[Risk of barotrauma when using non-reinhalation Waters valves: a comparative study on bench test]

Objective: Manual ventilation is delivered in the operating room or the intensive care unit to intubated or non-intubated patients, using non-rebreathing systems such as the Waters valve. New generation Waters valves are progressively replacing the historic Waters valve. The aim of this study was to evaluate maximal pressure delivered by these 2 valves.

Type of study: Bench test.

Material and method: Thirty-two different conditions were tested, according to 2 oxygen flow rates (10 and 20L/min), without (static condition) or with manual insufflations (dynamic condition) and 4 valve expiratory opening pressures. The primary endpoint was maximal pressure measured at the exit of the valve, connected to a model lung and a bench test.

Results: Measured pressures were different for most evaluated conditions. Increasing oxygen flow from 10 to 20L/min increased maximal pressure for both valves. Increasing valve expiratory opening pressure induced a significant increase in maximal pressure for the new generation valve (from 4 to 61cmH2O in static conditions and from 18 to 68cmH2O in dynamic conditions). For the historic valve, maximal pressure increased significantly but remained below 15cmH2O in both static and dynamic conditions.

Conclusion: Use of new generation Waters valves should be different from historic Waters valves. Indeed, barotrauma could be caused by badly adapted valve expiratory opening pressure settings.