ANAESTHETIC MACHINE

Typical Number in Hospital: 40

Cost Bands: 4

References: 2

Sometimes referred to as the anaesthetic trolley, this normally refers to a trolley on which are mounted gas cylinders and/or pipelines for various gases used in anaesthesia, together with the various valves, controls and ancillary equipment used by the anaesthetist.

These are found in all operating theatres and also in special procedure rooms in the X-ray department, accident and emergency unit, dental clinics and some community clinics. On the trolleys, the gases can be dispensed and mixed. These usually include oxygen, nitrous oxide and carbon dioxide, and sometimes medical air, cyclopropane and anaesthetic vapours such as halothane, ether, etc. The vapours are usually provided in special vaporizers which may be interchangeable according to the particular anaesthetic procedure required.

Simpler machines may also be referred to as anaesthetic machines which only dispense a mixture of nitrous oxide and oxygen. These may be controllable devices such as the Walton 5 or operate from premixed bottled gases (Entonox unit). These latter may be used either on the ward or as a portable unit in ambulances or by district midwives. An anaesthetic machine may also be used in conjunction with, or be incorporated into, a ventilator.

The maintenance of such equipment requires especially formal arrangements and quality control measures, since incorrect operation may cause permanent injury to the patient.

The main components of an anaesthetic machine are high- pressure gas reservoirs and/or pipelines, pressure reducing valves, flowmeters (usually of the rotameter type), pressure gauges, carbon dioxide absorbers, a fresh gas outlet, oxygen flush assembly, and vaporizers. The trolley may also carry monitoring equipment such as ECG and pressure monitors, oxygen meters, oscillotonometer, temperature gauges and pulse monitors, and a Wright's respirometer. Some modern ventilators are also carried on the trolley and become an integral part of the anaesthetic circuit when in use. Other important parts of the system are the suction apparatus and gas scavenging devices.