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Pressure stability with CPAP devices: A bench evaluation
Bruno Louis1, Karl Leroux, Maud Boucherie
1INSERM, Unit 841, and Université Paris 12, Faculté de Médecine, Créteil F94010, France.
Background:
Continuous 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.
Method:
Flow contour, respiratory system compliance and total lung-airway resistance of a patient under CPAP were simulated. The devices were tested at a CPAP of 15cm H(2)O with a heated humidifier and a nasal pillow, which increased circuitry resistance and with and without a simulated unintentional leak.
Results:
With no leak, positive end-expiratory pressure (PEEP) at the interface varied across devices from 14.0 to 15.3cm H(2)O. With a leak of 1L/s, PEEP varied from 11.5 to 17.1cm H(2)O. Imposed inspiratory WOB ranged from less than 0.1J/min to 0.45J/min with no leak, and the range broadened with leaking. Findings were similar for the imposed expiratory WOB.
Conclusion:
The 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.
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