Pneumatic performance of the Boussignac CPAP system in healthy humans.

BACKGROUND The Boussignac continuous positive airway pressure (CPAP) device effectively treats acute pulmonary edema, but data on airway pressure with the Boussignac CPAP system are sparse. OBJECTIVE To evaluate the Boussignac CPAP system's ability to maintain stable inspiratory and expiratory pressure levels, and to evaluate perceived exertion during breathing with the Boussignac CPAP system. METHODS With 18 healthy volunteers we recorded airway pressure and air flow during 10-min sessions at 5.0, 7.5, and 10.0 cm H(2)O. The participants were blinded to the sequence of the CPAP levels. Each session was ended with 10 forced breaths. We measured perceived exertion with the Borg category ratio 10 (Borg CR10) scale. RESULTS When the participants breathed at 20% of vital capacity and a peak expiratory flow of 14% of FEV(1), the maximum pressure difference between inspiration and expiration was 4.0 cm H(2)O at CPAP 10 cm H(2)O. The changes in airway pressure were never large enough to reduce airway pressure to below zero. During the forced breaths, the expiratory volume was 38-42% of vital capacity and peak expiratory flow was 49-56% of FEV(1). As air flow increased, both the drop in inspiratory airway pressure and the increase in expiratory airway pressure increased. CONCLUSIONS With CPAP, pressure changes are considered to be associated with increased work of breathing. The device's pneumatic performance is adequate during normal breathing with low air flow, but during forced breathing (high air flow) it did not maintain stable airway pressure, which could increase the work of breathing and cause respiratory fatigue. Thus, the Boussignac CPAP system might be less suitable for a patient breathing at a higher frequency.