[Long-term respiratory effects of neonatal hypoxia in rats]

Rats maintained in a hypoxic environment during the first week after birth (NH rats) show a decrease in body growth and oxygen consumption and an increase in ventilation. At the same time the lungs undergo changes in structure which suggests protection of the gas exchange area. In this study, the extent to which these adaptive changes would persist after return to normoxia was investigated. Control rats (C) were given 10% O2 during the first week of life, then returned to normoxic breathing (NH), and rats exposed to the same level and duration of hypoxia after weaning (AH). Body weight increased very little during the week of hypoxia, but after return to normoxia body growth was more than in control rats, and eventually body weight reached the control value at 2 month of age. Both oxygen consumption and minute ventilation were above control levels in the first week after hypoxia, probably reflecting the higher O2 demands of the rapidly growing animals. However, minute ventilation remained elevated even at 7-8 week of age at a time when both body weight and oxygen consumption were the same as in controls. Measurements of blood gases at this age indicated that the persistent hyperventilation was not due to hypoxemia, and was accompanied by hypocapnia and alkalosis. Hematocrit and total heart weight, elevated in hypoxia, returned to control values within 1 week, whereas dry lung weight and right side heart weight remained above the control values as much as during the hypoxic exposure.(ABSTRACT TRUNCATED AT 250 WORDS)