Respiratory Failure and Non-Invasive ventilation

Sophie FletcherConsultant Respiratory Physician

Key Learning Points

SpRs• NIV settings• What do the buttons do?• What do you do when it is

not working?

Respiratory Consultants/ ITU• Patient selection• Don’t forget to treat the

patient

Underlying physiology

Overview

• Physiology • NIV settings• BIPAP in practice• What to do when NIV isn’t working• Case studies

Gas transport

Oxygen

• Carried in Hb• pO2 >10kPa -sats 100%

saturatedThen • Exchange dependent on VQ

match

Gas transport

CO2

CO2

CO2

CO2

Carbon Dioxide

• In solution• Exchange dependent capillary/

alveolar partial pressure gradientTherefore

• Exchange is dependent on ventilation (minute volume)

Minute volume = tidal volume x respiratory rate

Terminology of Breathing

• Tidal volume is the amount of air in each breath

• Functional Residual Capacity is the volume that is left in the lungs when we have breathed out from a normal breath

Terminology of CPAP and NIV

• CPAP• BIPAP/ NIPPV• EPAP/ PEEP• IPAP

CPAP• Continuous positive

airways pressure– Same pressure (5-10

cmH2O) throughout respiratory cycle

• Increases intra-alveolar and intra-bronchiolar pressure– Recruits alveoli– Pulmonary oedema– Increase FRC and decreases

tidal volume

5-10cmH2O

BIPAP

• Bi-level Positive Airways Pressure– Lower positive pressure

during expiration (EPAP) (equivalent to CPAP)

– Higher positive airways pressure during inspiration (IPAP)

• CPAP + Increases tidal volume

5-10cmH2O12-20cmH2O

IPAPEPAP

BIPAP

• EPAP (PEEP)

– Recruits alveoli– Increases VQ matching– Improves oxygenation

• IPAP – EPAP (pressure support)

– Increases tidal volume– Reduces CO2

5-10cmH2O

12-20cmH2O

IPAP

EPAP

Putting it into practice

Aims of respiratory support

• Prevent tissue hypoxia• Control acidosis and hypercapnia• Support medical management

– Maximise lung function– Reverse precipitating cause

Respiratory support

• Oxygen therapy• Respiratory stimulants• Non invasive ventilation• Invasive mechanical ventilation

Medical management

• Bronchodilators• Systemic steroids• Antibiotics• Physiotherapy• Mucolytics

pH as a marker of severity

• Not the absolute level of PaCO2• But the magnitude and speed of change, as

reflected in the pH

What’s the evidence?• Warren et al. Lancet 1980; i:467-70.

– Increased mortality with age and worsening acidosis (pH <7.26)

• Jeffrey et al. Thorax 1992; 47:34-40.– Prospective, 139 episodes in 95 patients.– Death in 10/39 when pH<7.26– No difference in hypoxia or hypercapnia

• Plant et al. Thorax 2000; 55:550-4.– 1 yr prevalence study– Mortality with normal pH – 6.9%– Mortality with pH<7.35 – 13.8%

Oxygen therapy

Balancing hypoxia with respiratory acidosis

Achieving the balance

• All hypercapnic patients are at risk of acidaemia with oxygen therapy

• Aim for sats 88-92% (7.3-10 kPa)• Use Venturi mask• Regular monitoring• Use of an oxygen prescription chart

When to consider a respiratory stimulant

• Very rarely• Awaiting NIV to be initiated• NIV not available• NIV poorly tolerated• Reduced respiratory drive

Implementing BIPAP in practice

What underlying conditions?

Resp HDU

• Acute exacerbation COPD (AECOPD)

• Obesity related hypoventilation syndrome (OHS)

• (Neuromuscular disease)

ITU (unless IPPV inappropriate)

• Asthma• Chest wall deformity

• Usual causes of Type 1 respiratory failure– Pneumonia– Cardiac failure– (ILD)

Checklist for starting BIPAP

• Type 2 respiratory failure with acidosis• Medical treatment of underlying condition has

been implemented• Medical treatment and controlled oxygen

therapy has not controlled the acidosis• There is no contraindication to NIV

– Pneumothorax excluded• IPPV is not immediately indicated• NIV is according to the patients wishes

Start with the end in mind

• What are the limits of care?– Is escalation to IPPV appropriate?– Has a decision been made regarding resuscitation?– What are the patient’s wishes and expectations?– What are the patient’s / relatives’ wishes and

expectations?

