guide the rate of compression.
In an observational study, chest compression rates were lower in non-survivors than survivors (mean 90±17
and 79±18) (Abella et al. 2005). In that work, the rate was recorded with a handheld recording device, so
depth or other measurements found in other studies of CPR quality were not recorded (Wik et al. 2005,
Abella et al. 2005). However, the depth of chest compression has correlated with improved haemodynamics
and primary survival in animal studies (Babbs et al. 1983, Bellamy et al 1984, Ristagno et al. 2007). Thus, the
question arises of whether or not the improved haemodynamics and survival are the result of the rate or
depth of chest compression and whether these two elements of CPR quality are related to each other.
2.3.2.4.
Rescuer’s fatigue
Performing manual CPR is heavy work, and rescuer’s fatigue has been documented to affect chest
compression depth in manikin studies even after one minute (Ochoa et al. 1998b, Hightower et al. 1995),
although the rescuers themselves indicate fatigue onset later, at around four to five minutes (Hightower et
al. 1995). Clinically, chest compression depth declines after 90 seconds of continuing chest compression, but
this decline is clinically insignificant (Sugerman et al. 2009). In manikin studies, the scenario duration has
been short at 3 to 5 minutes, but in clinical situations, the duration of CPR is much longer than these
scenarios. The mean duration of CPR for all initiated CPR episodes is 15–22 minutes; for survivors of inhospital CA, it is 14–16 minutes (Hajbaghery et al 2005, Peters, Boyde 2007). There are no data concerning
rescuer’s fatigue in long resuscitation periods with a chest compression ventilation ratio of 30:2. In addition,
data are lacking on the effect of rate guidance or the surface underneath the patient on chest compression
depth as an indicator of rescuer’s fatigue.
2.3.3.
Monitoring CPR quality
Clinical monitoring of CPR quality has enabled identification of what defines poor quality during
resuscitation (Wik et al. 2005, Abella et al. 2005). These observations have led to changes in the guidelines
16
and a wider knowledge of and interest in quality during CPR. Basically, monitoring of CPR quality can be
divided into two main areas: simply monitoring what we do clinically or in training sessions, or monitoring
to provide immediate feedback for improving the quality of CPR clinically or in training sessions.
In manikin studies and training with manikins, monitoring of at least chest compression depth has been
done for more than 20 years (Weaver et al. 1979). Although manikin studies have limitations, they do allow
comparison of the quality of CPR with different resuscitation strategies (e.g., compression/ventilation ratios
(Dorph et al 2002), different surfaces (Perkins et al. 2003, Perkins et al. 2006), different defibrillators (Pytte et
al. 2007a), and effect of different instructions to bystanders (Brown et al. 2008)). Manikins with features that
allow measurement of CPR quality are in common use in CPR teaching and training.
In clinical resuscitation, there are many ways to monitor CPR quality. Probably the oldest is the palpable
pulse, which was used as an indicator of good CPR quality in the 1990s (Wik et al 1994, Gallagher et al 1995,
Van Hoeyweghen et al. 1993). There are some limitations with this method because it is difficult and timeconsuming to check a pulse even with a pumping heart (Eberle et al. 1996, Ochoa et al. 1998a).
Also, monitoring EtCO2 as an indicator for cardiac output during CPR is an old method (Weil et al. 1985,
Falk et al 1988). One technique to monitor CPR quality clinically is simple observation in real time (Spaite et
al. 1993) or via review of video recordings (Chiang et al. 2005). The problem with simple observation or
video recording is that time without chest compression or chest compression rate can be monitored, but
chest compression depth likely cannot. At least in manikin studies, it is impossible to determine chest
compression depth only by looking (Ramirez et al. 1977).
The rediscovery of the issue of CPR quality emerged with developments in the use of defibrillator
technology in late 1990s to make possible easy measurement of CPR quality in the clinical setting (Sunde et
al. 1999). In clinical situations, chest compression depth can be directly measured using an accelerometer
(Aase, Myklebust 2002) or a linear potentiometer mounted on the patient’s chest (Gruben et al. 1990).
Indirectly it can be estimated with a force detector on the patient’s chest (Perkins et al. 2005). The most
important studies addressing CPR quality are done with an accelerometer technique (Wik et al. 2005, Abella
17
et al. 2005). The defibrillators record chest compressions via a sternal pad fitted with an accelerometer and
capture ventilations based on changes in thoracic impedance between the defibrillator pads.
2.3.4.
Current status of CPR quality in clinical situations
The quality of CPR in clinical studies is poor. The most important studies regarding CPR quality were
published in 2005. With an in-hospital setting, Abella found a slow compression rate (<80/min) in 37%, tooshallow chest compressions in 37%, and 24% of time with no compressions at all during in-hospital CPR
(Abella et al. 2005). In an out-of-hospital setting, Wik et al. documented similar results: chest compressions
were not given 48% of the time without spontaneous circulation; an average 28% of the chest compressions
had the recommended depth of 38–51 mm; and the mean compression rate was 121/minute (Wik et al.
2005). Others have also documented similar findings (Losert et al. 2006, Valenzuela et al. 2005, Ko et al.
2005). With highly trained professionals in an emergency department, CPR quality is better; in one study,
the mean rate was 114/minute, depth was too shallow in only 7%, and the no-flow ratio was 12.7% (Losert et
al. 2006).
2.4.
CPR EDUCATION
CPR is not easy task to perform, because CA is a relatively rare phenomenon, but when it does occur,
survival is a battle against time. Thus, skills and techniques to perform CPR must be at the ready when they
are needed, but it is almost impossible to provide the necessary real-world training in clinical situations.
Some recommendations target CPR teaching (Chamberlain et al. 2003, Eisenburger, Safar 1999). In the 2003
ILCOR advisory statement, ‘education in resuscitation’, there were specific recommendations for
laypersons, those with a duty to respond, and healthcare professionals. The major themes of education were
outlined in this statement (Chamberlain et al. 2003), but in practise, education is performed by trainers
authorized by national resuscitation councils or the Red Cross. These courses for different levels are
standardised and training material is comprehensive (Baskett et al. 2005). There are no such
18
recommendations or standardised courses for different levels of students training as healthcare
professionals.
2.4.1.
A short history of manikins and CPR education
In CPR education there is an evident need for training manikins. In the early 1960s, two famous researchers
in resuscitation development, Peter Safar from the United States and Bjørn Lind from Stavanger Hospital,
asked toymaker Åsmund Laerdal from Stavanger to develop a resuscitation manikin. Laerdal’s plastic-toy
company created a popular doll named Anne (later called "Resusci Anne") (Tjomsland, Baskett 2002). The
first manikin was developed purely to facilitate mouth-to-mouth ventilation, and by 1960 in Norway, 6900
students had been taught to provide mouth-to-mouth ventilation (Lind 1961). After closed-chest CPR
became part of clinical practise, chest compression training with Laerdal’s manikin became possible.
Recording properties were implemented in the manikin in 1971 when the Recording Resusci Anne was
introduced, equipped with a printer and in the same time ‘Arrhythmia Anne’ was developed making
rhythm analysis and treatment possible (Tjomsland, Baskett 2002).
2.4.2.
The significance of CPR education
The importance of CPR education with the goal of handling even a single clinical CA patient is clear.
However, the teaching of CPR carries a broader influence, as was concluded in The International Liaison
Committee on Resuscitation (ILCOR) statement in 2003. ILCOR identified three factors that affect overall
outcome from CA (Chamberlain et al. 2003).:
(1) the quality of resuscitation guidelines,
(2) the local ‘chain of survival’,
19
(3) the quality of education for CPR providers that enables them to put the theory into
practise
In addition, ILCOR recommended that all healthcare professionals receive their initial training in BLS while
students (Chamberlain et al. 2003).
The term ‘chain of survival’ brings the question of which groups should receive CPR education and
training. The answer is all groups: bystander, dispatchers, and the entire EMS system, along with inhospital providers. It is evident that every group has to train with a specific program, targeted for them.
These different levels of standardised training programs are organised by ERC and different National
Resuscitation Councils (Baskett et al. 2005, Hoke, Handley 2006).
2.4.3.
The problems with CPR education and retention of skills
The problems with CPR education are multiple; who, how and how often. Not all groups that could benefit
from training actually receive it, especially bystanders. In Sweden, CPR education was evaluated in the
population via a questionnaire sent to 5000 adults. The response rate was 63%, and 45% of the responders
had had some kind of CPR training (Axelsson et al. 2006). ILCOR has recommended that all healthcare
professionals must receive their initial training in BLS while students (Chamberlain et al. 2003). It is quite
unknown how this recommendation is put into practise, because there are only few studies concerning this.
The total amount of resuscitation education was evaluated in 1999 in 168 European medical schools (GarciaBarbero, Caturla-Such 1999). Medical students received a median 14 hours of CPR lessons and 20 hours of
CPR practise. There are no such studies concerning paramedics, Firefighters or EMT’s students.
