Anesthesia Machine..Part3..The Pressures

The machine components can also be logically conceptualized by the amount of pneumatic pressure they are exposed to:

1. The High-pressure circuit consists of those parts which receive gas at cylinder pressure
   • hanger yoke (including filter and unidirectional valve)
   • yoke block
   • cylinder pressure gauge
   • cylinder pressure regulators
2. The Intermediate pressure circuit receives gases at low, relatively constant pressures (37-55 psi, which is pipeline pressure, or the pressure downstream of a cylinder regulator)
   • pipeline inlets and pressure gauges
   • ventilator power inlet
   • Oxygen pressure-failure device (fail-safe) and alarm
   • flowmeter valves
   • oxygen and nitrous oxide second-stage regulators
   • oxygen flush valve
3. The Low-pressure circuit includes components distal to the flowmeter needle
   • valves
   • flowmeter tubes
   • vaporizers
   • check valves (if present)
   • common gas outlet