British Journal of Anaesthesia 1997; 79: 159–171
Management of the airway and ventilation during resuscitation
D. A. GABBOTT AND P. J. F. BASKETT
The management of the airway and ventilation is a
vital component in the resuscitation of patients with
respiratory and cardiac arrest.
In recent years considerable emphasis has been
placed on the cardiac and vascular elements of
resuscitation as the value of early defibrillation has
become appreciated as the principal element in
producing a return of spontaneous circulation in
those with cardiac arrest.31 39 Nevertheless, the role
of maintaining oxygenation during the resuscitative
process is no less important in order to ensure
protection of the vital organs from hypoxic damage.
In June 1996 the Airway and Ventilation
Management Working Group of the European
Resuscitation Council published their guidelines for
the basic and advanced management of the airway
and ventilation during resuscitation.34 35 Since then
several national resuscitation councils in continental
Europe, the UK, Australasia and Southern Africa
have adopted these guidelines in principle.
The airway in resuscitation
Airway obstruction may be a prime cause of cardiorespiratory arrest or may occur as a consequence of
unconsciousness. Common causes are listed in
figure 1. Untreated, the wholly obstructed airway
will, within a very short period (generally accepted as
2–5 min except in unusual circumstances, e.g. hypothermia or intoxication with sedative or opioid
drugs) cause neurological or other vital systemic
damage which may be irreversible or fatal.
BASIC ASSESSMENT
Assessment of the airway is based on a check for
unresponsiveness, examining chest movements and
feeling for air flow from the mouth and nose. The
assessment should be made in the position in which
the patient is found, especially if trauma is suspected
(see below). If breathing is absent the patient should
be turned to the supine position (using manual
in-line stabilization of the head and neck if there is a
potential cervical spine injury). The head and neck
(Br. J. Anaesth. 1997; 79: 159–171).
Key words
Airway. Heart, resuscitation. Complications, cardiac arrest.
Ventilation, resuscitation.
Figure 1
Common causes of airway obstruction.
D. A. GABBOTT, MA FRCA, Gloucestershire Royal Hospital, Great
Western Road, Gloucester GL1 3NN. P. J. F. BASKETT, BA, FRCA,
MRCP, Frenchay Hospital, Bristol BS16 1LE.
160
British Journal of Anaesthesia
Figure 2
Suggested plan for assessment of the airway and ventilation.
should be aligned in the clear airway position using
head and chin lift tilt (omitted if there is a possibility
of cervical spine injury), and jaw thrust. Ideally, the
head should be placed on a small pillow to achieve
the “sniffing the morning air position”. When the
head and neck are aligned the assessment should be
complemented by seeking other signs, such as
cyanosis, pallor, excessive salivation, gastric contents
or foreign body in the mouth or pharynx, and
evidence of head, maxillofacial, neck or chest trauma.
Abnormal phonation or breath sounds and wheeze or
stridor indicate a particularly obstructed airway.
Stridor occurring during inspiration generally
indicates obstruction above the larynx, wheeze occurring during expiration usually indicates obstruction
below the larynx. A suggested plan for assessment of
the airway and breathing is shown in figure 2.
Management of the upper airway obstructed
by foreign material (choking)
CAUSES AND SIGNS
In adults the commonest causes are aspiration of
Management of the airway and ventilation
Figure 3
161
Algorithm for the management of upper airway obstruction caused by foreign material (choking).
gastric contents or blood associated with loss of the
protective laryngeal reflexes and choking on large
portions of poorly chewed food. In children and the
mentally challenged, a large number of other
ingested articles may be added to these causes, for
example peanuts, marbles, pen tops, beads, etc.
Choking is heralded by respiratory distress, stridor,
wheezing and coughing. As the obstruction becomes
more complete, airflow is reduced, the patient is
unable to speak or breathe and cyanosis occurs.
Unconsciousness supervenes and death occurs if the
obstruction is not relieved immediately. The patient
may clutch or point to his or her neck—a universal
distress signal for imminent choking.
MANAGEMENT
While there appears to be adequate air movement the
patient should be encouraged to cough and be
observed closely. Oxygen, if available, should be
administered. If air movement is poor or absent and
the patient becomes cyanosed, immediate positive
action is required. The obstruction may be cleared by
head and neck alignment, back blows, abdominal or
chest thrusts, lateral positioning or finger sweeps, or
by using a laryngoscope with suction, Magill forceps
or a Kelly clamp to remove the obstruction under
direct vision. As a last resort upper airway obstruction may be bypassed by a surgical airway using
cricothyroidotomy or needle jet ventilation provided
the appropriate skills and equipment are available.
