汽车驾驶员模拟精神负荷与心率变异性的相关性分析

汽车驾驶员精神负荷状态下的心率变异性分析对于揭示驾驶员职业应激特点,预防驾驶员职业疾病,保护驾驶员身体健康及提高行驶安全性有重要意义.本文在实验室条件下采用警惕任务代替驾驶员实际精神负荷,应用功率谱分析研究了模拟应激状态下心率变异性(TP,LF,HF,LF/HF)的变化趋势.本实验中,心率变异性频域主要指标如LF、HF、LF/HF表现出显著的线性趋势.结果表明,健康人在持续应激状态下,交感神经张力显著增加,迷走神经张力显著降低.实验结果表明HRV与精神疲劳具有较好的相关性.     

亚健康人群心率变异性特点的研究

目的 探讨亚健康状态人群自主神经功能的特点.方法 随机选取70例亚健康状态人员,75例健康状态人员分别接受短时(5分钟)心率变异性分析,以正常心动周期的标准差(SDNN)、总功率(TP)、低频功率(LF)、高频功率(HF)、低频功率与高频功率比值(LF/HF)为考察指标,记录并进行统计学分析.结果 亚健康状态人群正常心动周期的标准差和总功率都显著低于健康人群(t=-4.643,P=0.00;t=-3.492,P=0.002);同时与健康人群比较,亚健康状态人群的低频功率增高,但未达统计学意义(t=0.898,P=0.377);高频功率有所下降,亦未达到统计学水平(t=-0.899,P=0.376);亚健康状态人群的低频功率与高频功率比值(LF/HF)与健康人群没有差异(t=0.943,P=0.354).结论 亚健康状态人群心率变异性降低,自主神经系统功能减退.     

咖啡摄入前后心率变异性的对比研究

目的研究中等剂量咖啡摄入对青年受试者心率变异性的影响,明确咖啡对心脏自主神经活性的作用。方法无咖啡因摄入习惯的16名健康青年受试者(身高167 cm±7.2 cm、体重61.3 kg±6.3kg、年龄24.9岁±2.8岁)参与本项研究,在摄入含6 mg/kg咖啡因的咖啡饮品后,于8:40~10:45应用动态心电图记录仪(Holter)进行咖啡摄入前后心电信号的采集及心率(heart rate,HR)和心率变异性指标的分析。心率变异性指标包括R-R间期标准差(SDNN)、相邻R-R间期差值的均方根值(r MSSD)、相邻的R-R间期之差大于50 ms的心搏数占总心搏数的百分比(PNN50)、标化低频(normalized low frequency power,LFnorm)、标化高频(normalized high frequency power,HFnorm)、低频功率(low frequency,LF)与高频功率(high frequency,HF)的比值(LF/HF)。结果饮用咖啡后,心率、心率变异性指标均发生改变且具有统计学意义,HR、LFnorm和LF/HF分别降低了7.5%、17%和35%。r MSSD、PNN50和HFnorm分别提高了82%、80%和58%。其中HR及LF/HF随着时间的变化趋势最明显。HRV参数在饮用咖啡前后的差值ΔLF与ΔHF,ΔLF与ΔLF/HF均显著相关,相关系数为-0.980和0.903。结论中等剂量咖啡可引起心率变异性的改变和心率的降低,抑制交感神经活性,提高副交感神经活性。     

6周六字诀锻炼对不同体位姿势状态下心率变异性的影响

观察6周六字诀锻炼对不同体位姿势状态下心率变异性频域指标的影响.采用MCA-3C心脏(功能)信息综合检测仪记录分析比较了健康女大学生6周六字诀锻炼前后坐位、平仰卧位、站立位及-25°仰卧位时心率变异性频域指标中LFnorm、HFnorm及LF/HF的变化.与锻炼前相比:(1)六字诀组(n=9)站立位及坐位时LFnorm呈极显著性减少(P＜0.01),HFnorm呈极显著性增加(P＜0.01);平仰卧位时LFnorm呈显著性减少(P＜0.05),HFnorm呈显著性增加(P＜0.05).对照组(n=7)坐位时LFnorm则呈显著性增加(P＜0.05),HFnorm呈显著性减少(P＜0.05).(2)六字诀组站立位时LF/HF呈极显著性减少(P＜0.01);坐位及平仰卧位时LF/HF呈显著性减少(P＜0.05).对照组各种姿势状态下LF/HF均无显著性差异(P＞0.05).(3)-25°仰卧位时两组各指标均无显著性差异(P＞0.05).6周的六字诀锻炼可使自然呼吸状态下安静时心率变异性低频段成分降低、高频段成分增加,显示交感神经紧张性相对减弱、迷走神经紧张性相对增强.锻炼效果主要体现在站立位、坐位和平仰卧位时,而在-25°仰卧位时则表现不明显.     

