Pressure stability with CPAP devices: A bench evaluation

BackgroundContinuous positive airway pressure (CPAP) maintains a constant pressure to reduce the patient’s work of breathing (WOB). The aim of this study was to measure the additional WOB imposed by four current CPAP devices during simulation of a difficult but commonly encountered clinical situation.MethodFlow contour, respiratory system compliance and total lung-airway resistance of a patient under CPAP were simulated. The devices were tested at a CPAP of 15 cm H2O with a heated humidifier and a nasal pillow, which increased circuitry resistance and with and without a simulated unintentional leak.ResultsWith no leak, positive end-expiratory pressure (PEEP) at the interface varied across devices from 14.0 to 15.3 cm H2O. With a leak of 1 L/s, PEEP varied from 11.5 to 17.1 cm H2O. Imposed inspiratory WOB ranged from less than 0.1 J/min to 0.45 J/min with no leak, and the range broadened with leaking. Findings were similar for the imposed expiratory WOB.ConclusionThe performances of CPAP devices are variable. The device that calibrated for the pressure loss in the circuitry under dynamic conditions and made appropriate pressure adjustments outperformed the other devices.