Objective: Severe hypoxia/ischemia is a major cause of neonatal cardiorespiratory dysfunction and mortality. We tested whether prenatal hypoxia preconditioning would augment hypoxic and hypercapnic ventilatory responses, and thereby reduce neonatal mortality.
Methods: Pregnant rats at 19 days' gestation were exposed to six episodes of intermittent hypoxia (10-min of 15% O(2) followed by 10-min of normoxia/episode, PPC), or room air (CON) per day until delivery. The ventilatory responses to 1 min of 10% O(2) and 10% CO(2), and 5 min of 5% O(2) were performed in anesthetized pups. The conscious pups were exposed to 5% O(2) for approximately 105 min, and their mortality and dry/wet weight of the lung and brain were evaluated.
Results: We found that augmented ventilatory responses to 1 min of 10% O(2) and 10% CO(2) were similar in the two groups (P>0.05). In contrast, 5 min of 5% O(2) initially caused a ventilatory peak response followed by a decline that was markedly diminished (35%, P=0.013) by PPC. PPC also significantly decreased neonatal mortality by 22% (P=0.044) as compared with CON.
Conclusion: We conclude that prenatal hypoxia preconditioning reduces neonatal mortality apparently by improving the severe hypoxic ventilatory response.