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 400 kPa. It may take the form of:

 Hard plumbing, usually copper pipe and compression connectors
 Flexible hose

Identification

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

 Colour coding of pipework and hoses
 Gas-specific connectors used on the hose running from remote cylinders to the anaesthetic machine

Quick connectors

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

Some common hose end fittings

Hazards

 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 oxidising ability of oxygen and nitrous oxide: no grease may be 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
 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. 


(O₂ pressure >200 kPa)  (O₂ pressure <200 kPa)
 
Some machines also incorporate an audible low oxygen pressure alarm.