title: Passage of pathogenic microorganisms through breathing system filters used in anaesthesia and intensive care.
abstract: Invasive ventilation poses a risk of respiratory infection that can be drug-resistant. One means of reducing transmission of infection is the use of a breathing system filter. Filters are intended to be used with dry gas. Current international standards do not require that filters prevent bacterial transfer when wet. It is not known whether microorganisms pass through wet filters, but theory predicts that this might occur. We tested six filters from three different manufacturers. We passed a suspension of microorganisms through the filters using the least pressure necessary, and incubated a sample of the filtrate on blood agar. All the filters tested allowed free passage of both Candida albicans and coagulase-negative staphylococci. The median (IQR [range]) pressure required for fluid to flow across the filter varied greatly between different filter types (20 (0-48 [0-138]) cmH(2)O). We conclude that even large microorganisms pass across moist breathing system filters in conditions that are found in clinical practice.
authors.affiliation: Department of Anaesthesia, Critical Care and Pain Medicine, University of Edinburgh, Royal Infirmary of Edinburgh, Edinburgh, UK. david.scott@ed.ac.uk
authors.forename: D H T
authors.initials: DH
authors.lastname: Scott
authors.forename: S
authors.initials: S
authors.lastname: Fraser
authors.forename: P
authors.initials: P
authors.lastname: Willson
authors.forename: G B
authors.initials: GB
authors.lastname: Drummond
authors.forename: J K
authors.initials: JK
authors.lastname: Baillie
mesh_terms: D000776:Anesthesiology / Q000295:instrumentation*; D002176:Candida albicans / Q000302:isolation & purification; D003422:Critical Care; D003428:Cross Infection / Q000517:prevention & control / Q000635:transmission*; D004866:Equipment Contamination / Q000517:prevention & control; D005374:Filtration / Q000295:instrumentation* / Q000592:standards; D006801:Humans; D006813:Humidity; D008422:Materials Testing / Q000379:methods; D012121:Respiration, Artificial / Q000295:instrumentation*; D012141:Respiratory Tract Infections / Q000517:prevention & control / Q000635:transmission*; D013210:Staphylococcus / Q000302:isolation & purification