有氧锻炼对心血管自主神经调节的影响

为研究有氧锻炼对心血管自主神经调节的影响,采用动态心电、血压监测技术,对6名男性中长跑运动员和7名健康男性大学生6个月长跑训练(20～25km/周)前后的下体负压(LBNP)耐力,Valsalva动作的心率、血压反应,心率变异性(HRV),血压变异性(SBPV)以及自发性压力感受器-心率反射反应的斜率(BRS)进行了测量.结果表明,有氧锻炼可以导致LBNP耐力降低,Valsalva动作Ⅱ期舒张压恢复幅度与最大心率值显著减小,平卧位HRV谱总功率(TP)、低频(LF)与高频(HF)成分功率呈减小变化,平卧位SBPV谱TP、LF成分功率与平均自发性BRS值减小,LBNP作用下HRV谱LF/HF值明显增大.说明有氧锻炼可导致心血管自主神经调节功能下降,可考虑将上述有关指标变化用于监测有氧锻炼强度以及个体敏感性,更科学地对有氧锻炼进行卫生指导.     

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。     

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增快，相邻RR间期之差的均方根值（RMSSD）显减小，LFn.u.(LF的标准化单位）和LF／HF显增大，HF和HFn.u.(HF的标准化单位）显减小，两组比较，缺氧5－10min时，LFn.u.和LF／HF 在B组显大于A组，缺氧10－15min时，RMSSD在B组显小于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。     

民航飞行人员高血压病危险因素与心率变异性及压力反射敏感度的联系

目的：探讨民航飞行人员高血压病危险因素暴露与心率变异性（HRV）及压力反射敏感度（BRS）之间的联系。方法：在参加年度大体检的450名血压正常的民航飞行人员中,根据有无危险因素暴露将其分为年龄≥40岁组、体重超重组、血胎异常组、吸烟组、饮酒组及相应对照组。采用常规自回归谱分析方法对各组飞行人员的短时程HRV信号进行分析,同时采用序贯法计算其BRS。结果：与对照组相比,年龄≥40岁的飞行人员HRV明显降低,表现为总功率（TP）、低频功率（LF）、高频功率（HF）及归一化高频成分（HFn）显著降低（P＜0．01）,而归一化低频成分（LFn)与LF／HF则显著增加（P＜0．05）;其BRS亦显著降低（P＜0．01）。其他危险因素暴露时,HRV的TP、LF及HF均显著降低（P＜0．05）,而LFn、HFn及LF／HF则无明显变化,BRS亦显著降低（P＜0．05）。结论：民航飞行人员高血压病危险因素的暴露与HRV及BRS的降低密切联系;提示在高血压病发病之前,心血管自主神经调节功能即已发生异常。在对飞行人员进行高血压病的早期危险性预报时应重视对其自主神经调节功能的评价。     

模拟高海拔氦氧潜水对潜水员心率变异性的影响

目的 观察模拟高海拔缺氧和潜水条件下自主神经的交感-副交感的反应,探讨高海拔缺氧和潜水活动中自主神经系统的交感-迷走神经对心脏功能的互动调控作用.方法 4名潜水员作为受试者在高、低压舱内分别暴露于模拟海拔3000、4000和5200 m,各逗留2d,在此期间摸拟30 m和50m氦氧潜水60 min.记录受试者在高海拔暴露和模拟潜水时的心电图,运用频谱分析法对其总功率(TP)、高频(HF)、低频(LF)和低频/高频(LF/HF)的比值等指标进行分析.结果 人体暴露于海拔高度3000、4000和5200 m时,心率变异性(HRV)的TP、HF、LF,HF/(LF/HF)比海平面值明显减少,LF/HF 则明显升高.与高海拔相比,在模拟30和50 m潜水时发生明显相反的变化,HRV的各参数出现由高海拔暴露值向平原对照值回归转化的现象.结论 高海拔暴露引起交感神经活性升高,副交感神经活性降低,在潜水时发生相反的变化,HRV有向海平面值回归转移的趋势.     

