Cardiac measures of nuclear power plant operator stress during simulated incident and accident scenarios

Maintaining optimal performance in demanding situations is challenged by stress‐induced alterations in performance. Here, we quantified the stress of nuclear power plant (NPP) operators (N = 20) during a full‐scale simulator training for incident and accident scenarios. We compared the ambulatory electrocardiography measurements of heart rate (HR) and heart rate variability (HRV), and self‐reported stress during baselines and simulated scenarios. Perceived (scale 0–10) and physiologically measured stress were low during baseline after the scenarios and normal NPP operation (means 1.8–2.2, mean HR 75–80 bpm). During a cognitively challenging scenario simulating a sensor malfunction, the operators' stress was mild to moderate (mean 3.4; HR + 12% from baseline). During simulations of severe accidents of fire and radioactive steam leakage, the experienced stress and cardiac activity were on a moderate to high level (means 4.2 and 4.6; HR + 23% and + 14% from baseline, respectively). Cardiac activity paralleled the self‐reported stress: correlation of self‐reported stress to HR was 0.61 (p < .001) and to HRV features RMSSD, HF, LF/HF, SD1, and SD1/SD2 were ?0.26, ?0.28, 0.35, ?0.40, and ?0.39 (p < .01), respectively. The low shared variance (22%) between HR and physical activity further support the interpretation that the cardiac activity was strongly linked to the experience of stress and not accountable by operators' movement within the simulator. Cardiac measurements in naturalistic settings can thus reveal relevant information on acute stress with the benefit of not interrupting the primary task.     

Relation between cardiac vagal tone and performance in male military personnel exposed to high stress: three prospective studies

Vagal tone has been proposed both as an index of emotion regulation and cognitive ability. To assess the relation between vagal tone and emotion regulation and cognitive ability, the present research prospectively measured vagal tone (measured either as high-frequency spectral power or respiratory sinus arrhythmia) in healthy participants exposed to high stress. The participants were active duty military personnel (men) enrolled in high intensity military training: Survival School (Experiments 1 and 3) and Combat Diver Qualification Course (Experiment 2). We consistently observed a significant relationship between low vagal tone and superior performance. The data suggest that vagal suppression is associated with enhanced performance under conditions of high stress and that this enhanced performance may be related to emotion regulation and cognitive functioning.     

Resting sympathetic arousal moderates the association between parasympathetic reactivity and working memory performance in adults reporting high levels of life stress

The neurovisceral integration model stipulates that autonomic function plays a critical role in the regulation of higher‐order cognitive processes, yet most work to date has examined parasympathetic function in isolation from sympathetic function. Furthermore, the majority of work has been conducted on normative samples, which typically demonstrate parasympathetic withdrawal to increase arousal needed to complete cognitive tasks. Little is known about how autonomic regulation supports cognitive function in populations exposed to high levels of stress, which is critical given that chronic stress exposure alters autonomic function. To address this, we sought to characterize how parasympathetic (high‐frequency heart rate variability, HF‐HRV) and sympathetic (preejection period, PEP) measures of cardiac function contribute to individual differences in working memory (WM) capacity in a sample of high‐risk women. HF‐HRV and PEP were measured at rest and during a visual change detection measure of WM. Multilevel modeling was used to examine within‐person fluctuations in WM performance throughout the task concurrently with HF‐HRV and PEP, as well as between‐person differences as a function of resting HF‐HRV and PEP levels. Results indicate that resting PEP moderated the association between HF‐HRV reactivity and WM capacity. Increases in WM capacity across the task were associated with increases in parasympathetic activity, but only among individuals with longer resting PEP (lower sympathetic arousal). Follow‐up analyses showed that shorter resting PEP was associated with greater cumulative risk exposure. These results support the autonomic space framework, in that the relationship between behavior and parasympathetic function appears dependent on resting sympathetic activation.     

