Root Mean Square Of Successive Differences Research Articles

Fluctuations of prolonged grief disorder reactions in the daily life of bereaved people: an experience sampling study

AbstractLoss-adaptation has been described as being characterized by ‘waves of grief’, which may result in a Prolonged Grief Disorder (PGD). Although this assumption about the fluctuating nature of grief is supported by theoretical work, it is not (yet) supported by empirical work. We are the first to explore to what extent PGD reactions fluctuate in everyday life and whether fluctuations in PGD reactions are related to overall PGD levels using experience sampling methodology (ESM). Data from 38 bereaved individuals (74% women, on average 6 years post-loss, 47% lost a parent) were analyzed. For two weeks, five times per day, participants reported on the severity of 11 PGD reactions in the past three hours (ESM-PGD). At baseline, overall PGD severity (B-PGD) in the past two weeks was assessed with telephone-interviews using the Traumatic Grief Inventory–Clinician Administered. Root Mean Square of Successive Differences (RMSSD) were calculated to reflect fluctuations in ESM-PGD. Spearman correlations between RMSSD values of the 11 ESM-PGD reactions and B-PGD scores were computed. Mean B-PGD scores were below the clinical cut-off. Some fluctuations in ESM-PGD reactions were found, as indicated by varying RMSSD values, but also floor effects were detected. B-PGD levels were related to RMSSD values for ESM-PGD (ρ between 0.37 and 0.68, all p <.05; and between 0.36 and 0.63 after removal of floor effects). We found that (some) ESM-PGD reactions fluctuated in everyday life. This may offer new theoretical insights into loss-adaptation, which may result in optimizing PGD treatment.

Fetal Heart Rate Analysis in Pregnancies Complicated by Gestational Diabetes Mellitus: A Prospective Multicentre Observational Study.

Establish whether pregnancies complicated by gestational diabetes mellitus (GDM) are associated with a fetal cardiac phenotype that predisposes to arrhythmia; utilising measurements derived from non-invasive abdominal fetal ECG. Prospective observational study. Three tertiary obstetric units, United Kingdom. Women aged ≥ 16 years with either GDM or uncomplicated pregnancy (control) who were > 20 weeks gestational age. The MonicaAN24 non-invasive abdominal fetal ECG monitor was fitted for overnight recording. Calculation of the fetal heart rate (FHR) and fetal heart rate variability (HRV) time domain metrics standard deviation of normal-to-normal intervals (SDNN), root mean square of successive differences (RMSSD) and the PR, QRS, QT intervals was performed. Groups were compared using linear regression models (stratified by sleep state) and adjusted for fetal sex and ethnicity. Ninety-six participants were included. For HRV in sleep state 1F, SDNN was higher for GDM than control participants 12.56 (10.45-16.62)ms versus 8.58 (5.83-9.73)ms [p = 0.01] [median (IQR)]. There were no differences in SDNN in sleep state 2F. No differences were identified in RMSSD in either sleep states or in the cardiac time intervals. We observed a negative correlation between HRV and body mass index/HbA1c and a positive correlation between FHR and body mass index/HbA1c in sleep states 1F/2F. Alterations of HRV and FHR rate may be associated with a diagnosis of GDM, likely secondary to altered autonomic function in utero.

Unraveling the complex interplay between curved tunnels and drivers’ physiological responses: An HRV perspective

