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。     

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。     

耐力训练后急进高原心率变异性与急性高原反应关系研究

目的:分析不同强度耐力训练后模拟急进高原24h内心率变异性(HRV)与急性高原反应(AMS)的关系。方法:选择分别经过极限强度、有氧、无氧耐力训练的男性新兵43例,检测在模拟急进4500m高原24h期间2、10、20h的HRV,分析其与AMS的关系。结果:极限耐力组、有氧耐力组RMSSD、PNN50均显著下降,无氧耐力组呈先下降后升高曲线;有氧耐力组LF/HF先下降后增高,无氧耐力组、极限耐力组则呈先增高后下降曲线;极限耐力组、有氧耐力组SDNN、TP呈下降趋势,无氧耐力组则无显著变化。AMS症状评分与模拟急进高原后10、20h时LF/HF呈显著正相关(P<0.05);与SDNN、RMSSD、PNN50、HFn呈显著负相关(P<0.05,P<0.01)。结论:极限强度耐力训练和有氧耐力训练不利于对急进高原环境的习服;无氧耐力训练使交感和副交感神经活动维持相对稳定状态,增强ANS的调节能力,有助于提高急进高原的适应能力。     

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。     

训练者和无训练者的心脏自主神经功能及其对中等强度有氧运动的反应特征

目的：比较训练者和无训练者的自主神经功能及其对一次30分钟中等强度有氧运动的反应特征。方法：17名有训练健康男性和20名无训练健康男性采用60%VO2max强度进行30 min跑台运动，测试运动前安静状态（PRE）、运动中（EX）、运动后50～60 min(POST1)和次日晨（POST2）的心率变异性（HRV），比较有训练者和无训练者安静状态、运动状态和运动后恢复期的HRV差异以及有训练者和无训练者运动前、运动中、运动后的HRV变化特征。结果：（1）安静状态训练者相邻RR间期差值的均方根（RMSSD）、相邻RR间期相差大于50 ms的数量占总心搏数的百分比（PNN50）、总功率（TP）、高频功率（HF）、低频功率（LF）均高于无训练者（P<0.05），而低频高频比值（LF/HF）两者无显著差异；运动中训练者的RMSSD、HF、LF高于无训练者（P<0.05）,LF/HF两者无差异；运动后50～60 min训练者相邻RR间期标准差（SDNN）、RMSSD、PNN50、TP、HF、LF高于无训练者（P<0.05）,LF/HF两者无差异；运动后次日晨训练者SDNN、RMS...     

心率变异时域及频域分析对儿童病毒性心肌炎的临床价值

目的监测病毒性心肌炎患儿的心率变异时域、频域指标,评价其对儿童病毒性心肌炎的临床价值。方法采用计算机心电监测系统,分别对42例病毒性心肌炎患儿和42例健康儿童进行HRV时域、频域指标检测,对两组间检测结果进行比较分析。结果病毒性心肌炎患儿心率变异时域指标、心率总体标准差（SDNN）、心率差值均方的平均根（RMSSD）均降低,频域指标低频成分（LF）、高频成分（HF）降低,而LF/HF增高。与对照组均有显著性差异（P〈0.05）。结论病毒性心肌炎患儿自主神经功能受损,表现以迷走神经活性降低为主,HRV指标可为儿童病毒性心肌炎的早期诊断提供参考,提示重新调整自主神经平衡对病毒性心肌炎的防治有不可忽视的价值。     

三维滚轮在飞行人员前庭功能稳定性选拔中的应用评价

目的探讨电动三维滚轮在飞行人员前庭功能选拔中的作用。方法对20名飞行人员分别进行转椅90 s和三维滚轮5 min的测试,观察在此过程中被试者的血压、心率、心率变异性(heart rate variability,HRV)和呼吸等各项生理指标,并依据症状和主诉对其前庭功能进行评级并对比两者通过率。结果相较于转椅测试,飞行人员在三维滚轮测试过程中的心率显著升高,LFn显著降低,HFn显著升高,LF/HF明显降低(P0.05)。二者前庭自主神经稳定性分级结果一致,合格率均为95%。结论电动三维滚轮可以用于飞行人员前庭功能稳定性的选拔。     

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。     

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.     

