Secondary Logo

Journal Logo


Checking the anaesthesia machine

Scott, David H.T.

Author Information
European Journal of Anaesthesiology: February 2021 - Volume 38 - Issue 2 - p 193-194
doi: 10.1097/EJA.0000000000001310
  • Free


Grüßer et al.1 are to be congratulated on highlighting the importance of checking all aspects of anaesthetic equipment before attaching the equipment to patients. As equipment gets more and more complicated it is increasingly easy to make a mistake in setting up breathing systems. If such mistakes are not detected before the patient is attached to the machine, some of the patients die.2

When I first gave an anaesthetic in 1970, there were many connectors with different diameters. Starting the day involved a hunt to get enough adaptors to fit together a working circuit with a respiratory monitor. There were 15, 22, 23-mm connectors, imperial connectors, tapered connectors, bulbous connectors, barbed connectors and many more. Most of the tubing was rubber and the elastomeric waterproof tape ‘sleek’ was a vital part of the connection systems.

Industry, clinicians and regulatory bodies have worked hard to standardise anaesthetic and respiratory systems and reduce the chances of cross-connectivity with other types of tubing such as feeding tubes, intravascular tubing and blood pressure cuffs.

Most breathing tube connectors in current adult practice are standardised to 22 or 15 mm connectors. Sensible design of equipment places the connections for the reservoir bag well away from the inspiratory and expiratory ports. Scavenging tubing has 30-mm connections.

ISO TC 121 is the International Organisation for Standardisation committee for Anaesthetic and Respiratory equipment. The committee was made aware of the several cases in which a problem of the accidental shortcut of respirator tubes at the level of water traps occurred. As the problem gets wider publicity, more and more cases have been reported. Several solutions have been discussed. The two-bag test has been in use in the United Kingdom for many years. I was taught it in the 1970s and it is enshrined in the Association of Anaesthetist's Safety Guideline ‘Checking Anaesthetic Equipment 2012’.3

Two-bag test

A two-bag test should be performed after the breathing system, vaporisers and ventilator have been checked individually.

  • (1) Attach the patient-end of the breathing system (including angle piece and filter) to a test lung or bag.
  • (2) Set the fresh gas flow to 5 l min−1 and ventilate manually. Check the whole breathing system is patent and the unidirectional valves are moving (if present).
  • (3) Check the function of the adjustable pressure limiting (APL) valve by squeezing both bags.
  • (4) Turn on the ventilator to ventilate the test lung. Turn off the fresh gas flow or reduce to a minimum. Open and close each vaporiser in turn.

There should be no loss of volume in the system.

Breathing systems should be protected with a test lung or bag when not in use to prevent intrusion of foreign bodies.

Earlier adoption of the two-bag test throughout Europe would have avoided the problems highlighted by the authors of the editorial. I found it particularly helpful transferring patients from Cardiac Theatres to ICU to find the ventilator already puffing away on a reservoir bag. There was no need to remember to switch on the ventilator.

Acknowledgements relating to this article

Assistance with the letter: none.

Financial support and sponsorship: none.

Conflicts of interest: none.


1. Grüßer L, Staender S, Rossaint R. Safety first: checking the anaesthesia machine. Eur Anaesthesiol 2020; 37:837–838.
2. The Guardian newspaper. ‘Neglect’ behind operation death [Accessed 17 August 2020].
3. Association of Anaesthetists of Great Britain and Ireland. Checking anaesthetic equipment 2012. Anaesthesia 2012; 67:660–668.
Copyright © 2020 European Society of Anaesthesiology and Intensive Care. Unauthorized reproduction of this article is prohibited.