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Ventilatory supportOxygen to NIV

Dr Henry Bettinson

Consultant in Respiratory and Intensive Care Medicine

Oxford University Hospitals

Aims

• Two cases

• Oxygen Therapy

– Controlled vs Uncontrolled

– High flow (nasal) oxygen

• Continuous Positive Airways Pressure

• Non-invasive Ventilation

Case 1

• 63 year old male

• Presented with increased breathlessness

• Background

– Type 2 diabetes mellitus

– Panic attacks

– COPD

• 100 pack years

• ET 250 yards

• No previous hospital admissions

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Case 1

• Increasing breathlessness over one week

• On admission breathless at rest

• Minimal white sputum

• On examination– Cyanosed

– Using accessory muscles

– Speaking in sentences

– Widespread wheeze

– SpO2 92% on FiO2 0.24

– HR 70 / min bounding BP 187/85 mmHg

– No oedema

Case 1

• CXR

Case 1

• ABG on FiO2 0.24

– pH 7.32

– PaCO2 7.48

– PaO2 7.66

– HCO3 25.4

– BE 1.5

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Case 1

• Initial treatment– Prednisolone

– Nebulised salbutamol and ipratropium

– Controlled oxygen therapy

• ABG after 3h unchanged

• ABG after 5h

• FiO2 0.24– pH 7.28

– PaCO2 7.62

– PaO2 8.21

– HCO3 23.2

– BE -1.2

Case 1

• Aminophylline commenced

• ABG after 7h

• FiO2 0.24

– pH 7.25

– PaCO2 7.30

– PaO2 10.1

– HCO3 21.0

– BE -4.0

Case 1

• NIV commenced– 12/6 FiO2 0.25

• ABG after 5h– pH 7.37

– PaCO2 6.21

– PaO2 9.24

– HCO3 25.4

– BE -1.1

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Mortality COPD

4000 patients

4% in-hospital mortality

22% mortality survivors at 1 year

Mortality in COPD

Plant PK et al Early Use of Non-invasive ventilation for acute exacerbations of COPD Lancet 2000;355:1931

Mortality COPD

• Mortality of patients undergoing NIV in

COPDClin Respir J. 2019 Jan 19. doi: 10.1111/crj.12994. [Epub ahead of print]

Temporal trends in survival following ward-based NIV for acute hypercapnic

respiratory failure in patients with COPD.

Trethewey SP1, Edgar RG2,3, Morlet J1, Mukherjee R1, Turner AM1,3

• Retrospective cohort study

– 547 pts 2x6 year cohorts 2004 and 2013

– First episode ward-based NIV

– Mortality 17% and 20%

– No difference in intubation, ICU or ceilings of care between

cohorts

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Case 2

• 78 year old female

• Retired nurse

• Background

– Mild interstitial lung disease

– Hypertension

– Unlimited exercise capacity

Case 2

• ‘Cold’ for one week

• Day before admission diarrhoea and

vomiting

• Treated with imodium and rehydration by

GP

• Night before admission breathlessness

• Morning of admission Temp 39°C

Case 2

• On examination

– Temp 38°C

– HR 105 BP 78/53 mmHg HS normal

– SpO2 97% on 15L O2

– RR 26 Coarse crackles throughout

– Abdo soft, non-tender. Bowel sounds present

– Alert and orientated

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Case 2

Case 2

• ABG

– pH 7.14

– PCO2 6.46

– PO2 7.90

– HCO3 15

– BE -10.9

– Lac 3.2

Case 2

• Diagnosis:

