Non Invasive Ventilation – a guide to difficult choices Dr Sanj Fernando

NIV Why? How?

Respiratory Failure Ventilation Failure Gas exchange Failure Forces resisting ventilation > Forces of respiratory effort Ventllation failure Forces resisting ventilation: Elastic recoil of lungs Airway (+ tubing) resistance Intrinsic PEEP Intrinsic vs extrinsic PEEPi Absent in healthy lung Caused by Tachypnoea Airflow obstruction (small airway) Gas exchange failure Alveolar problem Stuff in the alveoli APO Pneumonia Decreased alveoli COPD Alveolar-Blood barrier problem Thickened barrier – connective tissue disorders Circulation problem VQ mismatch Blood problem Decreased oxygen content Anaemia Haemoglobinopathy (thalassaemia, methaemaglobinaemia) Red cell disorder (sickle cell) Decreased Alveolar function / Circulation problem

68 yo man arrives at 6:30 am Awoke with SOB, mild chest pain Sweaty +++ Smoker + previous MI RR=40 Tripod posture Sats = 91% on NRB

What are we trying to achieve with NIV? Improve alveolar ventilation Reverse hypercarbia and acidosis Alveolar recruitment and increased FiO2 Reverse hypoxia Reduction in work of breathing Reduce respiratory muscle insufficiency Decrease metabolic demands Reduction in LV afterload and preload Improved cardiac function

CPAP vs PEEP vs IPAP vs BiPAP PEEP=EPAP=CPAP + IPAP = BiPAP BPAP} BiPAP®} Bilevel => NIV <= CPAP = EPAP = PEEP BIPAP®} CPAP 1 pressure5-10cmH2O Prevent alveolar collapse Clear mucus Alveolar recruitment and splinting Oxygenate better Decrease Work of breathing Increase intrathoracic pressure (good – dec. cardiac work; bad – may drop BP) BiPAP 2 pressures IPAP = 10 EPAP = 5 = PEEP = CPAP 10-5 = 5 cmH2O = Pressure support Pressure support => important for improving ventillation Better ventillation Decrease CO2 Decrease acidosis If high CO2 – increase IPAP and PS If low O2 – increase EPAP and FiO2 Remember if you increase EPAP without increasing IPAP => decrease Pressure support and decrease ventillation

CPAP vs PEEP vs IPAP vs BiPAP If high CO2 : increase IPAP and PS If low O2 : increase EPAP and FiO2 PEEP=EPAP=CPAP + IPAP = BiPAP BPAP} BiPAP®} Bilevel => NIV <= CPAP = EPAP = PEEP BIPAP®} CPAP 1 pressure5-10cmH2O Prevent alveolar collapse Clear mucus Alveolar recruitment and splinting Oxygenate better Decrease Work of breathing Increase intrathoracic pressure (good – dec. cardiac work; bad – may drop BP) BiPAP 2 pressures IPAP = 10 EPAP = 5 = PEEP = CPAP 10-5 = 5 cmH2O = Pressure support Pressure support => important for improving ventillation Better ventillation Decrease CO2 Decrease acidosis If high CO2 – increase IPAP and PS If low O2 – increase EPAP and FiO2 Remember if you increase EPAP without increasing IPAP => decrease Pressure support and decrease ventillation

Cardiogenic Pulmonary Oedema CPAP BiPAP Movement of lung water into interstitium + surfactant production Provides no clear advantage May increase rate of MI Recruits alveoli Sufactant production Reverses hypoxia Decreases VQ mismatch Reduces preload and afterload and myocardial catecholamine release increase in elastic recoil due to lung water and decreased surfactant Barrier to alveolar gas exchange Optimal CPAP pressure ?10cm H2O

COPD BiPAP recommended Number needed to treat to prevent death – 10 Both CPAP to recruit alveoli and IPAP to improve ventilation and decrease respiratory muscle work are useful Optimal settings Inspiratory support – 5-15 cm H2O CPAP – 4-8 cm H2O Increase incrementally to aid recruitment FiO2 titrated to lowest level to prevent hypoxia Primarily an increase in resistance to airflow – causes PEEPi Number needed to treat to prevent death – 10 Number needed to treat to prevent intubation – 4 Ram FSF, Picott J, etal. Noninvasive positive pressure ventilation for treatment of respiratory failure due to exacerbations of chronic obstructive pulmonary disease. Cochrane database of Systematic reviews 2004

Asthma Similar to COPD CPAP well established to be of benefit BiPAP has been shown to provide benefit but less well established Optimal settings CPAP – 5cm H2O in moderate to severe asthma BiPAP titrated settings over 30- 60 min FiO2 titrated to lowest level to prevent hypoxia

ARDS Little objective evidence High failure rate

Community Acquired pneumonia Intensive Care Medicine Journal 184 consecutive patients March 2012 NIV is more helpful if underlying cardiorespiratory disease Abandon NIV if after 1 hr: Higher heart rate Lower PaO2/FiO2 Lower bicarb

NOT SURE! Prepare patient!!! Take time to get the right mask Consider FiO2 needed Start at BiPap = 10/5 cm H2O or CPAP = 5 cm H2O Increase pressures by 2-3 cm H2O every 5-10m until satisfactory response – (max 15cm H2O)

68 yo man arrives at 6:30 am Awoke with SOB, mild chest pain Sweaty +++ Previous MI RR=40 Tripod posture Sats = 91% on NRB

CPAP At 5 cmH2O and FiO2= 25% O2 = 55 CO2 = 72

BiPAP I/E=12/6 FiO2 = 30% PaCO2= 72, PaO2 = 145 I/E=14/6 FiO2 = 24%

GETTING OFF NIV If patient condition improves markedly , NIV can be stopped abruptly Typical trial periods of 1 hr on 2 hrs off etc

When NOT to use NIV

Take home mesage If high CO2 : increase IPAP and PS If low O2 : increase EPAP and FiO2 PEEP=EPAP=CPAP + IPAP = BiPAP BPAP} BiPAP®} Bilevel => NIV <= CPAP = EPAP = PEEP BIPAP®} CPAP 1 pressure5-10cmH2O Prevent alveolar collapse Clear mucus Alveolar recruitment and splinting Oxygenate better Decrease Work of breathing Increase intrathoracic pressure (good – dec. cardiac work; bad – may drop BP) BiPAP 2 pressures IPAP = 10 EPAP = 5 = PEEP = CPAP 10-5 = 5 cmH2O = Pressure support Pressure support => important for improving ventillation Better ventillation Decrease CO2 Decrease acidosis If high CO2 – increase IPAP and PS If low O2 – increase EPAP and FiO2 Remember if you increase EPAP without increasing IPAP => decrease Pressure support and decrease ventillation