Nasal Cannula

Nasal Cannulae are used for their simplicity and patient convenience.

There is entrainment of air through the nostrils.

The LPM achieved is proportional to

a) the flow rate of oxygen (1-6 l/min),

b) the patients tidal volume, inspiratory flow rate and

c) the volume of the nasal pharynx.

Mouth breathing causes inspiratory air flow which produces a venturi effect in the posterior pharynx entraining oxygen from the nose