rebreathing

rebreathing /rēbrē″thing/ [L, re + AS, braeth, breath] , breathing in a closed system. Exhaled gas mixes with the gas in the system, and some of this mixture is then reinhaled. Rebreathing, which may result in progressively decreasing concentrations of oxygen and progressively increasing concentrations of carbon dioxide in the blood, can occur in poorly ventilated environments.