卧床不同训练方法对心血管自主神经调节变化的影响

目的以心率变异性 (HRV)频域变量 ,作为定量评价心血管自主神经调节变化的指标 ,观察卧床条件下 ,不同训练方法对心血管自主神经调节变化的影响。方法被试者为 1 5名年龄 1 9～ 2 2岁的健康男性 ,分为对照组、放松训练组和低氧训练组 ,每组 5人 ,头低位 (- 6°)卧床模拟失重时的心血管变化。在对照期 (第 2天 )、卧床期 (第 3、1 4、1 8天 )和恢复期 (第 7天 )记录 2 4h动态心电图 ,采用自回归模型进行 2 4h全程、放松和低氧训练前、中、后的心率变异性谱分析 ,其标准化的低频 (LF % ,0 .0 4～ 0 .1 5Hz)成分表示心交感神经的紧张度 ,标准化的高频 (HF % ,0 .1 5～ 0 .40Hz)成分独立地反映心迷走神经的活性 ,LF/HF的比值表明交感和迷走神经张力的平衡关系。结果卧床期对照组的LF %和HF %成分显著下降 (P <0 .0 5) ,LF/HF无明显变化。放松组在放松训练中HRV谱的HF %成分明显增加 (P <0 .0 5) ,而低氧组在低氧训练中 ,LF %成分显著增加 (P <0 .0 5)。结论卧床使交感和迷走神经的活性都降低 ,放松训练明显提高了迷走神经的兴奋性 ,而低氧训练明显提高了交感神经的兴奋性。提示 ,HRV指标有可能作为定量评价失重对抗措施的客观指标 ,值得进一步深入研究。     

民航飞行人员高血压病危险因素与心率变异性及压力反射敏感度的联系

目的：探讨民航飞行人员高血压病危险因素暴露与心率变异性（HRV）及压力反射敏感度（BRS）之间的联系。方法 在参加年度大体检的450名血压正常的民航飞行人员中，根据有无危险因素暴露将其分为年龄≥40岁组、体重超重组、血脂异常组、吸烟组、饮酒组及相应对照组。采用常规自回归谱分析方法对各组飞行人员的短时程HRV信号进行分析，同时采用序贯法计算其BRS。结果 与对照组相比，年龄≥40岁的飞行人员HRV明显降低，表现为总功率（TP)、低频功率（LF）、高频功率（HF）及归一化高频成分（HFn)显降低（P＜0．01），而归一化低频成分（LFn)与LF／HF则显增加（P＜0．05）；其BRS亦显降低（P＜0．01）。其他危险因素暴露时，HRV的TP、LF及HF均显降低（P＜0．05），而LFn、HFn、HFn及LF／HF则无明显变化，BRS亦显降低（P＜0．05）。结论 民航飞行人员高血压病危险因素的暴露与HRV及BRS的降低密切联系；提示在高血压病发病之前，心血管自主神经调节功能即已发生异常。在对飞行人员进行高血压病的早期危险性预报时应重视对其自主神经调节功能的评价。     

民航飞行人员高血压病患者心率变异性及压力反射敏感度分析

目的探讨民航飞行人员高血压病患者心血管自主神经调节功能的变化规律,为合理防治高血压病提供依据.方法利用常规AR谱分析方法对14例民航飞行人员高血压病患者和14例健康飞行人员的短时程心率变异性(HRV)信号进行分析,同时采用序贯法分析其压力反射敏感度(BRS).结果①与对照组相比,高血压病患者的HRV明显降低,差异有显著性意义(P＜0.05),表现为总功率(TP)、低频功率(LF)、高频功率(HF)及归一化高频成分(HFn)降低,而归一化低频成分(LFn)与LF/HF则增加;②高血压病患者的BRS较对照组降低,差异有非常显著性意义(P＜0.01).结论飞行人员高血压病患者心血管自主神经调节功能明显异常,交感神经调节活动相对增强,迷走神经调节活动受到抑制.在飞行人员高血压病的防治研究中,应加强对其自主神经调节功能的分析.     

头高位倾斜心率与血压变异性谱分析

观察头高位倾斜（HUT，＋65°）持续15min对10名健康男青年心率变异性（HRV）谱、血压变异性（SBPV）谱及压力反射敏感性（BRS）的影响。被试者由卧位转为HUT时，HRV高频谱峰功率（HFHRV）、总功率（TPHRV）及归一化高频谱成份（HFHRV，n）均显著降低（P＜0．01），低频谱峰功率（LFHRV）仅有升高趋势，但归一化低频谱成份（LFHRV，n）显著升高；SBPV谱高、低频谱峰功率（HFSBPV，LFSBPV）及总功率（TPSBPV）均显著升高（P＜0．01）；BRS显著降低（P＜0．01）。在HUT持续作用的6－12min期间，HRV、SBPV港的变化与HUT0－6min期间天显著性差别。结果提示立位应激时被试者心迷走神经活动降低、心交感及外周血管交感神经活动增强。     

