Spectral analysis of R-R and arterial pressure variabilities to assess sympatho-vagal interaction during mental stress in humans

Effects of a cool classroom microclimate on cardiac autonomic control and cognitive performances in undergraduate students

An inverted U-shape relationship between cognitive performance and indoor temperature with best performance peaking at 21.6 °C was previously described. Little is known on classroom temperature reduction effects on cognitive performances and cardiac autonomic profile, during the cold season. Fifteen students underwent electrocardiogram recording during a lecture in two days in December when classroom temperatures were set as neutral (NEUTRAL, 20-22 °C) and cool (COOL, 16-18 °C). Cognitive performance (memory, verbal ability, reasoning, overall cognitive C-score) was assessed by Cambridge Brain Science cognitive evaluation tool. Cardiac autonomic control was evaluated via the analysis of spontaneous fluctuations of heart period, as the temporal distance between two successive R-wave peaks (RR). Spectral analysis provided the power in the high frequency (HF, 0.15-0.40 Hz) and low frequency (LF, 0.04-0.15 Hz) bands of RR variability. Sympatho-vagal interaction was assessed by LF to HF ratio (LF/HF). Symbolic analysis provided the fraction of RR patterns composed by three heart periods with no variation (0 V%) and two variations (2 V%), taken as markers of cardiac sympathetic and vagal modulations, respectively. The students' thermal comfort was assessed during NEUTRAL and COOL trials. Classroom temperatures were 21.5 ± 0.8 °C and 18.4 ± 0.4 °C during NEUTRAL and COOL. Memory, verbal ability, C-Score were greater during COOL (13.01 ± 3.43, 12.32 ± 2.58, 14.29 ± 2.90) compared to NEUTRAL (9.98 ± 2.26, p = 0.002; 8.57 ± 1.07, p = 0.001 and 10.35 ± 3.20, p = 0.001). LF/HF (2.4 ± 1.7) and 0 V% (23.2 ± 11.1%) were lower during COOL compared to NEUTRAL (3.7 ± 2.8, p = 0.042; 28.1 ± 12.2.1%, p = 0.031). During COOL, 2 V% was greater (30.5 ± 10.9%) compared to NEUTRAL (26.2 ± 11.3, p = 0.047). The students' thermal comfort was slightly reduced during COOL compared to NEUTRAL trial. During cold season, a better cognitive performance was obtained in a cooler indoor setting enabling therefore energy saving too.

Ischemia and no obstructive coronary arteries in patients with stable ischemic heart disease

A large proportion of patients with suspected obstructive coronary artery disease (CAD) is found to have ischemia with no obstructive coronary artery disease (INOCA). Based on current evidence, these patients are at increased risk of adverse cardiovascular events, even though they have no obstructive CAD. Importantly, INOCA is associated with recurrent clinical presentations with chest pain, impaired functional capacity, reduced health-related quality of life, and high healthcare costs. Underlying coronary microvascular dysfunction (CMD), through endothelium-dependent and independent mechanisms contribute to these adverse outcomes in INOCA. While non-invasive and invasive diagnostic testing has typically focused on identification of obstructive CAD in symptomatic patients, functional testing to detect coronary epicardial and microvascular dysfunction should be considered in those with INOCA who have persistent angina. Current diagnostic methods to clarify functional abnormalities and treatment strategies for epicardial and/or microvascular dysfunction in INOCA are reviewed.

Central serous chorioretinopathy and heart rate variability analysis with a smartphone application

The purpose of this study was to quantitatively analyze heart rate variability (HRV) in patients with central serous chorioretinopathy (CSC) by using a smartphone-based application (ANBAI: DUMSCO Inc.) for measurement, and to clarify its relationships with CSC. The subjects were 64 CSC patients (mean age 48.7 ± 7.6 years, 57 males and 7 females). After providing consent, the patients downloaded ANBAI apps to their smartphones. HRV was measured by photoelectric volume pulse wave measurement with a smartphone camera each morning for a minimum of 1 week. The primary outcome was to analyze HRV by calculating log LF/HF (Low Frequency/High Frequency components), an index of autonomic tone, which was then compared with a control group of 35,226 individuals from the application. Secondary outcome measures included disease duration, body mass index, exercise habits, smoking history, steroid use, occupation, lifestyle regularity, psychological fatigue, physical fatigue, and average sleep time. The log LF/HF was significantly higher in the patient group than in the control group (P < 0.001). Log LF/HF was significantly lower in patients with exercise habits as a factor contributing to log LF/HF in the patient group (P = 0.019). Analysis of HRV in CSC patients showed an impairment of the autonomic nervous system. Exercise habits may also be associated with CSC.

Measuring Mental Stress During Otologic Surgery Using Heart Rate Variability Analysis

OBJECTIVES

Healthy individuals have significant beat-to-beat variability in heart rate, and this variability decreases with mental stress. We aim to use heart rate variability (HRV) to objectively compare mental stress levels in otologic surgeons at rest and during key portions of procedures.

DESIGN

Pilot study.

SETTING

Operating room and laboratory.

PARTICIPANTS

Two neurotology fellows performed six mastoidectomy and facial nerve (FN) dissections in the operating room and six in a cadaver lab while continuous electrocardiograms were measured wirelessly. Five-minute samples were recorded during resting, preoperative, mastoidectomy, and FN dissection. Beat-to-beat time intervals were analyzed in time and frequency domains. The standard deviation of normal beat-to-beat intervals (SDNN) and the ratio of low frequency to high frequency power (LF/HF, measure of sympathetic tone) were calculated. Decreases in SDNN and increases in LF/HF indicate elevated mental stress.

RESULTS

Mean resting SDNN was 43.9 ± 9.2 ms, not statistically different from preoperative SDNN (34.1 ± 8.2 ms, p = 0.13). SDNN decreased during mastoidectomy (29.4 ± 11.7 ms) and FN dissection (22.8 ± 3.1 ms), which was significant compared to preoperative values (p = 0.03). Intraoperative LF/HF increased for FN dissection (6.8 ± 2.6) compared to resting (2.2 ± 0.7, p = 0.004), indicating increased sympathetic tone. Mastoid and FN cadaveric procedures resulted in SDNN of 33.6 ± 3.8 and 32.9 ± 4.7 ms, respectively, not statistically different from preoperative values (p = 0.82 and p = 0.94, respectively). Cadaveric FN dissection did not result in increased LF/HF (2.4 ± 0.9) compared to resting (p = 0.94).

CONCLUSIONS

Decreased HRV and increased sympathetic tone were observed intraoperatively, indicating high levels of mental stress, particularly with FN dissection. Similar changes were not found during cadaveric dissections.

An Evaluation of the Impact of High-Fidelity Endovascular Simulation on Surgeon Stress and Technical Performance

OBJECTIVE

To measure the physiological stress response associated with high-fidelity endovascular team simulation.

DESIGN

This is a prospective cohort study.

SETTING

This study was performed at St Mary's Hospital (Imperial College London, London, UK), in a tertiary setting.

PARTICIPANTS

Thirty-five participants (10 vascular surgical residents, 4 surgical interns, 12 theatre nurses, 2 attending vascular surgeons, 6 medical students and 1 technician) were recruited from the Imperial Vascular Unit at St Mary's Hospital, Imperial College London by direct approach. All participants finished the study.

