PURPOSE:Hypercapnia increases minute ventilation (V’E) with little effect on heart rate (HR), whereas hypoxia may increase HR without affecting V’E. However, the effects of hypercapnia and hypoxia on both heart rate variability(HRV) and the clustering of heart beats during spontaneous breathing (respiratory sinus arrhythmia – RSA), are not clear. METHODS:In this study, 10 human volunteers breathed room air (RA), hypercapnic (5% CO2) or hypoxic (10%O2) gas mixtures, each for 6 min, while resting supine. ECG, mean arterial pressure (MAP), ventilatory flow, inhaled and exhaled fractions of CO2 and O2, were recorded throughout. RESULTS:Both V’E and MAP increased with 5%CO2, with no change in HR. Hypoxia did not change ventilation but increased HR. High frequency components of HRV, and the relative proportion of heart beats occurring during inhalation increased with 5% CO2, but neither changed with 10% O2. CONCLUSION:Increased RSA concomitant with increased MAP suggests RSA – vagal dissociation with hypercapnia. Elevated heart rate with acute hypoxia with no change in either frequency components of HRV or the distribution of heart beats during ventilation, suggested that clustering of heart beats may not be a mechanism to improve ventilation-perfusion matching during hypoxia.

译文

目的:高碳酸血症会增加分钟通气量(V’E),而对心率(HR)的影响很小,而低氧可能会增加HR而不会影响V’E。然而,高碳酸血症和低氧对自发性呼吸(呼吸窦性心律不齐– RSA)期间心率变异性(HRV)和心跳聚集的影响尚不清楚。
方法:在这项研究中,10名人类志愿者在仰卧休息时呼吸了室内空气(RA),高碳酸血症(5%CO2)或低氧(10%O2)混合气体,每次持续6分钟。整个记录心电图,平均动脉压(MAP),通气量,吸入和呼出的CO2和O2分数。
结果:V'E和MAP均随5%CO2的增加而增加,而HR不变。缺氧并没有改变通气,但增加了心率。 HRV的高频成分以及在吸入过程中发生的心跳的相对比例在5%CO2的情况下增加,但在10%O2的情况下都没有变化。
结论:RSA增加伴有MAP升高提示RSA –迷走神经脱离与高碳酸血症。急性缺氧时心率升高,HRV的频率成分或通气期间心跳的分布均无变化,提示心律聚集可能不是改善低氧时通气-灌注匹配的机制。

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