This study aims to unravel the complex interplay between curved tunnels and drivers’ physiological responses from an HRV (Heart Rate Variability) perspective.A group of 30 individuals with valid driver’s licenses was selected, and their HRV was monitored while driving through four curved tunnels in Yunnan Province, China. HRV indicators such as RMSSD (Root Mean Square of Successive Differences), SDNN (Standard Deviation of Normal-to-Normal Intervals), LF (Low Frequency), and LF/HF (ratio of Low Frequency to High Frequency) were analyzed. The independent variables included tunnel radius, turn direction, and zone characteristics. The results demonstrated that the radius, turning, and zone of the curved tunnel significantly influenced drivers’ HRV. Specifically, as the tunnel radius decreased, the mean RMSSD and SDNN of drivers decreased, while the mean LF and LF/HF increased. In left turns, drivers had lower RMSSD and SDNN values but higher LF and LF/HF ratios compared to right turns. Additionally, drivers showed the highest mean RMSSD and SDNN in the entrance zone of the tunnel, followed by the middle zone, and the lowest in the exit zone. Conversely, the exit zone had the highest mean LF and LF/HF, followed by the middle zone, and the entrance zone had the lowest. These results indicate that the characteristics of the curved tunnel have a substantial impact on drivers’ physiological responses. A smaller tunnel radius leads to increased stress and cognitive load, as reflected by the decreased HRV metrics and increased sympathetic activity. Turning maneuvers, particularly left turns, result in asymmetry in autonomic responses, with lower RMSSD and SDNN and higher LF and LF/HF during left turns. The variations in HRV across different zones within the tunnel suggest that environmental cues play a role in sympathetic activation, with the exit zone showing the highest sympathetic activity. These findings offer significant insights into the relationship between tunnel conditions and drivers’ physiological responses, emphasizing the importance of considering these factors in road safety and human factors engineering. By comprehending how tunnel characteristics affect drivers’ autonomic nervous system responses, we can formulate strategies to enhance driver well-being and safety.

Heart Rate Variability for Supplementing Withdrawal Assessment in Patients with Opioid Dependence: An Exploratory Study.

Management of opioid dependence requires titrating medication doses based on withdrawal symptoms, but its clinical assessment presents challenges when it comes to subjective reporting. This study aimed to find out the relationship between heart rate variability (HRV) and opioid withdrawal in patients with opioid dependence. Three groups of adult males were recruited: (a) patients with opioid dependence undergoing inpatient detoxification, (b) patients with opioid dependence stabilized on buprenorphine-based opioid substitution treatment, and (c) healthy controls. Frequency and time-domain parameters of HRV were used in the analysis. The opioid withdrawal was assessed using the Subjective Opiate Withdrawal Scale (SOWS). Resting heart rate was found to be significantly different across the three groups (higher in patients stabilized on buprenorphine than the other two groups). In time-domain parameters, the detoxification group had the highest beat-to-beat variability. In frequency-domain parameters, the total power was highest for the detoxification group and lowest for the opioid substitution treatment group. In contrast, the relative power of frequency bands (very low, low, and high) did not vary across the groups at baseline. The SOWS had a weak negative correlation with root mean square of successive differences (RMSSD) in the opioid substitution group and did not have any relationship with HRV parameters in the detoxification group. This exploratory study did not find HRV parameters to be robustly associated with subjective withdrawal, except for a negative association with the beat-to-beat variability among patients on opioid substitution treatment. This study adds to information on HRV in patients with opioid dependence.

Three-dimensional (3D) stimuli are always better than two-dimensional (2D) multi-tasking? A high cognitive load in 3D-MATB-II

ObjectiveThe objective of this study is to investigate the whether multi-tasking performance in (three-dimensional) 3D aid or impede cognition compare to (two-dimensional) 2D environments, as reflected by cognitive load. Specifically, we aim to examine the mechanism of multi-tasking under 3D (virtual reality [VR]) and 2D (PC monitor) conditions using the widely used Multi-Attribute Task Battery (MATB) II paradigm. MethodologyThe MATB-II sub-tasks, namely “Tracking” and “System Monitoring,” were conducted with varying task demands in both 3D conditions (Tracking Far - System Monitoring Near [TF-SN], Tracking Near - System Monitoring Far [TN-SF]) and a 2D condition with no depth perception (No Depth [ND]). Participants' cognitive load was assessed using subjective reporting (NASA-TLX) and physiological measure (root mean square of successive difference (RMSSD) of heart rate variability (HRV)). ResultsThe study found that performance was significantly better in the ND condition compared to the TF-SN and TN-SF conditions. Furthermore, higher NASA-TLX scores and lower RMSSD values were observed in the TF-SN and TN-SN conditions compared to the ND condition, providing additional support for the overall findings of the MATB-II paradigm. ConclusionThese findings suggest that processing multiple tasks in different depth planes may lead to poorer performance and increased subjective and physiological cognitive load.

