The Science Journal of the American Association for Respiratory Care

2006 OPEN FORUM Abstracts

A Bench Study to Compare the Performance Characteristics of CPAP Machines Featuring Expiratory Pressure Relief Algorithms

R. Diesem, G. Voss, R. McCoy, RRT, FAARC 

Background: CPAP devices equipped with an expiratory pressure relief feature are a relatively new addition to the CPAP market.  This unique feature is marketed as a more comfortable option for the OSA patient than standard CPAP therapy.  However, what is not widely identified is exactly how these features operate and what differentiates one unit from another.  The assumption is that these products perform similarly so purchasing decisions are then based on product reliability, warranty, additional features, and price.  The objective of this evaluation is to determine the performance characteristics and differences between three current CPAP devices that feature expiratory pressure relief algorithms. 

Methods: Three separate CPAP machines equipped with an expiratory pressure relief algorithm were tested on a Hans-Rudolph Series 1101 breathing simulator programmed with three distinct breathing patterns and set to record patient flow and airway pressures.  Each device was set to operate at a range of therapy pressures (5, 10, 15 and 20cmH2O) and was tested at each expiratory pressure relief setting.  The delivered pressures and resulting pressure profiles for each of the devices were compared on all tested breathing patterns.  Average pressure deviation from End-Exhalation pressure at each quarter of the expiratory phase of one breath was calculated and compared.  Work of Breathing values were calculated from the pressure deviation and tidal volume data. 

Results: With the expiratory pressure relief feature deactivated, there was little difference in performance characteristics among all three devices.  However, each CPAP device exhibited a markedly different response to patient exhalation when the expiratory pressure relief feature was activated.  As a result, pressure profiles varied greatly under all tested breathing patterns.  Pressure deviation from End-Expiratory pressure at all quarters of the expiratory phase varied for each device.  Work of Breathing values (per breath) ranged from 0.015 to 0.334 J/L. 

Conclusion: Each CPAP unit's response to a simulated patient, with expiratory pressure relief activated, was notably dissimilar to the other devices in this test.  A clinician or physician prescribing a CPAP device equipped with expiratory pressure relief should be familiar with the performance characteristics of each type of device and be aware of the differences between them.



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