Back blows
A series of five back blows are applied during expiration with the patient standing, sitting or in the lateral
position. Preferably the head should be positioned
below the chest to achieve the best gravitational
drainage advantage. Children should be placed
prone with a head down tilt on the rescuer’s thigh or
arm. If this fails to clear the obstruction, abdominal
thrusts should be used.
Abdominal thrusts (Heimlich manoeuvre)
Abdominal thrusts may be applied with the patient
standing, sitting or lying down in the supine
position. The supine position is used in unconscious
162
patients and in the very obese or when the rescuer
finds it impossible to encircle the abdomen of the
victim. Abdominal thrusts may result in damage to
the abdominal viscera or gastric regurgitation. The
technique is not recommended in infants and small
children33 or in advanced pregnancy.
The guidelines of the American Heart
Association32 do not recommend the application of
back blows in adults (although they do in infants and
small children73) and prefer early application of
abdominal thrusts. European, Australasian and
Southern African guidelines advocate the application
of back blows before abdominal thrusts.
British Journal of Anaesthesia
MANAGEMENT OF THE AIRWAY IN PATIENTS WITH
SUSPECTED SPINAL INJURY
Finger sweeps should be used only in the unconscious victim who does not have good reflexes or the
ability to bite the rescuer’s finger. The patient should
be placed in the lateral position. Blind sweeps are
not generally recommended in infants and small
children because of the risk of deeper impaction of
the foreign body at the laryngeal level but sweeps
using the little finger to extricate an obvious object
under direct vision are acceptable. An algorithm for
the management of choking is shown in figure 3.
Great caution must be taken in aligning the head and
neck in any trauma victim requiring resuscitation.
In these circumstances the cervical spine must be
maintained in a neutral mid-line position unless it
is physically difficult to do so or resistance is
encountered during any attempt at realignment.
Manual in-line stabilization is the technique of
choice in any trauma patient, with the head grasped
firmly at the mastoid processes and the occiput.52 58
Traction should be avoided as it may distract the
cervical spine and cause more neurological
damage.77 Jaw thrust is the only basic airway
opening manoeuvre appropriate for any patient with
suspected cervical spine injury. Suction and use of
forceps under direct vision using a laryngoscope with
the head and neck maintained in the neutral position
are the best methods of removing foreign material
from the mouth and pharynx but back blows and
abdominal or chest thrusts are acceptable only in
extreme conditions. The risk of hypoxic damage
from airway obstruction in an unconscious breathing
victim is likely to outweigh the risk of aggravating
cervical spine injury in the vast majority of cases and
such patients should be placed in the lateral position
using a log rolling technique with a minimum of four
attendants. The rescuer controlling the head and
neck with manual in-line stabilization should be in
command of the rotation procedure. When turned,
the lower limb should not be flexed unless a
thoracolumbar injury is not suspected. Movement of
the arms is not recommended.
The recovery position
Basic management of ventilation
The recovery position is used in unconscious
patients with adequate spontaneous breathing to
maintain a patent airway and reduce the possibility
of aspiration of gastric contents or foreign material in
the mouth or pharynx. Several different recovery
positions have been advocated (dependent arm
behind or in front of the trunk, uppermost arm
extended or flexed to place the hand under the
cheek, dependent leg extended or flexed, uppermost
leg extended or flexed). It has proved impossible
to obtain universal international agreement as to
the best position but there is consensus as to the
principles involved. These principles include:
! The patient should be in as near a true lateral
position as possible with the mouth dependent to
allow free drainage of fluid.
! The position should be stable.
! Any pressure on the chest that impairs breathing
should be avoided.
! Care should be taken to avoid compromise of the
circulation in either arm or peripheral nerve
compression in the arms and legs.
! It should be easy to turn the victim into the lateral
position and return to the supine position, having
particular regard to the possibility of injury to the
cervical spine.
! Good observation and access to the airway should
be possible.
In basic resuscitation the method of choice is
expired air ventilation using the mouth-tomouth, mouth-to-nose, mouth-to-mouth-and-nose
(neonates) or the mouth-to-mask method. The
mouth-to-mask method has aesthetic advantages
and may reduce the possibility of cross infection
between patient and rescuer. Some models of mask
permit the addition of oxygen if available. The
hitherto recommended sequence of ventilations in
relation to external chest compressions in patients
with cardiac arrest has been 1:5 (using two rescuers)
and 2:15 (using a single rescuer).32 Recently, the
European Resuscitation Council has recommended
that only the single rescuer method (2:15 sequence)
should be taught to lay people using the justification
that the second person’s priority should be to seek
and provide help (especially a defibrillator) and that
two lay people may find co-ordination of chest
compressions and ventilations difficult unless they
have practised together regularly. This teaching
is likely to be followed on a global scale by
authorities in Australasia, Southern Africa, the
United States, Canada, Latin America and the
Pacific Rim. While there is consensus regarding
the technique of application of expired air ventilation there is debate as to the sequence in relation to
chest compressions, inflation flow rate and volume
of ventilation.