Starting NIV

• Correct mask size• Experienced nurse

– Outreach– (RespHDU nurses)

• Explain what is going to happen to the patient• Start low

– IPAP 12– EPAP 4

• Stay with the patient

Choosing the settings

• Increase IPAP gradually – Increments of 2 cmH2O

• To decrease CO2

– Increase TV– Increase gap between

IPAP and EPAP

• To increase O2

– Increase EPAP– Increase FiO2

Obesity:• May need

higher pressures

Bullae:• Caution with

high pressures

It is not working

• Patient is deteriorating or getting agitated• CO2 is rising or not responding• Patient remains hypoxic• Patient is not tolerating the NIV

Exclude complications

• Pneumothorax• Retained secretions• Lobar collapse

• (Hypotension)– High pressures– Exclude dehydration

CO2 is not responding

• Mask leak• Patient not synchronising

– Fast respiratory rate• Reassurance and explanation

– Anxiety

• FiO2 is too high• Maybe need to increase IPAP

Hypoxia is not improving

• Increase EPAP• Increase FiO2

Agitated patient

• Reassurance• Check patient comfort

– Mask fit (leak into eyes)– Dry mouth/ nose

• Allow breaks from the machine

• (Anxiolytics)– Haloperidol,

Defining NIV treatment failure

• Patient intolerance / failure to co-ordinate• pH < 7.20 despite optimal support• pH 7.20 – 7.25 on 2 occasions 1 hour apart• Hypercapnic coma (GCS < 8 and PaCO2 > 8 kPa)

• PaO2 < 6.00 kPa despite max tolerated FiO2

• New onset of other initial exclusion criteria, particularly sputum retention, vomiting, or

pneumothorax • Cardiorespiratory arrest

Proceed to mechanical ventilation?What to consider

• Physiology – pH, RR• Severity of underlying disease• Reversibility of precipitating cause• QoL of patient• Co-morbidities• Patient wishes

Stopping NIV

• Not a death sentence• Can use opiates for distress• Controlled oxygen therapy

Audience participation

68 y.o. man, known COPD, current smoker 20/day, inhaled therapy only - presents following 2 weeks of increased cough,

sputum production and dyspnoea

Time Baseline

Oxygen 40 % facemask

GCS 13

PaO2 kPa 15.0

PaCO2 kPa 8.53

pH 7.27

H+ nmol/l 53

HCO3- mmol/l 24

SaO2 % 99

68 y.o. man, known COPD, current smoker 20/day, inhaled therapy only - presents following 2 weeks of increased cough, sputum production and dyspnoea

- control FiO2

Time Baseline 30 mins

Oxygen 40% facemask 24% f/mask

GCS 13 15

PaO2 kPa 15.0 9.7

PaCO2 kPa 8.53 6.8

pH 7.27 7.34

H+ nmol/l 53 46

HCO3- mmol/l 24 26

SaO2 % 99 95

68 y.o. man, known COPD, current smoker 20/day, inhaled therapy only - presents following 2 weeks of increased cough, sputum production and dyspnoea

Time Baseline

Oxygen 24 % facemask

GCS 15

PaO2 kPa 7.43

PaCO2 kPa 10.35

pH 7.34

H+ nmol/l 46

HCO3- mmol/l 39

SaO2 % 87

68 y.o. man, known COPD, current smoker 20/day, inhaled therapy only - presents following 2 weeks of increased cough, sputum production and dyspnoea

- standard therapy

Time Baseline 1 hour

Oxygen 24 % f/mask 24 % f/mask

GCS 15 15

PaO2 kPa 7.43 7.62

PaCO2 kPa 10.35 9.63

pH 7.34 7.36

H+ nmol/l 46 44

HCO3- mmol/l 39 39

SaO2 % 87 89

68 y.o. man, known COPD, current smoker 20/day, inhaled therapy only - presents following 2 weeks of increased cough, sputum production and dyspnoea

- standard therapy….failure

Time Baseline 1 hour

Oxygen 24% f/mask 24% f/mask

GCS 15 13

PaO2 kPa 7.43 6.35

PaCO2 kPa 10.35 12.48

pH 7.34 7.29

H+ nmol/l 46 51

HCO3- mmol/l 39 36

SaO2 % 87 81

68 y.o. man, known COPD, current smoker 20/day, inhaled therapy only - presents following 2 weeks of increased cough, sputum production and dyspnoea

- NIV - good response

Time Baseline 1 hour 2 hours

Oxygen 24% f/mask 24% f/mask NIV 15/5 + 3l/min

GCS 15 13 15

PaO2 kPa 7.43 6.35 7.3

PaCO2 kPa 10.35 12.48 9.94

pH 7.34 7.29 7.35

H+ nmol/l 46 51 45

HCO3- mmol/l 39 36 38

SaO2 % 87 81 86

68 y.o. man, known COPD, current smoker 20/day, inhaled therapy only - presents following 2 weeks of increased cough, sputum production and dyspnoea

