Respiratory Failure and Non-Invasive ventilation Sophie Fletcher Consultant 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% saturated Then Exchange dependent on VQ match

Gas transport C O 2 C O 2 C O 2 CO 2 Carbon Dioxide In solution Exchange dependent capillary/ alveolar partial pressure gradient Therefore 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 cmH 2 O) throughout respiratory cycle Increases intra-alveolar and intra-bronchiolar pressure – Recruits alveoli – Pulmonary oedema – Increase FRC and decreases tidal volume 5-10cmH 2 O

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 5-10cmH 2 O 12-20cmH 2 O IPAPEPAP

BIPAP EPAP (PEEP) – Recruits alveoli – Increases VQ matching – Improves oxygenation IPAP – EPAP (pressure support) – Increases tidal volume – Reduces CO cmH 2 O 12-20cmH 2 O 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: – Increased mortality with age and worsening acidosis (pH <7.26) Jeffrey et al. Thorax 1992; 47: – 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: – 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% ( 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 cmH 2 O To decrease CO 2 – Increase TV – Increase gap between IPAP and EPAP To increase O 2 – Increase EPAP – Increase FiO 2 Obesity: May need higher pressures Bullae: Caution with high pressures

It is not working Patient is deteriorating or getting agitated CO 2 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

CO 2 is not responding Mask leak Patient not synchronising – Fast respiratory rate Reassurance and explanation – Anxiety FiO 2 is too high Maybe need to increase IPAP

Hypoxia is not improving Increase EPAP Increase FiO 2

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 kPa) PaO 2 < 6.00 kPa despite max tolerated FiO 2 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

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 FiO 2

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

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

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

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

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

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

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

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 FiO 2

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

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

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

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