Chest thrusts
Chest thrusts are preferred in children and when
abdominal thrusts are contraindicated or ineffective.
Rhythmic thrusts are applied with both hands to the
anterior aspect of the chest in the same position as
used for external chest compressions.
Finger sweeps
Management of the airway and ventilation
SEQUENCE OF VENTILATIONS AND CHEST
COMPRESSIONS
Early guidelines from the American Heart
Association (AHA)68 69 proposed that four ventilations should be given at the beginning of resuscitation using a “step-on-step” technique of applying
each subsequent inflation before exhalation was
complete, thus introducing a form of positive endexpiratory pressure (PEEP). The rationale behind
this practice was the postulation that alveolar
collapse occurred with cardiorespiratory arrest and
that application of PEEP would improve the
situation. The “step-on-step” technique for the first
four breaths was rescinded in the guidelines of
198670 in the face of evidence that this method
generated high proximal airway pressures40 and that
the lower oesophageal sphincter opening pressures
were likely to be reduced.54 81
Both of these factors were likely to increase
the risk of gastric regurgitation and subsequent
pulmonary aspiration. The 1986 AHA standards
and guidelines reverted to initial application of two
normally spaced breaths followed by a one-rescuer
sequence (15 compressions/two ventilations) or a
two-rescuer sequence (five compressions/one
ventilation).
Clearly the 15:2 or 5:1 sequences which were
proposed in the late 1950s were based on a concept
of normal cardiorespiratory physiology. However,
this state of affairs is unlikely to apply in cardiorespiratory arrest when delivery of carbon dioxide to
the lungs is likely to be low, so reducing the emphasis
on ventilation frequency and volume. What is
paramount, however, in cardiac arrest is oxygenation
and there is a need for research to establish the best
compromise to provide satisfactory oxygenation and
carbon dioxide removal under these conditions.
For the future it may be that the frequency of
ventilation can be reduced to a sequence of 1 in 10
or even 1 in 20 interposed with external chest
compressions while oxygen is insufflated into the
lungs. However, in the absence of new positive
scientific evidence the principle of adherence to the
present recommendations applies.
VENTILATION FLOW RATES AND VOLUMES
Ventilation through an unprotected airway whether
using the expired air technique or a self-inflating
bag–valve–mask carries a very high risk of gastric
inflation and subsequent pulmonary aspiration.
Evidence of aspiration has been found in approximately 28% of failed resuscitations examined by the
coroner.45 Weiler, Heinrichs and Dick81 reported
evidence of gastric inflation in two of 31 anaesthetized patients with an unprotected airway
ventilated by experts and recommended that
inflation pressures should be limited to 20 cm H2O.
The following factors are relevant in considering the
possibility of gastric inflation during resuscitation.
! Alignment of the head and neck.
! Lower oesophageal sphincter opening pressures.
! Proximal airway pressure during inflation.
Optimal alignment of the head and neck has been
163
discussed above. The lower oesophageal sphincter
opening pressure has been estimated to be in the
region of 20 cm H2O in live patients.81 In swine
subjected to experimental cardiac arrest the
oesophageal sphincter opening pressure decreased
from 26 to 4 mm Hg.54 Although there are no
comparable data for humans it is likely that a similar
decrease occurs as suggested by the high incidence of
regurgitation reported during cardiac arrest.45
The proximal airway inflation pressure during
intermittent positive pressure ventilation is related to
the inflation flow rate and tidal volume.
The recommendations of the AHA stipulate that
either a tidal volume sufficient to make the chest
rise normally, or 800–1200 ml, should be applied
over 1–2 s at a rate of approximately 10 bpm.32
Clearly these numerical volumes aim to achieve
hyperventilation.
Training manikins equipped with auditory and
visual signals hitherto have been set to conform to
tidal volumes of 800–1200 ml. Analysis of these
numerical recommendations, however, reveals
several difficulties. To maintain inflation pressures at
reasonable values (approximately 20 cm H2O) a tidal
volume of, say, 1000 ml requires at least 2.5 s for
inflation and another 1 s for exhalation using a single
rescuer. Longer times are needed for patients with
reduced compliance. Thus two ventilations last at
least 7 s, 15 external chest compressions applied at a
rate of 80 per minute last 12 s, and therefore the total
time for each sequence is (7;12) 19 s. Just over
three sequences are completed in 1 minute (i.e. six
breaths and 45–50 chest compressions) and while six
breaths per minute may be adequate during cardiac
arrest, it is unlikely that 45 chest compressions
provide a viable circulation. Similar calculations can
be performed for a 1:5 sequence with similar results.