RESULTS

Junior surgeons experienced significantly increased sympathetic tone (Low frequency/high frequency (LF/HF) ratio) during team simulation compared to individual simulation (6.01 ± 1.68 vs. 8.32 ± 2.84, p < 0.001). Within team simulation junior surgeons experienced significantly higher heart rate (beats per minute) than their senior counterparts (82 ± 5.83 vs. 76 ± 6.02, p = 0.033). Subjective workload scores (NASA Task Load Index [NASA-TLX]) correlated moderately and significantly with sympathetic tone in surgeons across all stages of simulation. (r = 0.39, p = 0.01).

CONCLUSIONS

A discrete, measurable increase in stress is experienced by surgeons during high-fidelity endovascular simulation and differentially effects junior surgeons. High-fidelity team simulation may have a role to play in improving nontechnical skill, reducing intra-operative stress, and reducing error.

The Neuro-Immuno-Senescence Integrative Model (NISIM) on the Negative Association Between Parasympathetic Activity and Cellular Senescence

There is evidence that accumulated senescent cells drive age-related pathologies, but the antecedents to the cellular stressors that induce senescence remain poorly understood. Previous research suggests that there is a relationship between shorter telomere length, an antecedent to cellular senescence, and psychological stress. Existing models do not sufficiently account for the specific pathways from which psychological stress regulation is converted into production of reactive oxygen species. We propose the neuro-immuno-senescence integrative model (NISIM) suggesting how vagally mediated heart rate variability (HRV) might be related to cellular senescence. Prefrontally modulated, and vagally mediated cortical influences on the autonomic nervous system, expressed as HRV, affects the immune system by adrenergic stimulation and cholinergic inhibition of cytokine production in macrophages and neutrophils. Previous findings indicate that low HRV is associated with increased production of the pro-inflammatory cytokines IL-6 and TNF-α. IL-6 and TNF-α can activate the NFκB pathway, increasing production of reactive oxygen species that can cause DNA damage. Vagally mediated HRV has been related to an individual's ability to regulate stress, and is lower in people with shorter telomeres. Based on these previous findings, the NISIM suggest that the main pathway from psychological stress to individual differences in oxidative telomere damage originates in the neuroanatomical components that modulate HRV, and culminates in the cytokine-induced activation of NFκB. Accumulated senescent cells in the brain is hypothesized to promote age-related neurodegenerative disease, and previous reports suggest an association between low HRV and onset of Alzheimer's and Parkinson's disease. Accumulating senescent cells in peripheral tissues secreting senescence-associated secretory phenotype factors can alter tissue structure and function which can induce cancer and promote tumor growth and metastasis in old age, and previous research suggested that ability to regulate psychological stress has a negative association with cancer onset. We therefore conclude that the NISIM can account for a large proportion of the individual differences in the psychological stress-related antecedents to cellular senescence, and suggest that it can be useful in providing a dynamic framework for understanding the pathways by which psychological stress induce pathologies in old age.

Acute mental stress and surgical performance

Background

Stress has been shown to impact adversely on multiple facets critical to optimal performance. Advancements in wearable technology can reduce barriers to observing stress during surgery. This study aimed to investigate the association between acute intraoperative mental stress and technical surgical performance.

Methods

Continuous electrocardiogram data for a single attending surgeon were captured during surgical procedures to obtain heart rate variability (HRV) measures that were used as a proxy for acute mental stress. Two different measures were used: root mean square of successive differences (RMSSD) and standard deviation of RR intervals (SDNN). Technical surgical performance was assessed on the Operating Room Black Box® platform using the Generic Error Rating Tool (GERT). Both HRV recording and procedure video recording were time‐stamped. Surgical procedures were fragmented to non‐overlapping intervals of 1, 2 and 5 min, and subjected to data analysis. An event was defined as any deviation that caused injury to the patient or posed a risk of harm.

Results

Rates of events were significantly higher (47–66 per cent higher) in the higher stress quantiles than in the lower stress quantiles for all measured interval lengths using both proxy measures for acute mental stress. The strongest association was observed using 1‐min intervals with RMSSD as the HRV measure (P < 0·001).

Conclusion

There is an association between measures of acute mental stress and worse technical surgical performance. Further study will help delineate the interdependence of these variables and identify triggers for increased stress levels to improve surgical safety.

Highly sensitive index of cardiac autonomic control based on time-varying respiration derived from ECG

Frequency-domain indices of heart rate variability (HRV) have been used as markers of sympathovagal balance. However, they have been shown to be degraded by interindividual or task-dependent variability, and especially variations in breathing frequency. The study introduces a method to analyze respiration-(vagally) mediated HRV, to better assess subtle variations in sympathovagal balance using ECG recordings. The method enhances HRV analysis by focusing the quantification of respiratory sinus arrhythmia (RSA) gain on the respiratory frequency. To this end, instantaneous respiratory frequency was obtained with ECG-derived respiration (EDR) and was used for variable frequency complex demodulation (VFCDM) of R-R intervals to extract RSA. The ability to detect cognitive stress in 27 subjects (athletes and nonathletes) was taken as a quality criterion to compare our method to other HRV analyses: Root mean square of successive differences, Fourier transform, wavelet transform, and scaling exponent. Three computer-based tasks from MATB-II were used to induce cognitive stress. Sympathovagal index (HF_nu) computed with our method better discriminates cognitive tasks from baseline, as indicated by P values and receiver operating characteristic curves. Here, transient decreases in respiratory frequency have shown to bias classical HRV indices, while only EDR-VFCDM consistently exhibits the expected decrease in the HF_nu index with cognitive stress in both groups and all cognitive tasks. We conclude that EDR-VFCDM is robust against atypical respiratory profiles, which seems relevant to assess variations in mental demand. Given the variety of individual respiratory profiles reported especially in highly trained athletes and patients with chronic respiratory conditions, EDR-VFCDM could better perform in a wide range of applications.

Modulation of Cardiac Autonomic Function by Fingolimod Initiation and Predictors for Fingolimod Induced Bradycardia in Patients with Multiple Sclerosis

Objective: It is well-known that initiation of fingolimod induces a transient decrease of heart rate. However, the underlying cardiac autonomic regulation is poorly understood. We aimed to investigate the changes of autonomic activity caused by the first dose of fingolimod using a long-term multiple trigonometric spectral analysis for the first time. In addition, we sought to use the continuous Holter ECG recording to find predictors for fingolimod induced bradycardia.

Methods: Seventy-eight patients with relapsing-remitting multiple sclerosis (RRMS) were included. As a part of the START study (NCT01585298), continuous electrocardiogram was recorded before fingolimod initiation, and until no <6 h post medication. Time domain and frequency domain heart rate variability (HRV) parameters were computed hourly to assess cardiac autonomic regulation. A long-term multiple trigonometric regressive spectral (MTRS) analysis was applied on successive 1-h-length electrocardiogram recordings. Decision tree analysis was used to find predictors for bradycardia following fingolimod initiation.

Results: Most of the HRV parameters representing parasympathetic activities began to increase since the second hour after fingolimod administration. These changes of autonomic regulations were in accordance with the decline of heart rate. Baseline heart rate was highly correlated with nadir heart rate, and was the only significant predicting factor for fingolimod induced bradycardia among various demographic, clinical and cardiovascular variables in the decision tree analysis.

Conclusions: The first dose application of fingolimod enhances the cardiac parasympathetic activity during the first 6 h post medication, which might be the underlying autonomic mechanism of reduced heart rate. Baseline heart rate is a powerful predictor for bradycardia caused by fingolimod.