糖化血红蛋白对2型糖尿病首发急性心肌梗死患者心率变异性的影响

目的:分析糖化血红蛋白(HbA1c)水平对2型糖尿病首发急性心肌梗死(T2DM+AMI)患者心率变异性(HRV)指标的影响。方法:150例AMI患者按其是否有T2DM病史,分为T2DM+AMI组(A组,n=90)和AMI组(B组,n=60);A组患者再依其血清HbA1c水平分为≤6.0%(A1组);6.0%—7.5%(A2组);7.5%(A3组)。所有患者均于AMI发作48h行动态心电图(Holter)和超声心动图检查,选取HRV时域指标RR间期标准差(SDNN)、每5min RR间期均值标准差(SDANN)、相邻RR间期差≥50 ms个数占总心跳次数百分比(PNN50)及频域指标低频(LF, 0.04-0.15Hz)、高频(HF, 0.15-0.40Hz)、LF/HF比值和极低频(VLF, 0.0033-0.04Hz)。分析比较A、B两组及三亚组间上述指标的差异性。结果:A组患者HRV各时域指标均小于B组(P0.05),频域指标中LF、HF小于B组(P0.05),LF/HF和VLF与B组差异无统计学意义(P0.05)。三亚组间HRV时域指标中A3组的SDNN,SDANN水平也明显低于A1、A2组(均P0.05),频率指标LF,HF水平也明显低于A1、A2组(均P0.05)。而上述4指标在A1、A2组组间差异无统计学意义(P0.05)。同时LF/HF在三组间差异无统计学意义(P0.05)。结论:T2DM+AMI患者心脏自主神经功能受损比单独AMI患者严重;HbA1c7.5%可能加重上述损伤。     

汽车驾驶员驾驶过程中的心率变异性功率谱分析

驾驶疲劳是影响汽车乘坐舒适性及交通安全的重要因素。汽车驾驶员在长期驾驶情况下，尤其振动条件下，常表现出不同的生理、心理功能障碍或紊乱，影响驾驶员身心健康并诱发交通事故。本研究应用心率变异性功率谱分析并结合主观评估，分析了模拟实际驾驶条件下实验者的心脏自主神经功能状态。持续应激条件下，实验者心率变异性(HRV)表现出明显的变化，如交感神经活动性增加，迷走神经活动性降低。实验结果表明心率变异性(HRV)是精神负荷敏感的指标，可用于定量评估驾驶疲劳。     

全身麻醉状态下心率变异性的连续小波分析

为更准确地通过分析心率变异性(HRV)判断麻醉深度随时间的变化,需要密切关注麻醉状态下HRV低频(LF)和高频(HF)成分随时间的变化情况,采用连续小波变换(CWT),将CWT中的尺度转换为频率,对患者麻醉前后的HRV信号(RR间期序列)进行了时频分析。其时频能量图以及LF、HF能量值都表明麻醉后HRV信号的LF和HF成分受到了抑制,LF/HF值也由麻醉前的9.021 9降为麻醉后的3.557 3。CWT和传统的时频分析方法在分析同一麻醉后HRV的时频分布表明,CWT可以更准确地定位HRV时域信号中出现突变的时间以及引起频率变化的频段范围。因此,CWT作为分析麻醉状态下HRV的一种新方法,能提供HRV更为准确的时频定位,进而提供更为准确的麻醉深度监控结果。     