硬膜外阻滞对左心室肥厚围术期心率变异性影响的观察

目的：观察上胸段硬膜外阻滞（HEB）对高血压性左心室肥厚围术期心率变异性（HRV）的影响。方法：选择择期行胃部切除术且合并高血压性左心室肥厚40例,随机分为观察组和对照组各20例。对照组采用静吸复合全身麻醉,观察组在对照组基础上加用HEB,分别在入室静卧30min后、清醒拔管后即刻、术后第1天、第3天及第5天,以短时程频域分析法检测HRV变化。结果：麻醉及术后两组HRV总功率（TP）、高频（HF）、低频（LF）和HF/LF均较术前基础值显著下降,术后第5天观察组上述指标基本恢复到术前水平,而对照组除LF外,其余指标仍显著低于术前水平（P〈0.01）。结论：上胸段硬膜外阻滞可减轻高血压性左心室肥厚患者围术期心脏自主神经损害。     

卧床中及卧床后头高位倾斜对心率及血压变异谱的变化

观察了男性青年２１ｄ头低位６°卧床过程中以及卧床前、后７５°头高位倾斜（ＨＵＴ）时心率变异（ＨＲＶ）与动脉收缩压变异（ＳＢＰＶ）谱变化。卧床期间，完成者ＨＲＶ和ＳＢＰＶ谱的低，高频谱峰功率（ＬＦ和ＨＦ）均显著减小，ＨＲＶ谱低，高频谱峰功率比值（ＬＦ：ＨＦＨＲＶ）在卧床第１６ｄ有增大趋势，未完成者的相应谱指标有类似变化趋向，在卧床后ＨＵＴ初始６ｍｉｎ，所有被试者心率显著快于卧床前ＨＵＴ时相应值，而Ｌ     

心率/血压变异性与压力反射敏感度的年龄依赖性

目的 比较中年与青年男子心率变异性（ＨＲＶ）、收缩压变异性（ＳＢＰＶ）和压力反射敏感度（ＢＲＳ）的差别,探讨不同年龄组心血管自主神经调节的特点。方法 用自回归模型方法计算仰卧位与站立位ＨＲＶ和ＳＢＰＶ的谱指标,用序费法计算ＢＲＳ,并分析其间的相关性。结果 中年组两种体位下的ＨＲＶ谱指标及仰卧位时的ＢＲＳ均显著低于青年组（Ｐ〈０．０５,或Ｐ〈０．０１）。由仰卧位转为站立位后,中年组ＨＲＶ的总功率（Ｔ     

跨时区飞行对飞行员心率变异性的影响

目的　探讨跨时区飞行对飞行员心率变异性的影响 ,以评价其对飞行员自主神经系统的作用。　方法　采用 2 4h动态心电图方法检测 16名跨时区国际长途飞行的飞行员动态心电图及心率变异性 (HRV) ;另外检测 10名国内昼间飞行的飞行员动态心电图及HRV作为对照。检查指标 :①HRV的低频功率 (0 .0 4～ 0 .15Hz ,LF) ;②HRV的高频功率 (0 .15～ 0 .4 0Hz,HF) ;③HRV的总频功率 (0 .0 4～ 0 .4 0Hz,TF)。计算飞行员HRV谱成份的夜间调节指数。用两组飞行员调节指数的差值作为自主神经负荷程度的定量估计。　结果　对照组飞行员的HF反映迷走神经活性在 2 4h中显示明显的昼夜节律 ,即夜间HF增高 ,LF降低 ;白天HF降低 ,LF增高。交感神经活性在跨时区飞行组上述谱成份的昼夜节律性明显降低。②对照组飞行员的HF夜间调节指数为 0 .32± 0 .11,而跨时区飞行组HF夜间调节指数为 0 .0 6± 0 .0 2 (P <0 .0 5 )。对照组LF夜间调节指数为 - 0 .0 2± 0 .0 8,而跨时区飞行组LF夜间调节指数为 - 0 .0 9± 0 .0 4 (P <0 .0 5 )。　结论　跨时区飞行使飞行员HRV谱成份的昼夜周期节律显著降低     

Changes in cardiac autonomic activity during a passive 8 hour acute exposure to 5 500 m normobaric hypoxia are not related to the development of acute mountain sickness