Fingolimod initiation in multiple sclerosis patients is associated with potential beneficial cardiovascular autonomic effects

BACKGROUND

Fingolimod slows heart rate (HR) due to vagomimetic effects and might cause additional cardiovascular autonomic changes. While the time course of HR changes is well described, the extent and course of cardiovascular autonomic changes upon fingolimod initiation has not yet been evaluated. This study, therefore, intended to assess cardiovascular autonomic changes during the first 6 h after fingolimod initiation.

METHODS

In 21 patients with relapsing-remitting multiple sclerosis (RRMS), we recorded respiration (RESP), electrocardiographic RR interval (RRI), systolic and diastolic blood pressure (BPsys, BPdia) at rest, before and 0.5, 1, 2, 3, 4, 5, and 6 h after fingolimod initiation. We calculated parameters of total autonomic modulation [RRI standard deviation (RRI-SD), RRI coefficient of variation (RRI-CV), RRI-total powers], mainly sympathetic cardiac modulation [RRI low frequency (LF) powers], sympathetic BP modulation (BPsys-LF powers), parasympathetic modulation [square root of the mean squared difference of successive RRIs (RMSSD), RRI high frequency (HF) powers], sympatho-vagal cardiac balance (RRI-LF/HF ratios), and baroreflex sensitivity (BRS). We compared parameters between the eight measurements [analysis of variance (ANOVA) or Friedman test with post-hoc analysis; significance: p < 0.05].

RESULTS

After fingolimod initiation, RESP, BPsys, and BPsys-LF powers remained unchanged while RRIs, RRI-CV, RRI-SD, RRI-total powers, RRI-LF powers, RMSSD, RRI-HF powers, and BRS increased after 1 h and rose to peak values occurring after 5, 1, 2, 2, 1, 4, 4, and 4 h, respectively. After 3 h, BPdia had decreased significantly and was lowest after 5 h. RRI-LF/HF ratios decreased to a nadir after 4 h.

CONCLUSIONS

The increases in parasympathetic and overall cardiac autonomic modulation and in BRS seen with fingolimod initiation are theoretically beneficial for the MS patient's cardiovascular system. However, long-term studies must show whether these effects persist or are attenuated (e.g. due to S1P1 receptor down-regulation upon continued fingolimod therapy).

Short-Term Effect of Physical Exercise at Lactate Threshold on Choice Reaction Time

The duration of the enhancement of choice reaction task efficiency by physical exercise at lactate threshold was studied. After healthy male students completed the exercise or nonexercise (control) period for 10 min., they performed a three-choice reaction task for 20 min. The mean heart rate during the choice reaction task after the exercise was higher than that after the control period ( p<.05). For average percentage of correct answers, there were no significant differences between the exercise and control conditions. The reaction time during the first 8 min. of the 20-min. choice reaction task after the exercise period was less than that after the control period and increased gradually thereafter. In conclusion, whereas the choice reaction time was improved by physical exercise at around lactate threshold, the positive effects were seen mainly in the early stages of the task.

Psychosomatic effects of blanketing in nursing care

AIM

Blanketing, which involves covering patients with a blanket in order to maintain their body temperature and privacy and help alleviate the stress that is associated with medical procedures, is a fundamental skill in nursing care. However, the actual therapeutic effects of blanketing have not been adequately investigated. Therefore, the aim of the present study was to clarify the psychosomatic effects of blanketing in nursing care by observing autonomic nervous activity.

METHODS

This single-cohort, intra-participant, comparative cross-over study included 30 healthy female adolescents. Two of the 30 participants were excluded from the analysis. After splitting the participants into blanketing and non-blanketing groups, the stress and anxiety that patients undergo during nursing care was simulated and the responses were analyzed by using psychological and physiological indicators. The parametric data were analyzed by using a paired t-test or one-way ANOVA and the non-parametric data were analyzed by using the Wilcoxon signed-rank test. The significance level was <5%.

RESULTS

No significant difference was seen between the two groups in vital signs, salivary alpha-amylase activity, respiratory movement or skin surface temperature. However, the postintervention scores for "Tension-Anxiety" in the Profile of Mood States - Brief Form were significantly lower for the blanketed than the non-blanketed arm, "sense of ease" and "feeling protected" were significantly higher for the blanketed arm, and in the middle intervention segment, the parasympathetic nervous activity and sympathetic nervous activity were significantly higher and lower, respectively, for the blanketed arm.

CONCLUSION

These results suggest that blanketing is effective in relieving psychological stress and promoting a sense of ease among patients who are receiving nursing care.

Randomized controlled trial of multidisciplinary team stress and performance in immersive simulation for management of infant in shock: study protocol

BACKGROUND

Human error and system failures continue to play a substantial role in adverse outcomes in healthcare. Simulation improves management of patients in critical condition, especially if it is undertaken by a multidisciplinary team. It covers technical skills (technical and therapeutic procedures) and non-technical skills, known as Crisis Resource Management. The relationship between stress and performance is theoretically described by the Yerkes-Dodson law as an inverted U-shaped curve. Performance is very low for a low level of stress and increases with an increased level of stress, up to a point, after which performance decreases and becomes severely impaired. The objectives of this randomized trial are to study the effect of stress on performance and the effect of repeated simulation sessions on performance and stress.

METHODS

This study is a single-center, investigator-initiated randomized controlled trial including 48 participants distributed in 12 multidisciplinary teams. Each team is made up of 4 persons: an emergency physician, a resident, a nurse, and an ambulance driver who usually constitute a French Emergency Medical Service team. Six multidisciplinary teams are planning to undergo 9 simulation sessions over 1 year (experimental group), and 6 multidisciplinary teams are planning to undergo 3 simulation sessions over 1 year (control group). Evidence of the existence of stress will be assessed according to 3 criteria: biological, electrophysiological, and psychological stress. The impact of stress on overall team performance, technical procedure and teamwork will be evaluated. Participant self-assessment of the perceived impact of simulations on clinical practice will be collected. Detection of post-traumatic stress disorder will be performed by self-assessment questionnaire on the 7(th) day and after 1 month.

DISCUSSION

We will concomitantly evaluate technical and non-technical performance, and the impact of stress on both. This is the first randomized trial studying repetition of simulation sessions and its impact on both clinical performance and stress, which is explored by objective and subjective assessments. We expect that stress decreases team performance and that repeated simulation will increase it. We expect no variation of stress parameters regardless of the level of performance.

TRIAL REGISTRATION

ClinicalTrials.gov registration number NCT02424890.

The return trip is felt shorter only postdictively: A psychophysiological study of the return trip effect [corrected]

The return trip often seems shorter than the outward trip even when the distance and actual time are identical. To date, studies on the return trip effect have failed to confirm its existence in a situation that is ecologically valid in terms of environment and duration. In addition, physiological influences as part of fundamental timing mechanisms in daily activities have not been investigated in the time perception literature. The present study compared round-trip and non-round-trip conditions in an ecological situation. Time estimation in real time and postdictive estimation were used to clarify the situations where the return trip effect occurs. Autonomic nervous system activity was evaluated from the electrocardiogram using the Lorenz plot to demonstrate the relationship between time perception and physiological indices. The results suggest that the return trip effect is caused only postdictively. Electrocardiographic analysis revealed that the two experimental conditions induced different responses in the autonomic nervous system, particularly in sympathetic nervous function, and that parasympathetic function correlated with postdictive timing. To account for the main findings, the discrepancy between the two time estimates is discussed in the light of timing strategies, i.e., prospective and retrospective timing, which reflect different emphasis on attention and memory processes. Also each timing method, i.e., the verbal estimation, production or comparative judgment, has different characteristics such as the quantification of duration in time units or knowledge of the target duration, which may be responsible for the discrepancy. The relationship between postdictive time estimation and the parasympathetic nervous system is also discussed.

