Anaes · The anaesthetic machine
The anaesthetic machine
Also known as Anaesthetic machine · Anaesthesia workstation · Gas delivery system · Circle system · Pre-use check · Vaporiser
The anaesthetic machine for the fellowship exams: the gas supply (pipeline and cylinder), the Thorpe-tube flowmeters, the hypoxic guard and its limits, the oxygen flush, the circle breathing system, scavenging, and the AAGBI 2012 pre-use check.
Checked against its sources on 23 Oct 2026
Practise this topic
On this page
Study tools
Your progress
Saved on this device.
Target exams
Red flags
- Failure to check the anaesthetic machine and/or the breathing system features as a major contributory factor in many anaesthetic misadventures, including some that have resulted in hypoxic brain damage or death. A self-inflating bag must be immediately available in any location where anaesthesia may be given.
Meet the patient
A 45-year-old woman is anaesthetised for a cholecystectomy. Ten minutes after induction the oxygen pipeline pressure alarm sounds and the ventilator bellows collapses. The early use of an alternative means of ventilation (a self-inflating bag that does not rely on a source of oxygen to function) may be life-saving.[1]
The two questions the machine exists to answer: is the gas I am delivering what I think it is? (the flowmeters, the vaporiser, the agent analyser) and is it reaching the patient safely? (the breathing system, the valves, the scavenging). The pre-use check answers both before the patient arrives — never start an anaesthetic without it.[1]
References12ShowHide
- [1]Hartle A, Anderson E, Bythell V, et al. Checking anaesthetic equipment 2012: association of anaesthetists of Great Britain and Ireland Anaesthesia, 2012.PMID 22563957
- [2]Parthasarathy S The closed circuit and the low flow systems Indian J Anaesth, 2013.PMID 24249885
- [3]Tiviraj S, et al. Development of An Assessment Test for An Anesthetic Machine J Med Assoc Thai, 2016.PMID 27501622
- [4]Das S, Chattopadhyay S, et al. The anaesthesia gas supply system. Indian J Anaesth, 2013.PMID 24249882
- [5]De Cooman S, Schollaert C, et al. Hypoxic guard systems do not prevent rapid hypoxic inspired mixture formation. J Clin Monit Comput, 2015.PMID 25270987
- [6]Pauling M, Ball CM Delivery of anoxic gas mixtures in anaesthesia: case report and review of the struggle towards safer standards of care. Anaesth Intensive Care, 2017.PMID 28675797
- [7]Lauber R, Steiner A, et al. Accuracy, alarm limits and rise times of 12 oxygen analysers. Anaesthesia, 1994.PMID 7864324
- [8]Srivastava U Anaesthesia gas supply: gas cylinders. Indian J Anaesth, 2013.PMID 24249883
- [9]Goneppanavar U, Prabhu M Anaesthesia machine: checklist, hazards, scavenging. Indian J Anaesth, 2013.PMID 24249887
- [10]Garg R, Gupta RC Analysis of oxygen, anaesthesia agent and flows in anaesthesia machine. Indian J Anaesth, 2013.PMID 24249881
- [11]Mehta SP, Eisenkraft JB, Posner KL, Domino KB Patient injuries from anesthesia gas delivery equipment: a closed claims update. Anesthesiology, 2013.PMID 23835591
- [12]Feldman JM, Hendrickx J, Kennedy RR Carbon Dioxide Absorption During Inhalation Anesthesia: A Modern Practice. Anesth Analg, 2021.PMID 32947290