The effects of chewing versus caffeine on alertness, cognitive performance and cardiac autonomic activity during sleep deprivation

Chewing has been shown to alleviate feelings of sleepiness and improve cognitive performance during the day. This study investigated the effect of chewing on alertness and cognitive performance across one night without sleep as well as the possible mediating role of cardiac autonomic activity. Fourteen adults participated in a randomized, counterbalanced protocol employing a chewing, placebo and caffeine condition. Participants completed tasks assessing psychomotor vigilance, tracking, grammatical reasoning, alertness and sleepiness each hour across the night. All participants received either placebo or caffeine (200 mg), while the chewing condition also chewed on a tasteless and odorless substance for 15 min each hour. Heart rate (HR), root mean square of the successive differences in R-R intervals on the ECG (RMSSD), and preejection period (PEP) were simultaneously recorded. Alertness and cognitive performance amongst the chewing condition did not differ or were in fact worse when compared with placebo. Similarly, measures of HR and RMSSD remained the same between these two conditions; however, PEP was reduced in the later part of the night in the chewing condition compared with a relative increase for placebo. Caffeine led to improved speed and accuracy on cognitive tasks and increased alertness when compared with chewing. Relative increases in RMSSD and reductions in HR were demonstrated following caffeine; however, no change in PEP was seen. Strong associations between cardiac parasympathetic activity and complex cognitive tasks, as well as between subjective alertness and simpler cognitive tasks, suggest a differential process mediating complex versus simple cognitive performance during sleep deprivation.     

The effect of mental stress on heart rate variability and blood pressure during computer work

The aim was to evaluate the cardiovascular and subjective stress response to a combined physical and mental workload, and the effect of rest. Twelve females who had no prior experience of laboratory experiments participated in the study. Computer-work-related mental stressors were either added to or removed from a standardized computer work session in the laboratory. Beat-to-beat blood pressure and electrocardiogram (ECG) were recorded continuously during the experiment. The participants reported subjective experiences of stress in six categories using an 11-point scale before and at the end of the work. Heart rate variability (HRV) variables were calculated from the ECG recordings, and a reduction in the high-frequency component of HRV and an increase in the low- to high-frequency ratio were observed in the stress situation compared to the control session. No changes were seen in the low-frequency component of HRV. The stressors induced an increase in blood pressure compared to baseline that persisted, and for the diastolic pressure it even increased in the subsequent control session. No differences were observed for subjective experience of stress with the exception of a time trend in the exhaustion scale, i.e. a progression in reported exhaustion with time. The results—and the dissociation between HRV and blood pressure variables—indicate that HRV is a more sensitive and selective measure of mental stress. It could be speculated that heart rate-derived variables reflect a central pathway in cardiovascular control mechanisms (central command), while the blood pressure response is more influenced by local conditions in the working muscles that partly mask the effect of changes in mental workloads. In the rest period after each work session, HRV and blood pressure variables were partly normalized as expected. However, an 8-min period of rest was insufficient to restore blood pressure to resting values.     

Physiological coherence in healthy volunteers during laboratory‐induced stress and controlled breathing

Physiological coherence has been related with a general sense of well‐being and improvements in health and physical, social, and cognitive performance. The aim of this study was to evaluate the relationship between acute stress, controlled breathing, and physiological coherence, and the degree of body systems synchronization during a coherence‐generation exercise. Thirty‐four university employees were evaluated during a 20‐min test consisting of four stages of 5‐min duration each, during which basal measurements were obtained (Stage 1), acute stress was induced using validated mental stressors (Stroop test and mental arithmetic task, during Stage 2 and 3, respectively), and coherence states were generated using a controlled breathing technique (Stage 4). Physiological coherence and cardiorespiratory synchronization were assessed during each stage from heart rate variability, pulse transit time, and respiration. Coherence measurements derived from the three analyzed variables increased during controlled respiration. Moreover, signals synchronized during the controlled breathing stage, implying a cardiorespiratory synchronization was achieved by most participants. Hence, physiological coherence and cardiopulmonary synchronization, which could lead to improvements in health and better life quality, can be achieved using slow, controlled breathing exercises. Meanwhile, coherence measured during basal state and stressful situations did not show relevant differences using heart rate variability and pulse transit time. More studies are needed to evaluate the ability of coherence ratio to reflect acute stress.     

