The Science Journal of the American Association for Respiratory Care

1999 OPEN FORUM Abstracts

EFFECT OF FREQUENCY ON GAS EXCHANGE DURING HFO-PLV IN ARDS SHEEP MODEL

Munevuki Takeuchi, MD, Sven Goddon, MD, Jonathan Hromi, BA, Robert M Kacmarek, PhD, RRT. Anaesthesia and Respiratory Care, Massachusetts General Hospital and Harvard Medical School, Boston, MA

Both partial liquid ventilationTM (PLV) and high frequency oscillatory ventilation (HFOV) have been used to recruit lung in ARDS. The combination of PLV and HFOV would seem ideal, achieving alveolar recruitment with perflubron in the severely injured dorsal lung and protection of the less injured ventral lung by avoiding significant pressure and volume excursions. Pilot data revealed that high frequency oscillatory partial liquid ventilation (HFO-PLV) was most effective when mean airway pressure was set at the point of maximum curvature on the deflation limb of the quasistatic respiratory system PV curve. But no study evaluating the effects of frequency on gas exchange during HFO-PLV in large lungs is available. The aim of this study was to determine the effects of frequency on oxygenation as well as ventilation.

Methods: Five anesthetized sheep (25 to 35 kg) instrumented for hemodynamics and blood collection received lung injury by repeated lung lavage with warmed saline until PaO2/F1O2 ratio fell below 120 (VCV, PEEP 5 cm H2O, TV 12 mL/kg). After injury was established, all the sheep were filled with 10 mL/kg perflubron (LiquiVentÒ, Alliance Pharmaceutical Corp.) (VCV, PEEP 13 cmH2O, TV 12 mL/kg) and then were ventilated with HFOV (mean airway pressure 26 cmH2O, pressure amplitude 40 cmH2O, I:E ratio 1:1) after a recruitment maneuver (CPAP of 40 cmH2O for 1 min). Frequencies of 4, 6, 8 and 10 Hz were randomly applied for 30 min. The change in airway pressure across the endotracheal tube was also monitored.

Results: HFO-PLV improved gas exchange. However as frequency increased above 4 Hz, PaO2 decreased and PaCO2 increased. No hemodynamic differences at any frequency were observed.

injury post-fill VCV 4 Hz 6 Hz 8 Hz 10 Hz
PaO2x (F1O2 1.0) 81 ± 19* 240 ± 41* 480 ± 32 393 ± 49* 316 ± 102* 251 ± 123*
PaCO2x 45 ± 5 44 ± 6 35 ± 6 41± 8 47 ± 13 58 ± 16*
AaDO2x 587 ± 21* 429 ± 38* 198 ± 29 279 ± 51 349 ± 108 405 ± 117*
OI 15 ± 5 8 ± 1 5 ± 0 7 ± 1 10 ± 5 17 ± 18
trac press amp - - 11 ± 4 11± 5 13 ± 6 13± 4
x: units, mmHg. Mean ± SD
trac press amp: pressure swing (cmH2O) measured in the trachea. *p < 0.05 vs. 4 Hz

CONCLUSION: HFO-PLV improvements in gas exchange are markedly affected by frequency. Optimal CO2 elimination and oxygenation occurred at 4 Hz in this study. This study was funded by Alliance Pharmaceutical Corp., San Diego, CA.

OF-99-217

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