女飞行学员高空缺氧耐力的实验研究

观察男女飞行学员5000m缺氧的生理反应，旨在从高空缺氧耐力方面探讨我国女性从事歼击机飞行的可能性。以20名男性战斗机高教机飞行学员（21－23岁）和22名女飞行学员（21－23岁）为研究对象。采用DY－84型混氧仪，受受试者吸入10.5%低氧混合气持续15min，模拟高空5000m缺氧耐力检查。在模拟5000缺氧环境中，男女飞行员的心电图、心率、血氧饱和度差异无显著性意义（P＞0.05)，而血压变化差异有显著性意义（P＜0.05)。从缺氧耐力上讲，中国飞行学员可以从事战斗机飞行。     

间歇性常压低氧训练对心率变异的影响

目的观察间歇性常压低氧 (intermittentnormobarichypoxia ,INH)训练对低氧条件心率变异的影响。方法对 8名被试者进行为期 4周共 2 4d的INH训练 ,并对被试者训练前后暴露于 1 0 %低氧环境前、中、后的心率变异指标进行对比分析。结果经INH训练后 ,被试者低氧条件下R R间期均值、标准差、总功率、高频成分功率、低频成分功率显著增高 (P <0 .0 5～P <0 .0 0 1 ) ,而标准化高频成分功率、标准化低频成分功率、低频成分功率 /高频成分功率变化不明显。结论 1 )INH训练可提高被试者低氧条件下的心率变异性 ;2 )INH训练不仅可用于提高低氧耐受力 ,还有助于提高航天人员的飞行耐受力     

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.     

Spectral analysis of heart rate variability during exercise in trained subjects

PURPOSE: To investigate the effects of strenuous exercise on heart rate variability (HRV). METHODS: We evaluated the effects of exercise intensity and duration on HRV indices in 14 healthy trained subjects. Each subject exercised for 3, 6, and 9 min at 60 and 70% of the power achieved at maximal oxygen consumption (PVO2(max)) and for 3 and 6 min (or 3 min twice) at 80% of PVO2(max). The electrocardiogram RR intervals were recorded then processed by fast(FFT) and short-time (STFT) Fourier transform for determination of low-frequency (LF, 0.045-0.15 Hz) and high-frequency (HF, 0.15-1.0 Hz) components. RESULTS: The LF and HF components expressed as absolute power (ms2) decreased significantly at the onset of exercise (P < 0.05). However, with increasing exercise intensity, the HF component expressed as normalized units (n.u.) (reflecting parasympathetic modulation) increased significantly, whereas the LF component (n.u.) and LF/HF ratio (both reflecting sympathetic modulation) decreased significantly (P < 0.05). STFT showed that increasing exercise intensity was associated with a shift in HF peak frequency related to an increase in respiratory rate and a marked decrease in LF power (ms2). Moreover, HFn.u. rose (r = 0.918, P < 0.01) and LFms2 fell as minute ventilation increased (r = 0.906, P < 0.01). CONCLUSIONS: Parasympathetic respiratory control and nonautonomic mechanisms may influence the HF-peak shift during strenuous exercise. HRV and the usual indexes of sympathetic activity do not accurately reflect changes in autonomic modulation during exhaustive exercise.     

