Nasal Cannulas are used for their simplicity and patient compliance in delivering supplementary oxygen. Ambient air is entrained through the nostrils, with the FiO2 achieved being proportional to the flow rate of oxygen (1-6 l/min), the patient’s tidal volume, inspiratory flow rate, and 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 Cannulas prevent rebreathing and are comfortable for long periods.
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