Anesthesia breathing circuits protected by the DAR Barrierbac S® breathing filter have a low bacterial contamination rate

In order to reuse the same anesthesia breathing circuit for more than one patient, it has been proposed to add a breathing filter between the Y-piece and the artificial airway. The purpose of this study was to evaluate the in vivo bacterial filtration efficacy of an anesthesia filter in a usual clinical anesthesia setting. A sterile DAR Barrierbac S breathing filter was inserted at the Y-piece of a sterile single-use anesthesia breathing circuit before induction of general anesthesia. At the end of anesthesia, the breathing circuit connector of the filter and of the endotracheal tube connector were cultured separately on growth media (chocolate and blood agar). These were incubated for 48 hr and bacterial identification was conducted using standard methods. Bacterial cultures were negative on both sides of the filter membrane of 1842 of the 2001 filters studied. Cultures were positive on the patient side of 104 filters. In two of those, the same bacteria were found on both the circuit side and the patient side of the filter. Therefore these data indicate a clinical effectiveness of 99.9% (confidence interval, CI 95%, 99.6-99.998%), and an in vivo filtration efficacy of 98.08% (CI 95%, 92.54-99.67%). Using the upper limit of the CI, it can be assumed that the practice of using a sterile DAR Barrierbac S breathing filter for every patient while reusing the anesthesia breathing circuit would result in a cross contamination rate of the breathing circuit lower than once every 250 cases.