CPR education is difficult because CPR requires both knowledge about CA (for example, recognition and
calling for help) and the psychomotor skills to perform CPR. Knowledge persists longer than CPR skills
(Latman, Wooley 1980), and CPR skills decay rapidly (Weaver et al. 1979, Kaye et al. 1991), even as early as
2 weeks (Fossel et al 1983). It was documented over 25 ago that with an AHA standardised CPR course, 21%
of participants performed CPR adequately immediately after the course, and only 9% did so after three
months (Martin et al 1983).
20
In addition, there is a huge problem with ensuring that participants learn CPR performance in the first
place, partly because of the methods we use to teach CPR. Without objective tools during CPR training, the
skills cannot be reliable analysed and, perhaps, learned correctly (Weaver et al. 1979, Kaye et al. 1991,
Ramirez et al. 1977, Lynch et al. 2008).
Recording manikins became available more than 30 years ago (Tjomsland, Baskett 2002), and since that
time, their properties have expanded substantially (Eisenburger, Safar 1999). It has been clearly shown that
some objective tools are needed to evaluate a trainee’s CPR skills. Ramirez was among the first to document
this need, finding that when objective data from a recording manikin were used, less than 20% of
laypersons performed ventilations or chest compressions correctly immediately after training; yet instructor
ratings indicated that more than 95% of participants could perform these skills adequately (Ramirez et al.
1977). Many others later reported similar findings (Weaver et al. 1979, Lynch et al. 2008), and a review of 37
studies of lay and professional rescuers’ CPR performance showed that dramatically different percentages
of learners were rated as competent, even in studies that used the same course and the same assessment
methods (Kaye et al. 1991). Manikin recording properties enable easy feedback from the most clinically
important aspects of CPR, and investigators began recommending their use more than 10 years ago
(Brennan et al. 1996).
Retention of skills is an important problem. CPR skills decay very rapidly (Weaver et al. 1979, Kaye et al.
1991), even as early as 2 weeks (Fossel et al 1983). Regular post-graduate education is needed because of
this. In addition, CPR guidelines change every 5 years, indicating another need for training with any new
system or guideline; for example, learning and applying the new chest compression ventilation ratio.
21
22
3.
Aim of the study
The purpose of this study was to study CPR quality and education.
The specific aims can be described as:
1.
To describe current CPR quality of out-of-hospital and in-hospital care providers and to
evaluate the amount of education and methods used for ensuring chest compression
quality in the education of students of emergency medicine at different levels in Finland
(Studies I, II, IV)
2.
To evaluate the effect of the Resuscitation Guidelines change, surface characteristics and
the use of rate guidance on chest compression quality and rescuer fatigue during
simulated cardiac arrest (Studies I-III)
23
24
4.
Participants and methods
Studies I–III were simulated CA studies with manikin, and because of the nature of these studies, we did
not need approval from the ethics committee at our hospital. For manikin studies, all participants received
written information about the study and consented to participate voluntarily. For study IV about teaching
CPR at Finnish institutions, teaching of emergency medicine providers was performed with an Internet
survey, and answers were provided anonymously through a questionnaire form.
4.1.
PARTICIPANTS
For study I, we recruited 12 paramedic students studying at the Savonia University of Applied Sciences,
Kuopio, Finland, and 22 licensed paramedics from the Hospital District of Northern Savo, Kuopio, Finland.
All of them arrived voluntary to Kuopio University, where Study I was carried out in May 2006. Studies II–
III were done in November 2006 in the intensive care unit (ICU) of Kuopio University Hospital, Finland.
Altogether, 63 ICU nurses were recruited into these studies, 25 of whom participated in both studies and 38
of whom participated in one study. Studies II and III are done at different times and data concerning
participants in these studies are represented along with the study. Nurses recruited from normal duty.
Data concerning the participants of studies I–III are collected in Table 1.
Table 1:
Data of the participants
n
Mean
age
(range)
%
Working
Real-life
Height
Weight
female
experience
resuscitation
(cm)
(kg)
(years)
Study I
34
30 (21–49)
21%
7 (0-23)
Not recorded
Not recorded
Not recorded
Study II
44
38 (25–50)
80%
10 (0.5–26)
30 (2–100)
167
(153–
68.5 (54–93)
(153–
69 (54–105)
189)
Study
III
44
33 (24–50)
80%
10 (0.5–26)
23 (1–140)
167
192)
25
4.2.
INSTITUTIONS
In study IV, an internet survey was administered to medical professionals at Finnish institutes teaching
CPR to emergency medicine providers. Answering was performed anonymous with questionnaire forms
(appendix). Data were collected between 1.2. 2007 - 30.3.2007. Data represent status of year 2007 and also
the plans for term 2007-2008.
Hours spent teaching CPR with lessons or with small group training were evaluated. In addition, we
evaluated the methods used to teach correct chest compression rate and depth in small group training with
manikins, question form is appended in appendix. Of the 30 institutions included in the survey, 21
provided responses after two reminders. The specific data from the institutions are shown in Table 2.
Table 2
Characteristics of institutions that teach different emergency medical service providers
Type
of
Students
institution
Number
of
Duration
of
responses/total
studies,
number of institutions
(credit points)
years
Number
of
admitted annually per
school,
(median)
Medical schools
Medical
4/5
6 (360)
105–130 (120)
Paramedics
6/8
4 (240)
15–22 (20)
Emergency
10/16
3 (120)
5–60 (17)
1/1
1.5 (90)
180
students
Universities
of
applied
sciences
Colleges
medical
technicians
Emergency
Services
College
Fire fighters
students
range
26
4.3.
STUDY DESIGN
4.3.1.
Current status of CPR quality and educational methods to facilitate
this in Finland
Current status of CPR quality in Finland was evaluated from control groups of Study I and II. These studies
were done during the time when the ERC guidelines were recently changed; Study I in May 2006 and Study
II in November 2006. That is the reason for different resuscitation guidelines usage. The group for
describing the current status of CPR in out-of-hospital setting was participants who used ERC 2000
guidelines in Study I. Most participants were not familiar with the new prior to the study. We take ‘ERC
2000’-group to describe current status of CPR in out-of-hospital setting. The group for describing the
current status of CPR in in-hospital setting was participants of study II. In-hospital CPR in mainly
performed in the bed, so we take the ‘in the bed’-group to describe the current status of CPR in in-hospital
setting. The ERC 2005 guidelines have been implemented to ICU nurses during the year 2006, before the
Study III and ERC 2005 guidelines were used in Study II. Also the scenarios were different; in Study I there
was a 10 minute VF scenario with rhythm analysis, charging and defibrillating and In Study II there was a
10 minute two-rescuer BLS scenario. That’s why we did not evaluate no flow time or rescuer fatigue in
describing the current status of CPR in Finland.
The educational methods to teach correct chest compression depth and rate were analysed along with Study
IV, methods are described in detail in paragraph 4.2.
4.3.2.
Effect of external factors on CPR quality
Studies I–III were simulated CA studies with manikin (Skillmeter Resusci Anne, Laerdal Medical). In Study
I semi-automatic defibrillator, Philips MRX AED (Philips Medical Systems; Andover, MA, USA) was used
for rhythm analysis.
27
The groups for Studies I-III and the scenarios used are represented in Table 3. In a study I European
Resuscitation Guidelines (ERC) year 2000 and 2005 were compared in 10 minute VF scenario. The rhythm
was VF all the time to maximise time to analyse rhythm, charge and defibrillate with AED. The CA scenario
was treated by two rescuers using semi-automatic defibrillator (Philips MRX AED) and bag-mask
ventilation. When the scenario was treated according to ERC 2000 guidelines AED was set to give three
shocks every one minute, each after analyzing the rhythm first. The pulse was checked after the third shock
and the rescuer was changed when they felt tired. The chest compression - ventilation ratio was 15:2. When
the scenario was treated according to ERC 2005 guidelines AED was set to give one shock every two minute
after analyzing the rhythm first. The pulse was not checked after the shock and the rescuer was changed
every two minutes, when rhythm was analyzed. The chest compression - ventilation ratio was 30:2.
In a study II chest compression depth was compared when CPR was performed on the floor or in the bed in
a 10 minute CA scenario. The rhythm was not analysed, only two-rescuer BLS: chest compressions and bagmask ventilation performed. The participants comprised ICU nurses on duty that were divided into pairs of
rescuers that performed two different scenarios separated by at least a one hour break To avoid bias, we
did not use a crossover design, but in every resuscitation attempt (scenario) randomization was repeated.
Sealed opaque envelopes were used for randomization. Because in-hospital cardiac arrests usually occur in
the hospital bed, each scenario started with recognition of cardiac arrest as the manikin was in the bed. If
treatment, based on the randomization, was to be on the floor, participants first checked breathing and
responsiveness in a bed and then moved the manikin to the floor and started chest compressions. If
treatment was intended, based on the randomization, to be in the bed, breathing and responsiveness were
first checked, and chest compressions were then started. Each pair completed two scenarios: each
participant began the first scenario with ventilation and the second scenario with chest compressions. Ten
minutes of two-rescuer CPR was performed and the 2005 CPR guidelines were followed with a 30:2 chest
compression to ventilation ratio and change of the rescuer performing chest compressions every two
minutes on the investigator’s command to change the rescuer.