Appropriate sevoflurane concentration to stabilize autonomic activity during intubation with rocuronium in infants: a randomized controlled trial

Background

In infants, sevoflurane is commonly used for induction of anesthesia, following which a muscle relaxant is administered to facilitate tracheal intubation. When rocuronium is used as the muscle relaxant, intubation may be performed before reaching an adequate depth of anesthesia because of its rapid onset. The purpose of this study was to investigate the optimal sevoflurane concentration that would minimize the impact of intubation on hemodynamics and autonomic nervous system (ANS) activity in infants.

Methods

Sixty-one infants aged 1–6 months, undergoing cleft lip repair, were enrolled. Patients were randomly assigned to three end-tidal sevoflurane concentration (E’_Sevo) groups, 3%, 4% and 5%. Anesthesia was induced with 5% sevoflurane with 100% oxygen, and rocuronium (0.6 mg/kg) was administered. The concentration of sevoflurane was adjusted to the predetermined concentration in each group. Mechanical pressure control ventilation via a face mask was commenced. Five minutes after E’_Sevo became stable at the predetermined concentration, tracheal intubation was performed. Immediately after tracheal intubation, ventilation was restarted at the same ventilator settings and continued for 150 seconds. Heart rate (HR) and mean arterial pressure (MAP) were measured 5 times in the 150 seconds after intubation. Normalized units (nu) of high frequency (HF: 0.04-0.15 Hz) and the ratio of low frequency (LF: 0.15-0.4 Hz) to HF components (LF/HF) of HR variability were calculated by MemCalc/Tonam2C™. Normalized units of HF (HFnu) and LF/HF reflect cardiac parasympathetic and sympathetic activity, respectively.

Results

After intubation, HR increased slightly in all groups and MAP increased by 9.2% in the E’_Sevo-3% group. LF/HF increased (p < 0.01) and HFnu decreased (p < 0.01) in all groups 30 seconds after intubation. HFnu was lower (p < 0.001) and LF/HF was higher (p = 0.007) in the E’_Sevo-3% group than in E’_Sevo-5% group. ANS responses to intubation were reduced in a dose-dependent manner.

Conclusions

Sympathomimetic and parasympatholytic responses to intubation in the E’_Sevo-3% group were much greater than those in the E’_Sevo-5% group. During tracheal intubation in infants, 4% or 5% sevoflurane is appropriate for prevention of sympathetic hyperactivation and maintenance of ANS balance as compared to 3% sevoflurane, when a muscle relaxant is co-administered.

Trial registration

The study was registered at UMIN-CTR (UMIN000009933).

Assessing surgeon stress when operating using heart rate variability and the State Trait Anxiety Inventory: will surgery be the death of us?

AIM

Performance in the operating room is affected by a combination of individual, patient and environmental factors amongst others. Stress has a potential negative impact on performance with the quality of surgical practice and patient safety being affected as a result. In order to appreciate the level of stress encountered during surgical procedures both objective and subjective methods can be used. This study reports the use of a combined objective (physiological) and subjective (psychological) method for evaluating stress experienced by the operating surgeon.

METHOD

Six consultant colorectal surgeons were evaluated performing eighteen anterior resections. Heart rate was recorded using a wireless chest strap at eight pre-determined operative steps. Heart Rate Variability indices were calculated offline using computerized software. Surgeon reported stress was collected using the State Trait Anxiety Inventory, a validated clinical stress scale.

RESULTS

A significant increase in stress was demonstrated in all surgeons whilst operating as indicated by sympathetic tone (control: 4.02 ± 2.28 vs operative: 11.42 ± 4.63; P < 0.0001). Peaks in stress according to operative step were comparable across procedures and surgeons. There was a significant positive correlation with subjective reporting of stress across procedures (r = 0.766; P = 0.0005).

CONCLUSION

This study demonstrates a significant increase in sympathetic tone in consultant surgeons measured using heart rate variability during elective colorectal resections. A significant correlation can be demonstrated between HRV measurements and perceived stress using the State Trait Anxiety Inventory. A combined approach to assessing operative stress is required to evaluate any effect on performance and outcomes.

Relax, it's just laparoscopy! A prospective randomized trial on heart rate variability of the surgeon in robot-assisted versus conventional laparoscopic cholecystectomy

BACKGROUND

Laparoscopic surgery might be beneficial for the patient, but it imposes increased physical and mental strain on the surgeon. Robot-assisted laparoscopic surgery addresses some of the laparoscopic drawbacks and may potentially reduce mental strain. This could reduce the risk of surgeon's fatigue, mishaps and strain-induced illnesses, which may eventually improve the safety of laparoscopic surgical procedures.

METHODS

To test this hypothesis, a randomized study was performed, comparing both heart rate and heart rate variability (HRV) of the surgeon as a measure of total and mental strain, respectively, during conventional and robot-assisted laparoscopic cholecystectomy.

RESULTS

Both heart rate and HRV (the low-frequency band/high-frequency band ratio) were significantly decreased when using robotic assistance.

CONCLUSIONS

These data suggest the use of the daVinci® Surgical System leads to less physical and mental strain of the surgeon during surgery. However, assessing mental strain by means of HRV is cumbersome since there is no clear cutoff point or scale for maximum tolerated strain levels and its related effects on surgeon's health.

Exercise capacity is associated with endothelin-1 release during emotional excitement in coronary artery disease patients

Endothelin-1 (ET-1), a potent vasoconstrictor, IL-6, and catecholamines are increased and heart rate variability [SD of normal to normal R-R intervals (SDNN)] decreased during emotional excitement, but individual responses vary. We tested the hypothesis that exercise capacity is associated with physiological responses caused by real-life emotional excitement. We measured the plasma levels of ET-1, IL-6, catecholamines, heart rate, and SDNN in enthusiastic male ice hockey spectators (n = 51; age, 59 ± 9 years) with stable coronary artery disease (CAD) at baseline and during the Finnish National Ice Hockey League's final play-off matches. Maximal exercise capacity (METs) by bicycle exercise test and left ventricular ejection fraction (LVEF) were measured on a separate day. ET-1 response from baseline to emotional excitement correlated with maximal METs (r = -0.30; P = 0.040). In a linear stepwise regression analysis age, body mass index (BMI), METs, LVEF, basal ET-1, and subjective experience of excitement were entered the model as independent variables to explain ET-1 response. This model explained 27% of ET-1 response (P = 0.003). Maximal METs were most strongly correlated with ET-1 response (β = -0.45; partial correlation r = -0.43; P = 0.002), followed by BMI (β = -0.31; partial correlation r = -0.31; P = 0.033) and LVEF (β = -0.30; partial correlation r = -0.33; P = 0.023). Exercise capacity may protect against further cardiovascular events in CAD patients, because it is associated with reduced ET-1 release during emotional excitement.