In considering the alternative component of the
recommendations, clinical observation of the chest,
it is important to determine the tidal volume
associated with a “normal” breath. Baskett, Nolan
and Parr showed in anaesthetized patients that
adequate chest movement perceived by nurse and
medical observers was produced by tidal volumes of
400–500 ml.11 Calculating the number of chest
compressions and ventilations using a tidal volume
of, say, 500 ml with the same inflation rate, each
sequence would take 3.5 s (two breaths) plus 12 s
(15 compressions):15.5 s, resulting in just under
four sequences per minute, totalling eight breaths
and 60 chest compressions.
In clinical resuscitation practice the tidal volume
applied is gauged by the rise and fall of the chest and
is likely to be approximately 400–500 ml rather than
the 800–1200 ml required in manikin practice. It is
likely that many victims have survived using tidal
volumes of 400–500 ml during resuscitation and
certainly the minute volumes generated are more
than adequate to clear carbon dioxide during
anaesthesia with a normal cardiac output.
For this reason the European, Australasia and
Southern African Resuscitation Councils have
recommended a tidal volume of 400–500 ml (5–6 ml
kg91) during resuscitation and that training manikins
with visual or auditory signals, or both, should
164
British Journal of Anaesthesia
Figure 4
Flow chart for basic management of the airway and ventilation.
indicate satisfactory inflation at a tidal volume of
400–600 ml.35
Many questions remain in this field and can be
answered only by research studies which are not easy
in patients undergoing resuscitation. Perhaps even
smaller tidal volumes would suffice to eliminate
carbon dioxide? Would higher compression rates
(100–120 per minute) produce better perfusion of
vital organs and improved survival rates? Would
simple insufflation of oxygen through a patent
airway such as a laryngeal mask or tracheal tube
provide adequate oxygenation? Given sufficient
inspired oxygen concentrations, do standard chest
compressions provide adequate pulmonary ventilation to remove the carbon dioxide that is being
delivered to the lungs under these circumstances?
Or would active compression and decompression of
the chest (ACD CPR) using a device such as the
Cardiopump (Ambu) be more effective? Does Vest
CPR (Cardiologic Systems) provide adequate pulmonary ventilation? These and other questions
require an answer before more definitive recommendations can be made in such a fundamental matter as
the optimal method of producing satisfactory oxygenation and removal of carbon dioxide during
resuscitation. A flow chart for basic management of
the airway and ventilation35 is shown in figure 4.
Advanced management of the airway and
ventilation during resuscitation
Advanced airway management is required if basic
Management of the airway and ventilation
techniques are proving inadequate or more
experienced personnel and equipment are available.
Any technique can be described as advanced if it
involves the use of adjuncts, and the European
Resuscitation Council (ERC) has recently published
guidelines on the subject.34 The use of advanced
airway techniques ultimately must be a personal
choice depending on the training and experience of
the individual concerned.
The ERC algorithm for advanced airway management (fig. 5) begins with the apnoeic patient or an
unprotected airway. Clearly basic life support
165
measures may be in progress, for example mouth-tomouth ventilation or, if the hospitalized patient has
developed an immediate need for airway management, advanced techniques may be applied in the
first instance.
ADVANCED AIRWAY ADJUNCTS AND TECHNIQUES
Oral and nasopharyngeal airways
These are the simplest of the advanced airway
adjuncts. They are easy to insert and help provide a
Figure 5 Flow chart for advanced management of the airway and ventilation. *Tracheal intubation is best; the
laryngeal mask airway or Combitube are initial alternatives.
166
patent airway by limiting obstruction by the tongue.
They need to be appropriately sized, positioned
correctly and used in the relevant circumstances.
Oral and nasal airways that are too short are
ineffective and those that are too long may provoke
laryngeal spasm. Oral airways are poorly tolerated in
semi-conscious patients with active gag reflexes and
may be difficult to insert in patients with clenched
jaws. The nasal airway is often better tolerated in
these circumstances. The oral airway can be inserted
using the familiar rotational method or with a tongue
depressor, which is the favoured method when
dealing with children. The nasal route must be used
(if at all) with extreme caution in victims of trauma,
particularly if a base of skull fracture is suspected.
Placement of nasal airways into the cranial vault has
been described,24 furthermore the nasal route is far
more likely to cause haemorrhage than the oral
route. A recent modification of the oral airway
includes a pharyngeal cuff. The COPA airway
(Mallinkrodt Ltd) has a standard 22-mm connector
and may allow ventilation via a self-inflating bag or
anaesthesia system. None of these devices offers any
protection from regurgitation of gastric contents.
