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

Purpose: In order to reuse the same anesthesia breathing circuit for more t han 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 evalua te the in vivo bacterial filtration efficacy of an anesthesia filter in a u sual clinical anesthesia setting. Methods: A sterile DAR Barrierbac SO breathing filter was inserted at the Y -piece of a sterile single-use anesthesia breathing circuit before inductio n of general anesthesia. At the end of anesthesia, the breathing circuit co nnector 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 method s. Results: Bacterial cultures were negative on both sides of the filter membr ane of 1842 of the 2001 filters studied. Cultures were positive on the pati ent side of 104 filters. In two of those, the same bacteria were found on b oth the circuit side and the patient side of the filter. Therefore these da ta indicate a clinical effectiveness of 99.9% (confidence interval, Cl 95%, 99.6-99.998%), and an in vivo filtration efficacy of 98.08% (CI 95%, 92.54 -99.67%). Conclusion: Using the upper limit of the Cl, it can be assumed that the pra ctice of using a sterile DAR Barrierbac SO breathing filter for every patie nt while reusing the anesthesia breathing circuit would result in a cross c ontamination rate of the breathing circuit lower than once every 250 cases.