Effects of a synthetic analogue of the bovine appeasing pheromone on the overall welfare of dairy calves from birth through weaning

Environmental enrichment in the form of synthetic analogs of appeasing pheromones have shown promising results in improving the welfare of domestic animals including dogs, pigs, horses, and cattle. The main objective of this study was to determine if the use of the bovine appeasing pheromone (BAP) would improve the welfare of dairy calves; therefore, in this randomized controlled trial, 72 Holstein Friesian dairy calves were housed in individual hutches after birth and were randomly allocated to receive BAP or a placebo once every 2 weeks from birth through weaning. After weaning, calves were moved to group hutches according to treatment for 4 additional weeks. It was hypothesized that dairy calves treated with BAP would display fewer signs of stress compared with calves receiving the placebo during the weaning process. To operationalize stress, calves were fitted with triaxial accelerometers on the hind leg after birth, and activity levels were monitored throughout the experiment. Data on live weight gain (ADG) and cortisol levels in saliva and hair were also obtained. Calves were fitted with heart rate monitors every week for at least 24 h to assess heart rate variability (HRV). The use of BAP had a positive effect on ADG after weaning and during group housing and resulted in increased resting time after weaning. Moreover, BAP, was associated with a reduction in the activation of the neuroendocrine system evidenced by higher HRV parameters after weaning, including increased standard deviation of beat to beat of normal sinus beats (SDNN) and root mean squares of successive differences (RMSSD). These results suggest a potential welfare benefit of the use of BAP during the artificial rearing of dairy calves.

Heart rate variability, electrodermal activity and cognition in adults: Association with short-term indoor PM2.5 exposure in a real-world intervention study

BackgroundLong-term effects of ambient fine particulate matter (PM2.5) exposure on mortality and morbidity are well established. The study aims to evaluate how short-term indoor PM2.5 exposure affects physiological responses and understand potential mechanisms mediating the cognitive outcomes in working-age adults. MethodsThis real-world randomized single-blind crossover intervention study was conducted in an urban office setting, with desk-based air purifiers used as the intervention. Participants (N = 40) were exposed to average PM2.5 levels of 18.0 μg/m3 in control and 3.7 μg/m3 in intervention conditions. Cognitive tests, heart rate variability (HRV), and electrodermal activity (EDA) measures were conducted after 5 h of exposure. Self-reported mental effort, exhaustion, and task difficulty were collected after the cognitive tests. ResultsParticipants in the intervention condition had significantly higher HRV during cognitive testing, particularly in the standard deviation of normal-to-normal intervals (SDNN), root mean square of successive differences (RMSSD), and high-frequency power (HF) indices. Mediation analysis revealed that elevated PM2.5 exposure reduced HRV indices, which mediated the effect on two executive function-related cognitive skills out of 16 assessed skills. No significant differences were found in EDA, self-reported task difficulty, or exhaustion, but self-reported mental effort was higher in the control condition. ConclusionsLower indoor PM2.5 level was associated with reduced mental effort and higher HRV during cognitive testing. Furthermore, the association between indoor PM2.5 exposure and executive function might be mediated through cardiovagal responses. These findings provide insights on the mechanisms through which fine particle exposure adversely affects the autonomic nervous system and how this in turn affects cognition. The potential cardiovascular and cognitive health benefits of PM2.5 reduction warrants further research.

The Effects of a Single Vagus Nerve's Neurodynamics on Heart Rate Variability in Chronic Stress: A Randomized Controlled Trial.

The modulation of the autonomic nervous system's activity, particularly increasing its parasympathetic tone, is of significant interest in clinical physiotherapy due to its potential benefits for stress-related conditions and recovery processes. This study evaluated the effectiveness of the addition of neurodynamics in enhancing parasympathetic activation in subjects with chronic stress. A clinical trial randomly assigned participants to a group with neurodynamics (6 bpm breathing protocol + manual therapy + neurodynamic technique) or a group without neurodynamics (6 bpm breathing protocol + manual therapy only). Metrics of heart rate variability (HRV), including the Mean Heart Rate (Mean HR), standard deviation of intervals between consecutive heartbeats (SDNN), Heart Rate Difference (Diff. HR), Root Mean Square of Successive Differences (RMSSD), number of intervals differing by more than 50 ms (NN50), percentage of consecutive NN intervals that differed by more than 50 ms (pNN50), and the high-frequency component measured in standardized units (HF), were assessed before, during, and after the intervention. During the intervention, the group with neurodynamics showed significant changes in all variables except in the pNN50 and HF while the group without neurodynamics only showed improvements in the Mean HR, SDNN, and RMSSD. In the post-intervention phase, the group with neurodynamics maintained an increase in HRV while the group without neurodynamics experienced a decrease, suggesting an increase in sympathetic activity. Vagal nerve neurodynamics appear to represent an effective method for enhancing parasympathetic activation in patients with chronic stress. The results highlight the importance of a more comprehensive analysis of HRV variables in order to obtain a correct picture of the impact of interventions on the complex and multifaceted functioning of the autonomic nervous system.

