The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

ACTIVE EXHALATION VALVE CONTROL: EVALUATION OF ITS PERFORMANCE IN EXPIRATORY RESISTANCE AND PRESSURE RELEASE

John Newhart CRT, UCSD Medical Center, San Diego, California, Chi-Yuan Chuang, MD, Graduate Institute of Medical Science, Taipei Medical University, Taiwan.

Background: The advent of computerization of mechanical ventilation has brought many improvements in synchrony with the patient. One of these is the "active exhalation valve" (AEV), which theoretically allows the patient to exhale freely even during the ventilator's inspiratory phase. This study is to objectively evaluate the performance of pressure release in the ventilators with AEV, in comparison with an older ventilator without AEV.

Methods: An Ingmar Active Test Lung (ASL5000) was programmed to simulate a patient spontaneous inspiratory effort followed by a forced expiratory effort during the ventilator's inspiratory phase. The test lung settings were as follows: R10, C50, inspiratory max Pmus of -5cmH2O, and expiratory max Pmus of +10 cmH2O. The new ventilators tested were the Drager Evita XL, Newport e500, PB 840, and Maquet Servo i. A PB 7200 represented an older generation ventilator. Airway pressure overshoot and the resistance to flow as the result of the patient's forced expiratory effort during the ventilator inspiratory phase were measured and calculated.

Results: Our data indicate that the ease of the pressure release was markedly improved in the new generation of ventilators with AEV versus the older generation with non-active exhalation valve.

Conclusion: Active exhalation valve control eases the resistance to the patient efforts, thus improves patient-ventilator synchrony.

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