妊娠期糖尿病孕妇心率变异性变化

目的:探讨妊娠期糖尿病孕妇心率变异性变化。方法:选取阳春市妇幼保健院2018年1月至2020年4月收治的50例妊娠期糖尿病患者作为观察组,选取同期健康孕检孕妇50例作为对照组,年龄20~36岁,孕周24~40周。所有孕妇给予动态心电图监测,比较两组孕妇平均心率(AHR)、正常窦性RR间期的总体标准差(SDNN)、每5 min窦性RR间期均值标准差(SDANN)、24 h相邻连续性窦性RR间期差值的均方根(rMSSD)、相邻RR间期的差值超过50 ms百分比(PNN50)等时域指标,及总频率(TF)、低频谱功率(LF)、高频谱功率(HF)、LF/HF等频域指标。结果:观察组SDNN、SDANN、TF、LF、HF均低于对照组(P<0.05),两组PNN50、LF/HF、AHR、rMSSD比较,差异无统计学意义(P>0.05)。结论:妊娠期糖尿病孕妇自主神经调节功能下降,通过动态心电图能够发现心率变异性变化差异。     

小儿心肌炎的心率变异性

目的:探讨小儿心肌炎的心率变异性。方法:采用ECG-LA2.OGold型心电综合分析系统,描记肢体导联采样5分钟,应用时域及功率谱分析法,通过计算机计算出全部R-R间期的标准差(sDNN),极低频(VLF)低频(LF)高频(HF)。结果:以SDNN<27ms为阳性诊断标准,将57例小儿心肌炎病儿分为两组,一组SDNN<27ms共17例,病情较重,另一组SDNN>27ms共41例,病情较轻。结论:病情较重的心肌炎患儿短程HRV降低SDNN<27ms。     

低体温与心率变异性和血压变异性的关系

目的: 研究低体温与自主神经功能变化的关系。方法: 采用体表物理降温法逐步降低直肠温度,直肠温度变化范围为19-37 ℃。分别记录不同直肠温度下大鼠动态心电和血压信号。应用心率变异性和血压变异性分析系统评价低体温对心率变异性和收缩压变异性的影响。结果: 心率变异分析表明，直肠温度下降到29 ℃以下,R-R间期均延长（P<0.01）,提示心率明显降低;当直肠温度下降到19-21 ℃时,心率变异归一化低频功率降低（P<0.05）和归一化高频功率增加（P<0.05），而且自主神经的平衡向心迷走神经张力增强的方向发生了转移（P<0.05）。血压变异性分析表明，体温下降到31℃时与呼吸有关的归一化高频功率开始增加（P<0.01）；直肠温度下降到29 ℃以下(除27 ℃外),与呼吸有关的归一化高频功率增加（P<0.05或P<0.01），同时自主神经的平衡也发生了改变（P<0.05）。结论： 随着体温的降低，心血管迷走神经活性增加，自主神经的平衡向迷走神经张力增强的方向转移。低体温对血压变异性的影响敏感于心率变异性。     

The effect of ventilation on spectral analysis of heart rate and blood pressure variability during exercise

Heart rate variability (HRV) and systolic blood pressure variability (BPV) during incremental exercise at 50, 75, and 100% of previously determined ventilatory threshold (VT) were compared to that of resting controlled breathing (CB) in 12 healthy subjects. CB was matched with exercise-associated respiratory rate, tidal volume, and end-tidal CO(2) for all stages of exercise. Power in the low frequency (LF, 0.04-0.15 Hz) and high frequency (HF, >0.15-0.4 Hz) for HRV and BPV were calculated, using time-frequency domain analysis, from beat-to-beat ECG and non-invasive radial artery blood pressure, respectively. During CB absolute and normalized power in the LF and HF of HRV and BPV were not significantly changed from baseline to maximal breathing. Conversely, during exercise HRV, LF and HF power significantly decreased from baseline to 100% VT while BPV, LF and HF power significantly increased for the same period. These findings suggest that the increases in ventilation associated with incremental exercise do not significantly affect spectral analysis of cardiovascular autonomic modulation in healthy subjects.     

