RESOURCES for OXYGEN
and a
COMPREHENSIVE CRITICAL CARE STRATEGY
Dr Simon Mardel
OBE MSc DTM&H FFARCSI FRCSEd
Consultant in Emergency Medicine Leicester UK & Short Term Consultant WHO
98%
Isolation Ward Kenema
Government Hospital Sierra
Leone
Simulation training for H5N1
Republic of Moldova
Abulfaz Karayev Children
Hospital Azerbaijan
Any country where
demand for timely
critical care exceeds
capacity
subgroup that
develops
respiratory
failure (or other
organ failure) will
have a much
greater mortality
if:
1. Co-morbidities
2. Late referral
3. Poor supportive
care
4. Reduced access
to advanced care
Co-morbidities
Infected
Hospitalised
Respiratory
failure
No co-morbidities
Population
exposed to
Influenza A
(H1N1)
Contents
1. Why measure oxygen saturation?
2. How to correct hypoxaemia more
effectively
3. How to rapidly increase availability
(surge capacity)
1. Why measure oxygen saturation?
2. How to correct hypoxaemia more
effectively
3. How to rapidly increase availability
Hypoxaemia
• Hypoxaemia means low oxygen levels in the
blood. It is a life-threatening condition that
occurs frequently in pneumonia
• Even the best combinations of clinical signs
commonly misdiagnose hypoxaemia
• The best way to detect and monitor hypoxaemia
is with pulse oximetry. Oximetry is accurate,
simple, non-invasive, and cost efficient.
Hypoxaemia - additive relationships
A-a* gradient in viral pneumonia increases
rapidly to below hypoxic threhold
+ A-a gradient is already significant in
obesity or most pre-existing lung diseases
+ Alveolar oxygen reduced by altitude
- Alveolar oxygen increased by increasing
inspired oxygen concentration
*Aleveolar-arterial gradient
Examples of pulse oximeters
The normal range of Sp02 at sea level is
94 - 100%
An SpO2<90% is considered by most clinicians
as an appropriate indication for giving oxygen
98
99
Low Oxygen saturations
80
e.g. SaO2 = 80%
What does this number
really mean?
The answer
involves the “S”
Sigmoid shape of
THE OXYGEN
HAEMOGLOBIN
DISSOCIATION
CURVE
Early Warning Score Charts
Comprehensive Critical Care
Strategy - Levels of care
Level 0
Simple nursing care
No technical facilities
Level 1
Observation and simple
support for actual or
potential single organ failure
Support for single organ
failure or step down or step
up from Level 3
Capable of treating
multiorgan failure
the most critical
increase in surge
capacity
Level 2
Level 3
1. Why measure oxygen saturation?
2. How to correct hypoxaemia more
effectively
3. How to rapidly increase availability
“SaO2 should be maintained over 90%”
“Patients with severe hypoxia need high
flow oxygen (e.g. 10 l/min) delivered by
face mask”.
Oxygen treatment
- what flow rate?
- what device?
high flow rates are necessary
for severe hypoxaemia
e.g. 10-15 litres per minute.
The reason
involves
another graph !
expiration
pause
pause
expiration
pause
inspiration
inspiration
30
Flow rate l/min
expiration inspiration
Can you guess the peak flow rate during
INSPIRATION ?
When an adult breathes in, there is a peak inspiratory flow
of around 30 litres per minute
expiration inspiration
Flow rate of
40
With pneumonia the breathing rate
and the peak inspiratory flow rates
increase
Depending on the patient’s respiratory rate and
depth, and flow of oxygen, a variable
concentration is administered
Mexico H1N1: Use of devices and
monitoring to maintain SaO2
Nasal prongs (nasal cannulae)
Nasal Prongs are a
device that ends in two
short tapered tubes
(about 1 cm in length)
designed to lie just
within the nostrils.
“Nasal cannulae do not permit high flow rates of
oxygen and are only effective for management
of mild hypoxemia”.
Example of “non re-breathing” or
“100% mask”
Poor compliance!
Some adults will not
tolerate oxygen
masks well
complaining of
claustrophobia, the
smell and a dry
throat. Often
encouragement
improves
compliance but
since many hypoxic
patients are restless
all confused and this
may be a particular
problem
“Some patients may
experience
difficulties with
compliance
and require the close
involvement of
nursing staff (and
parents
of children)”.
Lessons from H5N1
In Azerbaijan 2 children
with severe H5N1
pneumonia were
successfully treated by
this paediatric hospital
team. The children
required high flow
oxygen by face mask
and did not require
ventilation.
fast pulse low SaO2 fast breathing
140.0
140
Case 1. Age
17y hypoxia
severe and
prolonged
120.0
100.0
Case“u”2.15y
Age
Case
Female
120
100
temperature15y
highesthypoxia
severe
axillary
Respiratory Rate
temperature
highest axillary
80.0
Respiratory Rate
80
Pulse
6
6
3 /0
3 /0
Oxygen saturation
lowest Oxygen
saturation
16
/0
3/
20
06
18
/0
3/
20
06
20
/0
3/
20
06
22
/0
3/
20
06
24
/0
3/
20
06
6
3 /0
20
6
20.0
3 /0
40.0
40
6
60
3 /0
60.0
Pulse
“SaO2 should be maintained
over 90%”
who else helped the child with more severe
hypoxaemia to receive oxygen by mask
continuously –initially at 8 l/min ?
The mother was shown her own SaO2(normal)
and her childs SaO2, and how the SaO2
increased when her child received high flow
oxygen by face mask.
She then helped her child to comply with 7
days of oxygen treatment that was required
O2 is part of the
chain of survival
Hypoxia!
