collapsible bellows In these systems, a bellows is contained within a closed chamber

Anesthesia machines are equipped with mechanical ventilators that employ several different mechanisms to deliver gases to the patient. Conventional anesthesia machines are fitted with a mechanical ventilator that uses a collapsible bellows. In these systems, a bellows is contained within a closed chamber. The bellows is compressed when oxygen or air is directed into the chamber outside the bellows. Compressing the bellows causes the pressure in the breathing system to rise. Bellows ventilators come in two types: (1) ascending bellows that are attached to the bottom of their chamber and rise during exhalation, and (2) descending bellows that are attached to the top of their chamber and fall during exhalation. Draeger anesthesia machines typically use a piston to directly compress gas within the system, though one Draeger machine, the Perseus, uses a turbine fan to generate gas pressure within the system. Getinge anesthesia machines use a novel system where oxygen is metered directly into the breathing system to generate increased pressure. The oxygen is added to the system near the scavenger, and it is separated from the rest of the breathing system by a large dead space to prevent the composition of the inhaled gases from being affected. Although gas-driven ventilators can be safely driven with either oxygen or air, most often oxygen is chosen and is supplied by pipeline. Cylinder gases can be used to drive the ventilator in the event of pipeline failure. If the machine is set up to drive the ventilator using cylinder oxygen, mechanical ventilation should be discontinued in the event of pipeline failure to conserve oxygen in the cylinder.