In a study III chest compression depth was compared when 10 minute CPR scenario was performed with
and without metronome guidance for chest compression rate. The rhythm was not analysed, only two-
28
rescuer BLS; chest compressions and bag-mask ventilation performed. The participants comprised ICU
nurses on duty that were divided into pairs of rescuers that performed two different scenarios separated by
at least a one hour break. We used a crossover design and asked the participants not to inform the other
ICU nurses about the scenario set-up. We did the first scenario without metronome (Korg metronome MA30, Korg inc, China) and the second with metronome to minimize the bias of learning effect on correct chest
compression rate from metronome guidance. CPR was performed on a manikin (Skillmeter Resusci Anne,
Laerdal Medical, Stavanger, Norway) by kneeling on the floor beside the manikin. The 2005 CPR guidelines
were followed with a 30:2 chest compression to ventilation ratio and change of the rescuer performing chest
compressions every two minutes on the investigator’s command to change the rescuer.
Study IV was an Internet survey administered to medical professionals at Finnish institutions teaching CPR
to emergency medicine providers. Answers were provided anonymously through a questionnaire form.
Data were collected between February 1, 2007, and March 30, 2007. The data represent the status of CPR
training in 2007 and the plans for the term covering 2007–2008.
Table 3: Design of cardiac arrest studies
Study
Groups
Scenario
Ventilation–
Defibrillation
compression
CPR
duration
between shocks
ratio
I
Guidelines 2000
10 minutes, VF,
2:15
two rescuer
AED:
1 minute
3 shocks,
every 1 minute
Guidelines 2005
10 minutes, VF,
2:30
two rescuer
AED:
1 shock,
every 2 minutes
II
Floor
10 minutes, two
2:30
None
2:30
None
rescuers, CPR
Bed
II
Metronome
10 minutes, two
rescuers, CPR
Free rate
2 minutes
29
4.4.
QUALITY OF CPR
In studies I–III, the manikin we used was a new Skillmeter Resusci Anne (Laerdal Medical, Stavanger,
Norway). The manikin was connected to a laptop, and Skillmeter software (PC Skillmeter, Laerdal Medical)
was used for data collection. This software collected sternum movement information (chest compression
and release) and also analysed the depth and rate of chest compressions. Reference values for compressions
were 90–110 compressions/min for an adequate rate and 38–51 mm for adequate depth in Skillmeter
software. Compression was defined as compression when depth was greater than 10 mm. Chest
compression rate was calculated as the average rate during each cycle of 30 compressions between
ventilations (compression rate per min) and as the number of actually performed chest compressions
(performed compressions per min). In all three manikin studies, we were interested only in the adequacy of
the compression part of CPR; the manikin received bag-valve mask ventilation, but we did not evaluate the
quality or success of ventilation. In none of the manikin studies could participants see the Skillmeter
software feedback monitor, and the investigators provided no feedback regarding CPR during the scenario.
4.5.
TIME FACTORS
In study I, no-flow time was the main outcome. In study III, time factors, including time used for ventilation
and no-flow time, were minor outcome factors. The manikin Skillmeter software calculates total no-flow
automatically (e.g., the time without chest compressions). In studies I and III, we needed more detailed
information and calculated some time factors manually from Skillmeter software graphics.
In study I, we wanted to distinguish time without chest compression (total no-flow time) from time used to
operate with defibrillator (rhythm analysis, charge, defibrillation) and time used for human procedures
(start CPR, apply electrodes, ventilation). The sources used to determine the time used for these tasks are
given in Table 4. The start time was marked when the automated external defibrillators (AED) was
30
switched on and the time was visible, in minutes and seconds, on the AED monitor. From that point, we
recorded time to apply electrodes and delay to start CPR. Time factors to operate with the defibrillator are
designated as device factors, and the principles used to calculate these times manually are represented in
Figure 1.
Table 4:
Sources of data for no-flow time as divided into human or device factors
Human factors
Data source
Time needed to apply electrodes
AED
Delay in starting CPR
AED
Time needed for ventilation
Skillmeter software
Device factors
Time to perform the rhythm analysis
Skillmeter software graphics
AED charging time
Skillmeter software graphics
Defibrillation time
Skillmeter software graphics
31
Figure 1:
An example of getting time factors using guidelines 2000. No flow time, separated into time due to human or device
factors.
Human factors:
(a) indicates time needed to apply electrodes,
(b) indicates the delay in starting CPR and
(c) indicates the time needed to establish ventilation.
Device factors:
(d) indicates time needed for rhythm analysis and AED charging and defibrillation.
The arrowhead indicates the AED command, “Clear patient, analysing rhythm,”
the arrow indicates the AED command, “If no pulse, start CPR,” and
the lightning-arrow indicates defibrillation.
In study III, we defined total no-flow time as time without chest compressions, and this value was retrieved
from the Skillmeter software. We wanted to determine whether or not metronome usage would affect time
used for ventilation, and we therefore analysed time used for ventilation. We defined the pause for
ventilation as time used to perform two ventilations between 30 chest compressions. This value was
manually calculated from Skillmeter software graphics using 0.5-second sensitivity (Figure 1, time factors
‘c’, time needed to establish ventilation). Total time used for ventilation was the sum of pauses for
ventilation during the 10-minute scenario. The number of ventilation pauses during the whole scenario was
also manually calculated. The duration of a single ventilation pause (to perform two ventilations with a bag
and mask) was calculated by dividing the total time used for ventilation during a 10-minute scenario by the
number of pauses for ventilation.
32
4.6.
RESCUER’S FATIGUE AND ‘SIGNATURE’
We calculated the mean compression depth and rate for each minute for every scenario manually from the
Skillmeter software graphics. We did this by calculating the depth of every single chest compression during
every scenario by placing a computer cursor on the tip of each chest compression; the Skillmeter Software
program then gave the depth of this single chest compression in millimetres (Figure 2).
Figure 2:
Depth of single chest compression was measured with computer cursor placed on the tip of each chest compression
When we analysed correlation of rescuers weight or height to mean chest compression depth, we took into
account the individual performing the chest compressions. Also when we analysed individual rescuer’s
chest compression style (the rescuer’s ‘signature’), mean chest compression depth and rate for each minute
were associated with each individual rescuer. But when we analysed rescuer’s fatigue during the 10-minute
scenario, the indicator was mean chest compression depth minute by minute, and we did not take into
account the individual performing the chest compressions.
33
4.7.
PARTICIPANTS’ OPINIONS
The participants’ demographic data (studies I, II, III) and their opinions regarding CPR performance in
different scenarios (studies II and III) were registered on data collection forms filled out immediately after
each scenario. The participants of Study I were last year paramedic students studying at the Savonia
University of Applied Sciences, Kuopio, Finland and licensed paramedics from the Hospital District of
Northern Savo, Kuopio, Finland. The participants of Studies II and III were ICU nurses of Kuopio
University Hospital. Participants reported their age, weight, height, working experience in ICU and
estimated number of real-life resuscitation. Each participant was asked to rate the following statements
using a 100-mm visual analogue scale (VAS): “The chest compressions I performed were effective”, scale:
0=not effective, 100=very effective; “It was exhausting to deliver chest compressions”, scale: 0=no exhaustion
at all, 100=“extreme exhaustion, can’t perform any more chest compressions”.
4.8.
SAMPLE SIZE
Sample size analyses were done for studies I and III. For Study I the primary endpoint was no flow time
and we simply calculated the estimated no flow time difference during 10 minute VF scenario if it is treated
according to ERC 2000 or ERC 2005 guidelines would be 3 minutes and with a power of 80% and an α level
of 0.05, the sample size would be 34.
For study II we did not perform sample size calculations, because there were no similar prior studies. For
study III the primary endpoint was the percentage of chest compressions that achieved the correct depth
during 10 min scenario. We did not have data from similar prior studies that would serve as a basis for
sample size calculation; thus, based on other studies (Wik et al 2005) we estimated that 40% of chest
compression would achieve the correct depth without the metronome and 80% with the metronome. Using
a power of 80% and a two-sided α level of 0.005, we calculated that a sample size of 44 (22 pairs) would be
adequate.
34
4.9.
STATISTICAL METHODS
In all studies, data were analysed using the SPSS statistical software package for Windows, version 13.0. In
addition, in all studies the normally distributed data were presented as the mean or percentage with SD and
were analysed using an independent sample t-test. Alternatively, data that were not normally distributed
were presented as the median along with the range and were analysed using the Mann-Whitney U test.
Correlation of mean chest compression depth with rescuer’s weight and height was analysed with Pearson
correlation coefficient.
