Less is more in:
Emergency Oxygen Therapy
Dr Ronan O’Driscoll
Consultant Respiratory Physician
Salford Royal University Hospital
Salford M6 8 HD
[email protected]
Oxygen is the most
commonly used drug
in emergency medicine
• 34% of emergency
ambulance patients receive
oxygen
• Oxygen is used in about 2
million ambulance journeys
in the UK each year
Oxygen in Hospital
• 15-17% of UK
hospital patients were
receiving oxygen
during BTS audits
•
About 18,000 people every day
•
More than 2 million per year
Oxygen saves lives
But too much oxygen may cause death
• Essential in severely ill patients with low blood oxygen
levels
• High concentration oxygen probably causes >1,000
avoidable COPD deaths per year in the UK
>100,000 COPD admissions per annum in UK with 7.5% mortality:
Mortality 9% on high concentration O2 but 4% with controlled O2
• Hyperoxaemia is linked to increased risk of death in
strokes, ICU patients and survivors of cardiac arrest
Chaos reigned until 2008
• Most patients were given too much oxygen
And there was disagreement about how much oxygen to give
• Oxygen was rarely prescribed
68% of UK hospital patients who were using oxygen in 2008 had no
prescription and most prescriptions were incomplete
• Doctors and nurses had very little
knowledge about safe use of oxygen and
many false beliefs
UK Emergency Oxygen
Guideline published 2008
The
Solution
Endorsed or
supported
by 21 other
Societies and
Colleges
R O'Driscoll AAGBI WSM 2012
Key Principles
of the Guideline
• Oxygen is a treatment for Hypoxemia
(Giving oxygen does not relieve breathlessness or increase the oxygen supply to vital
organs if the patient’s oxygen level is normal to start with)
• Aim for a normal or near-normal oxygen
saturation level for most patients (94-98%)
• Aim at a lower level for (88-92%) for those at
risk from higher doses of oxygen
•Doctors prescribe a “target range”
•Nurses adjust equipment and flow rates to
achieve the desired target range
What is normal
and what is
dangerous?
Normal Range for Oxygen saturation
Normal range for healthy young adults
is approximately 96-98%
Slight fall with advancing age
SpO2 ~0.5% lower above age 70
Effects of sudden hypoxia
(e.g Removal of oxygen mask at altitude or in a pressure chamber)
• Impaired mental function; Onset at mean SaO2 64%
No evidence of mental impairment above SaO2 of 84%
• Loss of consciousness: Onset at mean saturation of 56%
• Organ damage: Brain tissue is the most sensitive
• Death: Risk depends on extent and speed of onset and duration
of hypoxia (no experimental studies in man)
Test Pilots in decompression chambers do not experience
breathlessness when the oxygen tension is lowered
Defining safe
lower and upper
limits of oxygen
saturation
What is the minimum arterial oxygen
level recommended in acute illness
Target oxygen Saturation
Critical care consensus guidelines
Minimum 90%
Surviving sepsis campaign
Aim at 88-95%
But these patients have intensive levels of nursing &
monitoring
BTS guideline recommends a minimum
of 94% for most patients – combines
what is near normal and what is safe
Pulmonary Oxygen Toxicity
Lorrain-Smith Effect
Exposure to high concentrations of
oxygen may be harmful
•
•
•
•
•
•
•
•
•
•
Absorption Atelectasis even at FIO2 30-50%1
Intrapulmonary shunting and post-operative hypoxaemia (on return to room air)1
Risk to COPD patients2
Coronary vasoconstriction3
Increased Systemic Vascular Resistance3
Reduced Cardiac Index after coronary bypass surgery4
Possible reperfusion injury post Myocardial Infarction5
Oxygen therapy increased mortality in non-hypoxic patients with mild-moderate stroke6
Hyperoxaemia was associated with increased mortality in survivors of cardiac arrest7
Hyperoxaemia was associated with increased mortality in the first 24 hours on ICU8
BTS guideline recommends an upper limit of 98%
for most patients.
Combination of what is normal and safe
What is a safe lower Oxygen
level in acute COPD?
