Introduction PEEP valves are used to provide a preset positive end-expiratory pressure (PEEP) together with self-inflating bags (SIB). It has recently been shown that such valves may deliver unreliable PEEP. We hypothesized that material fatigue due to repeated thermo-sterilization was responsible for decreasing reliability of PEEP valves.
Methods Laboratory study of 10 factory new PEEP valves. Valves were tested before (measurement 1) and after 10, 20 and 30 (measurements 2, 3, 4) cycles of routine thermo-sterilization for 7 min at 134°C by using a neonatal lung model (compliance 0.2ml*kPa-1). Settings were: peak inspiratory pressure (PIP)=20 and 40cm H2O, PEEP=5 and 10cm H2O, respiratory rate=40 and 60/min, flow=8l/min. PEEP was recorded using a respiratory function monitor.
Results Before thermo-sterilization, a mean (SD) PEEP of 4.0 (0.9) and 7.7 (1.0)cm H2O was delivered by the 10 valves when set to 5 and 10cmH2O, respectively. One new valve only delivered 2.0 (0.0) and 5.0 (0.0)cm H2O. Four of the 10 investigated valves showed relevant variations in PEEP (CV>10%) throughout the thermo-sterilization process. Valve No. 8 completely lost its function after the second cycle of thermo-sterilization. 6/10 valves maintained the ability to provide PEEP despite repeated autoclavation. Some valves showed tears or displacement of the rubber seal.
Conclusion The reliability of PEEP valves is affected by repeated thermo-sterilization. Valves should be tested before each use and substituted if necessary.