Effect of magnitopuncture on sympathetic and parasympathetic nerve activities in healthy drivers--assessment by power spectrum analysis of heart rate variability

The object of this study was to assess the effects of magnitopuncture applied to Dazhui (DU14) point and Neiguan (PC6) points on sympathetic and parasympathetic nerve activities by power spectrum analysis of heart rate variability in healthy drivers during simulated driving. Using power spectrum analysis, the low frequency (LF) and high frequency (HF) components of heart rate variability can be calculated reflecting the sympathetic and parasympathetic activity. The 40 healthy male subjects were randomly divided into two groups: A (study group) and B (control group). All subjects were required to be well rested before the experiment. The subjects of both groups were required to perform a simulated driving task for 3 h. During the driving, magnitopunctures were applied to the DU14 and PC6 points for A while the subject performed the task for 2.5 h, and for B magnitopunctures were applied to non-acupuncture points which were 1.5 cm away from the two acupuncture points respectively over the same time. Subjective response to a questionnaire was obtained after the simulated task in the two groups. At the end of the driving task the LF component in normalized units (NU) had decreased significantly (P<0.05) indicating a reduced sympathetic nerve activity and the HF component (NU) increased significantly (P<0.05) indicating a increased parasympathetic nerve activity for A compared with pre-stimulation while for B no significant differences were observed. There were significant group differences in LF (NU), HF (NU) and LF:HF at the end of the driving task (P<0.05). It was concluded that a modulating effect of magnitopuncture on sympathetic and parasympathetic nerve activities in healthy subjects was associated with the acupuncture points. The findings represent physiological evidence that magnitopuncture may reduce mental fatigue in healthy drivers. Electronic Publication     

Effects of acupuncture on heart rate variability in normal subjects under fatigue and non-fatigue state

The objective of this study was to assess the effects of acupuncture applied at Hegu (LI 4) points and Neiguan (PC6) points on heart rate variability (HRV) in normal subjects under fatigue and non-fatigue states using power spectral analysis. Twenty-nine normal male subjects were randomly divided into three groups. Subjects in Group A and Group B performed a simulated driving task for 3 h and acupuncture needles were then inserted perpendicularly into the LI 4 points in the middle of the dorsal thenar muscle and PC 6 points situated between the tendons of the palmaris longus and carpi radialis muscles for 15 min for Group A but inserted subcutaneously to the acupuncture points for Group B as a control. Acupuncture needles were directly inserted perpendicularly into the LI 4 points and PC 6 points for 15 min for Group C. Stimulations of the acupuncture points induced a significant decrease in heart rate (HR), HRV total power (TP), low frequency (LF) power and ratio of low frequency to high frequency (LF/HF), and a significant increase in the HF power in normalized units (NU) during the post stimulation period in fatigue state (P<0.05). Stimulation of acupuncture points resulted in a significant increase both in the LF power and HF power in absolute units (AU) (P<0.05) but no significant change in NU was found during the post stimulation period in non-fatigue state. It was concluded that the modulating effect of acupuncture on heart rate variability not only depended on the points of stimulation such as acupuncture or non-acupuncture points but also on the functional state of the subject, namely whether the subjects are in a state of fatigue or not.     

Acute and chronic stress influence blood pressure variability in mice

There is evidence that alterations in heart rate and blood pressure variability (BPV) are associated with cardiovascular disease. We used a mice model to investigate the effects of acute and chronic stress on blood pressure variability (BPV) and heat rate variability (HRV). Shaker stress was given acutely (5 min, 150 cycles/min) and chronically (3 days, 2 min stress, 150 cycles/min, 45 sessions/day) in male C57BLJ mice. Systolic arterial pressure (SAP) and pulse interval (PI) time series were submitted to autoregressive spectral analysis with variability measured in the low-frequency (LF, 0.1-1.0 Hz) and high-frequency (HF, 1-5 Hz) ranges. In the acute experiment, MAP was increased significantly in the first 10 min poststress period (99+/-2 vs. 113+/-2 mm Hg) and returned to control levels 30 min poststress. HR was significantly higher in the initial poststress period (537+/-12 vs. 615+/-20 bpm). These alterations were associated with a marked increase in BPV (21+/-4 vs. 55+/-11 mm Hg2) and in power of LF oscillations (18+/-3 vs. 42+/-7 mm Hg2). On the other hand, chronic stress exposure produced a reduction in BPV (16+/-4 vs. 6+/-1 mm Hg2) and LF oscillations (11+/-3 vs. 3+/-1 mm Hg2). HRV was not altered after either acute or chronic stress. Spontaneous baroreflex sensitivity (SBS), determined by cross-spectral analysis between PI and BP, was reduced significantly in acute stress (-50%), but unchanged in chronic stress. Our results show that acute stress produced changes in BPV that may be associated with increased sympathetic activity and a reduction in blood pressure buffering. Under chronic conditions, there is no alteration in baroreflex sensitivity while BPV is reduced. This is likely related to the combination of sympathetic activation in the face of vasculature alterations.     