Alterations in the autonomic nervous system after ascent to high altitude may be related to the development of acute mountain sickness (AMS). So far, the time course of cardiac autonomic modulation in relation to AMS development during the early hours at altitude is not well established. As AMS develops sometimes as early as 1 h and typically within 6 to 10 h at altitude, evaluating this time period provides information on cardiac autonomic responses with regard to AMS development. Prior studies exclusively investigated autonomic modulations in hypobaric hypoxia. Because barometric pressure per se might influence autonomic nervous system activity, the evaluation of cardiac autonomic alterations caused by hypoxia alone might give new insights on the role of the autonomic nervous system in AMS development. To assess the early responses of acute hypoxia on cardiac autonomic modulation and its association to the development of AMS, 48 male subjects were exposed for 8 h to acute normobaric hypoxia (FiO2 11.0%, 5?500 m respectively). Heart rate variability (HRV) was determined by 5-min recordings of successive NN-intervals in normoxia and after 2, 4, 6 and 8 h in hypoxia. Compared with normoxia, acute exposure to hypoxia decreased total power (TP), high frequency (HF) and low frequency (LF) components as well as the standard deviation of all NN intervals (SDNN), the root mean square of differences of successive NN intervals (rMSSD) and the proportion of differences between adjacent NN intervals of more than 50 ms (pNN50). LF:HF ratio, heart rate (HR) and blood lactate (LA) were augmented, indicating an increase in cardiac sympathetic activity. No differences were found between those who developed AMS and those who did not. Our results confirm reduced HRV with a shift towards sympathetic predominance during acute exposure to hypoxia. However, changes in cardiac autonomic modulations are not related to AMS development in acute normobaric hypoxia.     

用心率变异性谱分析法研究振动性白指患者自主神经系统对冷刺激的反应

目的研究振动性白指患者的自主神经系统对冷刺激的反应。方法２２名振动性白指患者（ＶＷＦ组）及１９名正常对照（对照组）进行了局部冷水刺激实验,记录受试者的心电信号,实验后将记录的心电信号通过处理转化为ＲＲ间期信号,然后对这些ＲＲ间期信号进行功率谱分析,计算标准化的ＬＦ（０．０２～０．１５Ｈｚ）功量（ＬＦ％）,标准化的ＨＦ（０．１５～０．４０Ｈｚ）功量（ＨＦ％）,以及ＬＦ／ＨＦ比率。结果冷暴露开始后,ＶＷＦ组及对照组的ＨＦ％与暴露前的水平相比都有显著下降,ＶＷＦ组的ＬＦ／ＨＦ比率与暴露前的水平相比有显著增大,而且冷暴露中ＶＷＦ组的ＬＦ／ＨＦ比率显著高于对照组的相应的ＬＦ／ＨＦ比率。结论冷刺激导致ＶＷＦ组和对照组的副交感神经活动减弱,但对照组还能保持交感与副交感的平衡,而ＶＷＦ组却不能保持两者平衡,交感神经活动明显占优,冷刺激中ＶＷＦ组ＬＦ／ＨＦ比率明显高于对照组的ＬＦ／ＨＦ比率说明振动性白指患者的交感神经系统对冷刺激可能存在过敏反应。     

Gravity and gravidity: will microgravity assist pregnancy?

Abstract During the third trimester of pregnancy, exercise, deep ventilation and supine position may be particularly uncomfortable for pregnant women. Reduction of fetal weight by a microgravity environment may relieve some of this discomfort. This study assessed, by means of heart rate variability (HRV), the cardiovascular adaptation to the supine posture, to relaxing respiratory exercises (deep slow breathing) and to mild and moderate lower limb exercises in pregnant women, both in a dry environment and during a head-out water immersion, which mimics microgravity. Six third-trimester pregnant women (31±3 years; 67.8±8.3 kg; 163±3 cm; gestational age 26±6 weeks) were enrolled. Five-minute series of beat-to-beat RR intervals were recorded by a heart rate monitor in basal (B) state (on a separate day, comfortably sitting in a quiet room, 22° C) and in 2 different environments (G, gym, 22° C; W, water immersion at 34° C), on separate days, in 5 experimental conditions for each environment: (1) resting supine; (2) during upright mild lower limb exercise; (3) during upright moderate lower limb exercise; (4) during controlled deep ventilation (breathing rhythm, 0.1 Hz); (5) during controlled breathing (supine). Compared to B state, HR increased slightly in all experimental conditions in both G (+16%) and W (+8%) environments, whereas blood pressure did not. LF/HF ratio, a marker of sympathovagal balance, increased significantly during G at rest (5.0±2.4, p<0.05) but not in W at rest (2.7±1.5), and further increased during mild and moderate exercise in both G and W. During slow breathing in both environments (conditions 4 and 5), LF/HF paradoxically increased compared to B. Finally, LF/HF significantly increased (6.5±2.6, p=0.01) during ventilation in supine position, but only in G environment. Only HF decreased in both G_rest (-46.2%, p<0.05) and W_rest—24.6%, p<0.05) compared to B state, whereas LF was almost unchanged. Immersion in thermoneutral water, which mimics microgravity, produces some positive effects on the autonomic adaptation to different manoeuvres (supine position, exercise, deep slow ventilation) in third-trimester pregnant women. These effects are especially relevant in the assumption of supine posture, suggesting that microgravity will probably relieve the symptoms of aorto-caval compression produced by the fetus burden.     

