1999 OPEN FORUM Abstracts

COMPARISON OF MINUTE VOLUME DELIVERED WITH HIGH FREQUENCY VENTILATION USING TWO AIRWAY CLEARANCE DEVICES

David A. Blackney, RCP, RRT, Pulmonary Services, Sutter Children's Center, Sacramento, CA, USA

BACKGROUND: High frequency ventilation has been used in devices to create intrapulmonary percussive effects and promote airway clearance. Two percussive devices were evaluated, and the flow and volume waveform characteristics were compared for high frequency oscillation. The parameters important for intrapulmonary percussive type ventilation are: f - oscillation frequency (Hz), proximal PIP - Peak Inspiratory Pressure (cm-H₂O), OTV - Oscillatory Tidal Volumes (ml), and MV - Minute Volume (Liters) during inhalation and exhalation.

Methods: Each device was connected to a pressure tap and a flow sensor proximal to the mouthpiece to record pressure and flow waveforms using a computer data acquisition system sampling pressure at 100 Hz. Model IPVÒ-1 (PercussionaireÒ Corp.) was operated at both 20 and 40 PSIG at ?EASY? setting, and Percussive Tech HF^TM (VORTRAN Medical Technology 1, Inc.) was operated at 35 PSIG (approximately 60 L/min device flow). A 50 PSIG compressed air source was used. A trained respiratory care practitioner operated the devices and recorded pressure waveforms.

Results: The results of this evaluation are summarized below with flow waveforms.

DISCUSSION: The results indicate that oscillation frequencies vary slightly depending on the setting of the devices. The oscillation frequency f for the IPVÒ-1 was from 5 to 7 Hz and the PT-HF was at 11 Hz. The exhalation Minute Volume (MV_EXHL = OTV_EXHL ´ f) delivered by the IPVÒ-1 was 62 to 66 liters per minute at various frequencies. In comparison, the PT-HF delivered about 40 liters per minute at higher frequencies.

Conclusions: The flow waveform of the PT-HF is compatible to that of the IPVÒ-1. PIP is essentially the same with the PT-HF oscillating at higher frequencies and at a lower pressure. The MV_EXHL results suggest that patients were ventilated during the exhalation phase through the use of high frequency oscillation. Further studies should be done to evaluate the impact of volume delivered on patients during exhalation and on the effectiveness of airway clearance at various frequencies.

Supported by VORTRAN Medical Technology 1, Inc.

(See Original for Figure)

OF-99-077