Repeated thermo-sterilisation further affects the reliability of positive end-expiratory pressure valves
- Conflict of interest: None.
Correspondence: Julia Christine Hartung, Department of Neonatology, Charité University Medical Center Berlin, Charitéplatz 1, 10117 Berlin, Germany. Fax: 0049 30 450516910; email: email@example.com
Positive end-expiratory pressure (PEEP) valves are used together with self-inflating bags (SIB) to provide a preset PEEP during manual ventilation. It has recently been shown that these valves deliver highly variable levels of PEEP. We hypothesised that material fatigue due to repeated thermo-sterilisation (TS) may contribute to varying reliability of PEEP valves.
In a laboratory study 10 new PEEP valves were tested before and after 10, 20 and 30 cycles of routine TS (7 min at 134°C) by using a neonatal lung model (compliance 0.2 mL/kPa). Settings were positive inflation pressure = 20 and 40 cmH2O, PEEP = 5 and 10 cmH2O, respiratory rate = 40 and 60/min, flow = 8l/min. PEEP was recorded using a respiratory function monitor.
Before TS, a mean (standard deviation) PEEP of 4.0 (0.9) and 7.7 (1.0) cmH2O was delivered by the 10 valves when the PEEP was set to 5 and 10 cmH2O, respectively. One new valve only delivered 2.0 (0.0) and 5.0 (0.0) cmH2O when the PEEP was adjusted to 5 and 10 cmH2O, respectively. Four of the 10 investigated valves showed significant variations in PEEP (coefficient of variation >10%) throughout the autoclaving process. One valve completely lost its function after the 20th TS. Common defects were tears in the softer materials or displacement of the rubber seal. Six of the 10 valves continued to provide PEEP in spite of repeated TS.
The reliability of PEEP valves is affected by repeated TS. Multi-use PEEP valves should be tested for reliable PEEP provision following TS.