Relationship between electroencephalogram slow-wave magnitude and heart rate variability during sleep in humans

To explore whether depth of sleep is related to changes in autonomic control, continuous power-spectral analysis of the electroencephalogram (EEG) and heart rate variability (HRV) was performed in ten normal subjects during nocturnal sleep. Quiet sleep (QS) was associated with an increase in high-frequency power (HF) of HRV (0.15-0.4 Hz) but a decrease in low-frequency power (LF) (0.04-0.15 Hz) to HF ratio (LF/HF) compared with awakening. During QS, LF/HF was significantly and negatively correlated with delta power of EEG (0.5-4.0 Hz), whereas mean R-R interval and HF were not. We conclude that during QS, cardiac sympathetic regulation is negatively related to the depth of sleep, although vagal regulation is not. Our methodology offers a quantitative analysis to study the interaction between cerebral cortical and autonomic functions.     

Influence of intensive cycling training on heart rate variability during rest and exercise.

The current study examined whether changes in heart rate variability (HRV) following intensive cycling training contribute to the mechanism of training-induced bradycardia. Thirteen healthy untrained subjects, ages 18-27 years, underwent recordings of heart rate (HR) and VO2max before and after 8 weeks of cycling, 25-60 min/day, 5 days/week at > 80% maximum HR (HRmax). Heart rate recordings were obtained during supine rest and submaximal exercise and were analysed for the following components of HRV: low frequency (LF, 0.041-0.15 Hz); high frequency (HF, 0.15-0.40 Hz); LF/HF ratio and total power (TP, 0-0.40 Hz). At posttraining, VO2max was significantly increased while HR was significantly reduced at rest and all absolute exercise work rates. Training-induced lower HR was accompanied by significantly greater HF and TP during rest as well as LF, HF, and TP during all absolute exercise work rates. Posttraining HR and the majority of HRV measures were similar to pretraining values at the same relative exercise intensity (% HRmax). These results indicated that 8 weeks of intensive cycling training increased HRV and cardiac vagal modulation during rest and absolute exercise work rates but had little effect during relative exercise work rates. Increased vagal modulation resulting from intensive exercise training may contribute to the mechanism of training-induced bradycardia.     

Identification of low and high frequency ranges for heart rate variability and blood pressure variability analyses using pharmacological autonomic blockade with atropine and propranolol in swine

Understanding autonomic nervous system functioning, which mediates behavioral and physiological responses to stress, offers great potential for assessing farm animal stress and welfare. Evaluation of heart rate variability (HRV) and blood pressure variability (BPV), using time and frequency domain analyses may provide a sensitive and reliable measure of affective states and stress-mediated changes in sympathetic and parasympathetic tones. The aim of this research was to define low (LF) and high frequency (HF) power spectral ranges using pharmacological autonomic blockade, and to examine HRV and BPV parameter changes in response to atropine and propranolol in swine. Ten, 13-week old, barrows (n = 6) and gilts (n = 4) underwent surgery to place an intra-cardiac electrode and a blood pressure catheter attached to a biotelemetric transmitter; pigs had a 3-week recovery period prior to data collection. Each pig was subjected to administration of 4 intravenous (i.v.) drug treatments: a control treatment, 3 mL of saline, and 3 blockade treatments; 0.1 mg/kg of atropine, 1.0 mg/kg of propranolol, and .1 mg/kg of atropine together with 1.0 mg/kg of propranolol. All treatments were delivered by injection in the jugular vein with a minimum of 48 h between individual treatments. Behavior, ECG and blood pressure data were recorded continuously for a total of 1 h, from 30 min pre-injection to 30 min post-injection. For data analyses, two 512-beat intervals were selected for each treatment while the pig was lying and inactive. The first interval was selected from the pre-injection period (baseline), and the second was selected between 10 and 30 min post-injection. Time and frequency domain (power spectral density) analyses were performed on each data interval. Subsequent, LF and HF bands from the power spectral densities were defined based on general linear and regression analyses. The HRV and BPV were computed with a covariate (baseline) factorial analysis of treatment by sex interaction, and day of injection, with mixed models and Tukey's post-hoc tests. The best-fit range for LF was 0.0-0.09 Hz, and HF was 0.09-2.0 Hz (r²: 0.41 and 0.43, respectively). Propranolol and saline injections led to a greater overall total power and overall higher inter-beat interval, HF and LF power. Atropine led to a dominant sympathovagal balance of the cardiac activity in pigs. In addition, atropine led to an increase in LF power of both systolic and diastolic blood pressures in gilts suggesting vagal tone mediation of BPV. The understanding of autonomic regulation of HRV and BPV in domestic swine facilitates our ability to detect and quantify stress responses, and broadens its application in assessing farm animal welfare.     

