Various lines of clinical evidence point to an association between perinatal hypoxia and the genesis of hyaline membrane disease in human infants. The question of whether hyaline membranes can be caused by hypoxia alone was investigated in experimental animals. Newborn guinea pigs, rabbits, rats, and mice were placed in a chamber where they breathed a mixture of oxygen-nitrogen or oxygen-nitrogen-carbon dioxide for a period of up to several days. Their reactions were noted, the period of their survival recorded, and their lungs were examined histologically and compared with controls. All species showed a remarkable tolerance to hypoxia as newborns: most animals were able to survive for hours in mixtures ranging down to 3% or 4% oxygen. For each species there appeared to be a critical oxygen pressure needed for survival. Below this level all individuals promptly died. Carbon dioxide in the gas mixture was found to protect against initial hypoxic convulsions, prolong the period of hyperventilation, and prolong survival at the same level of oxygen tension. In no instance did the severe and prolonged hypoxia to which the newborns were subjected result in the histological picture of hyaline membrane disease: diffuse atelectasis, hyaline membranes, and vascular congestion. This is taken as evidence that, for these species at least, hypoxia alone is not sufficient to reproduce the respiratory distress syndrome of human infants.

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