卧床中及卧床后头高位倾斜时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ＬＦ∶ＨＦＨＲＶ和ＳＢＰＶ谱的ＬＦ与卧床前ＨＵＴ时相应值比较无显著变化。未完成者在卧床后ＨＵＴ时，未能出现舒张压与平均动脉压升高反应；而其在卧床前ＨＵＴ时，以及完成者在卧床前、后ＨＵＴ时，均出现舒张压与平均动脉压升高反应。结果说明，较长时间卧床后心脏迷走神经与外周血管交感神经的活动水平降低，心脏交感神经活动水平相对增高；但卧床后ＨＵＴ时心血管自主神经调节反应仍基本存在。未完成者卧床后ＨＵＴ时血压升高反应消失的机理，可能还与卧床后外周血管的收缩反应性降低有关。     

下体负压作用下人心率,血压变异性谱的变化及其与心血管反应…

观察了－６。６７ｋＰａ下体负压（ＬＢＮＰ）持续作用期间人心率变异性（ＨＲＶ）、血压变异性（ＳＢＰＶ）谱的变化，并探讨了谱特征与心血管反应之间的关系。结果表明：耐力良好者ＨＲＶ谱的调频峰功率（ＨＦＨＲＶ）显著降低，归一化高频参数（ＨＦＨＲＶ，ｎ）与低频参数（ＬＦＨＲＶ，ｎ）分别呈明确的降低或升高变化；ＳＢＰＶ谱的低频峰功率（ＬＦＳＢＰＶ）ＬＢＮＰ作用时降低，后又回升，至实验终止时已超出对照水平。ＬＢ     

下体负压作用下人心率、血压变异性谱的变化及其与心血管反应的关系

观察了－６．６７ｋＰａ下体负压（ＬＢＮＰ）持续作用期间人心率变异性（ＨＲＶ）、血压变异性（ＳＢＰＶ）谱的变化，并探讨了谱特征与心血管反应之间的关系。结果表明：耐力良好者ＨＲＶ谱的高频峰功率（ＨＦＨＲＶ）显著降低，归一化高频参数（ＨＦＨＲＶ，ｎ）与低频参数（ＬＦＨＲＶ，ｎ）分别呈明确的降低或升高变化；ＳＢＰＶ谱的低频峰功率（ＬＦＳＢＰＶ）ＬＢＮＰ作用时降低，后又回升，至实验终止时已超出对照水平。ＬＢＮＰ作用初期，耐力不良被试者ＨＲＶ、ＳＢＰＶ谱特征的变化趋势与耐力良好者相同，但在出现晕厥前症状时，ＬＦＳＢＰＶ及ＬＦＳＢＰＶ，ｎ均有较大幅度的降低。上述结果提示：耐力不良被试者心血管反应失代偿主要与外周血管交感神经活动水平的迅速降低有关。     

21天头低位(-6°)卧床前后下体负压和头高位倾斜暴露时的心血管反应

目的探讨２１天头低位（ＨＤＴ）卧床对人体立位应激下心血管反应的影响,以及比较下体负压（ＬＢＮＰ）和头高位倾斜（ＨＵＴ）两种立位应激下心血管反应的差异。方法６名受试者在２１天ＨＤＴ前、后分别进行ＬＢＮＰ（－４．００ｋＰａ／３ｍｉｎ、－６．６７ｋＰａ／３ｍｉｎ及－９．３３ｋＰａ／３ｍｉｎ）和ＨＵＴ试验（３０°／３ｍｉｎ、４５°／３ｍｉｎ、６０°／３ｍｉｎ及７５°／３ｍｉｎ）,以比较两种检测方法的血压（ＢＰ）和心率（ＨＲ）的变化情况。结果与ＬＢＮＰ（或ＨＵＴ）前相比：①ＬＢＮＰ（ＨＵＴ）时ＨＲ显著增加（Ｐ＜０．０１）,ＳＢＰ显著降低（Ｐ＜０．０５）;卧床后相应的变化量增加。②ＬＢＮＰ时ＤＢＰ降低（卧床后达显著,Ｐ＜０．０５）;而ＨＵＴ时ＤＢＰ增加（卧床后达显著,Ｐ＜０．０５）。③ＬＢＮＰ时ＭＡＰ均显著降低（Ｐ＜０．０５）;而ＨＵＴ时在卧床前无变化（Ｐ＞０．０５）,在卧床后显著增加（Ｐ＜０．０５）。结论ＬＢＮＰ和ＨＵＴ引起的ＣＶＳ反应并不相同。笔者认为,ＨＵＴ更能促进心血管系统对立位应激的调节作用。     

