Tzeng Y C, Larsen P D, Galletly D C
Department of Surgery & Anaesthesia, Wellington School of Medicine & Health Sciences, University of Otago, Wellington, New Zealand.
Am J Physiol Heart Circ Physiol. 2007 May;292(5):H2397-407. doi: 10.1152/ajpheart.00817.2006. Epub 2007 Jan 12.
Normally, at rest, the amplitude of respiratory sinus arrhythmia (RSA) appears to correlate with cardiac vagal tone. However, recent studies showed that, under stress, RSA dissociates from vagal tone, indicating that separate mechanisms might regulate phasic and tonic vagal activity. This dissociation has been linked to the hypothesis that RSA improves pulmonary gas exchange through preferential distribution of heartbeats in inspiration. We examined the effects of hypercapnia and mild hypoxemia on RSA-vagal dissociation in relation to heartbeat distribution throughout the respiratory cycle in 12 volunteers. We found that hypercapnia, but not hypoxemia, was associated with significant increases in heart rate (HR), tidal volume, and RSA amplitude. The RSA amplitude increase remained statistically significant after adjustment for respiratory rate, tidal volume, and HR. Moreover, the RSA amplitude increase was associated with a paradoxical rise in HR and decrease in low-frequency-to-high-frequency mean amplitude ratio derived from spectral analysis, which is consistent with RSA-vagal dissociation. Although hypercapnia was associated with a significant increase in the percentage of heartbeats during inspiration, this association was largely secondary to increases in the inspiratory period-to-respiratory period ratio, rather than RSA amplitude. Additional model analyses of RSA were consistent with the experimental data. Heartbeat distribution did not change during hypoxemia. These results support the concept of RSA-vagal dissociation during hypercapnia; however, the putative role of RSA in optimizing pulmonary perfusion matching requires further experimental validation.
正常情况下，在静息状态时，呼吸性窦性心律不齐（RSA）的幅度似乎与心脏迷走神经张力相关。然而，最近的研究表明，在应激状态下，RSA与迷走神经张力分离，这表明可能存在不同的机制来调节阶段性和持续性迷走神经活动。这种分离与以下假设有关：RSA通过在吸气时优先分配心跳来改善肺气体交换。我们研究了高碳酸血症和轻度低氧血症对12名志愿者在整个呼吸周期中心跳分布相关的RSA-迷走神经分离的影响。我们发现，高碳酸血症而非低氧血症与心率（HR）、潮气量和RSA幅度的显著增加有关。在对呼吸频率、潮气量和HR进行调整后，RSA幅度的增加仍具有统计学意义。此外，RSA幅度的增加与HR的反常升高以及频谱分析得出的低频与高频平均幅度比值的降低相关，这与RSA-迷走神经分离一致。尽管高碳酸血症与吸气期间心跳百分比的显著增加有关，但这种关联在很大程度上是由于吸气期与呼吸期比值的增加，而非RSA幅度。对RSA的额外模型分析与实验数据一致。低氧血症期间心跳分布未发生变化。这些结果支持了高碳酸血症期间RSA-迷走神经分离的概念；然而，RSA在优化肺灌注匹配中的假定作用需要进一步的实验验证。