In studies II and III, participant opinion (regarding CPR on different surfaces) using the VAS scale was
analysed with the non-parametric Wilcoxon signed-rank test. In these two studies, rescuer’s fatigue was
estimated using the mean chest compression depth and rate per minute. These data were normally
distributed and analysed using repeated measures ANOVA. The percentage of correct depth chest
compressions at each time period was not normally distributed, and these data were analysed using the
non-parametric Friedman’s test. The individual rescuer’s ‘signature’ refers to a rescuer’s individual
signature CPR style. The individual rescuer’s chest compression depth and rate per minute on different
surfaces were analysed using correlation coefficients and coefficients of variation. Individual rescuer’s chest
compression depth with and without metronome use were analysed in a similar way.
In study IV, we did not perform any statistical tests because that study was meant to be descriptive.
35
36
5.
Results
5.1.
THE PARTICIPANTS
Data concerning the participants of studies I–III are collected in Table 5. There were no significant
differences between the groups in any of these characteristics in studies I-III. The groups for evaluating the
current status of CPR quality were group ERC 2000 from Study I (out-of-hospital setting) and group Bed
from study II (in-hospital setting).
Table 5:
Data of the participants
n
Mean age
% female
(range)
Working
Real-life
Height
Weight
experience
resuscitation
(cm)
(kg)
Not recorded
Not recorded
Not recorded
(years)
Study I
34
30 (21–49)
21%
7 (0-23)
ERC2000
17
31 (21-41)
24%
4 (0-17)
ERC2005
17
31 (23-49)
18%
10 (2-23)
Study II
44
38 (25–50)
80%
10 (0.5–26)
30 (2–100)
167 (153–189)
68.5 (54–93)
Floor
22
37 (27-49)
82%
12 (1.5-21)
33 (16-60)
167 (153-189)
67 (54-93)
Bed
22
37 (25-50)
77%
10 (0.5-26)
28 (2-100)
169 (156-186)
71 (55-86)
Study III
44
33 (24–50)
80%
10 (0.5–26)
23 (1–140)
167 (153–192)
69 (54–105)
Metronome
22
34 (24-49)
82%
9 (0.5-26)
29 (5-140)
169 (157-192)
74 (55-105)
Free
22
37 (25-50)
77%
12 (0.5-22)
33 (1-100)
167 (153-188)
67 (54-101)
5.2.
CURRENT
STATUS
OF
CPR
AND
EDUCATIONAL
METHODS
TO
FACILITATE THIS IN FINLAND
The percentage of chest compression given at correct rate was nearly zero in both groups (Table 6). The
percentage of chest compression given at correct depth was 79% in out-of-hospital and 58% in-hospital
37
group. There were no differences in chest compression rate, depth or percentage of chest compressions with
correct rate or correct, too deep or too shallow depth between out- or in-hospital settings. The only
difference between the groups was that for in-hospital setting the number of actually performed
compressions per minute was higher in in-hospital group. The number of responses for each Finnish
institution is represented in Table 7.
Table 6:
The current quality of CPR in out-of-hospital and in-hospital setting.
Compressions
Out-of-hospital
In-hospital
P value
Compression rate (min−1)1
127±20
139±19
P=0.090
Performed compressions (min−1)1
50±10
108±14
P<0.001
Rate 90–110 (%)2
2(0-91)
0.5 (0–24)
P=0.204
43.6±7.7
43.0 ± 5.9
P=0.779
79 (3–98)
58 (0–92)
P=0.497
0 (0–95)
6 (0–62)
P=0.408
3 (0–96)
20 (1–99)
P=0.321
100(26-100)
96 (68–100)
P=0.523
Depth (mm)
1
2
Correct depth 38–51 mm (%)
2
Too deep (>51 mm) (%)
2
Too shallow (<38 mm) (%)
2
Correct release (%)
1
Values are given as mean ± SD and data were analyzed with an independent sample t-test
2
Values are given as median values with range and data were analyzed using a Mann-Whitney U-test
38
Table 7:
The number of responses and total number of institution
Type of institution
Students
Number of responses/total number of
institutions
Medical schools
Medical students
4/5
Universities of applied sciences
Paramedics
6/8
Colleges
Emergency medical technicians
10/16
Emergency Services College
Fire fighters
1/1
In Finnish institutions that educate students of emergency medicine at different level the instructor’s visual
estimation was the sole method used to teach correct chest compression depth in 28.5% (6/21 institutions) of
institutes and correct rate also in 33.3% (7/21 institutions), Table 8.
Table 8: Methods used to teach adequate chest compression rate and depth in small-group training
CPR instruction method
Total
CPR compression rate
- Visual estimate
6/21 (28.5%)
- Using a watch
7/21 (33.3%)
- Using an audible tone
2/21 (9.5%)
- Using graphics
6/21 (28.5%)
CPR compression depth
- Visual estimate
7/21 (33.3%)
- Manikin light indicator
5/21 (23.8%)
- Using graphics
11/21 (52.3%)
39
5.3.
THE EFFECT OF EXTERNAL FACTORS ON CPR QUALITY
5.3.1.
Effect of resuscitation guideline change
5.3.1.1.
No flow time with different resuscitation guidelines
The mean total no flow time was significantly higher with the ERC 2000 guidelines as compared to the ERC
2005 guidelines (P<0.001; Figure 3).
Figure 3:
Total no flow ratio in a scenario of 10 min of ventricular fibrillation treated according to ERC 2000 or ERC 2005
guidelines (P< 0.001 for the difference between groups)
40
Factors that explain the difference in no flow time between the two groups are shown in Table 9 which
shows that the difference was caused by device factors.
Table 9:
A simulated VF scenario lasting 10 minutes (=600 seconds) was performed using either ERC 2000 or ERC 2005
guidelines.
Chest compression time=total time spent on chest compressions during a scenario. Total no flow time= time without
chest compression. The no flow ratio= [(total no flow time/total duration of the scenario) × 100)]. Data are shown as
the mean±SD and P values for differences from two-sided independent samples t-tests.
ERC 2000
ERC 2005
P value
Chest compression time (s)
206±19
410±23
P<0.001
Total no flow time (s)
393±19
190±23
P<0.001
No flow ratio (%)
66±3
32±4
P<0.001
Time to apply electrodes (s)
6±4
5±3
P=0.281
Time to ventilate (s)
100±17
95±17
P=0.350
Delay to start CPR (s)
8±6
8±4
P=0.949
Device factors (s)
290±19
92±15
P<0.001
Human factors (s)
5.3.1.2.
Chest compression quality with different resuscitation guidelines
The total number of chest compressions was higher when ERC 2005 guidelines were used. The mean
compression rate was faster than guidelines recommend for both groups, with no significant difference
between them. The number of actually performed compressions per minute was significantly higher when
the ERC 2005 guidelines were used (P<0.001). The mean compression depth and the percentage of
appropriate and too-deep chest compressions were not significantly different between two groups. There
was a modest difference in the proportion of chest compressions that were too shallow between the groups
(Table 10).
41
Table 10
CPR quality data for the ERC 2000 and ERC 2005 groups.
Compressions
ERC 2000
ERC 2005
P value
458±90
808±92
P<0.001
51±10
83±8
P<0.001
127±20
117±15
P=0.09
44±8
47±6
P=0.14
79 (3–98)
73 (15–96)
P=0.58
Too deep (>51 mm) (%)2
0 (0–95)
12 (0–85)
P=0.068
Too shallow (<38 mm) (%)2
3 (0–96)
1 (0–53)
P=0.031
Correct release (%)2
100 (26–100)
100 (43–100)
P=0.84
Total number of chest compressions
1
Performed compressions/min1
Compression rate/min
1
Compression depth (mm)
1
Compression depth 38–51 mm
(%)2
1
Values are given as mean ± SD and data were analyzed with an independent sample t-test
2
Values are given as median values with range and data were analyzed using a Mann-Whitney U-test
5.3.2.
5.3.2.1.
THE EFFECT OF THE SURFACE UNDERNEATH THE MANIKIN
The quality of chest compressions on different surfaces
The mean compression depth during the whole 10-minute scenario was 45 mm on the floor and 43 mm in
the bed (P=0.3). A total of 1060 chest compressions were given on the floor, and 44% of those were within
the correct depth. A total of 1068 chest compressions were given in the bed, and 58% were within the correct
depth. The percentage of too-deep chest compressions was higher on the floor, but otherwise there were no
statistical
differences
in
chest
compressions
between
the
two
surfaces
(Table
11).
42
Table 11:
The quality of CPR performed on the floor and in the bed in 44 scenarios.
