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Low-pressure Gas Supply

The low pressure gas supply carries gas from the regulator to the flowmeters, quick-flush and ventilator at a pressure of 50 psi. It may take the form of:

  • Hard-plumbing, usually copper pipe and compression connectors.
  • Flexible hose.

Correct identification of the gas being supplied to the patient remains vital. This may be achieved by:

  • Color-coding of pipework and hoses.
  • Gas-specific connectors used on the hose running from remote cylinders to the anesthetic machine.

Several different quick-connect systems are available that enable rapid disconnection and re-connection of the anesthetic machine from a central piped gas supply.


  • Leaks in the low pressure gas supply are quite common and should be repaired as soon as possible.
  • Fires and explosions may be caused by the oxidizing ability of oxygen and nitrous oxide: no grease must used in the threads of the valves or connectors.
  • Cross-connection of gas hoses is potentially lethal, but should be prevented by use of the correct, gas-specific connectors.
       This problem is most likely to occur in veterinary practices that attempt to economize by using inexpensive compressed air fittings for both oxygen and nitrous oxide. This practice is very dangerous.
  • Hypoxic gas mixtures
    Most modern machines incorporate some form of device to prevent it from supplying a hypoxic gas mixture if the oxygen supply fails. This shuts off the other gases (such as nitrous oxide) when the pressure in the oxygen line falls.

Some machines also incorporate an audible low oxygen pressure alarm.


Comments on this article should be addressed to Dr Guy Watney
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