• Initial treatment– Fluids 4.5L crystalloid

– IV augmentin, gentamicin and clarithromycin

• ABG after 3h 15L/min O2

– pH 7.22

– PCO2 6.5

– PO2 9.1

– HCO3 19

– BE -5.5

– Lac 3.6

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Case 2

• High Flow Nasal Oxygen commenced

– 60 L/min FiO2 0.8

• 2h later

– pH 7.35

– PaCO2 6.0

– PaO2 9.16

– HCO3 21

– BE -3

Case 2

• Initially stabilized

• Reduction in FiO2 to 0.4 over next 2 days

• Sudden desaturation to 60% on 3rd day

• CTPA no PE. Increasing bibasal

consolidation

• 3x 1g Methylprednisolone

• No significant improvement over next

week

Case 2

• Patient and family discussion

• Palliative measures instituted

• HFNO weaned once no apparent distress

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Mortality exacerbation of IPF

• Prognosis dependent on extent of pre-

existing disease and spirometry

• 3 month mortality 55% vs 81%Kishaba T, Tamaki H Shimaoka Y et al. Staging of acute exacerbation in patients with

idiopathic pulmonary fibrosis Lung 2014;192:141-9

• Systematic review

• 1 month mortality 60%Agarwal J, Jindal SK. Acute exacerbation of idiopathic pulmonary fibrosis: a systematic

review Eur J Intern Med 2008;19:227-35

Oxygen Guidelines

Aims of emergency

oxygen therapy

• To correct or prevent potentially harmful

hypoxaemia

• To alleviate breathlessness if hypoxaemic

Oxygen has no effect on breathlessness if the oxygen saturation

is normal

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Oxygen Guideline

• Prescription by target saturation

– 94%-98% for most patients

– 88%-92% for patients with or at risk of type 2

respiratory failure

• Administer oxygen to achieve target saturation

Oxygen Guideline

• Monitor oxygen saturation and titrate to keep in target range

• Taper oxygen dose and stop when stable

Oxygen guidelines

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NEWS2

Exposure to high concentrations of

oxygen may be harmful

• Absorption atelectasis even at FIO2 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

• Worsens systolic myocardial performance

• Oxygen therapy INCREASED mortality in non-hypoxic patients with mild-moderate stroke

Upper limit of 98% for most patients

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

Ronning OM et al. Stroke 1999; 30

Fallacies regarding Oxygen Therapy

“Routine administration of supplemental

oxygen is useful, harmless and clinically

indicated”

• Little increase in oxygen-carrying capacity

• Renders pulse oximetry worthless as a measure of ventilation

• May prevent early diagnosis & specific treatment of hypoventilation

This guideline only recommends supplemental oxygen when SpO2 is below the target range

or in critical illness or CO Poisoning

John B Downs MD Respiratory care 2003;48:611-20

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What is a safe lower Oxygen

level in acute COPD?

• In acute COPD

PaO2 above 6.7 kPa

will prevent death

SpO2 above about 88% SaO

2

mmHg

PaO2

OxyHaemoglobin Dissociation Curve

Minimum SpO2 of 88% for most COPD

patients

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

Devices

• Non re-breathing Reservoir

Mask.

• Critical illness / Trauma

patients.

• Post-cardiac or respiratory

arrest.

• Delivers O2 concentrations

60%-80% or above

• Effective for short term

treatment.

High Concentration Reservoir Mask

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Nasal Cannulae

• Recommended in the Guideline as suitable for most patients with both type I and II respiratory failure.

• 2-6L/min gives approx 24-50% FIO2

• FiO2 depends on oxygen flow rate and patient’s minute volume and inspiratory flow and pattern of breathing.

• Comfortable and easily tolerated

• No re-breathing

• Low cost product

• Preferred by patients (vs simple mask)

Simple face mask(Medium concentration,

variable performance)

• Used for patients with type I respiratory failure.

• Delivers variable O2 concentration 35%-60%.

• Low cost product.

• Flow 5-10 L/min

Flow must be at least 5 L/min to avoid CO2 build up and resistance to breathing

(although packaging may say 2-10L)

Venturi or Fixed Performance Masks

Aim to deliver constant oxygen concentration

within and between breaths.