Compressions
On the floor
In the bed
P value
Total counted number of chest
1060±118
1068±141
0.843
145±20
139±19
0.314
109±13
108±14
0.776
44.9±6.2
43.0 ± 5.9
0.300
Rate 90–110 (%)
0 (0–27)
0.5 (0–24)
0.970
Correct depth 38–51 mm (%)2
44 (17–90)
58 (0–92)
0.139
26 (0–80)
6 (0–62)
0.043
16 (0–83)
20 (1–99)
0.833
95 (39–100)
96 (68–100)
0.531
139 (60)
130 (45)
0.579
compression1
Compression rate (min−1)1
−1 1
Performed compressions (min )
Depth (mm)
1
2
2
Too deep (>51 mm) (%)
2
Too shallow (<38 mm) (%)
2
Correct release (%)
1
Total no flow time (seconds)
1
Values are given as mean ± SD and data were analyzed with an independent sample t-test
2
Values are given as median values with range and data were analyzed using a Mann-Whitney U-test
Rescuer’ weight did not correlate with mean chest compression depth on the floor (r=0.243, P=0.275) or in
the bed (r=0.124, P=0.564). Rescuer’s height did not correlate with mean chest compression depth on the
floor (r=0.350, P=0.110) or in the bed (r=-0.003, P=0.990) either.
5.3.2.2.
Rescuer’s fatigue: the effect of surface on CPR quality
The effect of rescuer fatigue on chest compression quality was analysed in all 44 scenarios. The mean chest
compression depth declined over time on both surfaces (P<0.001), but this decline did not differ between
groups (P=0.305) (Fig. 4). The percentage of chest compressions of correct depth did not decrease over time
(P=0.458). In addition, the mean chest compression rate did not change during the 10-minute scenario
(P=0.671), and there were no differences between the two groups (Fig. 5).
43
Figure 4:
Chest compression depth for each minute during a 10-minute scenario performed on the floor (circles) and in the bed
(squares).
44
Figure 5:
The mean chest compression rate for each minute during a 10-min scenario performed on the floor (circles) and in the
bed (squares).
45
5.3.2.3.
Rescuer’s fatigue: opinions
Because of the randomisation before each scenario, only 24 of the participants completed the scenarios on
both surfaces. The opinions of these participants were collected using the VAS. A majority of the
respondents felt that CPR on the floor was more efficient, but there was no difference in personal opinions
regarding fatigue (Table 12).
Table 12:
Subgroup analysis of 24 participants, who performed chest compressions on both surfaces
On the floor
In the bed
P value
VAS fatigue
46 (3–90)
56 (2–100)
P=0.136
VAS efficacy
84 (61–100)
70(42-95)
P<0.001
5.3.2.4.
Rescuer’s ‘signature’
Twenty-four of our participants performed CPR on both surfaces. The variation between the surfaces was
6% in rate and 7% in depth. The correlation with chest compression depth on the floor with chest
compression depth in the bed was high (r=0.864, P<0.001) (Figure 6), as was the correlation between chest
compression rate on the floor with chest compression rate in the bed (r=0.930, P<0.001) (Figure 7).
46
Figure 6: Correlation of the individual rescuer’s chest compression depth on the floor and in the bed. Circles indicate
individual rescuer.
Figure 7: Correlation of the individual rescuer’s chest compression rate on the floor and in the bed. Circles indicate
individual rescuer
47
5.3.3.
5.3.3.1.
THE EFFECT OF METRONOME USE
The quality of CPR with and without metronome
The mean compression rate for each 30-compression cycle between ventilations was higher (137±18/min)
when chest compressions were performed freely than when chest compressions were performed with
metronome guidance (98±2/min, P<0.001). Including pauses during ventilations, the average number of
actually performed chest compressions was also higher without the metronome (104±12/min) than with
metronome guidance (79±3/min, P<0.001).
The mean compression depth during the entire 10-minute scenario was 47±8 mm without and 43±6 mm
with metronome guidance (P=0.09). Without metronome guidance, the total number of chest compressions
was 1022, and 42% were within the correct depth range. In contrast, with metronome guidance, the total
number of chest compressions was 780 and 61% were within the correct depth range. The percentages of
correct compression depths with and without metronome guidance were not statistically different (P=0.09).
There were no significant differences in compression styles, except the percent of chest compressions
considered too deep was higher without than with metronome guidance. The average no-flow time was
shorter with metronome guidance (P<0.001) (Table 13).
48
Table 13:
The quality of CPR with and without metronome guidance. Values are given as mean±SD except that the percentage of
compressions given at the correct rate, the correct depth, too deep, too shallow, and with correct release, are given as
median values and ranges.
Compressions
Total counted number of chest compressions
−1
Compression rate (min )
1
−1
Performed compressions (min )
Depth (mm)
1
1
Correct rate 90–110 (%)
2
Correct depth (38–51 mm) (%)
Too deep (>51 mm) (%)
2
Too shallow (<38 mm) (%)
Correct release (%)
2
2
2
Total no-flow time (seconds)
1
1
Free rate
Metronome
P value
1022±119
780±29
<0.001
137±18
98±2
<0.001
104±12
79±3
<0.001
46.9±7.7
43.2±6.3
0.09
3 (0–27)
91 (63–98)
<0.001
42 (1–85)
61 (12–99)
0.09
33 (0–99)
9 (0–80)
0.027
4 (0–83)
11 (0–88)
0.280
97 (57–100)
91 (69–100)
0.128
153±18
130±14
<0.001
1
Values are given as mean ± SD and data were analysed with an independent sample t-test.
2
Values are given as median values with range and data were analysed using the Mann-Whitney U test.
Rescuer’ weight did not correlate with mean chest compression depth with metronome guidance (r=0.0.214,
P=0.0.366) or without metronome guidance (r=-0.100, P=0.0.674). Rescuer’s height did not correlate with
mean chest compression depth with metronome guidance (r=-0.042 P=0.0.862) or without metronome
guidance (r=-0.117, P=0.624) either.
49
5.3.3.2.
Rescuer’s fatigue: effect of metronome guidance on CPR quality
The effect of rescuer’s fatigue on chest compression quality was analysed using one-minute frames. The
mean chest compression depth per minute did not decline over time (P=0.079), and metronome guidance
did not affect fatigue (P=0.259) (Figure 8).
Figure 8:
Chest compression depth for each minute during a 10 minute scenario of simulated cardiac arrest. The outside bars
represent the standard error of the mean (+/-). The change of rescuer performing chest compressions is represented by
omitting the lines connecting the time points. The decline in mean chest compression depth per minute was
insignificant when performed with metronome guidance (open squares) or without metronome guidance (filled circles).
50
Chest compression rate did not change over time (P=0.193) during either of the 10-minute scenarios (P=0.79)
(Figure 9).
Figure 9:
The mean chest compression rate between mask ventilation for each minute during the 10 min scenarios. The outside
bars represent the standard error of the mean (+/-). The change of rescuer performing chest compressions is represented
by omitting the lines connecting the time points. Chest compression rate did not change over time (P= 0.193) when
performed with metronome guidance (open squares) or without metronome guidance (filled circles) during the 10 min
scenarios.
51
5.3.3.3.
Rescuer’s fatigue: opinions
All participants performed CPR scenarios with and without metronome guidance, and the opinions
regarding CPR were assessed with visual analogue scale (VAS). Performing chest compressions without
metronome guidance was reported to be more exhausting (VAS 61 versus 23, P<0.001) and less efficient
(VAS 71 versus 78, P=0.009) (Table 14).
Table 14:
Participant’s opinions regarding fatigue and chest compression efficacy without and with metronome guidance. Visual
analogue scale (VAS) was used and results are presented as medians (range) and analysed with the Wilcoxon test.
without metronome
with metronome
P-value
guidance
VAS fatigue
VAS efficacy
5.3.3.4.
61(5-100)
71(10-93)
23(2-95)
78(10-100)
<0.001
0.009
Rescuer’s ‘signature’ effect on chest compression rate and rescuer’s fatigue
Individual participants performed chest compressions with consistent depths with or without metronome
guidance. The coefficient of variation for compression depths was 11.4%. The correlation between chest
compression depths with and without metronome guidance was fairly high (r2=0.537, P<0.001) (Fig. 10).
52
Figure 10: Correlation between chest compression depth with and without metronome guidance. Circles indicate
individual participants; r2=0.537, P<0.001.
5.4.
Undergraduate CPR education in Finland
The range of time spent on lessons on the theory behind CPR was 2–28 hours (median, 8 hours). The range
for small group practical training was 3–40 hours (median, 10 hours). The size of small groups varied a
great deal. In medical schools compared to other educational institutions, these groups were the largest and
the hours of small group training and theory lessons were the least (Table 15).
53
Table 15
Time spent on theoretical lessons on CPR and small-group hands-on training
Trainees
Hours of theory,
range (median)
Hours of small-group training,
Number of students in small
range (median)
group, range
Medical students
2–5 (2.5)
3–10 (7)
6–18
Paramedics
8–28 (16)
10–40 (17)
2–10
EMTs
4–20 (9)
4–20 (10)
2–12
Firefighters
6
16
2–10
TOTAL
2–28 (8)
3–40 (10)
Methods for teaching adequate chest compression rate were instructors’ visual estimation in 28.5% of the
institutions, and the use of a watch in 33.3%, a metronome in 9.5%, and manikin graphics (displayed by a
laptop computer) in 28.5%. Methods used to teach adequate chest compression depth were the instructors’
visual estimation in 33.3% of the institutions, manikin light indicators in 23.8%, and manikin graphics in
52.3% (Table 16).
