07/18/2022
Did you know that the cleaning of breathing system tubing cannot be supported by current literature?
Most of the breathing systems used in veterinary medicine are designed for single use in human medicine, therefore there are no official guidelines on how to clean these.
But there is good news! Due to the high concentrations of oxygen that are used with everyday anaesthesia, this is actually bactericidal itself (du Moulin and Hedley-Whyte 1982). Also, let’s take a step back here and appreciate that a lot of the bugs in respiratory moisture do not survive when they dry out anyway. The same study by du Moulin and Hedley-Whyte found that during “quiet breathing”, which is differentiated from forceful exhalation during forceful speech or coughing etc, no airway bacteria actually leaves the patient’s airway! Additionally, most respiratory bacteria colonise themselves in the nose or pharynx, not from deep within the airway structure – plus, you need a lot of it to infect another patient anyway. Honestly, I am LOVE with this study, I could snack on the fun-facts all day.
Interestingly, this leads to the conclusion that routine use of a bacterial filter or a sterilised breathing system in veterinary medicine cannot be supported by current evidence (Pelligand et al. 2007). You’ll see a very key word here – routine. So if there is a risk that a patient has a contagious respiratory infection, just in case, the breathing system should be disposed of or reliable bacterial or viral filters could be used e.g. in cases of Feline Infectious Peritonitis, Bordetella bronchiseptica etc. Viral filters are proven to ensure the virus stays with the patient and doesn’t move into the breathing system (Dubler et al., 2016).
If the breathing systems are cleaned with misc disinfectants, this may actually put the patient at risk of inhaling dried chemical residue which can lead to airway irritation. If you do wish to clean your breathing system tubing, just use hot soapy water to clean any gross material from the outside (like blood or prophy paste) otherwise use the appropriate type of chemical cleaner for the type of tubing material you have – and you must hang this to dry in a clean area itself (Barry et al., 1984).
But what about circle systems I hear you say? Well, the soda lime reaction with carbon dioxide is in a bactericidal alkaline pH of 11-14 and also there are still environments of high concentrations in oxygen as well as humidity shifts that the bugs cannot bear. In saying this – the job of soda lime is not to be a true barrier for bacteria or viruses, so it shouldn’t be relied on completely but the food for thought is satisfying.
Ya gal loves a bit of evidence.
Let’s get lit:
Barry, A., Noble, M., Marrie, T. and Paterson, I., 1984. Cleaning of anaesthesia breathing circuits and tubings: A Canadian survey. Canadian Anaesthetists’ Society Journal, 31(5), pp.572-575 - https://link.springer.com/article/10.1007/BF03009546
Dubler, S., Zimmermann, S., Fischer, M., Schnitzler, P., Bruckner, T., Weigand, M., Frank, U., Hofer, S. and Heininger, A., 2016. Bacterial and viral contamination of breathing circuits after extended use - an aspect of patient safety?. Acta Anaesthesiologica Scandinavica, 60(9), pp.1251-1260 - https://pubmed.ncbi.nlm.nih.gov/27470996/
du Moulin, G., Hedley-Whyte, J. (1982) "Bacterial Interactions between Anesthesiologists, Their Patients, and Equipment", Anesthesiology, 57(1), p. 37-41 - https://pubmed.ncbi.nlm.nih.gov/7046515/
Pelligand, L., Hammond, R., Rycroft, A. (2007) "An investigation of the bacterial contamination of small animal breathing systems during routine use", Veterinary Anaesthesia and Analgesia, 34(3), p. 190-199 - https://pubmed.ncbi.nlm.nih.gov/17444932/