In acute COPD
pO2 above 6.7 kPa
or 50 mm Hg
will prevent death
SaO2 above about 85%
SaO2
OxyHaemoglobin Dissociation Curve
(Keep SpO2 ≥88% to allow for oximeter
error and ensure SaO2 >85% )
mmHg
PaO2
Murphy R, Driscoll P, O’Driscoll R Emerg Med J 2001; 18:333-9
BTS guideline recommends a minimum
saturation of 88% for most COPD patients
What is a safe upper limit of oxygen
target range in acute COPD ?
• 47% of 982 patients with exacerbation of COPD were
hypercapnic on arrival in hospital
• 20% had Respiratory Acidosis (pH < 7.35)
• 5% had pH < 7.25 (and were likely to need ICU care)
• Most hypercapnic patients with pO2 > 10 kPa were acidotic
(equivalent to oxygen saturation of above ~ 92%)
i.e. They had been given too much oxygen Plant et al Thorax 2000; 55:550
RECOMMENDED UPPER LIMITS
Keep PaO2 below 10 kPa and
keep SpO2 ≤ 92% in acute COPD
Recent clinical evidence
• Mortality in acute COPD was 9% when high
concentration oxygen was given compared
with 4% mortality with controlled oxygen
(target range 88-92%)1
• Mortality in acute COPD was 11% when
>35% oxygen was given but 7% when lower
doses of oxygen were used2
• Need for ventilatory support; 22% v 9%2
1. Austin MA, et al. BMJ. 2010 Oct 18;341:c5462. doi: 10.1136/bmj.c5462
2. Roberts CM et al. Thorax 2011: 66: 43
Recommended target saturations
The target ranges are a consensus agreement by
the guidelines group and the endorsing colleges
and societies
Rationale for the target saturations is combination of
what is normal and what is safe
Most patients
94 - 98%
Risk of hypercapnic respiratory failure
88 – 92%*
*Or patient specific saturation on Alert Card
Oxygen saturation on air and survival
for 37,593 acute medical admissions
Smith GB et al. Resuscitation 2012 ;83:1201-5
Oxygen saturation on air and survival
for 37,593 acute medical admissions
Smith GB et al. Resuscitation 2012 ;83:1201-5
“Our findings suggest
that the BTS should
consider changing its
target saturation for
actively treated
patients not at risk of
hypercapnic
respiratory failure to
96-98%”
Thus giving
Oxygen to an
extra 20% of all
medical patients
BUT….
• There was an average 2% fall in mean and
median saturation above age 65
(and age is a strong predictor of death)
• Hypoxaemia is a marker of disease severity just
like tachycardia and tachypnoea
• Would normalising the respiratory rate with
morphine and normalising the heart rate with
beta blockers and increasing blood oxygen
content by 2% be expected to save lives?
Why is oxygen
used?
Aims of emergency
oxygen therapy
• To correct / prevent potentially harmful hypoxaemia
• To alleviate breathlessness (only if hypoxaemic)
Oxygen has no effect on breathlessness if the oxygen saturation is normal
Five common beliefs
(But wrong in most circumstances)
• Routine administration of supplemental oxygen is
useful, harmless and clinically indicated
• Giving oxygen is the most effective way to increase
oxygen delivery to the tissues
• Oxygen relieves breathlessness at normal oxygen
saturations
• High concentration oxygen is safe in all emergency
situations apart from COPD
• Many patients are at risk from hypoxaemia and only a
few “near terminal” COPD patients are at risk from
hyperoxaemia
Prophylactic oxygen
Less or More?
