Scavenging Systems

Case Synopsis

A 25-year-old man with no significant medical history presents for tonsillectomy. After induction of anesthesia and tracheal intubation, anesthesia was maintained using a mixture of O ₂ /N ₂ O/isoflurane at a total fresh gas flow (FGF) of 6 L/min. The patient was breathing spontaneously from a circle breathing system. At the request of the surgeon, the anesthesia machine was moved a little to the side, after which the breathing circuit reservoir bag became increasingly distended. Opening of the adjustable pressure limit (APL or “popoff”) valve maximally failed to decrease the pressure in the bag. The breathing circuit needed to be intermittently disconnected from the anesthesia machine to relieve the pressure. When the FGF was decreased to 2 L/min, intermittent disconnections of the circuit became necessary less frequently. A hissing sound was audible arising from the closed reservoir waste gas scavenging system interface, and the interface reservoir bag was noted to be completely collapsed.