LUNG MORPHOMETRIC CHANGES AFTER EXPOSURE TO HYPOBARIA AND OR HYPOXIA AND UNDERNUTRITION/

Lung morphometry was studied in rats between 4 and 7 weeks of age. The animals were divided into 5 groups: general controls (fed ad libitum) , hypobaric normoxic, normobaric hypoxic, hypobaric hypoxic, and weigh t-matched controls (weight matched to the hypobaric hypoxic group). In both hypobaric and normobaric hypoxia, lung volume, alveolar surface area and total alveolar number increased compared to weight-matched co ntrols. In normobaric hypoxia, mean linear intercept, mean chord lengt h of alveoli increased and number of alveoli/unit volume decreased com pared to weight-matched animals. In hypobaric hypoxia, only mean chord length increased. Dysanaptic index decreased in both. In hypobaric no rmoxia, alveolar size and lung volume diminished compared to general c ontrols. Lung growth was impaired in weight-matched controls without a ffecting airspace dimensions. Hypobaric and normobaric hypoxia increas e lung growth overcoming nutritional effects but is dysanaptic. Lung g rowth in hypobaric hypoxia is mainly determined by low oxygen but low pressure may also produce subtle structural alterations.