Low‐frequency heart rate variability is related to the breath‐to‐breath variability in the respiratory pattern

Changes in heart rate variability (HRV) at “respiratory” frequencies (0.15–0.5 Hz) may result from changes in respiration rather than autonomic control. We now investigate if the differences in HRV power in the low‐frequency (LF) band (0.05–0.15 Hz, HRV_LF) can also be predicted by respiration variability, quantified by the fraction of tidal volume power in the LF (V_LF,n). Three experimental protocols were considered: paced breathing, mental effort tasks, and a repeated attentional task. Significant intra‐ and interindividual correlations were found between changes in HRV_LF and V_LF,n despite all subjects having a respiratory frequency above the LF band. Respiratory parameters (respiratory period, tidal volume, and V_LF,n) could predict up to 79% of HRV_LF differences in some cases. This suggests that respiratory variability is another mechanism of HRV_LF generation, which should be always monitored, assessed, and considered in the interpretation of HRV changes.     

Instantaneous changes in heart rate regulation due to mental load in simulated office work

The cardiac regulation effects of a mental task added to regular office work are described. More insight into the time evolution during the different tasks is created by using time–frequency analysis (TFA). Continuous wavelet transformation was applied to create time series of instantaneous power and frequency in specified frequency bands (LF 0.04–0.15 Hz; HF 0.15–0.4 Hz), in addition to the traditional linear heart rate variability (HRV) parameters. In a laboratory environment, 43 subjects underwent a protocol with three active conditions: a clicking task with low mental load and a clicking task with high mental load (mental arithmetic) performed twice, each followed by a rest condition. The heart rate and measures related to vagal modulation could differentiate the active conditions from the rest condition, meaning that HRV is sensitive to any change in mental or physical state. Differences between physical and mental stress were observed and a higher load in the combined task was observed. Mental stress decreased HF power and caused a shift toward a higher instantaneous frequency in the HF band. TFA revealed habituation to the mental load within the task (after 3 min) and between the two tasks with mental load. In conclusion, the use of TFA in this type of analysis is important as it reveals extra information. The addition of a mental load to a physical task elicited further effect on HRV parameters related to autonomic cardiac modulation.     

Autonomic nervous function and localization of cerebral activity during lavender aromatic immersion.

Changes in the autonomic nervous activity can be induced by various sensory and emotional stimuli. The authors examined whether the power spectral analysis of heart rate variability (HRV) could detect changes in autonomic tone following a lavender aroma treatment or not. Healthy young women (n=10, 23+/-3 years old) underwent continuous electrocardiographic (ECG) monitoring before and after (10, 20, 30 minutes) the lavender fragrance stimuli. HRV was expressed by three indices: low (0.04-0.15 Hz) and high (0.15-0.40 Hz) frequency components (nLF and nHF, respectively) as well as LF/HF ratio. Increases in the parasympathetic tone were observed after the lavender fragrance stimulus as seen as increases in the HF component and decreases in the LF/HF. Additional measurement with positron emission tomography (PET) demonstrated the regional metabolic activation in the orbitofrontal, posterior cingulate gyrus, brainstem, thalamus and cerebellum, as well as the reductions in the pre/post-central gyrus and frontal eye field. These results suggested that lavender aromatic treatment induced not only relaxation but also increased arousal level in these subjects.