Effects on the right ventricle, pulmonary vasculature, and carotid bodies of the rat of exposure to, and recovery from, simulated high altitude.

Three groups of 10 adult male Wistar albino rats were studied. The first was kept for five weeks in a hypobaric chamber exposed to a barometric pressure of 380 mmHg, equivalent to a simulated altitude of 5,500 m above sea level. The second was exposed to the same barometric pressure for five weeks and then allowed to recover in room air for a further period of five weeks. The third group acted as controls and was kept at normal barometric pressure throughout. At necropsy right ventricular weight was expressed as an inverse ratio of left ventricular weight (LV/RV ratio). The thickness of the media of the pulmonary trunk was expressed as a ratio of that of the aorta. The volumes of the carotid bodies were measured by applying Simpson's rule to histological sections. In the first group, exposed to chronic hypoxia without relief, there was hypertrophy of the right ventricle and media of the pulmonary trunk and there was an increase of carotid body volume, as compared with the values obtained in the controls. In the recovery group these three measurements had returned almost to normal. The results appear to be applicable to hypoxic cor pulmonale in man. They suggest that hypoxia rapidly produces pulmonary hypertension and its morbid anatomical associations while recovery is equally rapid once the hypoxic stimulus is removed.