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The venturi mask, also known as an air-entrainment mask (and sometimes by the brand name Ventimask®), is a medical device to deliver a known oxygen concentration to patients on controlled oxygen therapy. The mask was invented by Moran Campbell as a replacement for intermittent oxygen treatment, a practice he described as "bringing a drowning man to the surface- occasionally".
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 therapy. The kits usually include multiple jets in order to set the desired FiO2 which are usually color-coded.
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 venturi effect.
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.
As a rule of thumb, 60 L/min is considered the minimum flow rate to qualify as a high flow device.