• Little increase in oxygen-carrying capacity
(e.g. 3% rise in blood oxygen content at SpO2 97%)
• Renders pulse oximetry worthless
as a measure of ventilation
• May prevent early diagnosis & specific treatment of
hypoventilation
Perioperative Oximetry
• Data from 23,000 patients in Cochrane Review
• Hypoxaemia was 1.5 to 3 times less common
amongst patients monitored with oximetry if the
results were made available to the clinicians
• More oxygen was given to these patients compared
with patients where the oximetry reading was
concealed from the clinicians
• No difference observed in complications or mortality
i.e. Correcting modest hypoxaemia may confer no benefit to patients
although clinicians who saw oximeter results believed that they had
prevented harm to several patients
Five common beliefs
(But wrong in most circumstances)
• Routine administration of supplemental oxygen is
useful, harmless and clinically indicated
• Giving oxygen is the most effective way to
increase oxygen delivery to the tissues
• Oxygen relieves breathlessness at normal oxygen
saturations
• High concentration oxygen is safe in all emergency
situations apart from COPD
• Many patients are at risk from hypoxaemia and only a
few “near terminal” COPD patients are at risk from
hyperoxaemia
Oxygen therapy is only one element in
the resuscitation of a critically ill patient
The oxygen carrying power of blood may be increased by
•
•
•
•
•
•
Safeguarding the airway
Enhancing circulating volume
Correcting severe anaemia
Enhancing cardiac output
Avoiding/Reversing Respiratory Depressants
Increasing Fraction of Inspired Oxygen (FIO2)
• Establish the reason for Hypoxaemia and
treat the underlying cause (e.g Bronchospasm, LVF etc)
• Patient may need, CPAP or NIV or Invasive ventilation
Five common beliefs
(But wrong in most circumstances)
• Routine administration of supplemental oxygen is
useful, harmless and clinically indicated
• Giving oxygen is the most effective way to increase
oxygen delivery to the tissues
• Oxygen relieves breathlessness at normal oxygen
saturations
• High concentration oxygen is safe in all emergency
situations apart from COPD
• Many patients are at risk from hypoxaemia and only a
few “near terminal” COPD patients are at risk from
hyperoxaemia
Does oxygen relieve breathlessness
in COPD and in Palliative Care?
• “Short Burst Oxygen Therapy” administered after exercise
does not relieve breathlessness in non-hypoxaemic
patients with COPD1
• Nasal oxygen did not relieve breathlessness in palliative
care patients with PaO2 > 7.3 kPa2
Five common beliefs
(But wrong in most circumstances)
• Routine administration of supplemental oxygen is
useful, harmless and clinically indicated
• Giving oxygen is the most effective way to increase
oxygen delivery to the tissues
• Oxygen relieves breathlessness at normal oxygen
saturations
• High concentration oxygen is safe in all emergency
situations apart from COPD
• Many patients are at risk from hypoxaemia and only a
few “near terminal” COPD patients are at risk from
hyperoxaemia
Patients at risk of hypercapnia/acidosis
due to high concentration oxygen
(even with PaO2 in the normal range)
• Chronic hypoxic lung diseases
– COPD
– Severe Chronic Asthma
– Bronchiectasis / Cystic Fibrosis
• Chest wall disease
– Kyphoscoliosis
– Thoracoplasty
• Neuromuscular disease
• Obesity hypoventilation
Patients at potential risk from
hyperoxaemia
• COPD patients and other groups shown in the previous
slide are at risk if oxygen saturation is elevated beyond
92% are at increased risk if SpO2 is raised above 98%
• Myocardial Infarction1
• Increased mortality in non-hypoxic patients with mildmoderate stroke randomised to oxygen (controlled trial)2
• Hyperoxaemia was associated with increased mortality in
survivors of cardiac arrest3
• Hyperoxaemia was associated with increased mortality in
the first 24 hours on ICU4
Hospital Mortality
Hyperoxia 63%
Normoxia 45%
Hypoxia
57%
Mortality according to calculated oxygen saturation level
Adapted from deJonge et al Critical Care 2008;
Mortality for each quintile
40
Overall
mortality
31%
35
30
25
20
15
10
5
0
<93%
93-95.7%
95.7-97.5%
