MICROVASCULAR HEMODYNAMICS IN THE SICKLE RED-BLOOD-CELL PERFUSED ISOLATED RAT LUNG

In this study the effects of alveolar hypoxia on pulmonary microvascular hemodynamics in sickle red blood cell (HbSS-RBC) perfused rat lungs were studied under conditions of high and low oxygen tensions and compared with lung perfused with rat (HbRat) and normal human (HbAA) RBC controls. Independent of the RBC suspension (hematocrit 5%) used, ventilation with the room air gas mixture did not result in any significant differences in the pulmonary arterial pressure (P(pa)), capillary pressure (P(pc)), total pulmonary vascular resistance (R(T)), or angiotensin II pressor response. Ventilation of HbSS-RBC perfused lungs with a hypoxic gas mixture significantly increased the P(pa), P(pc), and R(T) above that which was seen in HbRat and HbAA controls. The increase in R(T) occurred mainly in the pulmonary artery independent of RBC suspension. In addition, no significant accumulation of lung water occurred in HbSS-RBC perfused lungs compared with HbRat and HbAA controls, as indicated by the change in capillary filtration coefficient and wet-to-dry lung weight ratio. In conclusion, deoxygenation of the HbSS-RBC and hypoxic pulmonary vasoconstriction is additive in altering pulmonary microvascular hemodynamics.