Autonomic rehabilitation: Vagal and sympathetic impacts of modified occipitomastoid suture V-spread.

Autonomic rehabilitation using osteopathic manipulative treatment (OMT) to stimulate the vagus nerve may be a good adjunct therapy by physiatrists who treat dysautonomia. Heart rate variability (HRV) may provide quantitative evidence for the benefits of OMT on autonomic nervous system function. Elevated HRV indicates optimal health and reduced mortality risk, whereas low HRV is associated with stress, pain, and chronic disease pathology. To analyze the impact of modified occipitomastoid suture v-spread OMT technique on vagal tone by measuring HRV. Within-participant design with 5-minute HRV measurement pre- and post-OMT treatment. Clinical examination suites. Thirty healthy osteopathic medical students. A modified occipitomastoid suture v-spread treating somatic dysfunction by osteopathic physicians trained in osteopathic neuromusculoskeletal medicine. HRV variables related to vagal tone including root mean square of successive differences (RMSSD), percentage of successive normal sinus RR intervals >50 ms (pNN50), high frequency (HF), Parasympathetic Nervous System Index (PNSI), and Sympathetic Nervous System Index (SNSI). Repeated measures t-test analyzed the difference in mean HRV values after OMT. There were statistically significant increases in each of the HRV measures after OMT. Participants had a mean (95% confidence interval) RMSSD of 50.5 ms (38.3-62.8) at baseline and 55.0 ms (41.2-68.7, p = .013) post-OMT. pNN50 was 24.5% (17.6-31.3, n = 30) at baseline and 28.2% (20.8-35.6, p = .003) post-OMT. HF was 1549.6 ms2 (389.8-2709.4) at baseline and 1901.8 ms2 (618.2-3185.4, p = .103) post-OMT. PNSI was -0.1 (-0.5 to 0.2) at baseline and 0.1 (-0.3 to 1.5, p < .01) post-OMT, and SNSI was 0.2 (-0.1 to 0.6) at baseline and 0.05 (-0.3 to 0.4, p < .01) post-OMT. Normalization, due to high baseline variance, results include RMSSD 1.1 ms (1.0 to 1.1, p = .012), pNN50 1.3 (1.1 to 1.4, p = .011), and HF 1.2 ms2 (1.1 to 1.4, p = .018). Modified occipitomastoid suture v-spread may provide clinical benefit through increased vagal tone and decreased sympathetic activity.

Insight of autonomic dysfunction in CLN3 disease: a study on episodes resembling paroxysmal sympathetic hyperactivity (PSH)