Effect of mental processing on low back load while lifting an object

STUDY DESIGN

Biomechanical study using a 3D motion analysis system conducted in a laboratory setting.

OBJECTIVE

To determine the effect of mental processing on low back load during lifting.

SUMMARY OF BACKGROUND DATA

In addition to ergonomic factors such as frequent lifting, work-related psychosocial factors are significant in the onset of disabling back pain. Although the ergonomic effects on low back load while lifting have been investigated and are widely accepted in the workplace, few studies have investigated the effect of psychosocial factors on low back load while lifting.

METHODS

Thirteen healthy subjects lifted a box from the ground in 4 different lifting tasks in randomized order: (1) squat posture with knees flexed; (2) stoop posture with knees extended; (3) squat posture with mental processing using arithmetic tasks; and (4) stoop posture with mental processing using arithmetic tasks. We used a 3D motion analysis system and 4 force plates to record kinematic and kinetic data. We calculated dynamic triaxial low back joint moments and low back compression force as index parameters of low back load under these experimental conditions.

RESULTS

Mental processing significantly increased peak low back compression force and low back extension moment, but not lateral flexion or rotation moment, while lifting in both lifting postures. Also, mental processing increased trunk bending angles in the squat posture. Although a tendency for decreased pelvic forward tilt was observed, mental processing did not significantly decrease forward pelvic tilt in the stoop posture.

CONCLUSION

Mental processing during lifting tasks seems to affect both trunk and pelvis angles in the sagittal plane for squat and stoop postures, resulting in increased low back load. The present findings might help explain the effect of ergonomic demands of lifting tasks as well as psychosocial factors responsible for the onset of disabling back pain.

LEVEL OF EVIDENCE

2.

From stress to functional syndromes: an internist's point of view

In this brief review we address schematically the relationship between two emerging issues in clinical medicine: stress and functional syndromes. It is becoming increasingly clear that they demand a multidimensional approach, considering simultaneously elements of behavioral therapy with traditional pharmacological treatment, guided by a better physiopathological understanding including autonomic assessment. New techniques, based on innovative analysis of continuous segments of electrocardiogram and non invasive arterial pressure recordings capable to extract hidden oscillations, provide quantitative indices of sympathetic and vagal modulation of the cardiovascular system. This more complete diagnostic process facilitates explanation of symptoms and reassurance of patients, based on functional evidence. The described clinical approach implies in addition an active collaboration of patients requiring the implementation of a creative alliance. Physical exercise, eating habits and muscular-mental relaxation are combined with pharmacological tools as needed.

The Acute Effects of Acupuncture Upon Autonomic Balance in Healthy Subjects

Restoration of the sympathovagal (S/V) balance, involving a lowering of sympathetic and/or an augmentation of vagal modulation or a combination of both is associated with improvements in cardiovascular morbidity and mortality. To determine whether acupuncture exerts a favorable influence upon resting blood pressure and sympathovagal balance, a single-blind cross-over investigation was used to study the acute effects of acupuncture on S/V balance in normal healthy subjects. The ANOVA revealed a significant lowering of the sympathovagal balance (LF:HF) during rest for the acupuncture treatment from pre (4 ± 2 nu) to post (2.2 ± 1.8 nu)(p < 0.05). No such change was seen during sham treatment. The ANOVA revealed significant differences in systolic blood pressures during rest (114 ± 4 vs. 108 ± 3 mmHg) for the acupuncture treatment (p < 0.05). No significance was found during the sham treatment. The ANOVA failed to reveal any significant improvements in sympathovagal balance during the sustained isometric contraction. The clinical significance of these findings appears to suggest that acupuncture treatment might be beneficial in lowering blood pressure at rest. Furthermore, the lowering of the blood pressure might be in part due to a lowering of the sympathovagal balance. These findings are of importance since acupuncture treatments are non-pharmacological and have no known detrimental side-effects. This investigation employed healthy volunteers, yet acupuncture has been found to have more potent effects in animal models of hypertension and or in the presence of an autonomic imbalance.

Autonomic and cardiovascular effects of pentobarbital anesthesia during trigeminal stimulation in cats

Stimulation of the trigeminal nerve can elicit various cardiovascular and autonomic responses; however, the effects of anesthesia with pentobarbital sodium on these responses are unclear. Pentobarbital sodium was infused intravenously at a nominal rate and the lingual nerve was electrically stimulated at each infusion rate. Increases in systolic blood pressure (SBP) and heart rate (HR) were evoked by lingual nerve stimulation at an infusion rate between 5 and 7 mg·kg⁻¹·h⁻¹. This response was associated with an increase in the low-frequency band of SBP variability (SBP-LF). As the infusion rate increased to 10 mg·kg⁻¹·h⁻¹ or more, decreases in SBP and HR were observed. This response was associated with the reduction of SBP-LF. In conclusion, lingual nerve stimulation has both sympathomimetic and sympathoinhibitory effects, depending on the depth of pentobarbital anesthesia. The reaction pattern seems to be closely related to the autonomic balance produced by pentobarbital anesthesia.

Arterial pressure oscillations are not associated with muscle sympathetic nerve activity in individuals exposed to central hypovolaemia

The spectral power of low frequency oscillations of systolic arterial pressure (SAP(LF)) has been used as a non-invasive surrogate of muscle sympathetic nerve activity (MSNA) in both experimental and clinical situations. For SAP(LF) to be used in this way, a relationship must exist between SAP(LF) and MSNA within individuals during sympathetic activation. Using progressive central hypovolaemia to induce sympathetic activation, we hypothesised that SAP(LF) would correlate with MSNA in all subjects. ECG, beat-by-beat arterial pressure and MSNA were recorded in humans (n = 20) during a progressive lower body negative pressure (LBNP) protocol designed to cause presyncope in all subjects. Arterial pressure oscillations were assessed in the low frequency (LF; 0.04-0.15 Hz) domain using a Fourier transform. For the entire group, SAP(LF), MSNA burst frequency, and total MSNA increased during LBNP. Values for coefficients of determination (r(2)) describing the linear associations of SAP(LF) with MSNA burst frequency and total MSNA were 0.73 and 0.84, but rose to 0.89 and 0.98 when curvilinear fits were used, indicating that the relationship is curvilinear rather than linear. Associations between SAP(LF) and MSNA within each individual subject, however, varied widely for both MSNA burst frequency and total MSNA, whether derived by linear (r(2) range, 1.7 × 10(-6) to 0.99) or polynomial (r(2) range, 0.09 to 1.0) regression analysis. Similar results were obtained when relationships between low frequency oscillations in diastolic arterial pressure and MSNA were evaluated. These results do not support the use of low frequency oscillations in arterial pressure as a non-invasive measure of sympathetic outflow for individual subjects during sympathetic activation.

Mental fatigue caused by prolonged cognitive load associated with sympathetic hyperactivity

Background

It is known that chronic fatigue is associated with sympathetic hyperactivity. However, the relationship between autonomic function and mental fatigue caused by a prolonged mental load in healthy humans is still unclear. Thus, in order to clarify the mechanisms underlying mental fatigue, we examined the association between mental fatigue and autonomic functions.

Methods

The study group comprised 10 healthy participants. To induce mental fatigue, participants performed mental tasks, which consisted of the advanced trail making test, kana pick-out test and mirror drawing test, for 8 hr, corresponding to a normal work day. Autonomic functions were measured by accelerated plethysmography before and after the fatigue-inducing mental tasks. As a control, the same participants completed an 8-hr relaxation session 4 weeks before the fatigue session.

