High Flow oxygen delivery devices are also called as fixed performance devices because their performance is not affected by changes in patient’s tidal volume and respiratory rate and therefore deliver accurate oxygen concentration. High Flow oxygen devices are more effective in treating hypoxemia then low flow systems.
Disadvantages of High Flow oxygen devices are:
a. Low patient acceptance (due to high flow).
b. Increased cost (again due to high flow).
These work on Venturi principle which states that if a gas is passed through a narrow orifice at high pressure it creates shearing forces around the orifice which entrain room air in specific ratio.
The inspiratory gas flows should be 3 to 4 times of minute volume.
The capacity of bag should be more than the patient tidal volume. The bag should be made anti- static (not effected by electric current produced by gas flow).
These High Flow oxygen devices deliver accurate inspired oxygen (Fio2) [error is only 1 to 2 %]. High flow system includes:
i. Venturi-mask: These are most commonly used high flow systems and are available in different colors. So the maximum oxygen that can be delivered by a venturi mask is 60%.
|Colour||Flow rate of 02|
(litre per mm.)
Other High Flow oxygen devices available are
ii. Air entertainment nebulizers, There are special high flow nebulizers.
iii. High flow air-oxygen blunders.
iv. Bag & mask ventilation is also considered as High Flow oxygen device.