Microbiological risk of anaesthetic breathing circuits after extended use

Daily change of breathing circuits in the operating theatre requires a lot of resources and is time and labour consuming. The extended use of breathing circuits could reduce the workload of the staff and health care costs. The aim of the present study was to evaluate the contamination rate of anaesthesia breathing circuits changed after 24, 48 or 72 h of use.

The study was performed as an experimental observational study. Microbiological samples were taken from 112 breathing systems including both parts of the ventilator circuit (inspiration and expiration) and analysed using microbiological standard techniques. Breathing circuits were changed according to three different schedules. In the 24-h group, breathing circuits were changed every day, whereas in the 48-h group changing of the circuits took place on Mondays, Wednesdays and Fridays. A period of 72 h operating use was tested on weekends.

A total of 112 breathing systems comprised of 224 samples from the ventilator circuit were tested for bacteria and yeast contamination. A non-significant increase in the contamination rate was observed with the extended use for breathing circuits (24 h: 3.33%, 48 h: 4.35% and 72 h: 5.56%; P for trend=0.66). Similarly, no significant increase in contamination rate could be observed at the sample level (24 h: 1.67%, 48 h: 3.26% and 72 h: 2.78%; P for trend=0.71).

The extended use of breathing circuits for 48 and 72 h does not increase significantly the risk of contamination, provided that HME filters are changed separately for every patient.