Catherine

Jones

June 2017

1

OXYGEN THERAPY

2

ACKNOWLEDGEMENT

To revise why Oxygen is important

To identify the indications for Oxygen Therapy

To identify problems with administration of

oxygen

To discuss different devices/interfaces

available in critical care

3

LEARNING OUTCOMES

Aerobic Metabolism:

Anaerobic Metabolism

4

WHAT DOES OXYGEN DO?

OXYGEN + FUEL ENERGY + CARBON DIOXIDE + WATER

GLUCOSE ENERGY + LACTIC ACID

• Altered mental state

• Dyspnoea, cyanosis, tachypnoea, arrhythmias, coma

• Hyperventilation when PaO2 <5.3kPa(SpO2 <72%)

• Loss of consciousness ~ 4.3 kPa(SpO2 -56%)

• Death approximately 2.7 kPa

5

CLINICAL FEATURES OF HYPOXAEMIA

BLOOD GASES: PaO2 and SaO2

PaO2 = Arterial oxygen partial pressure in blood gas specimen

SaO2 =Arterial oxygen saturation measured

OXYGEN SATURATION

Easily measured by pulse oximetry & widely available

SpO2 = Oxygen saturation measured by pulse oximeter

Normal range in healthy adults 96-98%

CYANOSIS

Often not recognised

Absent with anaemia

6

ASSESSMENT/MEASUREMENT OF

HYPOXAEMIA

CYANOSIS

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WHY IS OXYGEN

USED?

• To correct potentially harmful hypoxaemia & support the delivery of oxygen to cells

• To alleviate breathlessness (only if hypoxaemic)

Oxygen has not been proven to have any consistent effect on the sensation of breathlessness in non-hypoxaemic patients

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AIMS OF OXYGEN THERAPY

• Little increase in oxygen-carrying capacity if SpO2 is normal

• BTS (2017)guideline only recommends supplemental oxygen when SpO2 is below the target range.

10

OXYHAEMAGLOBIN DISSOCIATION CYRVE

11

WHAT ARE THE TARGETS?

OXYGEN THERAPY IS ONLY ONE

ELEMENT OF RESUSCITATION

OF A CRITICALLY ILL PATIENT The oxygen carrying power of blood may be

increased by

• Safeguarding the airway

• Sit the pt up where possible

• Enhancing circulating volume

• Correcting severe anaemia

• Enhancing cardiac output

• Avoiding/Reversing Respiratory Depressants

• Increasing Fraction of Inspired Oxygen (FIO2)

• Establish the reason for Hypoxia and treat the underlying cause (e.g Bronchospasm, LVF etc)

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13

PROBLEMS WITH

OXYGEN THERAPY?

Production & accumulation of Reactive Oxygen

Species leads to cell damage & necrosis. Cell

death initiates further inflammatory processes

causing further lung damage.

Atelectasis caused by

Inhibits pulmonary surfactant production causing

alveoli to collapse on expiration.

Increased viscosity of tracheal mucous – reduces

clearance & contributes to plugging

Hyperoxic inflammation

OXYGEN TOXICITY

SOME PATIENTS ARE AT RISK OF

CO2 RETENTION AND ACIDOSIS IF

GIVEN HIGH DOSE OXYGEN*

Chronic hypoxic lung disease

COPD

Severe Chronic Asthma

Bronchiectasis / CF

Chest wall disease

Neuromuscular disease

Morbid obesity and OHVS (Obesity

Hypoventilation Syndrome)

*Blood gases should be checked for all such patients if they

need oxygen

*Target saturation range is 88-92% if CO2 level is elevated (or if

it was high in the past) 12/05/2017

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HIGH CONCENTRATION OXYGEN MAY

DOUBLE THE RISK OF DEATH IN

ACUTE EXACERBATIONS OF COPD

(AECOPD)

DANGER OF REBOUND

HYPOXAEMIA

If you find a patient who is severely hypercapnic

due to excessive oxygen therapy……

Do NOT stop oxygen therapy

abruptly

It is safest to step down to 35% oxygen if the

patient is fully alert or provide mechanical

ventilation if the patient is drowsy

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DELIVERY &

DEVICES

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Record delivery system,

flow rate, % & sign on

med chart

Always check expiry

dates on cylinder

Record SpO2

Target for acutely ill….??

