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.