Fig. 3. Diagram showing the principle of fresh gas decoupling (FGD). During positive-pressure ventilation, the ventilator and the inspiratory part of the internal circuitry are decoupled from the fresh gas flow in inspiration. Thus, fresh gas passes to the reservoir bag  via the carbon dioxide absorber in inspiration and is subsequently fed directly into the breathing system together with the stored volume  via a nonreturn valve (fresh gas decoupling valve) in expiration. PAW = airway pressure. 