Extrinsic Positive End-Expiratory Pressure due to Failure of the Positive-Pressure Relief Valve Within the Scavenging System: A Case Report.

The anesthesia gas scavenging system (AGSS) removes waste gases from the anesthesia machine. Within the AGSS, safety features prevent excessive pressures from affecting ventilation. Although the literature contains reports describing failures of the AGSS, we found no reports of positive-pressure relief valve (PPRV) malfunctions. We encountered 2 cases of extrinsic positive end-expiratory pressure (PEEP) resulting from a malfunctioning PPRV. Both cases suffered delayed identification intraoperatively but patients did not experience postoperative complications. These cases highlight the importance of daily scavenger system prechecks, the potential physiologic implications of AGSS malfunctions, and the importance of preplanned contingencies for machine failure.