97.5-98.8%
>98.8%
Estimated oxygen saturation based on conversion from PaO2
Adapted from table 2 in de-Jonge et al Critical Care 2008, 12:R156
Multivariate regression analysis of in-hospital mortality based on arterial oxygen
tension in first 24 hours on ICU
Overall hospital mortality for 36,307 consecutive ICU patients was 31%
Five common beliefs
(But wrong in most circumstances)
• Routine administration of supplemental oxygen is
useful, harmless and clinically indicated
• Giving oxygen is the most effective way to increase
oxygen delivery to the tissues
• Oxygen relieves breathlessness at normal oxygen
saturations
• High concentration oxygen is safe in all emergency
situations apart from COPD
• Many patients are at risk from hypoxaemia and
only a few “near terminal” COPD patients are at
risk from hyperoxaemia
Audit of 7956 blood gas samples at one
hospital over one year
• 10% of samples outside A&E had Type 1
respiratory failure with PO2 <8 kPa and normal
or low PCO2 (30% of A&E samples showed Type 1 Failure)
• 22% had Type 2 respiratory failure (including
7% with respiratory acidosis)
• 24% of patients who had blood gases sampled
had risk factors for Type 2 Respiratory Failure
and 73% of these samples had saturation >92%
• 26% of samples had saturation >98%
Oxygen prescription
Model for oxygen section in hospital prescription charts
DRUG
OXYGEN
(Refer To Trust Oxygen Policy)
Circle target oxygen saturation
88-92%
94-98%
Other___
STOP
DATE
Starting device/flow rate________
PRN / Continuous
Tick if saturation not indicated
PHARM
(Saturation is indicated in almost all cases except
for palliative terminal care)
SIGNATURE / PRINT NAME
DATE
ddmmyy
What device and
flow rate should
you use in each
situation?
Standard Oxygen Therapy 1960s-2008
Acute Patients
Stable Patients
Oxygen therapy 2008 onwards
Selected
COPD
patients
Critical
illness
Most
patients
BTS Recommendations
Serious Illness Requiring Moderate Levels
of Oxygen if the Patient is Hypoxaemic
COPD and Other Conditions Requiring
Controlled or low-dose Oxygen Therapy
Conditions for which patients should be
monitored closely but oxygen therapy is not
required unless the patient is hypoxaemic
Prescribe to target
Critical Illness Requiring High Levels of
Oxygen Supplementation
Some patients need high-dose
oxygen to normalise saturation
(Usually for short periods of time)
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Severe Pneumonia
Severe LVF
Major Trauma
Sepsis and Shock
Major atelectasis
Pulmonary Embolism
Exacerbation Lung Fibrosis
etc
Titrating Oxygen up and down
.
This table below shows APPROXIMATE conversion values.
Venturi 24% (blue) 2-4l/min
OR
Nasal specs 1L
Venturi 28% (white) 4-6 l/min
OR
Nasal specs 2L
Venturi 35% (yellow) 8-10l/min
OR
Nasal spec 4L
Venturi 40% (red)10-12l/min
OR
Simple face mask 5-6L/min
Venturi 60% (green) 15l/min
OR
Simple face mask 7-10L/min
Reservoir mask at 15L oxygen flow
seek medical advice
I f reservoir mask required
seek senior medical Input immediately
Monitoring patients
• Oxygen saturation and delivery system
should be recorded on the monitoring
chart
• Delivery devices and/or flow rates should
be adjusted to keep oxygen saturation in
target range
Implementation and Dissemination
Incorporation of Emergency Oxygen
Guidelines in other Guidelines
• JRCALC (Joint Royal Colleges Ambulance Liaison
Committee) Oxygen Guideline April 2009
• BTS Pneumonia Guideline 2009
• NICE Guideline for Chest Pain of Recent Onset –
March 2010
• Resuscitation Council (UK) Guideline 2010
• European Resuscitation Guideline 2010
• BTS-SIGN Asthma Guideline 2011
Summary
Oxygen is like every other drug
Use no more than is necessary
•
If it is used properly for the right indications, it is
beneficial and safe
•
Giving oxygen to those who do not need it or giving
too much or too little oxygen may cause harm
•
Compared with present practice, it is likely that a
reduction in oxygen use will deliver safer care,
especially for patients at risk of hypercapnia.
Further information at www.brit-thoracic.org.uk
Who was the first person to realise that moderate
oxygen may be safer than pure oxygen?
Less is More