Detect & Treat
In every location
1. Why measure oxygen saturation?
2. How to correct hypoxaemia more
effectively
3. How to rapidly increase availability
“Output from oxygen generators can vary in
concentration and flow rate, and may be
insufficient for correcting severe
hypoxemia.”
“If piped oxygen is not available in the
medical ward, a supply of large cylinders
will be needed.”
Infection control “hazards”
E.g. A heavily
contaminated
bubble humidifier
in use on a ward
DO NOT USE
THESE FOR
SIMPLE FACE
MASK DELIVERY!
Oxygen – practical
8-10 litres per minute
= 600 litres per hour
= 14,400 litres per day
In Azerbaijan we used
18 large size
cylinders to treat 2
cases!
Approx. 10USD per
cylinder refill
(In the absence of medical gases, industrial
oxygen for face mask delivery would suffice
if certain precautions are observed)
“WHO has included oxygen in the Essential
Medicines list since 1979 but it is still not
widely available in some countries. If
medical oxygen is not available, then
industrial oxygen can be used (e.g.
delivered by face mask) provided it
conforms with national guidelines.”
• ..\My Documents\cpmpaq desktop 13
march2008\pdf files to be sorted and
refs\ITU pyramid critical care.jpg
END TALK
• THE FOLLOWING SLIDES MAY
RESPOND TO QUESTIONS FROM
AUDIENCE
DO NOT OVERHYDRATE
• Use oral fluids if the GI tract is unaffected and
not in shock
• Uncertainty about “running patients dry”
• Some patients arrive in ITU in Positive fluid
balance.
• Many Intensivists report improvement in hypoxia
by use of diuretics or restricting fluids
• Some intensivists allow creatinine to rise a little if
this avoids worsening the hypoxia.
The Intensivists Dilemma
EARLY IPPV
v.
• Allows lung
protective strategy
• Avoids crisis from
sudden
deterioration
BUT
• Risks e.g. VAP*
and Resource
• Intense
•Ventilator Associated Pneumonia risk
proportional to days on IPPV
TRY TO AVOID
IPPV
• Patient might recover
with simple
measures
BUT
• Risks from hyppoxia
• Patient may
deteriorate quickly
• Late IPPV as rescue
– difficult to use lung
protective strategy
Lessons from H5N1
Human avian influenza (AI) caused by A (H5N1) has a
high case fatality rate of 61%, and is highest between
ages 10-19 years, even where intensive care facilities
have been used.
Many patients arrive at. these facilities having
suffered prolonged uncorrected hypoxaemia as
a result of viral pneumonia. Early diagnosis is
difficult as symptoms are initially
indistinguishable from common illnesses, as
pneumonia develops the patient deteriorates
rapidly and it is at this point that most patients
present to a reference hospital.
Clinical characteristics of ten H5N1 patients on
Admission and their final outcome*
Yellow highlights the higher oxygen saturations on admission of the only 2 survivors
Pink highlights the case numbers with chest radiographs published (next 3 slides)
Case Number
1
2
3
Age
Day since onset
Respiratory rate (breaths
/min)
Oxygen saturation** during
receipt of 40% oxygen
Outcome (R =
12y
3d
65
5y
7d
70
10y
7d
64
8y
5d
60
8y
8d
40
13y 16y
6d
5d
40
40
18y
6d
60
24y
5d
50
23y
7d
28
50
%
70
%
86
%
50
%
95
%
85
%
67
%
81
%
80
%
90
%
died
died
Died
died
R
died
died
died
died
R
4
5
6
7
8
9
10
Recovered/recovering)
The 8 patients who died received mechnical ventilation during the first 48hrs after
admission, their oxygen saturations are very low, especially as they are receiving
oxygen therapy
*avian influenza A(H5N1) in 10 patients in Vietnam
N Engl J Med 350;12 ,18 March 2004. (Data from tables 2 and 3).
Below SpO2 of
90% Curve
here is
relatively steep
Curve here is
relatively flat
Small changes in
SpO2 between 90 to
100%
---
Small falls
--- may result in
in PaO2 ---
much larger falls
in SpO2!
--- reflect large
changes in PaO2!
Below SpO2 of 90%
Peak Inspiratory Flow Rate
of e.g. 30 litres per minute
Are you surprised at how high this is?
Remember we measure peak expiratory
flow rates in asthma – and values are
often 100 – 500 litres per minute !
Venturi masks or High Airflow
Oxygen Enrichment Masks
Relatively high flows of
oxygen passing across a
narrow orifice
entrained
room air
entrained
room air
allow
entrainment of additional
room air to the mask to
meet the inspiratory flow of
the patient. The masks
deliver a fixed amount of
oxygen that can be
prescribed – common
percentages include 24%,
and 28%, 35% and 60%.
Venturi masks or High Airflow
Oxygen Enrichment Masks
Entrainment of room air
causes high flow over
30 litres per min !
entrained
room air
Noisy and uncomfortable
for patients.
These devices deliberately
dilute the oxygen and ARE
NOT indicated for
correcting hypoxia except
in certain conditions where
inspired higher oxygen
should be avoided.
The very high flow of
venturi devices raised
concerns about aerosol
spread during SARS.
Industrial oxygen will have to
contribute to any massive increase
in surge capacity
Humidification
• When oxygen is used at low flow rates (less than
4 L per minute) through nasal catheter or
prongs, humidification is not necessary.
• Humidification is only necessary for some
methods of oxygen delivery.
• Humidification is essential in patients with an
endotracheal tube or tracheostomy.
• A major safety concerns of water humidifiers is
bacterial contamination.