Assessment of phasic work stress using autonomic indices

The present paper concerns the assessment of phasic work stress using autonomic indices such as skin temperature, respiratory measures, and heart rate, blood pressure, and their variabilities. A physiological model of the autonomic regulation of the cardiovascular and respiratory systems is also introduced in order to simulate and interpret the changes in these indices. Two experiments were conducted to investigate high tension and monotony as two types of mental work stress. A tracking task was used to induce high-tension work stress with and without an instruction intended to induce additional emotional stress. The same tracking task was repeated 12 times to simulate monotonous work stress. Fifty healthy adults participated in each experiment. Many physiological measures showed task-dependent changes in the high-tension experiment and at the beginning of the monotonous stress condition. These changes were explained by sympathetic activation, parasympathetic withdrawal, and respiratory rate activation. An additional drop in skin temperature and an additional HR increase were caused by the stressful instruction, which may reflect an emotional strain and can be explained by sympathetic activation. Furthermore, the mid-frequency component (approx. 0.1 Hz) of respiration and respiratory instability showed an obvious increase during the course of the monotonous stress experiment, which may reflect boredom and disgust. It was concluded that multidimensional recordings of autonomic measures that can be obtained during work without extra load on the worker would be helpful to assess different types of phasic work stress. The proposed model was further shown to be able to detect periods of stress in a complex work environment.     

Intra-amygdala injection of GABAA agonist, muscimol, reduces tachycardia and modifies cardiac sympatho-vagal balance during restraint stress in rats

At present, little is known about the brain origin of stress-induced cardiac sympathetic drive responsible for stress-induced tachycardia. Our aim was to determine the effect of bilateral microinjections of the GABA(A) receptor agonist, muscimol, into the amygdaloid complex on both the heart rate and cardiac autonomic activity during restraint stress. Experiments were performed in male Sprague-Dawley rats (n=9), with pre-implanted electrocardiographic electrodes. Heart rate increased sharply after the onset of the restraint and reached a peak 1-2 min later (from 344+/-6-440+/-20 BPM). Subsequently, heart rate began to fall, and during the next 10-15 min approached the steady-state level of 384+/-11. After vehicle, mean heart rate during each of three 10-min restraint epochs was significantly higher compared with the pre-restraint level. After muscimol, mean heart rate was significantly elevated only during the first 10 min of restraint. There was no difference in the early peak tachycardia between both conditions. Muscimol substantially accelerated the fall of the HR from the peak to the steady-state level, and thus the area under the curve value for muscimol (503+/-162 BPM x min) was significantly smaller than that for vehicle (1221+/-231 BPM x min); P<0.05. After vehicle, the high-frequency spectral power of the heart rate decreased and the low-frequency power increased during the restraint, resulting in a significant rise of the low frequency/high frequency ratio from 1.2+/-0.2-2.8+/-0.6 (n=9, P<0.05). Muscimol suppressed these stress-induced effects. We conclude that inhibition of the amygdala neurons abolishes the sustained component of tachycardia during the restraint, has no effect on the early tachycardic component, and prevents stress-induced alterations in the heart rate variability indices.     

心率变异性生物反馈对高血压前期患者应激反应的干预效果

目的探讨心率变异性生物反馈（HRV BF）干预高血压前期患者心血管应激反应的效果。方法比较高血压前期者与正常血压者应激反应上血压变化的差异;将36位高血压前期受试者随机分为心率变异性生物反馈（HRV BF）组、慢腹式呼吸（SAB）组和空白对照组。干预组受试者接受每次30 min,每周2次,持续2个月共15次的训练;空白对照组不予干预。实验间隔期嘱受试者每天进行不少于20 min的家庭训练。所有受试者在实验开始前及实验结束后均接受连续2 d同一时间点进行的两种应激测试。结果高血压前期者较正常血压者在应对心算应激时收缩压和舒张压反应性更大。干预2个月后,HRV BF和SAB组收缩压和舒张压平均降压幅度分别为15.4/10.2 mmHg、11.6/7.4 mmHg;空白对照组干预后血压无明显变化。HRV BF能显著降低受试者心算应激时收缩压反应性,较SAB更为明显。结论高血压前期者应激反应性较高,HRV BF训练可以降低受试者应对心理应激时心血管的反应,并降低高血压前期者血压。     