24-40% Venturi Masks operate accurately

A 60% Venturi mask gives ~50% FIO2

With TACHYPNOEA (RR >30/min) the oxygen

supply should be increased by 50%

Increasing flow does not increase oxygen

concentration

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Operation of Venturi valve

O2

O2

+

Air

Air

Air

For 24% Venturi mask, the typical oxygen flow of 2 l/min gives a total gas flow of

51 l/min

For 28% Venturi mask, 4 l/min oxygen flow, gives a total gas flow of 44

l/min(Table 10.2)

Oxygen Flow Meter

The centre of the ball indicates the correct flow rate.

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2

1

3

2

1

This diagram illustrates the correct

setting of the flow meter to deliver

a flow of 2 litres per minute

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High flow oxygen

High flow oxygen interfaces

High flow oxygen

• Advantages

– Patient comfort

– Permits controlled high flow oxygen delivery

– Matches patient’s peak inspiratory flow

– Delivers some CPAP/ PEEP

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High flow oxygen

• Disadvantages

– Airvo requires electricity supply

– Not portable

– MR850 system noisy

– Risk of pressure sores with prolonged use

High flow oxygen

• Disadvantages

– Second O2 point necessary for using other

devices eg nebulisers

– Risk of humidification chamber running dry

– Increased staff training necessary

– May prolong terminal phase of illness

High flow oxygen

• Indications– Type 1 respiratory failure

– Type 2 respiratory failure where accurately titrated

humidified O2 is necessary

– Pre and post extubation

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High flow oxygen

• Indications– Weaning from NIV or CPAP

– Claustrophobia to O2 masks

– Tracheostomy patients

– Increased humidifcation to help with sputum

clearance

High flow oxygen

• Contraindications

– Nasal septal defects

– Epistaxis

– Severe facial injuries

– Base of skull fracture

High flow oxygen

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High flow oxygen

• 26 ICUs

• 310 patients

• HFNO vs STD vs NIV

• Primary outcome intubation rate

• 38% vs 47% 50%

• HR death 2.01 standard vs HFNO

• HR death 2.5 NIV vs HFNO

High flow oxygen

• Management of HFNO in palliation

– Use not recommended routinely

– Weaning/ withdrawal may be indicated

– Management depends on time-scale

• Involve patients and families where possible

• Discuss balance of benefits and harms

• Explain symptom management

• Ensure good symptomatic relief prior to any

weaning

OUHFT O2 Prescription and Administration Policy Jan 2019

Types of NIV

• CPAP

• Non-invasive ventilation

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CPAP

Normal CPAP

Inspiration

Inspiration

ExpirationPaw

0

Paw

0

5

cmH2O cmH2O

Expiration

t t

NIV

Inspiration

ExpirationPaw

0 Inspiration

Paw

0

Expiration

4

cmH2O cmH2O

t t

CPAP - indications

• Type I Respiratory failure

– Unresponsive to conventional management

• Pneumonia

• PCP

• Pulmonary oedema

• Acute lung injury

• Post-operative atelectasis

• Obstructive Sleep Apnoea

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CPAP – how does it work?

• P-V Curves

Pressure

Volume Inspiration

Expiration

CPAP – how it works (1)

• Operating at higher functional residual

capacity

• On straight-line part of curve

• Decreased work of breathing

CPAP – how it works (2)

• Improves ventilation – perfusion matching

– Shunting with some blood going to under-

ventilated areas

70%96%

96%

96%

70%

96%

83%

70%QT

QTQs

QT-QS

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CPAP – evidence in pulmonary

oedema

CPAP vs Standard

Reduces Intubation

RR 44%

NNT=7

Bilevel vs Standard

Reduces Intubation

RR 50%

NNT=8

CPAP vs Bilevel

No difference

CPAP vs Standard

Reduces Mortality

RR 59%

NNT=11

Bilevel vs Standard

Reduces Intubation

RR 50%

NNT=8

CPAP vs Bilevel

No difference

Intubation Rate Mortality

Peter 2006 Lancet 367:1155

NIV in pulmonary oedema -3CPO

3CPO

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3CPO

• No effect on 7 day mortality

• No effect on rates of intubation

• Drop in PaO2 at 1h

• Decrease in treatment failures

• Faster resolution of symptoms

• Faster resolution of physiology

3CPO

• Intention to treat analysis

• Crossover

– ? Type 2 error

• 10% overall mortality

• Low rates of intubation

• 2h in emergency departments

– Duration of treatment?