Table 16:
Methods used to teach adequate chest compression rate and depth in small-group training
CPR instruction method
Medical
Paramedics
EMTs
Fire fighters Total
students
CPR compression rate
- Visual estimate
3/4 (75%)
1/6 (16.6%)
2/10 (20%)
6/21 (28.5%)
- Using a watch
1/4 (25%)
2/6 (33.3%)
3/10 (30%)
- Using an audible tone
1/6 (16.6%)
1/10 (10%)
2/21 (9.5%)
- Using graphics
2/6 (33.3%)
4/10 (40%)
6/21 (28.5%)
1/1 (100%)
7/21 (33.3%)
CPR compression depth
- Visual estimate
2/4 (50% )
2/6 (33.3%)
3/10 (30%)
7/21 (33.3%)
- Manikin light indicator
1/4 (25%)
2/6 (33.3%)
2/10 (20%)
5/21 (23.8%)
- Using graphics
1/4 (25%)
4/6 (66.6%)
5/10 (50%)
1/1 (100%)
11/21 (52.3%)
54
6.
6.1.
Discussion
CURRENT STATUS OF CPR QUALITY AND EDUCATIONAL METHODS TO
FACILITATE THIS IN FINLAND
Current status of CPR quality in Finland in these simulation studies is poor, especially regarding chest
compression rate. CPR is performed with too high rate in both out- and in-hospital setting (127 versus
139/minute). That’s why percentage of chest compressions with correct rate is nearly zero. Mean chest
compression depth is within guidelines recommendations, but not all chest compressions are within correct
depth (79% out-of-hospital setting and 58% in-hospital setting). There were no differences between in or
out-of-hospital providers regarding CPR performance. The difference in the rate of actually performed chest
compressions per minute is due to different scenarios (BLS scenario for in-hospital providers and rhythm
analysis and treatment included in the scenario for out-of-hospital providers). In clinical studies from real
resuscitations the quality of CPR is better, but not optimal (Wik et al 2005, Abella et al 2005). Main
difference between our results and others is that in our study the mean chest compression rate for out-ofhospital providers (127/min) is higher than reported by Wik (121/min). Also for in-hospital providers our
providers’ compression rate (139/min) is much more than reported by Abella (105/min) or Losert (114/min).
The one possible reason for this is that other studies results are from clinical resuscitations and our results
are from simulated CAs. In many manikin studies chest compression rate is guided with metronome, so it
difficult to compare our results with other manikin studies.
The technological, objective methods to estimate adequate chest compression rate or depth are not routinely
used in Finnish institutions teaching students of emergency medicine at different levels. The instructors’
visual estimation is too often the only method to estimate adequacy of chest compressions, although is has
been clearly demonstrated that it is unreliable (Lynch et al 2008, Ramirez et al 1977). It is not demonstrated,
but possible that if these fundamental skills of CPR are not properly learned during studies, performance in
clinical situations is inadequate.
55
6.2.
THE EFFECT OF EXTERNAL FACTORS ON CPR QUALITY
6.2.1.
Resuscitation guideline changes
The resuscitation guidelines determine chest compression ventilation ratio, chest compression cycle, and the
number of defibrillations. Guideline changes had an enormous impact on no-flow time: using a two-rescuer
10-minute VF scenario with semiautomatic defibrillator and bag-mask ventilation, no-flow ratio was halved
from 66% to 32%. This huge difference in time without chest compressions in this study was the result of
defibrillator use (rhythm analysis, charging, and defibrillation), because there were no differences in time
related to human actions (applying electrodes, starting CPR, ventilation).
The guidelines change explains the difference in no-flow time, and the difference in no-flow time explains
the difference in total number of chest compressions given during the scenario. Our results with a great
difference in no-flow time and chest compressions administered, without differences in chest compression
depth or rate, has also been documented by Roessler in another manikin study (Roessler et al. 2009). There
are no clinical data available concerning the effects of guideline changes on no-flow time.
No-flow time with the manikin scenario in this study was longer than in clinical studies with the old
guidelines; our finding was 66% of the time, while in real resuscitation attempt 43–48% of the time patients
were without chest compressions (Wik et al. 2005, Valenzuela et al. 2005). Part of this difference between
our manikin and the clinical results is because of the scenario used, a 10-minute ongoing VF, which is
clinically quite rare. By using that scenario, we wanted to highlight the difference in no-flow time attributed
to the guidelines change. Another reason for the extremely long no-flow time could be that we used semiautomatic defibrillators. It has been documented with 2000 guidelines in animal models that using
automated versus manual defibrillators prolongs no-flow time and worsens outcome (Berg et al. 2003).
At least three interesting questions arise concerning no-flow time and guideline changes:
(1) What is the duration of single meaningful pause in chest compression depth?
2) What other than guideline changes can be done to minimise no-flow time?
56
(3) Do the guideline changes affect survival of CA patients?
In answering the first question, we are compelled to rely on ‘animal-based evidence’. Probably, the
meaningful duration of pause prior to defibrillation is around 10 seconds, because an 8-second pause does
not affect survival (Ristagno et al. 2008) but 15 seconds does (Yu et al. 2002a). Very short pauses of 3 to 4
seconds compromise haemodynamics (Berg et al. 2001, Ristagno et al. 2008).
Some factors other than guideline changes also affect no-flow time. If there is no need to pause chest
compression for ventilation, no-flow time is less. Intubation of the CA patient reduced no-flow time in a
clinical observational study (Kramer-Johansen, Wik & Steen 2006), but on the other hand intubation takes
time (Wang et al. 2009) and could fail with serious problems (Timmermann et al. 2007). In a manikin study,
supraglottic airway use also resulted in less no-flow time compared with bag-mask ventilation (Wiese et al.
2008). During resuscitation attempt intravenous line is accessed and drugs administered, although the
benefit of this procedure is controversial (Olasveengen et al. 2009a) and it has documented that drug
administration prior to defibrillation prolongs pre-shock pauses in simulation study (Hoyer et al 2010). The
choice of the defibrillator also influences no-flow time; it has been documented with 2000 guidelines in
animal models that using automated versus manual defibrillators prolongs no-flow time and worsens
outcome (Berg et al. 2003). In addition, the choice of a commercial mark may affect no-flow time because
variation in rhythm analysis + charging + defibrillation time is from 5 seconds to 28 seconds (Snyder,
Morgan 2004). With a one-shock protocol, this difference is not so important in terms of total no-flow time,
but it could be meaningful in terms of a full single pause prior to defibrillation. One possible solution to this
would be analysing the rhythm during resuscitation.
Answering the question of whether or not resuscitation guideline changes have an effect on patient survival
is more difficult. Data from animal models show that with year 2000 guidelines, using three shock protocols
with semi-automatic defibrillator resulted in a delay of one minute, 44 seconds to deliver the three shocks
(Valenzuela et al. 2005). When this difference in shock protocol was tested in an animal model, short-term
survival increased from 64% to 100% (Tang et al. 2006). But clinically when the guidelines changed, at the
same time, other aspects of CPR quality became important; most of all hypothermia treatment for port
57
resuscitation care came into routine use clinically (ECC Committee, Subcommittees and Task Forces of the
American Heart Association 2005). These confounding factors make it more difficult or even impossible to
distinguish a connection between guideline changes and survival.
Multiple states in the United States made local changes to resuscitation guidelines prior to official guideline
changes in 2005. Minimally interrupted cardiac resuscitation was implemented in Arizona in 2003, as was a
cardiocerebral resuscitation program in 2004 in Wisconsin and King County, WA. These changes are
basically the same as the ERC or AHA guidelines changes in 2005, except for calling for minimal or no
interruption for ventilations. All these program changes resulted in remarkable increases in survival.
Overall survival increased from 1.8% to 5.4% in Arizona (Bobrow et al. 2008), from 33% to 46% in King
County (Rea et al. 2006), and from 7.5% to 13.9% in Kansas City (Garza et al. 2009). In Wisconsin, before the
new program implementation, survival from witnessed VF was 20% (Kellum et al 2006b) but was 47%
during the three years after implementation of the new program. (Kellum et al. 2008).
Results from the ERC guidelines change in Europe were not as good: In Oslo, the ERC guidelines change
did not affect overall survival (11% before and 13% after implementation of the 2005 guidelines)
(Olasveengen et al. 2009b), but in Copenhagen survival improved (overall survival 8% versus 16%)
(Steinmetz et al. 2008). Differences in these results of the effect of guideline changes on survival could be
attributable to multiple reasons, including differences in EMS response times or EMS systems or differences
in ventilation protocols or overall interruptions in chest compressions. New resuscitation guidelines will be
published in late 2010.