Cognitive reappraisal moderates the quadratic association between heart rate variability and negative affectivity

There is uncertainty as to how high-frequency heart rate variability (HF-HRV), a marker of an individual's capacity for flexible physiological reactivity, relates to an individual's tendency to experience negative emotions. We propose that both excessively high and excessively low HF-HRV may reflect maladaptive physiological reactivity tendencies associated with high negative affectivity and that this association may be influenced by the use of emotion regulation strategies, such as cognitively reappraising negative environmental stimuli to downregulate the experience of negative emotions. The purpose of the current study was to examine the moderating role of cognitive reappraisal in the quadratic association between HF-HRV and negative affectivity. Electrocardiograms (ECG) were recorded at rest for 269 young adults (77% female; M = 19.7 years) who then completed self-report rating scales assessing trait negative affectivity and trait cognitive reappraisal. As predicted, high and low HF-HRV were associated with high negative affectivity at low levels of trait cognitive reappraisal. At high levels of trait reappraisal, the quadratic association between HF-HRV and negative affectivity was not significant. These results suggest that, contrary to traditional views, high HF-HRV may not always be an adaptive characteristic and may depend on an individual's use of emotion regulation strategies, such as cognitive reappraisal.     

Older people's cardiac responses as indicators of stress in familiar and unfamiliar environments

Little is known about older people's physiological and emotional responses to environmental triggers. We examined this by estimating cardiac stress from heart rate variability (HRV). Thirty-eight participants were monitored while observing environmental scenarios at familiar and unfamiliar locations. Image scenarios included pedestrian and driving scenes in a random order. HRV indices including heart rate (HR), QT variability index (QTVI) and Total HRV Power (TP) were quantified. Familiar locations were associated with higher HR (p<.0005) and lower TP (p=.005) than unfamiliar locations, suggesting they were more stressful. HRV responses to pedestrian and driving scenarios indicated that stress was not influenced by either the type of image scenario or the order of image presentation. There were no gender-related differences in cardiac responses. HRV is a useful surrogate of cardiac stress when assessing older people's responses to their environments.     

Pure purr virtual reality technology: measuring heart rate variability and anxiety levels in healthy volunteers affected by moderate stress

IntroductionTraditional approaches to stress management are difficult to learn and to implicate in daily life. Emerging technologies like virtual reality (VR) have become a target of extensive study for recreational and medical purposes. The autonomic nervous system (ANS) plays a crucial role in stress response, post-stress relaxation, and recovery. This study aimed to assess the effect of modified VR intervention on short-term heart rate variability (HRV) and perceived anxiety levels in healthy volunteers affected by moderate stress. The stressors included mental arithmetic tasks.Material and methodsThe study involved healthy adults, of both sexes, aged 20 to 60 years, without history of cardiovascular diseases, essential abnormalities on ECG, and with normal or moderate level of situational anxiety. The VR gadgets used in the study were commercially available Bobo-VR X1 headsets, one with modification for medical applications (Pure Purr technology) and one with none (sham technology). The investigational (Pure Purr) headset with an audio-visual sequence was modified by adding a binaural effect and was synchronised with the tract of respiratory movements and the frequency of heart rate. To track changes in the ANS, participants underwent both electrocardiography (ECG) and measurement of HRV.ResultsThe findings showed a significant increase in parasympathetic activity after 5-minute exposure to the investigational device compared to stress, as shown by high-frequency HRV (499.8 ms² and 340.5 ms², p < 0.001). RMSSD for a modified headset was higher (p = 0.02) compared to a sham headset with no modifications (RMSSD difference of 12.3% (2.6% to 23.1%)). The LF/HF ratio, however, was lower (difference of 14.5% (2.6% to 23.1%), p = 0.04).ConclusionsThese findings suggest that a medical device with pre-installed Pure Purr software had a significant effect on the recovery of the ANS in healthy volunteers affected by moderate stress.     