Target for hypercapnic

respiratory failure…??

19

ADMINISTRATION

Beware of air outlets They may be mistaken for oxygen outlets

Use a cover for air outlets or else remove the flow meter for air when not in use Oxygen outlet

(Usually white) Air outlet (usually black)

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OXYGEN FLOW METER

3

2

1

3

2

1

The centre of the ball indicates the

correct flow rate.

Non re-breathing Reservoir Mask

Delivers O2 concentrations

between 60 & 80% or above

Variable performance dependent

upon mask fit & breathing pattern

Effective for short term treatment

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High Concentration Reservoir Mask

Variable performance

1-6L/min gives approx 24-50%

FIO2

Comfortable and easily tolerated

No re-breathing

Able to eat & drink

Problems with nasal irritation

Don’t use where nose is blocked

or there are polyps

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NASAL CANNULAE

• Delivers variable O2

concentration between 35% &

60%.

• Flow 5-10 L/min – not useful

for pts requiring lower flows

• Low cost product.

• Flow must be at least 5

L/min to avoid CO2 build up.

• Not suitable for T2RF

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SIMPLE FACE MASK

VARIABLE PERFORMANCE DEVICES

• MV = 30 L/min

• 40 bpm x 740 ml/breath

• O2 flow rate = 2 L/min

• Inspired O2 concentration = 2 l/min of 100% O2 + 28 L/min

air drawn into mask

• (1x2) + (0.21x28) = FiO2 of 0.26 (or 26%)

30 L/min

Oxygen delivery is dependant on patients

minute volume (RR X VT)

Venturi or Fixed Performance

Masks (V) • Aim to deliver constant oxygen

concentration

• Venturi Valve delivers fixed %O2

• Increasing flow does not increase

oxygen concentration because it is a

fixed dose device

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OPERATION OF VENTURI VALVE

O2

O2

+

Air

Air

Air

Large volume nebulisation-based humidifiers

1 litre of saline & adjustable venturi valve

Useful for long term oxygen therapy

Always use humidification for tracheostomy

Humidification may be provided by cold or warm humidifiers

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HUMIDIFIED OXYGEN

“Neck breathing patients”

Adjust oxygen flow to maintain

target saturation

Prolonged oxygen use requires

humidification

Patients may also need suction

to remove airway mucus

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TRACHEOSTOMY MASK

OPTIFLOW

Delivers heated & humidified high flow

oxygen (up to 100%) via nasal cannula.

Provides low level of CPAP

New & very comprehensive Emergency O2 Guidelines

our – GO READ THEM!

FiO2 is important but key consideration is target

saturation

Take care when giving O2 to people at risk of AHRF

Lots of devices/interfaces..

Oxygen is a drug & should be treated as such

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SUMMARY

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ANY QUESTIONS..?

EXPOSURE TO HIGH

CONCENTRATIONS OF

OXYGEN MAY BE HARMFUL Absorption Atelectasis even at FIO 2 30-50% Intrapulmonary shunting Post-operative hypoxaemia Risk to COPD patients Coronary vasoconstriction Increased Systemic Vascular Resistance Reduced Cardiac Index Possible reperfusion injury post MI Increased CK level in STEMI and increased infarct size on

MR scan at 3 months Worsens systolic myocardial performance Association of hyperoxaemia with increased mortality in

several ITU studies

This guideline recommends an upper limit of 98% for most patients

Combination of what is normal and safe

• Harten JM et al J Cardiothoracic Vasc

Anaesth 2005; 19: 173-5

• Kaneda T et al. Jpn Circ J 2001; 213-8

• Frobert O et al. Cardiovasc Ultrasound 2004;

2: 22

• Haque WA et al. J Am Coll Cardiol 1996; 2:

353-7

• Thomaon aj ET AL. BMJ 2002; 1406-7

• Stub D et a;. Circulation 2015’; 131: 2143-50

• Helmerhorst HJ Crit Care Med 2015; 43:

1508-19

• Girardis M et al. JAMA 2016; 316: 1583-89

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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

(SpO2 above about

85%) S

aO

2

mmHg

PaO2

OxyHaemoglobin Dissociation Curve

This guideline recommends a minimum

saturation of 88% for most COPD patients

Murphy R, Driscoll P, O’Driscoll R Emerg Med J 2001; 18:333-9

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