6.2.2.
The effect of the surface underneath the manikin
In the out-of-hospital setting, resuscitation is mainly handled on the floor, and is done in the bed in the inhospital setting. In this study, the quality of chest compressions performed on a manikin on the floor versus
in the bed was studied using our 10-minute scenario with experienced ICU nurses. The mean chest
compression depth was within international resuscitation guidelines for both surfaces. However, only 44%
of all chest compressions on the floor and 58% in the bed reached the correct depth.
58
Evaluation of the effect of surface on chest compression depth has been studied by Tweed et al. (Tweed et al
2001) and Perkins et al. (Perkins et al. 2003). These studies compared also the quality of chest compressions
between the floor and the bed, but our scenario was longer and done with two-rescuers BLS. Also the
results are different. The mean compression depth on the bed in our study was deeper than that reported
by other investigators (ours, 43.0 mm; Perkins et al., 35.2 mm; Tweed et al., 37.5 mm). For chest
compressions performed on the floor, however, our results were in agreement with those of the other
studies: The mean chest compression depth in our study was 44.9 mm; it was 44.2 mm in Perkins et al., and
42.5 mm in the Tweed et al. study.
Several potential explanations may account for the discrepancies, including the weight of the manikin, the
rescuers’ experience, and practise before the scenario. First, our manikin weighed 21 kg, and we did not add
extra weight. In the other studies, the manikin was weighted to 40 (Tweed et al 2001) or 70 kg (Perkins et al.
2003). In other studies with no extra weight on the manikin and resuscitation attempted in the bed, the
results depended on rescuers’ experience: The mean compression depth was 43 mm with experienced
members of a hospital CA team (Andersen, Isbye & Rasmussen 2007) and 30 mm with second-year medical
students (Perkins et al. 2006). We chose not to use extra weights because manikin chest compression depth
is measured as the movement of the lung plate against the back plate of the manikin, and the surface under
the manikin should not affect the measured depth. Also in contrast to the other two studies, we did not
allow practising beforehand because even three minutes of practising chest compressions with verbal
feedback significantly improves chest compression depth (Handley, Handley 2003).
Both the surface and the position of the rescuer performing the chest compressions affect the performance.
In real-life resuscitations, half of our participants delivered chest compressions while standing on the floor
beside the bed, and half delivered chest compressions while kneeling beside the patient in the bed. Other
studies do not report how participants perform chest compressions in real life. Perkins et al. (Perkins et al.
2003) and Chi et al. (Chi et al 2007) have shown that simulated compression force is greatest when chest
compressions are performed while kneeling. We aimed to maximise the force of chest compressions by
asking rescuers to kneel beside the manikin on both surfaces. Chest compressions have been done in a
kneeling position on the floor in other studies, but the rescuer’s position has varied when compressions
59
were done on the bed. The position may be important because shallow compressions were reported when
rescuers stood beside the bed (Perkins et al. 2003). Use of a footstool may also increase the force, leading to
deeper chest compressions (Hightower et al. 1995), but this use may be difficult in clinical situations. One
solution to make chest compressions deeper in the bed is using a backboard, but data concerning the
efficacy of backboard use in terms of the quality of CPR in the bed is conflicting (Perkins et al. 2006,
Andersen et al 2007).
Another factor influencing how chest compressions are performed is the individual rescuer. In our results
with experienced ICU nurses rescuer’s weight or height did not correlate with chest compression depth.
Similar results have been reported by Jones with nurses and EMT’s (Jones and Lee 2008). On the other hand
Perkins et al reported correlation with rescuers weight and compression depth with inexperienced health
care students (Perkins et al 2003). Besides experience, the personal pattern of delivering chest compression
is important, maybe even more. In our study, after randomisation, 24 participants performed CPR on both
surfaces, and the depth and rate of chest compressions were almost identical on the floor and in the bed.
This personal pattern of delivering chest compressions could perhaps explain the similar quality of CPR on
both surfaces. It seems that individuals deliver chest compressions in the same way regardless of surface.
Larsen et al. previously reported similar findings of individuals delivering chest compressions in the same
way over time (Larsen et al 2002).
The mean compression depth decreased significantly during the 10-minute scenario, but the percentage of
chest compressions of correct depth and the mean compression rate stayed the same. In other words, there
were no differences in these indicators of rescuer fatigue between the surfaces. However, this decline in
chest compression depth was not clinically important because during the whole scenario, mean chest
compression depth remained above the guideline target of 4 cm.
The final truth about the influence of the surface underneath the patient remains unknown because it is
difficult to reproduce a clinically realistic scenario with clinically realistic participants. Also, how well
manikin results correlate with the real world remains unknown.
60
6.2.3.
The effect of metronome guidance
The metronome has been used for a long time both in research (Wolfe et al. 1988, Sunde et al. 1998, Kern et
al. 1992, Berg et al. 1994, Feneley et al. 1988) and in the clinical setting (Kellum, Kennedy & Ewy 2006a). In
our results, metronome use corrected the rate of chest compression to the target, but its use did not affect
chest compression depth or other elements of quality. Neither did metronome use affect an experienced
rescuer’s fatigue when measured using chest compression depth. Thus, our results suggest that previous
findings of an association between higher chest compression rate and improved haemodynamics in animal
models (Wolfe et al. 1988, Sunde et al. 1998), higher EtCO2 (Kern et al. 1992, Berg et al. 1994, Milander et al.
1995), and improved short-term outcome clinical studies (Abella et al. 2005) were most likely the result of
improvements in rate alone.
Chest compression rate can be measured as the rate for each cycle of 30 compressions between the mask
ventilations or as the number of chest compressions actually performed per minute, including pauses for
ventilation or other tasks. International guidelines recommend that the chest compression rate should be
100/min (ECC Committee, Subcommittees and Task Forces of the American Heart Association 2005,
Handley et al. 2005); however, the actual number of performed compressions per minute is a function of
both the compression rate and the pauses during ventilation or other tasks.
In our study, the mean chest compression rate for each cycle of 30 compressions between ventilations
(137/min without metronome guidance) was much higher than those recommended by the guidelines and
documented by other investigators (Wik et al. 2005, Abella et al. 2005, Losert et al. 2006). This compression
rate is too fast; in animal studies, no improvement was observed in coronary perfusion pressure when the
rate was increased from 90 to 120 per minute (Sunde et al. 1998), so the target right is likely around
100/minute. The use of the metronome in our study completely corrected the rate (98/ min) to that
recommended in the guidelines however, the number of chest compressions actually performed per minute
was only 79, because of pause for mask ventilation. This may be too low for survival; Abella et al. (Abella et
al. 2005) have shown that the rate of actually performed chest compressions was significantly correlated
61
with the initial return of spontaneous circulation, reporting mean chest compression rates of 90±1/min for
initial survivors and 79±18/min for non-survivors.
In our results, the scenario we used was responsible for the quite low rate of actually performed chest
compressions, 79/min. We used bag-mask ventilation, so after every 30 compressions there was a short
pause (mean 3.2–3.5 seconds) in ventilations. Also these pauses made a detectable but probably not
clinically important 23-second difference in no-flow time during 10 minute scenario. More important result
form mask-ventilation usage is that the number of actually delivered chest compressions was quite low. The
situation is different when the airway is secured with intubation or supraglottic airway devices, and there is
no need to interrupt chest compressions for ventilations. In such cases, metronome use will probably easily
correct the actually delivered chest compression rate. Whether rate correction would then affect rescuer
fatigue when there are no pauses for ventilation and rest from compression is unknown.
6.2.4.
CPR education
Proper CPR education is important because without proper education, elements of the ‘chain of survival’
and adequate guidelines are neglected. As noted previously, ILCOR identified three factors that influence
outcome from CA (Chamberlain et al. 2003):
(1) the quality of resuscitation guidelines;
(2) the local ‘chain of survival’;
(3) the quality of education for CPR providers that enables them to put this theory into
practise
In addition, ILCOR recommended that all healthcare professionals must receive their initial training in BLS
while students (Chamberlain et al. 2003). Our findings identify a potential weakness in the early stages of
the education process in Finnish institutions teaching different levels of EMS students.
In study IV results the amount of CPR education varied widely among different institutions teaching
different levels of EMS students, but also within same-level institutions. Different levels of standardised
training programs are organised by ERC and different national resuscitation councils (Baskett et al. 2005).
62
The course content, materials, and training requirement for instructors are standardised. In ERC training
programs the Immediate Life Support course, which is suitable for the majority of healthcare professionals
who attend cardiac arrests rarely but have the potential to be first responders or cardiac-arrest team
members. This course lasts one day. If we compare our results with this, all institutions do not reach even
this. Generally, an international or national standardised training program regarding teaching CPR to
qualified healthcare professionals or students who are future professionals does not exist but could be
useful.
