Effects of disposable or interchangeable positive end-expiratory pressure valves on work of breathing during the application of continuous positive airway pressure.

OBJECTIVE

To determine which of a series of disposable or interchangeable positive end-expiratory pressure (PEEP) devices functions with the least imposition of inspiratory and expiratory work during continuous positive airway pressure.

DESIGN

Prospective laboratory evaluation performed on a lung model.

SETTING

Research laboratory at a university medical center.

INTERVENTIONS

A spontaneously breathing lung model, created from a training test lung and a volume ventilator, were used to simulate a patient spontaneously breathing at a tidal volume of 0.4 L, peak inspiratory flow of 40 L/min, an inspiration/expiration ratio of 1:2, and a respiratory rate of 20 breaths/min. Ten PEEP valves attached to a continuous high-flow system were evaluated.

MEASUREMENTS AND MAIN RESULTS

All of the PEEP valves studied imposed high levels of both inspiratory and expiratory work of breathing. The BE-171 and BE-142 valves (Instrumentation Industries) imposed the least amount of inspiratory work. In general, imposed inspiratory work accounted for approximately 70% to 80% of total imposed work of breathing.

CONCLUSIONS

All of the disposable/interchangeable PEEP valves that were studied imposed a considerable amount of both inspiratory and expiratory work, even when the continuous flow provided exceeded the peak inspiratory flow demands of the lung model. The primary reason for the high imposed work levels is the high gas-flow resistance of all of the valves studied.