Anaesthetic machine

Anaesthetic Machine-ASTU

An anaesthetic machine. This particular machine is a "Flow-I" model, manufactured by Maquet, a division of Getinge Group, Getinge, Sweden.
Process type physical change
Industrial sector(s) anesthesia (medicine)
Main technologies or sub-processes vaporization
Feedstock inhalational anaesthetic agents, chiefly nitrous oxide and volatile anesthetics
Product(s) phase transition of feedstock from the liquid phase to the gas phase
Leading companies Leading companies using this industrial process
Main facilities hospitals and outpatient surgery centers
Inventor William T. G. Morton is widely credited for demonstrating the technique of vaporization of diethyl ether. However, many others were involved in its development. Please refer to History of general anesthesia article for more details.
Year of invention 16 October 1846

The anaesthetic machine (UK English) or anesthesia machine (US English) or Boyle's machine is used by anaesthesiologists, nurse anaesthetists, and anaesthesiologist assistants to support the administration of anaesthesia. The most common type of anaesthetic machine in use in the developed world is the continuous-flow anaesthetic machine, which is designed to provide an accurate and continuous supply of medical gases (such as oxygen and nitrous oxide), mixed with an accurate concentration of anaesthetic vapour (such as isoflurane), and deliver this to the patient at a safe pressure and flow. Modern machines incorporate a ventilator, suction unit, and patient monitoring devices.

The original concept of Boyle's machine was invented by the British anaesthetist Henry Boyle (18751941) in 1917. Prior to this time, anaesthetists often carried all their equipment with them, but the development of heavy, bulky cylinder storage and increasingly elaborate airway equipment meant that this was no longer practical for most circumstances. The anaesthetic machine is usually mounted on anti-static wheels for convenient transportation.

Simpler anaesthetic apparatus may be used in special circumstances, such as the TriService Apparatus, a simplified anaesthesia delivery system invented for the British armed forces, which is light and portable and may be used effectively even when no medical gases are available. This device has unidirectional valves which suck in ambient air which can be enriched with oxygen from a cylinder, with the help of a set of bellows. A large number of draw-over type of anaesthesia devices are still in use in India for administering an air-ether mixture to the patient, which can be enriched with oxygen. But the advent of the cautery has sounded the death knell for this device, due to the explosion hazard.

Many of the early innovations in U.S. anaesthetic equipment, including the closed circuit carbon-dioxide absorber (aka: the Guedel-Foregger Midget) and diffusion of such equipment to anaesthetists within the United States can be attributed to Richard von Foregger and The Foregger Company.

In dentistry a simplified version of the anaesthetic machine, without a ventilator or anaesthetic vaporiser, is referred to as a relative analgesia machine. By using this machine, the dentist can administer a mild inhalation sedation with nitrous oxide and oxygen, in order to keep his patient in a conscious state while depressing the feeling of pain.

Components of a typical machine

Simple schematic of an anaesthesia machine

A modern anaesthesia machine includes the following components:

Safety features of modern machines

Based on experience gained from analysis of mishaps, the modern anaesthetic machine incorporates several safety devices, including:

The functions of the machine should be checked at the beginning of every operating list in a "cockpit-drill". Machines and associated equipment must be maintained and serviced regularly.

Older machines may lack some of the safety features and refinements present on newer machines. However, they were designed to be operated without mains electricity, using compressed gas power for the ventilator and suction apparatus. Modern machines often have battery backup, but may fail when this becomes depleted.

The modern anaesthetic machine still retains all the key working principles of the Boyle's machine (a British Oxygen Company trade name) in honour of the British anaesthetist Henry Boyle. In India, however, the trade name 'Boyle' is registered with Boyle HealthCare Pvt. Ltd., Indore MP.

A two-person pre-use check (consisting of an anaesthetist and an operating department practitioner) of the anaesthetic machine is recommended before every single case and has been shown to decrease the risk of 24-hour severe postoperative morbidity and mortality.[1] Various regulatory and professional bodies have formulated checklists for different countries.[2] A free transparent reality simulation of the checklist recommended by the United States Food & Drug Administration is available from the Virtual Anesthesia Machine web site ( see below) after registration which is also free. Machines should be cleaned between cases as they are at considerable risk of contamination with pathogens.[3]

Anesthesia machine vs anesthesia cart

An anaesthetic machine

The Anesthesia machine contains mechanical respiratory support (ventilator) and O2 support as well as being a means for administering anesthetic gases which may be used for sedation as well as total anesthesia. An anesthesia cart holds extra IV push meds for anesthesia, sedation and reversal, extra equipment that the person giving anesthesia/sedation might need, and the hardware for respiratory support and resuscitation.

See also


  1. Arbous; et al. (2005). "Impact of anesthesia management characteristics on severe morbidity and mortality". Anesthesiology. 102 (2): 257–68; quiz 491–2. doi:10.1097/00000542-200502000-00005. PMID 15681938.
  3. Baillie, JK; P. Sultan; E. Graveling; C. Forrest; C. Lafong (2007). "Contamination of anaesthetic machines with pathogenic organisms". Anaesthesia. 62 (12): 1257–61. doi:10.1111/j.1365-2044.2007.05261.x. PMID 17991263.

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