Results

After the 8-hr relaxation session, low-frequency component power (LF), high-frequency component power (HF) and low-frequency component power/high-frequency component power ratio (LF/HF ratio) were not changed from baseline. In contrast, after the fatigue session, the HF and LF/HF ratio were significantly changed from baseline; specifically, the HF was lower and LF/HF ratio was higher as compared to those after the relaxation session.

Conclusions

Sympathetic hyperactivity based on decreased parasympathetic activity is associated with mental fatigue induced by prolonged cognitive load.

Hemodynamic and autonomic response to acute hemorrhage in streptozotocin-induced diabetic rats

Background

The various autonomic control systems lead to characteristic changes in heart rate (HR) and blood pressure (BP) during acute hemorrhage. However, cardiovascular autonomic neuropathy due to diabetes mellitus may interfere with the normal compensation for hemorrhage.

Materials and methods

A controlled graded bleeding (6 - 36% loss of estimated total blood volume: ETBV) was performed in streptozotocin-induced diabetic rats (STZ rats) under a conscious state. Hemodynamic and autonomic responses to acute hemorrhage were examined using analysis of BP-HR variability. The effects of dextran treatment after hemorrhage were also examined.

Results

A significant reduction in mean arterial pressure began at 12% ETBV loss in STZ rats and 18% in the control rats, respectively. When blood loss reached 18% of TEBV, the decrease in HR was prominent in STD rats due to the activation of a parasympathetic drive, as indicated by the increase in high frequency (HF; 0.75~3.0 Hz) power in HR variability, while in the control rats this response was not observed. The administration of dextran prevented the activation of the parasympathetic drive in STZ rats during hemorrhaging. In the control rats, the dextran treatment sustained the initial increase in HR with reduced HF power in HR variability.

Conclusion

STZ rats showed different hemodynamic and autonomic responses to acute hemorrhage from the control rats. STZ rats were prone to develop bradycardiac hypotension characterized by marked parasympathetic activation during hemorrhaging. This finding suggests enhancement of the Bezold-Jarisch reflex in STZ rats. Dextran treatment to maintain a normovolemic hemorrhage state inhibits this reflex.

The Imperial Stress Assessment Tool (ISAT): a feasible, reliable and valid approach to measuring stress in the operating room

BACKGROUND

Stress can impair surgical performance and may compromise patient safety. This prospective, cross-sectional study describes the feasibility, reliability, and validity of the Imperial Stress Assessment Tool (ISAT) as an approach to measuring stress during surgery.

METHODS

A total of 54 procedures were observed with 11 surgeons (4 attendings, 4 senior residents and 3 junior residents) in a large university teaching hospital in London, UK. Data collection involved physiological measures of operating surgeons [heart rate (HR) and salivary cortisol] and self-report questionnaires (State Trait Anxiety Inventory, or STAI).

RESULTS

In all, 23 of 54 procedures were stressful, as identified by self-reporting. For stressful procedures compared to nonstressful ones, STAI was higher (mean +/- SD) 9.81 +/- 2.20 vs. 12.87 +/- 4.27, t (30.64) = 3.15 as was the HR (mean +/- SD) 79.94 +/- 8.55 vs. 93.17 +/- 14.94, t(32.57) = 3.81) (p < 0.05). Significant positive correlations were obtained between the measures indicating concurrent validity: Pearson's r = 0.47 (HR vs. STAI), 0.34 (cortisol vs. STAI), and 0.57 (HR vs. cortisol) (p < 0.05). Perfect correlation of subjective and objective measures was found for 70% of the procedures. HR and cortisol had specificities of 78% and 91% and sensitivities of 91% and 70% respectively for detecting stress during surgery.

CONCLUSION

ISAT is a nonintrusive, feasible approach that combines subjective and objective methods for measuring stress in the operating room. The ISAT may increase understanding of the effects of stress on clinical performance and outcomes, leading to improved patient care.

The impact of stress on surgical performance: a systematic review of the literature

BACKGROUND

Safe surgical practice requires a combination of technical and nontechnical abilities. Both sets of skills can be impaired by intra-operative stress, compromising performance and patient safety. This systematic review aims to assess the effects of intra-operative stress on surgical performance.

METHODS

A systematic search strategy was implemented to obtain relevant articles. MEDLINE, EMBASE, and PsycINFO databases were searched, and 3,547 abstracts were identified. After application of limits, 660 abstracts were retrieved for subsequent evaluation. Studies were included on the basis of predetermined inclusion criteria and independent assessment by 2 reviewers.

RESULTS

In all, 22 articles formed the evidence base for this review. Key stressors included laparoscopic surgery (7 studies), bleeding (4 studies), distractions (4 studies), time pressure (3 studies), procedural complexity (3 studies), and equipment problems (2 studies). The methods for assessing stress and performance varied greatly across studies, rendering cross-study comparisons difficult. With only 7 studies assessing stress and surgical performance concurrently, establishing a direct link was challenging. Despite this shortfall, the direction of the evidence suggested that excessive stress impairs performance. Specifically, laparoscopic procedures trigger greater stress levels and poorer technical performance (3 studies), and expert surgeons experience less stress and less impaired performance compared with juniors (2 studies). Finally, 3 studies suggest that stressful crises impair surgeons' nontechnical skills (eg, communication and decision making).

CONCLUSION

Surgeons are subject to many intra-operative stressors that can impair their performance. Current evidence is characterized by marked heterogeneity of research designs and variable study quality. Further research on stress and performance is required so that surgical training and clinical excellence can flourish.

Central nervous system fatigue alters autonomic nerve activity

AIMS

Fatigue is a common symptom in modern society. In order to clarify the mechanisms underlying fatigue, we examined the association between central nervous system fatigue and autonomic nerve activity.

MAIN METHODS

The study group consisted of 20 healthy subjects. They performed the 2-back test for 30 min to induce fatigue. Just before and after the fatigue-inducing session, they completed the advanced trail making test (ATMT) for 30 min as a fatigue-evaluating task session. In order to measure autonomic nerve activity, electrocardiograms were monitored continuously throughout the experiment.

KEY FINDINGS

After the fatigue-inducing task session, impaired task performance was demonstrated based on the total trial number and error counts of the ATMT. During the task session, although task performance as measured using the accuracy and the mean reaction time of the 2-back test was almost unchanged, electrocardiographic R-R wave interval analyses showed a decreased high-frequency component power and an increasing trend in the low-frequency component power/high-frequency component power ratio.

SIGNIFICANCE

Decreased vagal nerve activity and increased sympathetic nerve activity are associated with central nervous system fatigue.

Three different types of surgeon-specific stress reactions identified by laparoscopic simulation in a virtual scenario

BACKGROUND

Minimally invasive surgery causes higher mental strain for surgeons than conventional surgery and is significantly more stressful in consecutive cases. This study aimed to investigate whether individual stress responses are associated with intraoperative alterations of manual surgical skills and technical errors of the laparoscopic surgeon.

METHODS

The LapSim virtual reality simulator was used. Stress measurement was carried out for 18 surgeons performing a virtual cholecystectomy using the LapSim simulator in the context of the patient simulator provided by the METI Corporation. In the course of the study, the surgeons were exposed to different external stressors (S1-S4) in defined intervals. The activity of the sympathetic nervous system was evaluated by skin resistance with the help of a sympathicograph.

