1658 REGIONAL AND LOBAR PULMONARY BLOOD FLOW WITH HIGH FREQUENCY VENTILATION

Abstract

We compared regional and lobar pulmonary blood flow in conventional mechanical ventilation (CV) and high frequency ventilation (HFV) to determine whether changes occur in the distribution of lung perfusion. Fourteen supine anesthetized, paralyzed dogs were ventilated with room air using CV and HFV (tidal volume=2.5 ml/kg, frequency=10 Hz.) Blood gases, pulmonary and systemic arterial pressures, and cardiac output were allowed to reach a steady state, at which time radioactive microspheres were injected. Arterial blood gases with CV showed PO₂=94.3 ± 2.2 torr (mean ± S.E.), PCO₂=34.5 ± 1.5 torr, and pH=7.35 ± .02. These values remained unchanged with HFV. Comparison of systemic and pulmonary arterial pressures, cardiac output and venous admixture showed no significant differences. In 11 dogs, tissue samples from apical, nondependent, and dependent areas of the lungs were analyzed for changes in blood flow. Regional pulmonary blood flow for apical, nondependent and dependent regions using CV were 44.82±7.06, 44. 89±5.04, and 94.45±6.49 ml/min/gm.dry wt, respectively. The corresponding flows using HFV were 44.27±6.69, 46.47±4.47, and 93.83 ±6.38 ml/min/gm dry wt. These differences were not significant. In the remaining 3 animals, each lobe was analyzed for changes in total lobar blood flow under conditions of CV and HFV, and total lobar blood flows were not different. We conclude that HFV does not produce significant changes in regional or lobar distribution or pulmonary blood flow, or in overall hemodynamics.

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