Abstract
The character of origin of the first extrauterine breaths was studied in experiments on dog, cat, and rabbit fetuses at the end of intrauterine development and born by caesarian section (after ligation of the cord) and also in the natural way. Corresponding observations were made on human fetuses born naturally. The first extrauterine breath is characterized by typical features of apnea, expressed as intensive contractile activity of the respiratory muscles causing stretching of the lung parenchyma. Activity of the respiratory muscles is combined with contractile activity of the skeletal muscles of the trunk and limbs. On the whole the first extrauterine breath has the character of a sustained and generalized respiratory response of the extensor type.
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Praznikov, V.P., Trakhtenberg, L.Y. Further analysis of the mechanism of origin of the first extrauterine breaths. Bull Exp Biol Med 78, 984–986 (1974). https://doi.org/10.1007/BF00796642
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DOI: https://doi.org/10.1007/BF00796642