[Breathing filters in hospital, COVID first-wave experience]

During the coronavirus pandemic, breathing filters have been essential in the medical care of infected patients. The worldwide demand caused a disruption in the supply, which led to a multiplication of the references used. The lack of formation available on the subject was an impediment for pharmacists (buyer, medical devices, intensive car unit) and it appears to be necessary to redact a formation about those filters, from the experience acquired during the sanitary crisis. Multiple breathing filters references exist which may be classify according to their filtration mechanism (mechanical filtration or electrostatic filtration) and by the eventual presence of a humidifying action (Heat and Moisture Exchangers; hydrophobic, hygroscopic, or mixed). In anaesthesia, the use of pure mechanical filter is preferred; in resuscitation unit, heat and moisture exchangers filter or simple filter plus heated humidifier are used. During the COVID-19 pandemic, the filters duration of use has been lengthened to limit the disruption risk.