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The nasal cannula is another way of delivering oxygen to a patient. They are simple devices that connect to the constant flow outlet of an oxygen cylinder and then the two small plastic prongs are placed into the nostrils.

Nasal cannulas are easy ways of delivering a lower concentration of oxygen at 24 to 44% depending on the flow rate of the oxygen and the amount the patient is breathing through their nose and how much they are speaking. Generally, it is difficult to gain oxygen concentrations over 30 to 35%. 

Nasal cannulas can only be given to patients who can breathe freely through their nose. They are usually tolerated well since they are not found to cause distress that a standard mask causes. The nasal cannula is only useful for patients who would benefit from a low concentration of oxygen. The maximum flow rate that you should use is 6 litres a minute at any higher rate would cause problems and discomfort.

The flow rate compared to an Oxygen concentration is as follows:

  • 1 litre per minute - 24%
  • 2 litres per minute - 28%
  • 3 litres per minute - 32%
  • 4 litres per minute - 36%
  • 5 litres per minute - 40%
  • 6 litres per minute - 44%

Nasal cannulas are not really used in first aid or out-of-hospital emergency treatment since a higher concentration of oxygen is usually required in those circumstances.