Effects of vagotomy on cardiac function in rats during postnatal ontogeny

We studied age-related peculiarities of changes in stroke volume, heart rate, and parameters of variational pulsogram after bilateral vagotomy in rats. Positive responses of stroke volume and heart rate to vagotomy appeared on postnatal week 4.     

Affects and autonomic cardiac reactivity during experimentally induced stress as related to precursors of insulin resistance syndrome

This study examined the association of insulin resistance syndrome (IRS) precursors with state affects and autonomic reactivity in randomly selected healthy young adults. It was asked whether IRS precursors are able to predict a person’s mental and physiological coping with acute stress over an 11-year follow-up period. IRS parameters were serum insulin, high-density lipoprotein cholesterol, triglycerides, systolic blood pressure, body-mass index, and subscapular skinfold thickness. In the psychophysiological experiment, state affects and cardiac responses (heart rate, respiratory sinus arrhythmia, and pre-ejection period) were measured during different challenges. The main result was that IRS precursors predicted high levels of negative emotions during the challenges; IRS accounted for 19% of the variance in tiredness. IRS was unrelated to cardiac reactivity. Mechanisms underlying the associations found are discussed.     

Effects of vital exhaustion on cardiac autononomic nervous functions assessed by heart rate variability at rest in middle-aged male workers

We investigated the effects of vital exhaustion (VE) on cardiac autonomic functions in relation to working conditions such as overtime and frequent business trips, and to lifestyles such as smoking on 52 healthy middle-aged male workers. VE was evaluated by an abbreviated Maastricht Vital Exhaustion Questionnaire. Cardiac autonomic function atsupine rest was assessed by spectral analysis of heart rate variability inanannual healthcheckup.Themeanamplitudeofthehigh frequency(HF: 0.15-0.4 Hz) component was lowerinthe high-VE group, whereas no significant difference in the ratio ofthe low frequency (LF: 0.04-0.15 Hz) component powerto HF power (the LF/HF ratio) was observed among VE groups. There were significant interactive effects of VE and smoking on HF amplitude, and of VE and frequent business trips on the LF/HF ratio. VE symptoms were related to the suppression of the cardiac parasympathetic nervous functionat rest in middle-aged male workers, but not to the alteration in sympathovagal balance. Smoking and overwork such as frequent business trips may amplify the autonomic dysfunction in relation to VE among workers with a pronounced feeling of VE.     

The relationship of trauma exposure to heart rate variability during wake and sleep in midlife women

Traumatic experiences are common and linked to cardiovascular disease (CVD) risk, yet the mechanisms underlying these relationships is less well understood. Few studies have examined trauma exposure and its relation to autonomic influence over cardiac function, a potential pathway linking trauma exposure to CVD risk. Investigating autonomic influence over cardiac function during both wake and sleep is critical, given particular links of sleep autonomic function to cardiovascular health. Among midlife women, we tested whether trauma exposure would be related to lower high frequency heart rate variability (HF-HRV), an index of vagal influence over cardiac function, during wake and sleep. Three hundred and one nonsmoking midlife women completed physical measures, a 24-hr electrocardiogram, actigraphy sleep measurement, and questionnaires about trauma (Brief Trauma Questionnaire), childhood abuse (Child Trauma Questionnaire [CTQ]), mood, demographics, and medical/psychiatric history. Relations between trauma and HF-HRV were assessed in linear mixed effects models adjusting for covariates (age, race, education, body mass index, blood pressure, psychiatric history, medication use, sleep, mood, childhood abuse history). Results indicated that most women had experienced trauma. Any trauma exposure as well as a greater number of traumatic experiences were associated with lower HF-HRV during wake and particularly during sleep. Relations were not accounted for by covariates. Among midlife women, trauma exposure was related to lower HF-HRV during wake and sleep. Trauma may have an important impact on vagal influence over the heart, particularly during sleep. Decreased vagal influence over cardiac function may be a key mechanism by which trauma is associated with CVD risk.     