– 24h mortality more appropriate?

• Not treating underlying cause of heart failure

Cochrane review 2008

• 21 studies 1071 (3-120) patients

• Improvement of resp rate

• No difference in oxygenation

• Decreased intubation (RR 0.53, CI 0.34-0.83, NNT 8)

• Decreased mortality (RR 0.62, CI 0.45-0.84, NNT 14)

• Decreased ICU LOS (1d), but not hospital

• No increase in acute MI (RR 1.24, CI 0.79-1.95)

• Trend to increased adverse events– Skin damage

– Gastric distension

• No additional benefit of Bilevel vs CPAP

Vital 2008 Cochrane database

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NIV

• Synonyms

– BiPAP Bilevel positive airway pressure

– PS Pressure support

– NIPPy Non-invasive positive pressure

NIV

• How does it work?

– PaCO2 α 1/ minute ventilation

– In COPD ventilation wasted in dead-space

– Impaired ventilation-perfusion matching

COPD pathophysiology

• Obstructed alveoli –

chronic bronchitis

• Gas trapping –

prolonged time

constants and

intrinsic PEEP

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COPD pathophysiology

• Flat diaphragm poor mechanical advantage

• Reduced tidal volume with rapid breathing -

• Increased VD/ VT ratio

• Large intrathoracic pressure swings

• Increased work of breathing

NIV in COPD

• Deeper breaths for less effort

• Applied expiratory pressure decreases

dynamic hyperinflation

• Better ventilation – perfusion matching

NIV in COPD

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NIV Indications

• Clear evidence

– Acute exacerbation of COPD

– Kyphoscoliosis and other chest wall deformity

– Neuromuscular weakness

– Bridge to transplant in cystic fibrosis

• Less clear evidence

– Pneumonia

– Acute respiratory distress syndrome

– Chronic heart failure

NIV in acute exacerbations of

COPD

• 14 studies in meta-analysis

– 7 ICU based

– 5 ward based

– 2 unspecified

• Multi-national and often multi-centre

– UK landmark study Plant 2000 14 UK centres

• 118 in each arm

• Mortality difference 10% vs 20% (p=0.05)

• Intubation difference 15% vs 27% (p=0.02)

• Faster improvements in respiratory rate and pH

Treatment failure

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Mortality

Intubation

Mortality according to pH

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Success or failure?

Success

• PaCO2 6-13 KPa

• pH >7.3

• Less severe A-a gradient

• Good level of consciousness

• Younger

• Minimal leaks

• Tolerance

• Rapid improvement in physiological parameters

Failure

• Confusion/ ↓ LOC

• >1 organ failure

• Copious respiratory secretions

• Pneumonia/ ARDS as underlying diagnosis

• Poor nutritional status

• Edentulous

Location?

• Respiratory ward?

– 236 patients Leeds and surrounding DGHs

– Intubation criteria reached in 15% NIV vs 27%

controls

– Lower in-hospital mortality rate

But

• For severely acidotic on ward benefit marginal

• No titration of inspiratory pressures

Plant Lancet 2000 355: 1931

Location

• ER?

– Small studies in 1990s suggested not

– Concerns over delayed intubation

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Interfaces

NIV for other indications

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CPAP in chronic heart failure

• Possibly if additional

OSA

• No deaths in 14

treated patients

Questions

?

Summary

• Oxygen

– Prescription

– Administration

• Indications and evidence

• Controlled

• High flow

• CPAP and NIV

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