A comparison of pathophysiological changes during hypobaric and normobaric hypoxia in rats.

Littermate male Wistar specific pathogen-free rats were divided into three groups at 28 days of age. The pathophysiological effects seen in rats exposed to normobaric hypoxia (NB) at 10% O2 were compared with those seen in animals exposed to hypobaric hypoxia (HB) at 500 mbar, equivalent to an inspired O2 concentration of 10%, and controls after periods of 5, 10 and 14 days. 5 days' exposure to a low oxygen environment resulted in less weight gain, the development of right ventricular hypertrophy and double elastic laminae in the pulmonary arterioles and an increase in haematocrit and plasma levels of atrial natriuretic peptide (ANP) in both the HB and NB animals compared to controls. There was no significant difference in these values between the two hypoxic groups. After 10 days' exposure to a low oxygen environment, body weight, ventricular ratio, plasma ANP levels and double elastic laminae were higher than the levels seen after 5 days in both NB and HB groups of rats. At day 14 only body weight and haematocrit were greater when compared to day 10 values in NB and HB groups. In conclusion the stress of this hypobaric environment caused no additional changes in the pathophysiological variables studied, compared with the changes seen in NB.