- NIV - hypoxaemia

Time Baseline 1 hour 2 hours

Oxygen 24% f/mask 24% f/mask NIV 15/5 + 3l/min

GCS 15 13 15

PaO2 kPa 7.43 6.35 6.28

PaCO2 kPa 10.35 12.48 10.57

pH 7.34 7.29 7.33

H+ nmol/l 46 51 47

HCO3- mmol/l 39 36 38

SaO2 % 87 81 79

68 y.o. man, known COPD, current smoker 20/day, inhaled therapy only - presents following 2 weeks of increased cough, sputum production and dyspnoea

- NIPPV - hypoxaemia - increase O2

Time Baseline 1 hour 2 hours 2.5 hours

Oxygen 24% f/mask

24% f/mask

NIV 15/5 + 3l/min

NIV 15/5 + 6 l/min

GCS 15 13 15 15

PaO2 7.43 6.35 6.28 7.39

PaCO2 10.35 12.48 10.57 10.21

pH 7.34 7.29 7.33 7.35

H+ 46 51 47 45

HCO3- 39 36 38 38

SaO2 87 81 79 85

78 y.o. woman, known COPD, IHD, DM, AF, multiple admissions, smokes 5/day, home nebs, LTOT,

housebound - increased cough, sputum, leg oedema over 48 hrs, confused at home

Time Baseline

Oxygen 15L and non rebreathe

GCS 5

PaO2 kPa 14.29

PaCO2 kPa 15.34

pH 7.06

H+ nmol/l 87

HCO3- mmol/l 34

SaO2 % 98

78 y.o. woman, known COPD, IHD, DM, AF, multiple admissions, smokes 5/day, home nebs, LTOT, housebound - increased cough,

sputum, leg oedema over 48 hrs, confused at home - control FiO2

Time Baseline 30 mins

Oxygen 15L 24% f/mask

GCS 8 10

PaO2 kPa 14.29 6.13

PaCO2 kPa 15.34 13.98

pH 7.06 7.12

H+ nmol/l 87 76

HCO3- mmol/l 34 34

SaO2 % 98 78

78 y.o. woman, known COPD, IHD, DM, AF, multiple admissions, smokes 5/day, home nebs, LTOT, housebound - increased cough,

sputum, leg oedema over 48 hrs, confused at home - control FiO2

Time 30 mins 1 hour 2 hours

Oxygen 24% f/mask 24% f/mask 24% f/mask GCS 10 13 12 PaO2 6.13 6.40 6.22 PaCO2 13.98 13.27 13.02 pH 7.12 7.21 7.23 H+ 76 62 59 HCO3- 34 34 35 SaO2 78 82 80

78 y.o. woman, known COPD, IHD, DM, AF, multiple admissions, smokes 5/day, home nebs, LTOT, housebound - increased cough, sputum, leg oedema over 48 hrs, confused at home NIV - good

response

Time 30 mins 1 hour 2 hours 3 hours

Oxygen 24% f/mask

24% f/mask

24% f/mask

NIV 14/4 + 3 l/min

GCS 10 13 12 14

PaO2 6.13 6.40 6.22 7.54

PaCO2 13.98 13.27 13.02 11.87

pH 7.12 7.21 7.23 7.31

H+ 76 62 59 49

HCO3- 34 34 35 36

SaO2 78 82 80 92

68 y.o. man, known COPD, current smoker 20/day, inhaled therapy only - presents following 2 weeks of increased cough, sputum production and dyspnoea

- NIV - persistent hypercapnia

Time Baseline 1 hour 2 hours

Oxygen 24% f/mask 24% f/mask NIV 15/5 + 3l/min

GCS 15 13 13

PaO2 kPa 7.43 6.35 6.85

PaCO2 kPa 10.35 12.48 12.29

pH 7.34 7.29 7.30

H+ nmol/l 46 51 50

HCO3- mmol/l 39 36 36

SaO2 % 87 81 82

68 y.o. man, known COPD, current smoker 20/day, inhaled therapy only - presents following 2 weeks of increased cough,

sputum production and dyspnoea- NIV - hypercapnia - increased IPAP

Time Baseline 1 hour 2 hours 2.5 hours

Oxygen 24% f/mask

24% f/mask

NIV 15/5 + 3 l/min

NIV 20/6 + 3 l/min

GCS 15 13 13 15

PaO2 7.43 6.35 6.85 7.42

PaCO2 10.35 12.48 12.29 9.87

pH 7.34 7.29 7.30 7.35

H+ 46 51 50 45

HCO3- 39 36 36 38

SaO2 87 81 82 86

Learning Points

• Hypercapnia ≠ BIPAP• Start with the end in mind• Diagnose and treat the underlying problem• Coach the patient