TEMPORAL HETEROGENEITY OF PULMONARY BLOOD FLOW IN PIGLETS. 2027

Abstract

Recent studies using fluorescent microspheres have demonstrated temporal heterogeneity of pulmonary blood flow (PBF) in adult dogs (Glenny RW, et al. Temporal heterogeneity of regional pulmonary perfusion is spatially clustered. JAP in press). Neither the distribution nor temporal changes in PBF in the neonatal animal have previously been evaluated. Six healthy, anesthetized, supine 10-14 day old piglets were ventilated with room air, tidal volume of 10-12 cc/kg, and respiratory rate to achieve a normal PaO2 and PCO2. Regional PBF was measured using 15 μm fluorescent microspheres injected into the internal jugular vein. Regional PBF was measured with different fluorescent colors every 20 minutes. After sacrifice, the animal's lungs were perfused with 2% Dextran, excised, dried at 25 cm H2O, sliced, and cored samples (0.16cm3) (n=599 ± 115 samples per animal) were taken. Spatial coordinates, weight, airway content were noted. Lung pieces were soaked in solvent for 48 hours and fluorescence determined. Heterogeneity of PBF was quantified by changes in the coefficient of variation (CV=standard deviation/mean) over time. All animals demonstrated temporal variability in PBF distribution with CV varying 11± 10.1% over 20 minute periods (Representative animal is shown inFigure). There was a large inter-animal variability(1.5 - 36.6% change in CV over 20 minutes). CV variability did not increase linearly over time. Maximal changes were noted as early as 20 minutes. Neonatal pigs demonstrate significant PBF temporal heterogeneity. Supported in part by a grant from the American Lung Association of Washington.