The total amount of resuscitation teaching was evaluated in 1999 in 168 European medical schools (GarciaBarbero, Caturla-Such 1999). Data were collected in 1996–1997. Medical students received a median 6 hours
of basic CPR lessons, 8 hours of advanced CPR lessons, 12 hours of basic CPR practise, and 8 hours of
advanced CPR practise. If we compare our results (theoretical lessons, median 2.5 hours, and practise
training, median 7 hours) with these prior findings, today in Finnish medical schools, the time devoted to
CPR teaching is far less. We found no studies to compare our results with others regarding teaching of CPR
in other institutions (in-training paramedics, EMTs, or fire fighters).
While it is unequivocally accepted that resuscitation guidelines need to be evidence based, it may be that we
should work towards evidence-based teaching. Unfortunately, our knowledge of the best way to teach CPR
is lacking. The methods used to teach CPR quality, including precise chest compression depth and rate,
were variable, and
technological, objective methods for estimating adequate depth and rate were
surprisingly infrequently used in Finnish institutions. However in many earlier studies clearly showed that
some objective tools are needed to evaluate trainees’ CPR skills (Weaver et al. 1979, Kaye et al. 1991,
Ramirez et al. 1977). On the other hand, technical equipment cannot replace an experienced instructor
because CPR requires both wide medical knowledge and technical skills. Technical skills are more reliably
evaluated by technical equipment, but overall performance requires an instructor’s judgement, most
reliably using a checklist (Brennan et al. 1996).
Leary and Abella examined the barriers to effective CPR training and performance and found that without
any form of monitoring or feedback, it may be difficult to recognise performance errors (Leary, Abella
63
2008). Adequate feedback is important in the very early stages of studies to properly learn BLS in the first
place (Spooner et al. 2007). In clinical situations, rescuers have a combined theoretical background and
hands-on experience, and combining an instructor’s debriefing and objective feedback with one’s own
performance in teaching CPR makes sense. It is very probable that in the upcoming 2010 resuscitation
guidelines, some kind of objective tool to evaluate CPR skills during training will be highly recommended
because it was recommended in a review article defining the guidelines (Yeung et al. 2009).
If the students participate CPR course, it does not necessarily mean can that student perform CPR. We
evaluated the content of a course in institutions, but we did not evaluate whether or not CPR skills were
assessed after course completion. A scientific statement from the AHA recommended that CPR instructional
programs should always include an objective CPR quality assessment for certification (Abella et al. 2008).
Different manikin properties, feedback methods, and other technical methods have been used to assess CPR
(Makinen et al. 2007). It may be that an objective skill assessment should be extended into teaching of
upcoming healthcare professionals.
In working life post-graduate education is important in the retention of skills. In studies I-III it was
demonstrated that experienced professionals performs CPR with too high rate and not all compressions
reach optimal depth. The need for ongoing CPR education is obvious. The decision about best method to
teach and assess the skills and interval between refresh courses are probably as its best when there are
workplace-specific.
64
7.
Study limitations
The major limitations of studies I–III were that they were manikin studies. It is unknown if determinants of
CPR quality recorded with a manikin reflect the clinical situation with humans. It is likely that no-flow time
and rate are the same in both settings, but for other elements, especially depth, how they compare is
relatively unknown. The manikin has a spring inside the thorax that produces resistance to chest
compression, and the stiffness of the manikin thorax can be manipulated with different kinds of springs
(Nysaether et al. 2008); however, the manikin used in these studies was a basic model. The manikin chest
compresses almost linearly; the greater the force applied, the greater the depth that results (Gruben et al.
1993). Human chest stiffness varies considerably (Gruben et al. 1993, Tomlinson et al. 2007a), however, and
the relationship between force and depth is nonlinear, so that it is not a given that with more force there will
be a greater depth. Nevertheless, the mean compression force required in Tomlinson’s study (Tomlinson et
al. 2007b) to compress the human thorax to a minimum adequate depth of 38 mm was 27.5±13.6 kg. Baubin
evaluated the force–depth relationship with different commercial manikins; the force required to compress
a 4-cm manikin thorax was 22.5–54 kilopond, which is 222–529 N/23–54 kg (Baubin et al. 1995). Thus,
whatever force or mass is used that results in insufficient depth with a manikin will probably also result in
insufficient depth with the human thorax.
Unfortunately, the spring also has somewhat of a tendency to recoil after compression, so it is possible that
it is not as exhausting to deliver long periods of chest compressions to a manikin as it might be delivering
them to a human for the same period. For this reason, the results of the evaluation of rescuer’s fatigue with
different surfaces and metronome guidance could be different with humans. Also in real resuscitation
attemp situation is different from these CA scenarios. In clinical CPR rescuer’s stress and motivation is
different and it could affect CPR quality and rescuer’s fatigue.
Another limitation for Study II and III is that sample sizes were probably too small. For study II we did not
perform sample size calculation in advance at all. So our sample size might have been too small to notice
the clinically meaningful, for example 20% difference in the percentage of chest compression of correct
65
depth. This probably also true for metronome study, the difference we noticed in the percentage of chest
compression of correct depth was around 20%. This could be clinically meaningful, but due to too small
sample size it was not statistically significant.
Another limitation is that participants of these CA studies were experienced: paramedics, last year
paramedic students and ICU nurses (members of our hospital cardiac arrest team). So these findings may
not be generalizable to other settings.
Concerning the CPR teaching study, the limitation is that the results represent only Finland’s way of
educating EMS students. Another limitation is that we allowed only one choice when answering the
question on methods of teaching correct chest compression rate or depth. Also, we did not evaluate how
CPR skills were assessed during the studies and what was the actual hands-on time per student with a
manikin in a small group and what other skills were additionally taught (e.g., airway manoeuvres and
drugs). Also we did not evaluate the educational methods, amount and interval of CPR training for our ICU
nurses or paramedics. So our evaluation about current status of CPR performance and educational methods
to facilitate this is limited only into basic education in institutions.
66
8.
Conclusions
Based on current studies, the following conclusions can be drawn:
1.
The current quality of CPR by out-of-hospital and in-hospital providers is not
ideal; especially chest compression rate is too high. The amount of CPR
education in lessons and in small-group training varies widely among Finnish
institutions, and about a third use some form of objective method to evaluate
chest compression rate and depth.
2.
External factors influencing CPR quality may be outlined as follows
i. The resuscitation guideline (years 2000 to 2005) changes halved no flow
time but did not affect chest compression depth and rate.
ii. The surface under the manikin does not affect chest compression depth or
rescuer fatigue.
iii. Rate guidance with a metronome during CPR corrects the chest
compression rate, but chest compression depth remains unchanged, and
metronome use did not affect rescuer fatigue.
67
68
9.
Future implications
The 2005 Resuscitation Guidelines have minimised time spent for rhythm analysis and defibrillation. In
order to reduce no-flow time further there are two main options; firstly, rapid securing of the airway would
enable early initiation of continuous chest compressions rather than CPR in cycles of 30 compressions and 2
ventilations. Secondly, attention should focus on methods enabling rhythm analysis and defibrillation
during the administration of continuous chest compression.
The metronome is a simple and effective method for guiding chest compression rate during CPR and it
should be routinely used in the clinical setting. Possible applications include metronome guidance during
dispatcher-assisted bystander CPR, a metronome within the defibrillator, or a separate metronome as part
of standard CPR equipment.
The effect of the surface underneath the manikin or patient requires further evaluation.
Objective tools in CPR education should be used to evaluate CPR performance during training. A more
widespread adoption of this strategy is probably possible with either national or international
recommendations for different levels of CPR education.
69
70
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10.
Appendix
Survey Questionnaire
Teaching in resuscitation
1.
Number of students admitted annually:
2.
Does the institution take students every year or every second year?
3.
How many hours of resuscitation teaching are given through the entire course of studies?
a.
Theoretical lecture (hours):
b.
Hands-on training in small groups (hours):
4.
Basic life support training in small groups; size of small group (number of students):
5.
How do you teach the correct rate of chest compression (choose one option)?
-Visual estimate
- Using a watch
- Using an audible tone
- Using graphics (laptop connected to the manikin)
6.
How do you teach correct depth of chest compression (choose one option)?
- Visual estimate
- Manikin light indicators
- Using graphics (laptop connected to the manikin)
Helena Jäntti
Cardiopulmonary
Resuscitation (CPR)
Quality and Education
Cardiopulmonary resuscitation (CPR)
maintains some perfusion to vital organ during cardiac arrest. The quality
of CPR is essential to survival. In this
study current quality of CPR, its education and the effect of some external
factors was evaluated. Resuscitation
guidelines have enormous impact on
time without chest compressions. A
metronome is an effective method
to guide chest compression rate during CPR. The surface underneath the
patient does not effect on CPR quality.
The amount of CPR education varied
widely in Finnish institutions educating CPR to emergency medicine providers and objective tools to educate
CPR quality were not routinely used.
Publications of the University of Eastern Finland
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