头低位－6°卧床时气功对尿皮质醇、尿醛固酮和超氧化物歧化酶的影响

６名年龄３５±６岁男性受试者作为对照组，６名年龄３６±６岁练气功的男性受试者为练气功组。实验程序包括２ｄ的准备期，７ｄ的头低位－６°卧床（ＨＤＢＲ－６°）期和２ｄ的恢复期。每天收集２４ｈ全尿，测定尿皮质醇（ＵＣＯＲ）和尿醛固酮（ＵＡＬＤ）；每两天采集耳血一次，测定超氧化物歧化酶（ＳＯＤ）的活性。结果表明：卧床前两组间ＵＣＯＲ和ＳＯＤ没有显著差异，而ＨＤＢＲ－６°后对照组ＵＣＯＲ和ＳＯＤ明显增加（Ｐ＜０．０１），练功组仅有增加的趋势，对照组和练功组相比在ＨＤＢＲ－６°期间差别显著（ｐ＜０．０１）。这表明练气功组比对照组有较好的耐受ＨＤＢＲ－６°的应激能力，对保持机体内环境稳定具有重要的意义。     

卧床模拟失重对人体急性缺氧耐力的影响

为探讨卧床模拟失重对机体缺氧耐力的影响，对６名受试者，头低位４°卧床（－４°ＨＤＢＲ）７ｄ，检查了卧床前后缺氧耐力和立位耐力，记录了ＥＣＧ、ＢＰ及ＨＲ的变化。结果表明：－４°ＨＤＢＲ模拟失重降低了机体的缺氧耐力；缺氧耐力与心血管失调间有很好的相关性。     

下体负压下的心率变异分析

为探讨下体负压下的心率变异变化及其与血液动力这指标的关系，４０名健康男性参加了下体负压实验，用Ｈｏｌｔｅｒ记录了受试者Ｖ５导联心电图，并进行了心率变异（ＨＲＶ）分析；用超声多谱勒技术测定ＳＶ，ＣＯ。结果表明：在ＬＢＮＰ过程中两组受试者均出现了ＨＲＶ的降低，尤以高频谱质量（ＨＦ）降低显著，ＬＦ／ＨＦ在ＬＢＮＰ过程中呈升高趋势，耐力低者的ＬＦ／ＨＦ升高比耐力良好者明显，提示：晕厥前症状的发生可能是由于     

有氧锻炼前后立位应激下血压变异性的比较

目的阐明下体负压（ＬＢＮＰ）作用下血压变异性的特征，以及有氧锻炼是否对其有一定影响。方法用常规ＡＲ谱、时变ＡＲ谱、粗粒化谱分析（ＣＧＳＡ）及近似熵（ＡｐＥｎ）四种方法，分析六个月有氧锻炼前、后大学生在两种ＬＢＮＰ作用下的收缩压变异性（ＳＢＰＶ），并与一组中、长跑运动员的结果进行横向比较。结果ＬＢＮＰ作用时，ＳＢＰＶ信号谐波成份的总功率及低频段（ＬＦ）功率增大，分形成份的谱指数（无显著变化，而ＡｐＥｎ则呈持续升高变化。有氧锻炼后，ＬＢＮＰ作用下各种ＳＢＰＶ指标的响应变化较锻炼前并无显著差别。大学生组与运动员组之间亦无显著差别。结论ＳＢＰＶ信号与心率变异性（ＨＲＶ）迥然不同：ＬＢＮＰ作用下，ＳＢＰＶ的ＬＦ成份被进一步激活，信号的复杂度显著升高；但ＳＢＰＶ信号的这种特征性变化并不受有氧锻炼的影响。     

前庭刺激对飞行人员心率变异的影响

为探讨前庭刺激对飞行人员的心率变异性（ＨＲＶ）及植物神经功能的影响，对两组飞行员在不同强度的科里奥利加速度刺激时，用时域分析和频域分析法对实验前和实验中的ＨＲＶ进行了检测和分析。结果表明；原始均值，标准差，最小值，最大值，极差，相关均值，Ｒ－Ｒ间期差值的均方根（ＲＭＳＳＤ），谱总功率（ＴＰ），低频（ＬＦ），高频（ＨＦ），ＬＦ／ＴＰ，ＨＦ／ＴＰ，ＬＦ／ＨＦ均有不同程度的增加（Ｐ〈０．０５～０．０１）     