Cricoid pressure
It is now clear that regurgitation and aspiration must
be considered as major hazards during resuscitation
if the airway is unprotected. Cricoid pressure
represents a protective measure during basic airway
management until advanced methods can be
applied. The technique is easily taught but requires
re-evaluation as many who have been trained in
applying it provide widely differing forces to the
cricoid cartilage.44 Recent work suggests that the
original value of 44 Newtons required to prevent
regurgitation is excessive and a value of approximately 30 Newtons is appropriate.78 The presence of
an oro- or nasogastric tube has been shown in
cadaver studies to increase the efficiency of protection provided by cricoid pressure and it should
therefore be left in situ.63 78
The use of cricoid pressure is not without
potential problems. If attempts are made to ventilate
a patient’s lungs manually using a face mask, after
applying pressure to the cricoid cartilage, there may
be significant reduction in expired tidal volume and
an increase in peak inspiratory airway pressure.
Furthermore, complete airway obstruction may
occur in up to 10% of cases.2 This may be because of
direct airway compression if cricoid pressure is
excessive or applied incorrectly. Furthermore, if
pressure is applied in a caudal direction (which
occurs if the patient’s head is flexed on a pillow) this
may cause closure of the laryngeal inlet via a
rotational effect on the arytenoid cartilages12
(R. Vanner, personal communication). Cricoid
pressure may also cause relaxation of the lower
oesophageal sphincter making regurgitation more
likely if pressure is applied poorly or released
transiently.75
Pressure can be applied with one hand or
bimanually with a hand supporting the posterior
cervical spine. Recent work suggests that the
British Journal of Anaesthesia
single-handed technique provides just as good a view
at laryngoscopy as using two hands.15 However,
supporting the cervical spine with a hand placed
beneath the neck is clearly of potential benefit in any
victim of trauma with a suspected broken neck. In
another recent study, single-handed cricoid pressure
caused significant movement of the neutrally
positioned cervical spine26 confirming that in trauma
patients, at least, some posterior support of the
cervical spine is indicated. Finally, if tracheal intubation is difficult or impossible, the use of other airway
adjuncts (e.g. laryngeal mask airway) in the presence
of cricoid pressure may be impaired.4–8 27
Tracheal intubation
The gold standard for advanced management of the
airway during resuscitation is tracheal intubation.
This provides a clear and secure airway allowing
ventilation, oxygenation and suction. The skill of
intubation is not easily taught, requires constant
practice and the technique is not without complications if performed poorly or attempts are prolonged.
There are a vast array of aids to intubation to help
with the difficult airway, including laryngoscopes,
bougies, stylets and light wands. Of the currently
available accessories, the gum elastic bougie and
McCoy laryngoscope appear to be two of the more
useful, particularly in cases of difficult intubation of
the trauma victim.
The gum elastic bougie has been shown to reduce
significantly the failure rate of oral tracheal intubation in patients where manual in-line stabilization
and cricoid pressure were applied58 despite a slightly
longer intubation time. The McCoy laryngoscope
was introduced in 1993 and is available in sizes 3 and
4 for adults and more recently in sizes 1 and 2 for
children. The laryngoscope causes elevation of the
epiglottis from a fulcrum deep within the hypopharynx and requires less force than the Macintosh
blade to expose the laryngeal structures.49 The
McCoy laryngoscope has also been shown to reduce
the stress response to laryngoscopy compared with
the Macintosh blade.48 Studies have demonstrated
that the laryngoscope improves the view at
laryngoscopy compared with the conventional
Macintosh blade and more importantly, the number
of difficult views (grades 3 and 4) is reduced
significantly.16 25 43 76
A variety of other intubation aids are available
and include other laryngoscopes (e.g. Bullard,
Upsherscope, Wuscope) and lighted stylets. An
assortment of tracheal tubes are available with
flexible tips (e.g. “Endotrol” tube), and a new stylet,
the Rusch intubating stylet, allows the curve of a
standard tracheal tube to be manipulated. The techniques of digital and blind nasal intubation have
their advocates but both require considerable skill
and constant practice. Nasal intubation is probably
not appropriate for the trauma victim and furthermore, a survey of ATLS trained personnel revealed a
poor success rate for intubation via this route.50 It
is now clear that in experienced hands, oral
intubation of the trachea is the preferred method,
particularly for the trauma patient.18 64 66 The view at
Management of the airway and ventilation
laryngoscopy is also significantly improved if the
cervical collar is removed36 and if there are enough
personnel available this should be done while the
neck is stabilized manually.
