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Oxygen Chemoreceptors in Low Birth Weight Infants

Extract: Serial studies of respiratory sensitivity to altered oxygen tensions (FIO2) were carried out on 39 infants ranging in birth weight from 800 to 4,140 g, and of gestational ages between 28 weeks and term. We used a modification of the Dejours single breath test to show that all infants, regardless of birth weight or gestational age, possess sensitivity to altered FIO2. The presence of periodic breathing or apnea on return to room air after exposure to 10% oxygen–90% nitrogen suggests a high level of chemosensitivity to oxygen in immature infants. Neurologic immaturity does not appear to be an explanation for the apnea or periodic breathing observed in premature infants.Speculation: The lack of sustained response to hypoxia seen by some observers may be a mechanical factor, not a neurologic one. The decreased compliance and increased resistance of lungs of neonates necessitate greater work on the part of the infant. Mechanical factors have been shown to play a part in limiting the ventilatory response to carbon dioxide in adults with obstructive disease, and the same factor may play a role in limiting the response to hypoxia in the low birth weight infant. This conclusion is suggested by the fact that a constant extrathoracic negative pressure has been shown to eliminate periodic breathing in premature infants. The present study suggests that the mode of action in this case may be either via improved mechanical factors accompanying larger lung volumes, or the effect of stabilizing the chest at a larger functional residual capacity and thus preventing oscillations in PaO2, which may produce periodic breathing.