－2kPa下体负压作用时人的心血管自主神经活动水平的变化

为研究心肺压力感受器卸荷对人心血管自主神经调节的影响，采用心率变异性（ＨＲＶ）和血压变异性（ＳＢＰＶ和ＤＢＰＶ）谱分析方法考察了在－２ｋＰａ下体负压（ＬＢＮＰ）条件下，心血管自主神经活动水平的变化。结果表明：ＬＢＮＰ作用１～７ｍｉｎ时基础胸阻抗（Ｚｏ）明显升高，心脏每搏量（ＳＶ）明显减少，致使前臂血管阻力（ＦＶＲ）明显增加、血流下降（ＦＢＦ），而心率（ＨＲ）及ＨＲＶ谱参数未发生显著变化，进一步证实了心肺压力感受器对外周血管交感神经和心脏自主神经活动的调节存在机能分化现象；ＬＢＮＰ作用时尽管有外周血管交感神经兴奋现象，但血压变异性谱参数均未发生显著改变，表明这两者在心肺压力感受器卸荷时的变化趋向存在差异。     

急性轻中度缺氧条件下心率及收缩压变异性谱变化

目的：应用心率及收缩压变异性（HRV、SBPV）谱分析方法评价急性轻中度缺氧条件下心血管自主神经调节的变化。方法：10名健康男性青年分别吸入氧13．7％（相当于海拔3500m)和11％（相当于海拔5000m）两种氮－氧混合气各20min,将对照和缺氧条件下的HRV和SBPV谱变化进行对比分析。结果：在两种缺氧条件下,受试者均出现血压下降、心率增快反应,HRV谱总功率（TP）和高频成分（HF）功率均显著减小,低频成分（LF）功率与LF／HF功率比值无显著变化,SBPV谱LF功率显著增大,3名缺氧耐力不良受试者尤为明显。不同水平缺氧之间的数值比较差异均无显著性意义。结论：急性轻中度缺氧条件下,人副交感神经抑制,交感神经兴奋,联合应用HRV与SBPV谱分析方法可对心血管自主神经调节活动进行评定;但HRV的LF成分变化机理较为复杂。     

Aerobic training and cardiovascular responses at rest and during exercise in older men and women

PURPOSE: The effects of an intense 8-wk aerobic training program on cardiovascular responses at rest and during exercise, including heart rate variability (HRV) as an expression of autonomic modulation, were evaluated in subjects over 70 yr (mean: 73.9 +/- 3.5 yr). METHODS: Before and after training in 7 men and 8 women: a) heart rate (HR), blood pressures (BPs), pulse pressure (PP), and oxygen uptake were measured at rest, during, and after exhausting incremental exercise; b) HRV power spectra were calculated at rest in supine and sitting, and during and after two submaximal constant loads (5 min). Power in low-frequency (LF, 0.04-0.15 Hz) and high-frequency (HF, >0.15 Hz) bands were expressed as a percent of total power minus power < 0.04 Hz. RESULTS: After training: a) at rest HR and HRV parameters (in both body positions) were unchanged, whereas BPs decreased; b) peak cycle resistance and oxygen consumption increased by 25% and 18%, respectively, but no change in maximal HR and BPs were found; c) during submaximal loads HR was unchanged at the same metabolic demand, whereas SBP and DBP were lower than before at low loads whereas PP was unchanged. LF power decreased and HF increased at oxygen uptakes above about 0.7 L.min-1 similarly before and after training; and d) recovery of all parameters was similar to pretraining and complete after 10 min CONCLUSIONS: The increase in exercise capacity without changes in cardiovascular parameters suggests that 8 wk of aerobic training augmented peripheral gas exchange but not delivery to muscle. The lack of effect on HRV indicates that the improvements in aerobic power and cardiac autonomic modulation, at least in subjects over 70 yr, are dissociated. Moreover, the metabolic demand seems to be the main factor for the changes in HRV power spectra that occur during exercise.     

Vasomotor sympathetic nerve activity in men during bed rest and on orthostasis after bed rest

BACKGROUND: Alterations in autonomic function are commonly seen during and after spaceflight, and its ground-based analog, 6 degrees head-down bed rest (HDBR). They may include peripheral vascular regulation, but vasomotor sympathetic efferent nerve discharges to peripheral vasculatures have not been examined. The aim of our study was to examine changes in vasomotor sympathetic nerve activity during HDBR and under orthostasis after HDBR. METHODS: We performed 6 d of HDBR on six male subjects, and measured muscle sympathetic nerve activity (MSNA) together with plasma norepinephrine concentrations in the supine position before HDBR and in 6 degrees head-down position on the sixth day (HDBR6) of HDBR. We also measured MSNA in head-up tilt (HUT) test before and after HDBR. RESULTS: On HDBR6, MSNA burst rate was the same (17+/-4 bursts x min(-1)) as that in supine position before HDBR (15+/-2 bursts min(-1)), but plasma norepinephrine concentrations were decreased to 1.14+/-0.10 pmol x ml(-1) compared with the supine value before HDBR (1.56+/-0.20 pmol x ml(-1), p<0.05). After HDBR, supine MSNA burst rate significantly increased by 58% to 24+/-4 bursts x min(-1). MSNA increment in response to HUT was similar between before (34+/-3 bursts min(-1) x sin HUT(-1)) and after (40+/-6 bursts x min(-1) x sin HUT(-1)) HDBR. CONCLUSIONS: Our findings suggest that: a) the relationship between MSNA and plasma norepinephrine concentrations was altered on the sixth day during HDBR; b) the vasomotor sympathetic nerve activity was enhanced after HDBR; and c) the augmentation of vasomotor sympathetic outflow to muscles under orthostasis was preserved after HDBR.     

