RESOURCES for OXYGEN and a COMPREHENSIVE CRITICAL CARE STRATEGY Dr Simon Mardel OBE MSc DTM&H FFARCSI FRCSEd Consultant in Emergency Medicine Leicester

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

LeoneAbulfaz Karayev Children Hospital

Azerbaijan

Simulation training for H5N1 Republic of Moldova

Any country where demand for timely critical care exceeds capacity

Population exposed to Influenza A (H1N1)

No co-morbidities

Infectedsubgroup 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

Hospitalised

Co-morbidities

Respiratory failure

Contents

1. Why measure oxygen saturation?

2. How to correct hypoxaemia more effectively

3. How to rapidly increase availability

(surge capacity)




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

9899

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

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

Level 2 Support for single organ failure or step down or step up from Level 3

Level 3 Capable of treating multiorgan failure

the most critical increase in surge

capacity




“SaO2 should be maintained over 90%”“Patients with severe hypoxia need high flow oxygen (e.g. 10 l/min) delivered by

face mask”.

high flow rates are necessary

for severe hypoxaemia

e.g. 10-15 litres per minute.

Oxygen treatment - what flow rate? - what device?

The reason involvesanother graph !

When an adult breathes in, there is a peak inspiratory flow of around 30 litres per minute

Flo

w r

ate

l/m

in

exp

ira

tio

n

ins

pir

ati

on

insp

iratio

n

expi

ratio

n

expi

ratio

n

insp

iratio

n

pa

use

pa

use

pa

use

Can you guess the peak flow rate during INSPIRATION ?

30

With pneumonia the breathing rate and the peak inspiratory flow rates

increase

Flo

w r

ate

of

ex

pira

tion

in

spira

tion

Depending on the patient’s respiratory rate and depth, and flow of oxygen, a variable concentration is administered

40

Mexico H1N1: Use of devices and monitoring to maintain SaO2

Nasal prongs (nasal cannulae)

“Nasal cannulae do not permit high flow rates of oxygen and are only effective for management of mild hypoxemia”.

Nasal Prongs are a device that ends in two

short tapered tubes (about 1 cm in length)

designed to lie just within the nostrils.

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)”.

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.

Lessons from H5N1

Case “u” 15y Female

20.0

40.0

60.0

80.0

100.0

120.0

140.0

temperature highestaxillary

Respiratory Rate

Pulse

lowest Oxygensaturation

20

40

60

80

100

120

140

temperaturehighest axillary

Respiratory Rate

Pulse

Oxygen saturation

fast pulse low SaO2 fast breathing

Case 2. Age 15y hypoxia severe

Case 1. Age 17y hypoxia severe and prolonged

who else helped the child with more severe hypoxaemia to receive oxygen by mask continuously –initially at 8 l/min ?

“SaO2 should be maintained over 90%”

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




“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 – practical8-10 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• 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

•Ventilator Associated Pneumonia risk proportional to days on IPPV

v.

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.

Lessons from H5N1

Clinical characteristics of ten H5N1 patients on Admission and their final outcome*

Age 12y 5y 10y 8y 8y 13y 16y 18y 24y 23y Day since onset 3d 7d 7d 5d 8d 6d 5d 6d 5d 7d Respiratory rate (breaths /min)

65 70 64 60 40 40 40 60 50 28

Oxygen saturation** during receipt of 40% oxygen

50%

70%

86%

50%

95%

85%

67%

81%

80%

90 %

Outcome (R = Recovered/recovering)

died died Died died R died died died died R

*avian influenza A(H5N1) in 10 patients in Vietnam N Engl J Med 350;12 ,18 March 2004. (Data from tables 2 and 3).

1 2 3 4 5 6 7 8 9 10Case Number

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)

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

Below SpO2 of 90%

--- reflect large changes in PaO2!

Small changes in SpO2 between 90 to

100% ---Curve here is relatively flat

--- may result inmuch larger falls

in SpO2!

Small falls

in PaO2 ---

Below SpO2 of 90% Curve here is relatively steep

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 !

Peak Inspiratory Flow Rate of e.g. 30 litres per minute

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

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.