急性缺氧条件下的心率变异性分析

目的 以心率变异性（HRV）为定量评价心血管自主神经调节变化的指标，观察模拟5000m急性缺氧条件下，自主神经变化特点，并探讨预测缺氧耐力不良的方法。方法 被试者为11名18－30岁的健康男性，以呼吸10．5％的低氧混合气30min模拟5000m急性缺氧，以时域和频域（粗粒化谱分析，CGSA）方法进行HRV分析。并根据是否完成实验过程将被试者分为耐力良好组（A组）和耐力不良组（B组）。结果 耐力良好组在缺氧时心率显著增快，相邻RR间期之差的均方根值（RMSSD）显著减小，LFn.u(LF的标准单位）和LF／HF显著增大，HF和HFn.u.(HF的标准化单位）显著减小。两组比较，缺氧5－10min时，LFn.u.和LF／HF在B组显著大于A组，缺氧10－15min时，RMSSD在B组显著小于A组。结论 在模拟5000m急性缺氧条件下，交感神经活动增强，迷走神经活动减弱；HRV分析对评价缺氧耐力有一定的预测性。

Analysis of Heart Rate Variability during Acute Exposure to Hypoxia

Objective. To investigate the changes of autonomic nervous system during acute exposure to an altitude of 5000 m by analysing heart rate variability (HRV). Method. 11 healthy male volunteers aged 18-30 were observed during inhalation of low oxygen gas mixture to simulate acute exposure to hypoxia. HRV was analyzed with both time domain and frequency domain methods. The eleven subjects were divided into two groups--Group A with good tolerance and Group B with poor tolerance. Result. During hypoxia heart rate increased markedly and RMSSD (the square root of the mean squared differences of successive RR intervals) decreased markedly; normalized low-frequency (LFn. u.) and LF/HF ratio increased significantly, while HF and normalized high-frequency (HFn. u.) reduced significantly. LFn. u. and LF/HF increased more apparently in group B than in group A during hypoxia of 5-10 min and RMSSD decreased more in group B during 10-15 min. Conclusion. The results suggested that cardiac sympathetic activity increased and cardiac vagal activity decreased during acute hypoxia. The analysis of HRV could predict the tolerance to hypoxia.