Confirmation of successful placement of the
tracheal tube in resuscitation is of paramount
importance and a variety of aids are available. The
gold standard is undoubtedly capnography but
misleading readings may occur because of reduced
carbon dioxide delivery to the lungs in the arrested
circulation. Furthermore, the apparatus is often not
immediately accessible in resuscitation situations
and more simple devices are appropriate. The
oesophageal detector80 is such a device. It has been
modified to include the use of an evacuator bulb59
and is highly sensitive at picking up oesophageal
placement of a tracheal tube. A variety of colorimetric carbon dioxide detectors are also available,
but these are not always accurate and may fail if
there is not enough expired carbon dioxide. They
may occasionally register a false positive result as a
consequence of carbon dioxide in the stomach,
either from poor basic life support techniques
associated with gastric inflation or, more rarely,
the presence of carbonated drinks in the gastric
contents.
A more recent adjunct used for confirmation of
successful tracheal intubation is the Scotti airway
detector.56 The device sends sound waves down the
tracheal tube and the reflected wave is detected. If
the tube is in the trachea, which is hollow, then the
reflected wave is different to that detected if the tube
is in the oesophagus, which is collapsed. The concept, while simple, is not without problems. The
device needs calibrating and a recent study has
demonstrated that it is not very specific.47
Finally, while the role of flexible fibreoptic
laryngoscopy is limited in resuscitation situations,
there are now hand-held, battery-operated fibreoptic
devices (e.g. Rapiscope; Cook Critical Care Ltd)
which, because they are readily portable, may find a
role in confirmation of tracheal tube placement. The
device has also been used to confirm correct
placement of a needle or catheter passed through
the cricothyroid membrane during formation of a
surgical airway.65
Laryngeal mask airway (LMA)
This airway device (fig. 6) has revolutionized
anaesthetic practice since its introduction in 1988.
More than 1000 scientific studies have testified to its
satisfactory and versatile application in a variety of
difficult circumstances. The device provides a clear
airway without the need for laryngoscopy and it can
be inserted from in front of the patient if necessary,
which may be useful for victims of entrapment.
Ventilation is more efficient and easier than with a
bag and face mask1 53 and it can also be inserted with
the neck maintained in a neutral position13 60 for
patients in whom cervical spine trauma is suspected.
The technique of insertion is easily taught to nurses,
paramedics and doctors1 19 30 53 61 and the device has
been used successfully by all of these groups in the
management of cardiac arrest both in and outside
167
Figure 6
The laryngeal mask airway.
hospital.29 42 74 Training on manikins has been shown
recently to be just as effective as training on patients
when learning the insertion technique62 and the
recently introduced Portex introducer may
encourage an even greater success rate for LMA
insertion by non-anaesthetic personnel.21
The LMA allows positive pressure ventilation
provided it is applied carefully and airway pressures
do not exceed 20–25 cm H2O. In patients with
poorly compliant lungs, for example those with
pulmonary oedema, aspiration or obstructive
airways disease, the lungs may not be ventilated
adequately using the device. Inadequate protection
of the airway is often quoted as a limitation of the
LMA. However, evidence that pulmonary aspiration
occurs in clinical practice is scant. In a multicentre
study using the LMA at cardiac arrests the reported
incidence of aspiration was only 1.5%.74 Furthermore, the LMA protects the airway against
aspiration from sources above the larynx.17 41 This
may have profound implications for some types of
patients requiring resuscitation. In a recent study of
trauma victims,51 of those who aspirated, the vast
majority aspirated blood. In nearly all cases this
blood originated from sources above the larynx.
Another potential problem with the LMA is its
ability to function adequately in the presence of
cricoid pressure. There are several studies4–8 27 that
have suggested that cricoid pressure impedes placement of the device. Furthermore, if cricoid pressure
is released and then re-applied after insertion of the
LMA, its function may still be impaired.6 A recent
radiographic study5 showed that cricoid pressure
caused upward displacement of the LMA which may
allow its aperture to sit against the base of the
tongue, thus impairing ventilation.
Despite this, the LMA remains an extremely
useful device for resuscitation. Its ease of insertion
and effectiveness suggest it should be used as a firstline airway adjunct for those who do not posses the
skill to intubate the trachea, such as nurses and
many doctors. If oral intubation is proving difficult
the device may provide a route for intubation by
allowing blind passage of a tracheal tube or gum
elastic bougie down the lumen and into then trachea.
The success rate for this procedure is variable
however, with one study quoting a success rate of
96%37 and another only 26%.28 Preloading the LMA
168
British Journal of Anaesthesia
with a tracheal tube or gum elastic bougie may
reduce the failure rate of this technique.20 An
intubating laryngeal mask has been designed and is
currently undergoing multicentre clinical studies
which may improve the intubation success rate using
this principle.
