Nasal Cannulae are used for their simplicity and patient convenience. There
is entrainment of ambient air through the nostrils. The FiO2 achieved is
proportional to a) the flow rate of oxygen (1-6 l/mni), b) the patients tidal
volume, inspiratory flow rate, and c) the volume of the nasal pharynx.
At an oxygen flow rate of 2 l/min the oxygen concentration in the hypopharynx
of a resting person is 25% – 30%. Nasal Cannula prevents Rebreathing and are
comfortable for long periods.
There is increased patient compliance with nasal cannula as patients are able
to speak, eat or drink. Local irritation and dermatitis may occur with high flow
rates. Use of humidified oxygen is recommended to reduce dryness of the mucosal
wall in the nasal cavities, particularly when using flows of greater than 4
l/min.