Inducing unconscious stress: Cardiovascular activity in response to subliminal presentation of threatening and neutral words

Stress‐related cognitive processes may occur outside of awareness, here referred to as unconscious stress, and affect one's physiological state. Evidence supporting this idea would provide necessary clarification of the relationship between psychological stress and cardiovascular (CV) health problems. We tested the hypothesis that increases in mean arterial pressure (MAP) and total peripheral resistance (TPR) and decreases in heart rate variability (HRV) would be larger when threatening stimuli are presented outside of awareness, or subliminally, compared with neutral stimuli. Additionally, it was expected that trait worry and resting HRV, as common risk factors for CV disease, would moderate the effect. We presented a subliminal semantic priming paradigm to college students that were randomly assigned to the threat (n = 56) or neutral condition (n = 60) and assessed changes from baseline of MAP, TPR, and HRV. Level of trait worry was assessed with the Penn State Worry Questionnaire. The findings indicate that CV activity changed according to the hypothesized pattern: A higher MAP and TPR and a lower HRV in the threat condition compared with the neutral condition were found with practically meaningful effect sizes. However, these findings were only statistically significant for TPR. Furthermore, changes in CV activity were not moderated by trait worry or resting HRV. This is the first study to explicitly address the role of subliminally presented threat words on health‐relevant outcome measures and suggests that unconscious stress can influence peripheral vascular resistance.     

依帕司他治疗糖尿病心脏自主神经病变疗效分析

目的评价依帕司他治疗糖尿痛心脏自主神经病变疗效。方法糖尿痛心脏痛心脏自主神经病变患者接受依帕司他50mg，每日3次治疗，服用4周，运用24小时动态心电图检测患者在服用依帕司他前后心率变异性指标的变化，明确依帕司他治疗糖尿病心脏自主神经病变的疗效。结果心率变异性各项指标治疗4周后较治疗前有显著提高。自主神经症状明显好转。结论依帕司他治疗糖尿病心脏自主神经病变的疗效显著，可以改善患者心率变异性。     

Ventromedial prefrontal cortex connectivity during and after psychological stress in women

The ventromedial prefrontal cortex (vmPFC) integrates sensory, affective, memory‐related, and social information from diverse brain systems to coordinate behavioral and peripheral physiological responses according to contextual demands that are appraised as stressful. However, the functionality of the vmPFC during stressful experiences is not fully understood. Among 40 female participants, the present study evaluated (a) functional connectivity of the vmPFC during exposure to and recovery following an acute psychological stressor, (b) associations among vmPFC functional connectivity, heart rate, and subjective reports of stress across individuals, and (c) whether patterns of vmPFC functional connectivity were associated with distributed brain networks. Results showed that psychological stress increased vmPFC functional connectivity with individual brain areas implicated in stressor processing (e.g., insula, amygdala, anterior cingulate cortex) and decreased connectivity with the posterior cingulate cortex and thalamus. There were no statistical differences in vmPFC connectivity to individual brain areas during recovery, as compared with baseline. Spatial similarity analyses revealed stressor‐evoked increased connectivity of the vmPFC with the so‐called dorsal attention, ventral attention, and frontoparietal networks, as well as decreased connectivity with the default mode network. During recovery, vmPFC connectivity increased with the frontoparietal network. Finally, individual differences in heart rate and perceived stress were associated with vmPFC connectivity to the ventral attention, frontoparietal, and default mode networks. Psychological stress appears to alter network‐level functional connectivity of the vmPFC in a manner that further relates to individual differences in stressor‐evoked cardiovascular and affective reactivity.     

Sympathetic and parasympathetic responses to social stress across adolescence

Many transformations that occur in adolescence are related to emotion and emotion regulation, yet very little is known about the autonomic underpinnings of these changes. The aim of the study was to document age-related differences in autonomic responses to social stress and relations to emotion regulation. Ninety-nine female adolescents engaged in a paced breathing and a spontaneous speech task while electrocardiography measurements were taken. Spectral decomposition of the heart period data was used to create measures of sympathetic and parasympathetic activity. Results revealed a positive correlation between age and sympathetic activity and a negative correlation between age and parasympathetic activity. These findings contribute to a better understanding of the age-related norms of cardiac variability across adolescence.