Oesophageal tracheal Combitube
This device (fig. 7) is a double-lumen tube which is
passed blindly into the mouth and allows ventilation
of the patient’s lungs whether the tube enters the
trachea or the oesophagus. There are apertures at a
supraglottic level from the “tracheal” lumen and a
distal opening from the “oesophageal” lumen. There
is a small-volume distal cuff and a large-volume
pharyngeal cuff. If the tube enters the trachea it can
be used in the same way as any tracheal tube and the
pharyngeal cuff is redundant. In the majority of cases
however, the tube enters the oesophagus, in which
case the distal and pharyngeal cuffs are inflated
and ventilation is possible via the supraglottic side
openings.
The Combitube may have certain advantages over
some of the other airway adjuncts available. It
requires no instruments for insertion, which makes
it useful in difficult situations and locations. It
occludes the oesophagus with a distal cuff and allows
some “venting” of oesophageal contents via one of
the two lumens. It can usually be inserted with the
neck in a neutral position, making it potentially
useful in trauma patients. Early studies using the
device showed improvement in arterial oxygenation
compared with tracheal intubation, probably
because of a PEEP effect when ventilation is applied
through the supraglottic apertures.23 It has been
used successfully during cardiorespiratory arrest by
intensive care nurses and paramedics with some
success.9 22 71 Recently, the oesophageal detector
device has been used to identify whether the
Combitube has been passed into the trachea or
oesophagus.79
Potential problems include the size of the device;
it is more difficult to insert than a laryngeal mask and
insertion has not been evaluated formally in the
presence of a cervical collar. The technique of
insertion requires training and the stomach is
inflated if ventilation is applied through the wrong
aperture when the device is placed in the
Figure 7
The oesophageal tracheal Combitube.
oesophagus. Because of its size, significant airway
trauma appears to occur in some patients. In recent
studies blood has been noted on the Combitube after
removal in 24%46 and 45% (Gabbott, unpublished
data) of patients. Airway pressures may also be
higher when ventilation is attempted through the
side holes. Finally, it has been suggested that
ventilation is more effective with the head in a
hyper-extended position.46 This presents a problem
when dealing with trauma patients where the neck
has to remain in a neutral position. Recent work,
however, has demonstrated that the presence of a
cervical collar does not appear to significantly impair
ventilation (Gabbott, unpublished data).
The Combitube therefore remains an airway
adjunct that, in theory, may prove to be useful.
Further assessment is required before it can be
advocated on a wide scale.
Surgical airway
Resort to the surgical airway is rarely necessary but is
a skill that anyone with a claim to expertise in
advanced airway management should be able to
perform. Direct surgical access to the trachea should
be made via the cricothyroid membrane unless there
is severe trauma to that region. This involves
removal of cricoid pressure, if applied, which makes
placement of devices such as the laryngeal mask and
Combitube more successful if they are to be used as
temporary oxygenation sources. Tracheostomy in
the emergency situation is very difficult and probably
has no place in advanced airway management during
resuscitation.
There are several methods of gaining access to the
airway via the cricothyroid membrane, including
needle and surgical cricothyroidotomy and blind stab
techniques using specifically designed equipment.
These methods are hazardous in the emergency situation and should be undertaken when there is no
other option and the procedure is life saving. Any of
the techniques should be performed only by trained
and practised operators. Training is accomplished by
the use of manikins, animal larynx specimens, such as
those used in the advanced trauma and advanced
paediatric life support courses (ATLS and APLS)
and by cadaver and post-mortem teaching if these
facilities are available.
Needle cricothyroidotomy. This technique, which is
the surgical airway of choice for all children because
of their small airway size, involves placing a needle
and catheter through the cricothyroid membrane
and ventilating via a catheter which is left in situ. The
bigger the catheter the easier is ventilation. However,
the technique is only suitable to buy time while a
more definitive surgical airway is created. Ventilation is difficult using a self-inflating bag but is more
successful when a high pressure source of oxygen is
used with inflation intermittently applied by occluding an aperture in the ventilation tubing. Careful
observation of chest movement is essential to avoid
barotrauma, and for the technique to be safe there
should always be a clear route through the larynx
and mouth for expired gases to escape. Sufficient
expiration through the narrow catheter is usually not
Management of the airway and ventilation
possible despite physical attempts to compress the
chest.
Surgical cricothyroidotomy. This technique is
gaining in popularity, particularly in the trauma
setting, although documented evidence of its
effectiveness in cardiopulmonary resuscitation is
lacking. The procedure involves incision of the
cricothyroid membrane under direct vision and
insertion of an appropriately sized tracheal tube.
Ventilation is highly effective and a secure airway is
created.