RESULTS

Three different surgeon-specific stress reactions (SSR) could be identified. The first, SSR-1, with significant stress reactions during the study without recovery, showed larger laparoscopic extensions of movement but fewer intraoperative complications than SSR-2 (recovery after the stress reactions) or SSR-3 (without significant stress reactions).

CONCLUSIONS

The mental load of the laparoscopic surgeon might be highly optimized by continuous activity of the sympathetic nervous system. The question of what extent or quality of stress produces adverse effects remains unclear.

Low-dose exercise training does not influence cardiac autonomic control in healthy sedentary men aged 55-75 years

The purpose of this study was to evaluate the effects of a realistic, feasible, and commonly used fitness training programme on cardiac autonomic control in 14 sedentary men aged 62.0 +/- 6.1 years (mean +/- s). All participants performed a one-year fitness training programme in which training intensity and frequency were specifically chosen to be compliant for the majority of the participants (2-3 sessions per week at moderate intensity). At the same time, a reference group consisting of 15 sedentary age-matched men (age 64.2 +/- 6.5 years) did not change their habitual physical activity. Measurements were performed before and after the training intervention. Cardiac autonomic control was inferred from resting values (supine and standing) of heart rate variability (HRV) computed in the frequency domain over 10-min intervals. Endurance capacity was evaluated during a maximal incremental bicycle ergometer test. In spite of an increase in peak oxygen consumption (VO2peak) by 6.4% after training, heart rate in the training group remained unchanged at rest and at the same metabolic demand. No changes in resting parameters of HRV were shown for either groups or positions. Results from this study provide no evidence of a clinically meaningful increase in the vagal modulation to the sinus node at rest after one year of low-volume and moderate-intensity fitness training in men aged 55-75 years.

Stress cardiovascular/autonomic interactions in mice

Studies evaluated the role of the autonomic nervous system in the cardiovascular response to stress using radiotelemetric blood pressure (BP) recording coupled with autoregressive spectral analysis. Conscious male C57/BL6 mice with carotid arterial telemetric catheters were exposed to acute episodes of shaker stress before and after administration of cholinergic, beta1-adrenergic and alpha1-adrenergic receptor antagonists. Pulse interval (PI) and systolic arterial pressure (SAP) were analyzed for variance and the low frequency (LF: 0.1-1.0 Hz) and high frequency (HF: 1-5 Hz) spectral components. Stress (5 min) increased BP and heart rate (HR) as well as PI and SAP variability. PI variance increased from 41+/-6 to 75+/-14 ms2 while SAP variance increased from 25+/-5 to 55+/-9 mm Hg2. Autonomic blockade had specific effects on stress-induced changes in PI and SAP and their respective variability. Atropine reduced the tachycardia and abolished the increase in PI variance and its LF component. Data documents that in mice the cholinergic system is fundamental for the maintenance of HR variability. Atropine had no effects on the BP responses, either the increase in SAP or the variance associated with stress. Atenolol blocked the increase in PI and SAP variability induced by stress. Prazosin reduced the tachycardia produced by stress and blocked the increase in PI (only LF) and SAP variability. Using quantitative spectral analysis of telemetrically collected BP data in mice along with pharmacological antagonism, we were able to accurately determine the role of autonomic input in the mediation of the stress response. Data verify the role of sympathetic/parasympathetic balance in stress-induced changes in HR, BP and indices of variance.

Hemodynamic and autonomic changes induced by Ironman: prediction of competition time by blood pressure variability

We hypothesized that the extreme endurance exercise of an Ironman competition would lead to long-standing hemodynamic and autonomic changes. We investigated also the possibility of predicting competition performance from baseline hemodynamic and autonomic parameters. We have investigated 27 male athletes before competition, 1 h after, and then for the following week after the competition. The Task Force monitor was used to measure beat-to-beat hemodynamic and autonomic parameters during supine rest and active standing. Heart rate ( P < 0.001) was increased, and stroke index ( P = 0.011), systolic blood pressure ( P = 0.004), diastolic blood pressure ( P < 0.001), total peripheral resistance index ( P < 0.001), and baroreceptor reflex sensitivity ( P < 0.001) were decreased after the competition. The 0.05- to 0.17-Hz band of heart rate and blood pressure variability was increased ( P < 0.001 and P < 0.001, respectively), the 0.17- to 0.40-Hz band of heart rate interval variability was decreased after the competition ( P < 0.001). All parameters returned to baseline values 3 days after the competition. After the competition, the autonomic response to orthostasis was significantly impaired. The 0.05- to 0.17-Hz band of diastolic blood pressure variability before competition and weekly net exercise training, but not the other hemodynamic and autonomic parameters, were related to competition time in multivariate regression analysis (multiple r = 0.70, P < 0.001). The marked hemodynamic and autonomic changes after an ultraendurance race, which are compatible with myocardial depression in the face of sympathetic activation and reduction of afterload, return to baseline after only 1–3 days. Because the 0.05- to 0.17-Hz band of diastolic blood pressure variability contributes to the prediction of competition time, the analysis of blood pressure variability in the frequency domain deserves further study for the prediction of endurance capacity.

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.

Effects on baroreflex sensitivity measurements when different protocols are used to induce regular changes in beat-to-beat intervals and systolic pressure

Baroreflex sensitivity is becoming an important clinical measurement. Nevertheless there is no recommend standard measurement protocol. This study assessed the ability of eight protocols to induce regular changes in cardiac beat-to-beat interval and systolic pressure (SP), and the effect each protocol had on baroreflex sensitivity (BRS). Twelve subjects had changes in cardiac beat-to-beat intervals and SP levels induced at 8 times a minute by following 8 different protocols, each for 3 min. These comprised breathing in a supine and standing posture, breathing through a resistance, breathing into a closed orifice (the breathing protocols), and performing handgrip exercises, being rocked, having legs raised and lowered, and being presented with mental arithmetic questions (the non-breathing protocols). Induction success of each protocol was determined by the percentage of cardiac beat-to-beat interval and SP level signals with a peak at 8 times per minute in their frequency spectra. The consistency of the induced changes was measured by a signal-to-noise ratio (SNR). BRS was calculated from the frequency spectra. The induction success was 85% for breathing and 31% for non-breathing protocols. The consistency of cardiac beat-to-beat interval changes was highest with supine breathing (SNR = 1.6 +/- 0.3) and resistance breathing (SNR = 1.5 +/- 0.5) protocols. The consistency of SP level changes was highest with resistance breathing (SNR = 1.0 +/- 0.3) and breathing into a closed orifice (SNR = 1.0 +/- 0.5) protocols. BRS values in the supine breathing protocol (24 +/- 10 ms mmHg(-1)) and the handgrip protocol (32 +/- 3 ms mmHg(-1)) were significantly greater (p < 0.05) than for standing breathing (11 +/- 5 ms mmHg(-1)), resistance breathing (17 +/- 8 ms mmHg(-1)) or breathing into a closed orifice (12 +/- 5 ms mmHg(-1)) protocols. Different protocols have different induction successes and degrees of effectiveness in inducing cardiac beat-to-beat and SP level changes. BRS is affected by the induction protocol used, highlighting the need for a standard measurement protocol.

