EVALUATION OF A HYBRID HIGH-FREQUENCY VENTILATOR IN A SURFACTANT DEFICIENT RABBIT MODEL AT SIMULATED ALTITUDE. 1263

Objective: We compared the effects of hypobaric pressure on ventilator and physiologic parameters in a surfactant deficient rabbit model, using a pneumatically-driven high-frequency ventilator (Duotron®, Percussionaire Corp.), which has potential use for neonatal air-evacuation. This abstract reports mid-point results, with 21 animals completed.Methods: Intubated, sedated and paralyzed adult New Zealand White rabbits were saline lavaged to produce a surfactant-deficient, atelectasis-prone subject with a pO₂<100 torr. Animals were randomized to conventional (CV) or high-frequency (HF) ventilation and to ambient or 8000 feet barometric pressure for 3-hours. CV settings post-lavage were adjusted to achieve pCO₂ of 45-55 torr and to maintain pO₂>50 torr (monitored continuously with indwelling sensor: NeoCath®, Biomedical Sensors). HF group settings were adjusted to yield P_aw(HF) = P_aw(CV) +2, and to achieve a pCO₂ of 45-55 torr. Once stable, no further ventilator adjustments were made. Ventilator, monitor (model CP-100, Bicore Corp.) and animal were placed in an altitude chamber for 1 hour at ambient pressure followed by 2 hours at either ambient or 8000 feet barometric pressure. Blood gases and ventilator data were collected through an access port. Results:Table shows pCO₂ and change in oxygenation index(OI) relative to post-lavage. Data shown as mean ± SD. The OI is improved for HF vs CV for animals exposed to simulated altitude. At this mid-point evaluation we do not see a significant difference for pCO₂ or pH (data not shown) in these groups, or in any parameter for the ambient pressure groups. Conclusions: The Duotron® ventilator may offer a potential means for high-frequency air-transport without the concems of electromagnetic emissions posed by non-pneumatic ventilators.

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