While surgical cricothyroidotomy appears to be a
simple technique, it is not without complications,
with some studies reporting a total failure rate of up
to 12%.67 Others, however, have reported a much
lower failure rate55 and this may depend on the skill
of the operator. Precautions that can be taken to
reduce complications include limiting the lateral
extent of any horizontal incision, incising the inferior
part of the cricothyroid membrane in an attempt to
avoid the cricothyroid arteries, and directing the
scalpel blade away from the head to avoid vocal cord
damage.
The technique is indicated in cases when lifethreatening upper airway obstruction is present and
all other attempts to secure the airway and ventilate
the patient’s lungs have failed. Persistent attempts at
tracheal intubation may result in worsening hypoxia
and in these cases an early decision to create a
surgical airway should be made. Because of the high
complication rate significant training and experience
are required.
Blind stab techniques. This method uses a single
stab technique through the skin, subcutaneous
tissues and cricothyroid membrane. Several commercially available kits (Portex, Cook Critical Care,
Rusch) allow access to the airway using the technique. Most are simply large trocars over which a
short, wide-bore tube is passed with a standard
22-mm connector. Some kits incorporate the use of
guide wires and others use a more graded, dilational
system.
Whichever product is used it is apparent that the
technique may present considerable problems if it is
not appropriately taught. Furthermore, access to the
airway in the patient who is attempting to breath
with a larynx that is constantly moving under the
skin can be very difficult. Nevertheless, the concept
of a readily available, rapid access device that does
not require additional pieces of equipment for
insertion is to be commended. Only by using and
practising inserting such devices can appropriate
experience be gained.
ADVANCED MANAGEMENT OF VENTILATION
Advanced ventilation methods are designed to overcome the shortcomings of expired air resuscitation
techniques. However, if applied poorly they can be
less effective and more hazardous than well executed
basic techniques.
During cardiopulmonary resuscitation oxygenation is paramount; carbon dioxide delivery is likely
to be low thus eliminating the requirements for
large tidal volumes11 and lung compliance may be
169
considerably reduced requiring higher inflation
pressures.
There is some experimental evidence suggesting
that ventilation itself may not be of paramount
importance during the first few minutes after cardiac
arrest. Indeed chest compression alone may generate
sufficient tidal volumes for adequate oxygenation
provided the airway is patent and a high inspired
oxygen source is provided.14 72 This may be significant during the first few minutes after cardiac arrest,
particularly if first responders are unwilling or unable
to provide suitable ventilatory assistance.
Work in humans using active compression–
decompression CPR has also demonstrated the
potentially satisfactory tidal volumes generated by
this technique alone, allowing sufficient ventilation
to maintain blood-gas values at near normal levels
provided the airway remains patent.38
Ventilation devices
Devices for advanced management of ventilation
include the self-inflating bag–valve–mask, anaesthesia systems, oxygen powered and automatic
resuscitators and devices for transtracheal jet ventilation. These latter devices allow some ventilation via
a cannula placed in the cricothyroid membrane, as
described above. The system uses a high pressure
oxygen source and a purpose designed injector. The
method is relatively inefficient at eliminating carbon
dioxide, although in cardiac arrest situations this
may not be of much importance initially.
The self-inflating bag–valve devices are still the
mainstay of ventilation for many during resuscitation. They are portable, robust and convenient but
require considerable skill when used with a face
mask, and a two-rescuer technique has therefore
been recommended.3 10 The importance of generating large tidal volumes has now been questioned,
however, and a single-rescuer technique may be
appropriate with smaller lung volumes equally
acceptable. Of greater importance is that oxygen is
provided at or close to an FIO2 of 1.0. This can only
be achieved effectively by the use of large volume
oxygen reservoir bags or the use of a demand valve.
Anaesthesia systems and manually triggered
ventilators have a limited place in resuscitation as
they are either in a fixed location or require the
operator’s hands for providing ventilation, or both.
Automatic ventilators, however, give the best all
round option; they provide an FIO2 of 1.0, consistent
tidal volumes and ventilatory frequencies, and free
the rescuer’s hands for other tasks. Many sophisticated models are now available57 some of which
incorporate air–oxygen mix facilities, the ability to
provide PEEP, disconnect alarms, variable I:E ratios
and airway pressure monitoring facilities. They are
compact, robust and lightweight and function under
a variety of climactic and environmental conditions.
The only drawback is the relatively large consumption of oxygen that may be used as the driving gas.
This may cause problems when no piped gas is
available and gas cylinders have to be used.
A flow chart for the advanced management of the
airway and ventilation34 is shown in figure 5.
170
Acknowledgement
Figure 1–5 are adapted from the Guidelines for basic and
advanced management of the airway and ventilation during
resuscitation of the European Resuscitation Council and are
reproduced with permission. Resuscitation 1996; 31: 187–230.
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