Plastic Surgeon???s Life: Marvelous for Mind, Exhausting for Body

Surgery is accepted as one of the most demanding professions that create both physical and mental strain on the performers. Therefore, the authors aimed to elucidate the mental burden of surgeons, which is dedicated to operative stress. They also tested the hypotheses that participating in surgery creates mental stress on surgeons that leads to cardiovascular changes, and that this stress is more pronounced for actual operators than for first assistants. The method chosen for this purpose was an analysis of heart rate variability. Twelve surgeons (five plastic surgery staff and seven plastic surgery residents) were monitored by a digital ambulatory Holter recorder on at least two occasions. Half of the recordings were carried out on operating days and the other half on office days. Heart rate variability indices (low frequency, high frequency, high frequency/low frequency ratio, and heart rate) were analyzed from those recordings using computerized research tool software. The heart rate variability indices of the operators showed statistically significant differences between operating days and office hours in favor of an increased sympathetic and decreased parasympathetic activity for the former. For first assistants, three of the parameters, with the exception of heart rate, changed in favor of a sympathetic predominance over parasympathetic activity; these changes were also statistically significant. These results showed a sympathetic hyperactivity for both operators and first assistants during the operations. When the sympathovagal balance of the actual operators was compared with that of assistants, the former group showed a more pronounced sympathetic arousal. This difference is accepted as a proof for the mental stress of the surgery being the main factor responsible for the sympathetic hyperactivity that we detected during the operations. Surgeons continuously face a unique mental strain that other professions rarely bring forth, and these psychological stressors are associated with alterations in cardiac autonomic control that may contribute to the development of cardiac disease. Prolonged sympathetic hyperactivity could anticipate cardiac discomfort in more experienced surgeons with marginal cardiac reserve. Such cardiac diseases would be reconsidered as occupation-related illnesses, which might be reimbursed to the physician. In addition, the legal responsibility of surgeons concerning their unfavorable results might be assessed with more understanding with a realization of their undue working conditions.

Does Halothane Really Preserve Cardiac Baroreflex Better Than Sevoflurane? A Noninvasive Study of Spontaneous Baroreflex in Children Anesthetized with Sevoflurane Versus Halothane

Heart rate profiles during the induction of anesthesia differ markedly between the administration of sevoflurane and halothane. Previous investigations have shown that halothane preserves cardiac parasympathetic activity more than sevoflurane. Because vagal drive to the sinus node is the main effector of arterial baroreflex control of heart rate, halothane may preserve cardiac baroreflex better than sevoflurane. To investigate cardiac baroreflex in anesthetized children, we used two noninvasive methods providing different approaches to the arterial blood pressure (BP) and R-R interval (RRI) relationship: the sequence methods investigating beat-to-beat changes in BP and RRI (time domain) and the cross-spectral analysis investigating relationships between oscillations of BP and RRI (frequency domain). Children were randomly assigned to mask induction with sevoflurane in 100% oxygen, sevoflurane in 50% nitrous oxide/50% oxygen, or halothane in 50% nitrous oxide/50% oxygen. After tracheal intubation, the inspired fraction of volatile anesthetic was reduced to 1 minimum alveolar anesthetic concentration (MAC). The spontaneous baroreflex (SBR) sensitivity was calculated with the sequence method at baseline, during induction, and after intubation. The cardiac baroreflex was also estimated with cross-spectral analysis at baseline and at 1 MAC (stationary conditions). In the three groups, the induction of anesthesia was associated with a marked decrease of SBR sensitivity, which occurred earlier with sevoflurane than with halothane. Five minutes after intubation (1 MAC), the sequence method showed a similar decrease of the SBR sensitivity in the three groups. Similarly, the cross-spectral analysis between systolic blood pressure and RRI showed a decrease of the gain calculated in the low-frequency band, but the gain in the respiratory band was higher with halothane compared with sevoflurane. In children, the induction of anesthesia with halothane and sevoflurane is associated with a marked decrease of cardiac baroreflex activity. The persistence of respiratory RRI fluctuations under halothane might reflect reflex respiratory arrhythmia rather than efficient parasympathetic baroreflex activity.

Influences of an anticholinergic antiparkinsonian drug, parkinsonism, and psychotic symptoms on cardiac autonomic function in schizophrenia

The arguments against the use of anticholinergic antiparkinsonian drugs for neuroleptic-induced parkinsonism have been based, in part, on their autonomic side effects. Except for anecdotal case reports, there is little evidence that antiparkinsonian drugs are the main factor causing autonomic dysfunction in schizophrenic patients with parkinsonism. Therefore, in the current study, the separate influences of the anticholinergic antiparkinsonian drug (biperiden), parkinsonism, and psychotic symptoms on cardiac autonomic function were investigated in 48 patients with schizophrenia. Biperiden was discontinued in 33 patients with or without parkinsonism and commenced in 15 patients with parkinsonism. Their parkinsonism and psychotic symptoms were assessed using rating scales, and their cardiac autonomic functions were assessed using the mean R-R interval and 3 methods of analyzing heart rate variability both before and after the change in medication. Consequently, the cardiac autonomic function was not affected by biperiden or the change in parkinsonism. Cardiac vagal function decreased when psychotic symptoms were more pronounced, but cardiac sympathetic function did not show a significant change. Therefore, it appeared that psychotic symptoms played the predominant role in modifying the cardiac autonomic function, implying the existence of autonomic changes associated with cognitive processing and a possible relation between psychotic symptoms and autonomic symptoms in schizophrenia.

Paradoxical autonomic response to mental tasks in autism

Autonomic responses to mental tasks requiring sustained attention were examined in individuals with autism and age- and ability-matched controls. Cardiac autonomic function (CAF) was evaluated based on heart rate variability. While the control group showed a significant decrease in the parasympathetic function during mental tasks, the autistic group showed no significant changes in CAF. When examined individually, parasympathetic function was suppressed in all subjects in the control group. On the other hand, parasympathetic function was activated in half of the autistic subjects. The paradoxical autonomic response suggests that some autistic subjects were more stressed under 'resting' conditions than while performing mechanical or repetitive mental tasks. The results seem to support autonomic hyperarousal in some people with autism.

[To understand blood pressure and heart rate variability]

OBJECTIVES

To review current data on the heart rate and blood pressure variability.

DATA SOURCES

Search through Medline databases of articles in french or english.

DATA SELECTION

Original articles and case reports were selected according to their quality and main advances. The articles were analysed in order to obtain current data about the methods of study and clinical application of blood pressure and heart rate variability.

DATA SYNTHESIS

Various regulatory systems in the cardiovascular system play crucial roles in controlling and assuring adequate perfusion of the peripheral tissues. Among them the baroreceptor reflex is the most important regulatory mechanism in the short-term control of the heart rate and blood pressure, and operates through the autonomic nervous system. The gain of the cardiac baroreflex further referred to, as baroreflex sensitivity is an interesting way to study this system. Unfortunately, with our current knowledge, it is not possible to predict the instantaneous output of the baroreceptor in response to instantaneous changes in input within a frequency range of physiological importance. The fast Fourier transform can describe variables as the sum of elementary oscillatory components and it has been established as practical clinical methods for detecting abnormalities in cardiovascular control. A time-frequency distribution provides an indication of how the spectral energy distribution varies with time and it is an interesting tool in non-stationary data. One of the major motivations behind spectral analysis is the hope that the combination of time-domain and frequency-domain analyses will provide dynamical informations about the relation between blood pressure and heart rate.