- Venturi mask
The venturi mask, also known as an air-entrainment mask, is a
medical deviceto deliver a known oxygenconcentration to patients on controlled oxygen therapy. Venturi masks are considered high-flow oxygen therapy devices. This is because venturi masks are able to provide total inspiratory flow at a specified FIO2 to patients itherapy. The kits usually include multiple jets in order to set the desired FIO2 which are usually color coded. The color of the device reflects the delivered oxygen concentration, for example: blue = 24%; white = 28%; orange = 31%; yellow = 35%; red = 40%; green = 60%. The color however varies with different brands and the user must check the instructions to determine the correct color for the desired FIO2.
Other brands of masks have a rotating attachment that controls the air entrainment window, affecting the concentration of oxygen. This system is often used with air-entrainment nebulizers to provide humidification and oxygen therapy.
The mechanism of action depends on the
Air entrainment masks, although considered high flow systems, are not always able to guarantee the total flow with oxygen percentages above 35% in patients with high inspiratory flow demands. The problem with air entrainment systems is that as the FIO2 is increased, the air to oxygen ratio decreases. For example, for 30% the ratio is 8 parts air to 1 part oxygen. For 40% the ratio decreases to 3 to 1. Since the jets in venturi masks generally limit oxygen flow at 12 to 15 liters per minute the total flow decreases as the ratio decreases. At an oxygen flow rate of 12 liters per minute and a 30% FIO2 setting, the total flow would be 108 L/min. At a 40% FIO2 setting, the total flow would decrease to 48 L/min. As a rule of thumb, 60 L/min is considered the minimum flow rate to qualify as a high flow device. [Egan's Fundamentals of Respiratory Care, Eighth Edition, Page 841, Mosby, Inc., 2003.]
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