Effect of acute hypoxia on heart rate variability at rest and during exercise

The purpose of this study was to investigate sympathovagal balance as inferred from heart rate variability (HRV) responses to acute hypoxia at rest and during exercise. HRV was evaluated in 12 healthy subjects during a standardized hypoxic tolerance test which consists of four periods alternating rest and moderate exercise (50 % V.O (2)max) in normoxic and hypoxic conditions. Ventilatory responses were determined and HRV indexes were calculated for the last 5 min of each period. In well-tolerant subjects, hypoxia at rest induced a decrease of root-mean-square of successive normal R-R interval differences (RMSSD) (p < 0.05) and of absolute high frequency (HF) power (p < 0.001). All absolute HRV indexes were strongly reduced during exercise (p < 0.001) with no further changes under the additional stimulus of hypoxia. A significant increase (p < 0.05) in the HF/(LF+HF) ratio (where LF is low frequency power) was found during exercise in hypoxia compared to exercise in normoxia, associated with similar mean changes in ventilation and tidal volume. These results indicate a vagal control withdrawal under hypoxia at rest. During exercise at 50 % V.O (2)max, HRV indexes cannot adequately represent cardiac autonomic adaptation to acute hypoxia, or possibly to other additional stimuli, due to the dominant effect of exercise and the eventual influence of confounding factors.     

Effects of exercise load and breathing frequency on heart rate and blood pressure variability during dynamic exercise.

It is known that heart rate (HR) variability decreases with dynamic exercise, but there are only few studies on blood pressure (BP) variability with exercise loads and the effect of breathing pattern has never been investigated. Thus, we studied HR and systolic blood pressure (SBP) signals by spectral analysis (FFT), in 9 healthy subjects, at different breathing frequencies (0.15, 0.2, 0.3, 0.4, 0.5, 0.6 Hz), at rest and during 3 exercise loads (25, 50 and 75% VO2max). BP was measured with a non-invasive device (Finapres) and continuously recorded. The power spectrum of R-R period significantly decreased with exercise loads in the low frequency band (LF: 0.04-0.128 Hz) and in the high frequency band (HF: 0.128-0.65 Hz), but with breathing frequency only in the HF part of the spectrum. The power spectrum of SBP significantly increased with exercise loads in LF and HF bands, and decreased in HF band with increasing breathing frequency. R-R and SBP HF peaks were centered on breathing frequency peaks. Therefore, spectral analysis of HR and SBP confirm the withdrawal of vagal control during exercise, while mechanical effect of respiration on SBP persists. LF/HF ratio of R-R spectral components decreased with increasing load, whereas cardiovascular sympathetic activity is known to rise, suggesting that this ratio is not a good indicator of cardiovascular autonomic modulation during exercise.     

Effects of intermittent hypoxia on heart rate variability during rest and exercise

Changes in heart rate variability induced by an intermittent exposure to hypoxia were evaluated in athletes unacclimatized to altitude. Twenty national elite athletes trained for 13 days at 1200 m and either lived and slept at 1200 m (live low, train low, LLTL) or between 2500 and 3000 m (live high, train low, LHTL). Subjects were investigated at 1200 m prior to and at the end of the 13-day training camp. Exposure to acute hypoxia (11.5% O(2)) during exercise resulted in a significant decrease in spectral components of heart rate variability in comparison with exercise in normoxia: total power (p < 0.001), low-frequency component. LF (p < 0.001), high-frequency component, HF (p < 0.05). Following acclimatization, the LHTL group increased its LF component (p < 0.01) and LF/HF ratio during exercise in hypoxia after the training period. In parallel, exposure to intermittent hypoxia caused an increased ventilatory response to hypoxia. Acclimatization modified the correlation between the ventilatory response to hypoxia at rest and the difference in total power between normoxia and hypoxia (r (2) = 0.65, p < 0.001). The increase in total power, LF component, and LF/HF ratio suggests that intermittent hypoxic training increased the response of the autonomic nervous system mainly through increased sympathetic activity.