Heart rate variability during high-intensity field exercise in female distance runners

The purposes of this study were to demonstrate the transition of heart rate variability (HRV) during trials in the field and to examine the relationship between peak frequency of high-frequency band (HF) and stride frequency. Ten healthy long-distance college female runners (age 19-21 years) performed a 3000 m realistic time trial. The time-series power spectrum analysis by maximum entropy method was used to evaluate cardiac autonomic nervous activity during the race. Cross-correlation coefficients were calculated to estimate the degree of linear co-ordination between the central peak frequency of HF and stride frequency. Just after starting, the decrease in HF (0.15-1.00 Hz) and a transient increase of low-frequency band (LF)/HF were found. After that, the HF remained at a low level and LF/HF decreased sharply. These findings suggested that the parasympathetic activity was suppressed and sympathetic activity increased just after starting, and the sympathetic activity reached the saturated level according to continuation of high-intensity exercise. In spite of the significant decrease of HRV during trials, peak frequency of HF could be differentiated clearly. The cross-correlation coefficient of peak frequency of HF and stride frequency was from 0.703 to 0.868. This finding indicated that exercise rhythm reflected HRV during high-intensity running in the field.     

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。     

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。     

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.     

平行秋千摆动刺激中的心率变异分析

目的 观察飞行员在平行秋千摆动前、中、后反映心脏植物神经调节功能的心率变异性（ＨＲＶ）特点,搪塞以此评价线性加速度作用下前庭＝植物神经反应性的可能性。方法记录３７名飞行员在秋千摆动前、中、后的连续心电图,进行频率谱分析并计算低频成分（ＬＦ）和高频成分（ＨＦ）之幽会对被试者中ＬＦ／ＨＦ值在不同摆动阶段变化类型及分布耐受摆动时间的关系进行初步分析。结果 摆动中的ＬＦ明显降低,ＨＦ明显增高,ＬＦ／ＨＪＦ     

Effects of a single bout of exercise on resting heart rate variability

PURPOSE: Chronic exercise training has been shown to have a positive influence on cardiac autonomic function as assessed by measures of heart rate variability (HRV). Recent evidence indicates that several benefits associated with exercise training (e.g., improved insulin action, reduced blood pressure, improved blood lipid profile) may be realized transiently after a single bout of exercise. As many of these effects of recent exercise are linked to cardiovascular control systems, the purpose of this investigation was to test the hypothesis that a single bout of exercise would result in favorable changes in cardiac autonomic function as assessed by frequency-domain measures of HRV. METHODS: Subjects were 11 healthy male volunteers ages 18-35 yr. Resting HRV measures were obtained during 5 min of paced breathing before and 1, 3, 6, and 22 h after a 60-min bout of cycling exercise at approximately 65% of peak oxygen uptake. Identical measures were obtained in a nonexercise condition based on a randomized crossover design. RESULTS: Exercise resulted in increased high-frequency HRV, decreased low-frequency HRV, and consequently a decrease in the ratio of low-frequency to high-frequency HRV compared with the nonexercise condition. Additionally, a time-domain measure of HRV (pNN50) was markedly higher in the exercise condition as compared to nonexercise. CONCLUSION: The changes in cardiac autonomic function observed are similar to those seen in investigations of long-term training. These changes indicate a shift in autonomic function toward increased parasympathetic nervous system activity and decreased sympathetic nervous system activity, suggesting a more stable autonomic environment for the heart. These results may provide further evidence of the cardioprotective effects of a single bout of submaximal exercise.     

重力应激下非平稳心率变异性的时变自回归谱分析方法

为分析重力应激下非平稳心率变异性信号，建立了时变自回归模型谱估计方法，藉此可得到各项谱指标随时间变化的曲线，以动态地观察，研究不同重力应激作用下心脏自主神经调节的过程，曾利用该方法处理８名被试者有氧锻炼前、后坐位下体负压高频谱成分逐步降低，以及低、高频谱成分比值（ＬＦ／ＨＦ）逐步升高直至稳定水平的过程；前者反映心迷走撤除，后者反应心交感激活的动态过程。还可以观察到有氧锻炼６个月后ＨＦｎ、ＬＦｎ变化