INSERM, U1099, Rennes, F-35000, France.
Sleep. 2012 Nov 1;35(11):1541-9. doi: 10.5665/sleep.2206.
Although hypercapnia and/or hypoxia are frequently present during chronic lung disease of infancy and have also been implicated in sudden infant death syndrome (SIDS), their effect on cardiac autonomic regulation remains unclear. The authors' goal is to test that hypercapnia and hypoxia alter sleep-wake cycle-dependent heart rate variability (HRV) in the neonatal period.
Experimental study measuring HRV during sleep states in lambs randomly exposed to hypercapnia, hypoxia, or air.
University center for perinatal research in ovines (Sherbrooke, Canada). INSERM-university research unit for signal processing (Rennes, France).
Six nonsedated, full-term lambs.
Each lamb underwent polysomnographic recordings while in a chamber flowed with either air or 21% O(2) + 5% CO(2) (hypercapnia) or 10% O(2) + 0% CO(2) (hypoxia) on day 3, 4, and 5 of postnatal age.
Hypercapnia increased the time spent in wakefulness and hypoxia the time spent in quiet sleep (QS). The state of alertness was the major determinant of HRV characterized with linear or nonlinear methods. Compared with QS, active sleep (AS) was associated with an overall increase in HRV magnitude and short-term self-similarity and a decrease in entropy of cardiac cycle length in air. This AS-related HRV pattern persisted in hypercapnia and was even more pronounced in hypoxia.
Enhancement of AS-related sympathovagal coactivation in hypoxia, together with increased heart rate regularity, may be evidence that AS + hypoxia represent a particularly vulnerable state in early life. This should be kept in mind when deciding the optimal arterial oxygenation target in newborns and when investigating the potential involvement of hypoxia in SIDS pathogenesis.
尽管婴儿期慢性肺部疾病常伴有高碳酸血症和/或低氧血症，并且这两者也与婴儿猝死综合征（SIDS）有关，但它们对心脏自主调节的影响仍不清楚。作者的目标是检验高碳酸血症和低氧血症是否会改变新生儿期睡眠-觉醒周期相关的心率变异性（HRV）。
这项实验性研究通过测量随机暴露于高碳酸血症、低氧血症或空气的羔羊睡眠状态下的 HRV。
加拿大舍布鲁克围产期研究大学中心，法国雷恩信号处理大学研究单位。
6 只未镇静的足月羔羊。
每只羔羊在出生后第 3、4 和 5 天在一个充满空气或 21% O(2) + 5% CO(2)（高碳酸血症）或 10% O(2) + 0% CO(2)（低氧血症）的腔室内进行多导睡眠描记术记录。
高碳酸血症增加了清醒时间，低氧血症增加了安静睡眠（QS）时间。警觉状态是 HRV 的主要决定因素，可通过线性或非线性方法进行描述。与 QS 相比，活跃睡眠（AS）与 HRV 幅度的整体增加、短期自相似性的增加以及心搏周期长度的熵减少相关，在空气条件下是如此。这种与 AS 相关的 HRV 模式在高碳酸血症中持续存在，在低氧血症中更为明显。
低氧血症增强了与 AS 相关的交感神经-副交感神经兴奋，同时增加了心率规律性，这可能表明 AS + 低氧血症代表了生命早期一个特别脆弱的状态。在决定新生儿最佳动脉氧合目标和研究低氧血症在 SIDS 发病机制中的潜在作用时，应牢记这一点。