速可眠、三唑仑催眠对健康人心率变异性的影响

目的 探讨服用催眠药对健康人心率变异性（HRV）的影响,为使用HRV评定此类催眠药的催眠效果提供方法和生理依据。方法 在噪声干扰条件下,连续记录8名健康男性青年（年龄18－20岁）在服用速可眠（Sec）或三唑仑（TZ）后的5h睡眠过程中HRV指标（时域、频域）的动态变化特征,并与自身基础状态和服用安慰剂时进行比较。结果 Sec组的正常R－R间期标准差（SDNN）、平均每5minR－R间期标准差（SDANN）、低频功率（HF）升高,与安慰剂组或基础对照组比,差异均有显著性意义（P＜0．05）。TZ组除SDNN、SDANN、LF与基础对照组比,差异无显著性意义（P＞0．05）外,余项指标与Sec组的变化相同。结论 催眠药对HRV指标均有显著影响,TZ可能以影响迷走神经活动为主,HRV对催眠药的催眠效果能作出更客观、准确的评价。     

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     

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。     

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.     

Heart rate variability during high ambient heat exposure

INTRODUCTION: This study observed heart rate variability (HRV) measured in order to detect the changes in sympathovagal activity during high ambient (74 degrees C) temperature. HRV is a measure of heart rate (HR) fluctuations around the mean HR and has been used to indicate the balance between parasympathetic and sympathetic function of the autonomic nervous system in medicine and exercise, but not in extreme environments. METHODS: There were 10 healthy male subjects who wore Polar HR monitors (PE 5000) during a 15-min exposure (74.3 +/- 5.9 degrees C). RESULTS: HR increased significantly (p < 0.05) from 66.5 bpm pre-exposure to 106.0 bpm during exposure to the dry heat. A significant decrease in parasympathetic drive was indicated by: (1) a reduction of 89.1 +/- 31.3% in the proportion of interval differences between two normal R-R intervals that were in excess of 50 ms in length (pNN50); (2) an 83.4 +/- 7.0% decrease in the root mean square of successive R-R differences (RMSSD); and (3) an 82.7 +/- 11.4% decrease in the normalized high-frequency (HF norm) values. An increase in a sympathetic drive was indicated by a significant increase in: (1) the normalized low-frequency (LF norm) values of (84.5 +/- 19.4%); and (2) the LF:HF ratio (10.9 +/- 10.8%). DISCUSSION: The results from this study show that exposure to high ambient temperature produces a significant increase in HR through an increase in sympathetic and decrease in parasympathetic drive.     

Heart rate variability in sportive elderly: relationship with daily physical activity

PURPOSE: Aging is associated with decreased heart rate variability (HRV). As aerobic training is known to increase HRV, the purpose of this study was to evaluate the influence of long-term lifestyle on HRV in very old adults with regard to their usual physical activity. METHODS: Twenty-four older adults (mean 75.7 +/- 0.2 yr) were divided into two groups according to their sport activities assessed by the Modified Baecke Questionnaire for Older Adults. Sedentary subjects (SED) were compared to elderly regularly involved in sport activities (SP). The subjects were supine for 20 min and the last 5 min were used to determine HR and HRV indexes as the standard deviation of normal intervals (SDNN), the root-mean-square differences of successive normal R-R intervals (RMSSD), and the high-frequency (HF) and low-frequency (LF) power. Physical activity was evaluated during 1 wk by triaxial accelerometry and analyzed in terms of intensity and duration. RESULTS: Daily physical activity energy expenditure given by the accelerometer was significantly higher in SP than in SED (P < 0.05). SP spent more time per week in activity of intensity higher than 3 resting metabolic equivalents (METs), but total activity time was significantly higher for SED than for SP (P < 0.05). SP showed significantly (P < 0.05) lower resting heart rate than SED, higher global HRV (SDNN), and higher parasympathetic-related HRV indexes (RMSSD, HF, and HF/(LF+HF)) (P < 0.05). CONCLUSIONS: Our results indicate that in very old subjects a long-term sportive lifestyle, which increases total daily energy expenditure and physical activity intensity, is associated with higher global HRV and vagal-related indexes and thus may counteract the age-related decline in cardiac autonomic control better than a sedentary lifestyle.