Chronic hypoxia decreases arterial compliance in rat lungs

Abstract

We hypothesized that the arterial remodeling seen with chronic hypoxic exposure would result in lower arterial compliance. Sprague‐Dawley rats were exposed to either normoxia (N) or hypobaric hypoxia (H) for 2 weeks, and then the lungs were isolated and perfused with a Kreb's Ringer solution containing 4% albumin. Vascular occlusions were performed and modeled using a 3 compliance (C), 2 resistor (R) model, such that arterial (Ca), capillary (Cc) and venous (Cv) compliances, as well as arterial (Ra) and venous (Rv) resistances could be determined. In the N lungs, Ca was 0.034 ± 0.004 ml/torr while in the H lungs, Ca was 0.015 ± 0.005 ml/torr (p<0.05). The distribution of vascular C was different (p<0.05 for all 3 compliances) between N and H lungs, with the vast majority of the vascular compliance residing in Cc in the H lungs (Ca 26 ± 3%; Cc 46 ± 6%; Cv 28 ± 3% N versus Ca 11 ± 4%; Cc 76 ± 6%; Cv 13 ± 2% H). Vascular resistance was greater in the H lungs and this was due to greater Ra (Ra 19.6 ± 1.8 torr/ml/min N versus 36.8 ± 9.8 torr/ml/min H), with little difference in Rv between the groups (Rv 19.9 ± 2.8 torr/ml/min N versus 25.6 ± 3.8 torr/ml/min H). These results demonstrate that the vascular remodeling associated with chronic hypoxia results in lower arterial compliance. These results have implications for right heart function in pulmonary hypertension.