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Types of NIV
CPAP = continuous positive airway pressure
Tight fitting mask which delivers fixed positive air pressure to keep the airways open
Similar to CPAP, but the air pressure increases during the patientβs inspirations
ePAP = pressure during expiration
iPAP = pressure during inspiration
Pressure support = difference in pressure between ePAP and iPAP (i.e. the amount of βhelpβ given on inspiration)
Indication: type 2 respiratory failure (e.g. COPD exacerbation) with acidosis (pH<7.35) or exhaustion despite optimal medical therapy
NB. The oxygen concentration in the air can be adjusted because tubing from an oxygen supply can plug directly into the machine
Background physiology
Hypercapnia
Hypoxia
Settings
CPAP
Start at 4cmH2O and gradually increase to reduce hypoxia
Maximum of 12cmH2O
Start with high FiO2 and titrate down
BiPAP
Start at 15/3cmH2O (i.e. iPAP of 15cmH2O, ePAP of 3cmH2O) and gradually increase iPAP to 20-30cmH2O as tolerated to optimise respiratory rate, chest expansion and tidal volumes (6-8ml/kg ideal body weight)
Maximum of 30/8cmH2O
Increase iPAP to reduce hypercapnia and achieve normal pH
Titrate FiO2 to reach target oxygen saturations (88-92% or PaO2~8)