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

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RESOURCES for OXYGEN and a COMPREHENSIVE
CRITICAL CARE STRATEGY Dr Simon Mardel OBE MSc
DTMH FFARCSI FRCSEd Consultant in Emergency
Medicine Leicester UK Short Term Consultant WHO

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Isolation Ward Kenema Government Hospital
Sierra Leone
Abulfaz Karayev Children Hospital Azerbaijan
Simulation training for H5N1 Republic of Moldova
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Any country where demand for timely critical care
exceeds capacity

Population exposed to Influenza A (H1N1)
Co-morbidities
No co-morbidities

• subgroup that develops respiratory failure (or
  other organ failure) will have a much greater
  mortality if
• Co-morbidities
• Late referral
• Poor supportive care
• Reduced access to advanced care

Infected
Hospitalised
Respiratory failure
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Contents

• Why measure oxygen saturation?
• How to correct hypoxaemia more effectively
• How to rapidly increase availability
• (surge capacity)

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• Why measure oxygen saturation?
• How to correct hypoxaemia more effectively
• How to rapidly increase availability

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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.

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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
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Examples of pulse oximeters
The normal range of Sp02 at sea level is 94 -
100 An SpO2lt90 is considered by most
clinicians as an appropriate indication for
giving oxygen
99
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Low Oxygen saturations
e.g. SaO2 80 What does this number really
mean?
The answer involves the S Sigmoid shape of
THE OXYGEN HAEMOGLOBIN DISSOCIATION CURVE
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Early Warning Score Charts
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Comprehensive Critical Care Strategy - Levels of
care
the most critical increase in surge capacity
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• Why measure oxygen saturation?
• How to correct hypoxaemia more effectively
• 3. How to rapidly increase availability

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SaO2 should be maintained over 90Patients
with severe hypoxia need high flow oxygen (e.g.
10 l/min) delivered by face mask.
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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 !
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When an adult breathes in, there is a peak
inspiratory flow of around 30 litres per minute
Can you guess the peak flow rate during
INSPIRATION ?
inspiration
inspiration
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Flow rate l/min expiration
inspiration
pause
pause
pause
expiration
expiration
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With pneumonia the breathing rate and the peak
inspiratory flow rates increase
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Flow rate of expiration
inspiration
Depending on the patients respiratory rate and
depth, and flow of oxygen, a variable
concentration is administered
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Mexico H1N1 Use of devices and monitoring to
maintain SaO2
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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.

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Example of non re-breathing or 100 mask
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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
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• Some patients may experience difficulties with
  compliance
• and require the close involvement of nursing
  staff (and parents
• of children).

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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.

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fast pulse low SaO2 fast breathing
Case 2. Age 15y hypoxia severe
Case u 15y Female
Case 1. Age 17y hypoxia severe and prolonged
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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
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O2 is part of the chain of survival
Hypoxia! Detect Treat In every location
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• Why measure oxygen saturation?
• How to correct hypoxaemia more effectively
• How to rapidly increase availability

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• Output from oxygen generators can vary in
  concentration and flow rate, and may be
  insufficient for correcting severe hypoxemia.

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• If piped oxygen is not available in the medical
  ward, a supply of large cylinders will be needed.

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Infection control hazards

• E.g. A heavily contaminated bubble humidifier in
  use on a ward
• DO NOT USE
• THESE FOR
• SIMPLE FACE
• MASK DELIVERY!

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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

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(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.

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  files to be sorted and refs\ITU pyramid critical
  care.jpg

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END TALK

• THE FOLLOWING SLIDES MAY RESPOND TO QUESTIONS
  FROM AUDIENCE

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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.

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The Intensivists Dilemma

• EARLY IPPV
• Allows lung protective strategy
• Avoids crisis from sudden deterioration
• BUT
• Risks e.g. VAP and Resource
• Intense

• 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

v.

• Ventilator Associated Pneumonia risk
  proportional to days on IPPV

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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. .
Lessons from H5N1

• 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.

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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
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 35012 ,18 March 2004.
(Data from tables 2 and 3).
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Small changes in SpO2 between 90 to 100 ---
Curve here is relatively flat
Below SpO2 of 90 Curve here is relatively steep
Small falls in PaO2 ---
--- may result inmuch larger falls in SpO2!
--- reflect large changes in PaO2!
Below SpO2 of 90
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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 !
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Venturi masks or High Airflow Oxygen Enrichment
Masks
Relatively high flows of oxygen passing across a
narrow orifice 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.
entrained room air
entrained room air
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Venturi masks or High Airflow Oxygen Enrichment
Masks
Entrainment of room air causes high flow over
30 litres per min !
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.
entrained room air
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Industrial oxygen will have to contribute to any
massive increase in surge capacity
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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.