The Science Journal of the American Association for Respiratory Care

2008 OPEN FORUM Abstracts

CAN A DIFFERENTIAL PRESSURE FLOW TRANSDUCER ACCURATELY TREND TIDAL VOLUME DELIVERY DURING HIGH FREQUENCY OSCILLATORY VENTILATION IN AN ADULT BENCH MODEL OF ARDS?

Tom Blackson1, Joseph A. Ciarlo1, David H. Horney1, Tim Cox2, Thomas H. Shaffer3



Background: The use of high frequency oscillatory ventilation (HFOV) has increased with the introduction of the Viasys 3100B adult oscillator. Despite its expanded use, there is a lack of agreement regarding the best strategy to use to accomplish lung protection during management of ARDS. One proposed benefit of HFOV is the ability to deliver safe, sub-deadspace tidal volume (VT). Although recent publications have validated the use of a hot-wire anemometer (HA), (Florian, Acutronics, Switzerland) for measurement of VT delivery during HFOV, to date, no objective monitor is commercially available to measure VT delivery and guide ventilator adjustments during HFOV.

Purpose: We evaluated the ability of a commercially available differential pressure transducer (DP) (CO2SMO, Wallingford, PA), to accurately measure VT delivery during HFOV of an adult bench model of ARDS when compared to the HA currently used for research purposes.

Materials & Methods:: A bench model of ARDS was created with a Michigan test lung, (Michigan Instruments, Grand Rapids, MI) set with a compliance of 0.02 L/cmH2O. The test lung was ventilated during all trials with a mean airway pressure: 30 cm H2O, bias flow: 30 L/min., and inspiratory time: 33%. We evaluated frequencies of 3, 4, 5, and 6 HZ in combination with pressure amplitudes between 30 and 90 cm H2O adjusted in 10 cm H2O pressure increments. Twelve consecutive volume measurements were recorded and used for analysis by placing the DP and HA volume monitors, independently, between the ventilator "Y" and the airway resistor. Airway resistance was varied using parabolic resistors #5 and #20 for each test condition.

Results: VT's measured by the DP were insignificantly different from those measured with the HA, (p>0.05) over the range of ventilator settings tested.

Conclusion: Use of the CO2SMO DP during HFOV produces VT measurements consistent with those generated from the previously validated Florian HA under the conditions tested. The CO2SMO DP, which is FDA approved in the US for ventilation monitoring, may be a useful tool to guide HFOV setting selection in situations when lung protection from volume overdistention is a clinical focus. Further clinical study is warranted.