Threshold of intermittent hypoxia-induced right ventricular hypertrophy in the rat

This study evaluated the threshold for intermittent hypoxia-induced right ventricular hypertrophy in the rat. Three groups of rats purchased from Hilltop Laboratory Animals, Inc., were exposed to air for 2 h, or an FIO2 = 0.1 for 1 h or 2 h daily for 28, 42 or 56 days. Packed cell volume (Hct) was significantly increased in both the 1 and 2 h hypoxic groups by 28 days. The ratios of (right ventricular wt)/(body wt) and the (right ventricular wt)/(left ventricular plus septum wt) significantly increased in the 2 h hypoxic group by 42 days. We conclude that 1 h of hypoxia per day for 28 days results in polycythemia and that 2 h of hypoxia per day for 42 days results in right ventricular hypertrophy in this rat strain.