Abstract
To compare pulmonary vascular effects of static(S) and dynamic (D) airway pressure(AP), 21 intact, two to four week lambs with L atrial(LA) lines were given chloralose and pancuronium, positioned supine, and ventilated (12-16cc/kg, 25 breaths/min.) Ratrium(RA), pulmonary artery and aorta were catheterized. Apneic SAP (2 and 15 cmH2O), and DAP (ventilation with 2 and 15 cmH2O end-expiratory pressure) were studied by recording vascular and airway pressures and by RA injection of 15μ radioactive microspheres. After experiments, upper(U) and lower(L) lung segments were sampled for scintillation counting. Pulmonary blood flow(PBF), U and L regional PBF, pulmonary vascular resistance(PVR) and mean airway pressure (MAP) were calculated. 5 successful studies (group 1) were obtained at low LA (4 cmH2O), and 6 (group 2) at LA=14. Within each group, 2 and 15 cmH2O AP trials were compared using Student's paired t test. At low LA, both SAP and DAP with 15 cmH2O reduced PBF(40%*,32%*), and elevated PVR(55%,116%). SAP and DAP reduced both UPBF(40%,49%*) and LPBF(36%*,29%*). At high LA, PVR was increased by both SAP and by DAP(9%,72%*), but significantly more so by DAP†. Furthermore, DAP reduced both UPBF and LPBF (17%, 29%), but SAP of comparable MAP(15 vs 19 cmH2O) reduced only UPBF (17%), and not LPBF. High LA, which should blunt Starling resistor effects of AP on LPBF, ablated the decrease in LPBF due to SAP, but not that due to DAP. This is compatible with a non-Starling, perhaps arteriolar effect of DAP on PVR.
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Fuhrman, B., Ring, J., Smith-Wright, D. et al. STATIC VS DYNAMIC AIRWAY PRESSURE AND REGIONAL LUNG BLOOD FLOW. Pediatr Res 18 (Suppl 4), 392 (1984). https://doi.org/10.1203/00006450-198404001-01792
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DOI: https://doi.org/10.1203/00006450-198404001-01792