Pressure stability with CPAP devices: A bench evaluation.
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.


METHODS
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.


CONCLUSIONS
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.
Louis
Bruno
B
INSERM, Unit 841, and Université Paris 12, Faculté de Médecine, Créteil F94010, France.
Leroux
Karl
K
Boucherie
Maud
M
Isabey
Daniel
D
Grillier-Lanoir
Véronique
V
Fauroux
Brigitte
B
Lofaso
Frédéric
F
D000403:Airway Resistance; D003198:Computer Simulation; D045422:Continuous Positive Airway Pressure / Q000295:instrumentation*; D019544:Equipment Failure Analysis; D006801:Humans; D006813:Humidity; D008170:Lung Compliance; D011175:Positive-Pressure Respiration; D012123:Pulmonary Ventilation; D014939:Work of Breathing