a device used in respiratory therapy that applies the Coanda effect to the movement of the flow of air or gases. As the airstream passes a wall, a pocket of turbulence forms a low-pressure bubble next to the wall, causing the airstream to adhere to the wall. As a gas travels faster over the pocket of turbulence, the surrounding gas molecules not in the stream acquire a higher pressure, holding the stream against the wall. The gas flow tends to remain in that pattern until it is diverted by a different input pressure. See also Coanda effect.