Components of a typical machine

Simple schematic of an anaesthesia machine

A modern machine typically includes the following components:

connections to piped hospital oxygen, medical air, and nitrous oxide. Pipeline pressure from the hospital medical gas system (wall outlet) should be around 400 kPa (60 psi; 4 atmospheres).

reserve gas cylinders of oxygen, air, and nitrous oxide attached via a specific yoke with a Bodok seal. Older machines may have cylinder yokes and flow meters for carbon dioxide and cyclopropane. Many newer machines only have oxygen reserve cylinders. The regulators for the cylinders are set at 300 kPa (45 psi; 3 atmospheres). If the cylinders are left on and the machine is plugged into the wall outlet, gas from the wall supply will be used preferentially, since it is at a higher pressure. In situations where pipeline gases are not available, machines may safely be used from cylinders alone, provided fresh cylinders are available.

a high-flow oxygen flush which provides pure oxygen at 30 litres/minute

pressure gauges, regulators and ‘pop-off’ valves, to protect the machine components and patient from high-pressure gases (referred to as ‘barotrauma’).

flow meters (rotameters) for oxygen, air, and nitrous oxide, which are used by the anaesthesiologist to provide accurate mixtures of medical gases to the patient. Flow meters are typically pneumatic, but increasingly electromagnetic digital flow meters are being used. Read the rest of this entry »

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