BackgroundRecurrent non-epileptic episodes resembling paroxysmal sympathetic hyperactivity (PSH) have been observed in adolescents with Juvenile Ceroid Lipofuscinosis (CLN3-disease) and a possible association to an autonomic dysfunction has been suggested. The objective of the present study was to investigate the dynamics of the autonomic activity up to, during, and in the time after individual attacks. We include all seven suitable CLN3 patients in Denmark ≥ 15 years of age. HRV parameters were assessed from continuous heart rate monitoring during seven consecutive days and a particular focus of HRV parameters was obtained in close temporal context to clinically recurrent PSH-like episodes. In addition, the likelihood of PSH was assessed by caregiver’s description and by video documentation.ResultsRespectively eight and five episodes were recorded in two patients (18 and 20 years of age). The episodes were all safely superior to the cut off values of the clinical assessment score to be considered PSH-like episodes. During all 13 episodes, HRV revealed a statistically significant decrease in root mean square of successive differences (RMSSD) and standard deviation of the Poincaré-Plot interval (SD1) in the minutes prior to the clinical onset of the episodes, both indicating a sudden decrease in parasympathetic activity in advance of the onset. The reduced activity remained low during the episodes, and 15–30 min following the attack cessation, the parasympathetic activity had returned to pre-attacks levels. The sympathetic HRV parameters were unchanged resulting in a sympathetic overactivity during the episodes. In a third participant (32 years of age), in whom severity of PSH-like episodes had been gradually reduced during the last years, five episodes were registered. A similar temporally related reduction of the parasympathetic activity was found, but because the sympathetic activity decreased as well, no sympathetic dominance developed, which most reasonable is the reason to the clinically reduced expression of the episodes.ConclusionThe documented transient withdrawal of parasympathetic activity leading to a paroxysmal unbalanced sympathetic hyperactivity most probably accounts for the PSH-like episodes occurring in post-adolescent CLN3 patients. The findings shed new light on both aetiology and possible preventative and therapeutic measures.

A Familiar Working Environment Influences Surgeon's Stress in the Operating Room: A Multi-Specialty Prospective Cohort Study.

To determine the influence of operating room familiarity on surgeon stress. Regulating surgeon stress may improve patient safety. This study evaluated how assisting surgeon and operating room familiarity influence intraoperative heart rate variability among surgeons. Attending surgeons from seven specialties within four university hospitals in France were enrolled from 11/01/20-12/31/21. Vagal tone, an indicator of stress derived from heart rate variability, was assessed during the first five minutes after incision using the root mean square of successive differences (RMSSD). Higher RMSSD values indicate greater vagal tone. Team familiarity was quantified as the cumulative time the attending and assisting surgeons had operated together in the past, while operating rooms in which the surgeon conducted >10% of their operations were termed familiar. The effect of each on the RMSSD was assessed via a linear mixed-effect model adjusting for the random effect of the surgeon and possible confounders. Overall, 643 surgeries performed by 37 surgeons were included. Median surgeon age was 49 years, 29(78.4%) were male, and 22(59.5%) were professors. Surgeons spent an average of 21.2 hours with the assisting surgeon prior to surgery and conducted 585(91.0%) of their operations in a familiar operating room. For every 10 additional hours spent operating together, ln(RMSSD) significantly increased by 0.018 (95%CI: 0.003 to 0.033, P=0.016). Familiar operating rooms also tended to increase surgeon ln(RMSSD) [0.098 (95%CI: -0.007 to 0.203, P=0.068)]. Familiar assisting surgeons, and potentially operating rooms, increased surgeon vagal tone. Maintaining a stable operating room environment may improve surgeon stress and patient care.

Association of hyperventilation-induced heart rate variability and sudden unexpected death in epilepsy in drug-resistant epilepsy.

Within the general epilepsy population, the incidence of Sudden Unexpected Death in Epilepsy (SUDEP) ranges from approximately 0.35 to 2.3 per 1,000 individuals per year. We aimed to evaluate the relationship between SUDEP risk factors and heart rate variability (HRV) parameters as a potential biomarker of SUDEP in patients with drug-resistant epilepsy (DRE). There were 52 patients diagnosed with DRE and under follow-up, and controls including 45 healthy subjects, included in the study. Hyperventilation-induced HRV (HRVHV) parameters, including the standard deviation of all RR intervals (SDRR), mean heart rate (HR), root mean squares of successive differences (RMSSD), SD of mean NN intervals recordings (SDANN), and HRV triangular index, were assessed during resting. To predict the risk of SUDEP, the relationship between HRV parameters and SUDEP risks was evaluated using the Risk Assessment for Sudden Death in Epilepsy (SUDEP-7) Risk Inventory. No statistically significant difference was found in sympathetic skin response (SSR) latency and amplitudes between the patient and control groups. In comparing healthy control subjects with patients experiencing DRE, we observed significant decreases in SDRRHV and hyperventilation-induced RMSSD (RMSSDHV) values, specifically within HRVHV. Notably, a significant correlation emerged concerning the RMSSDHV values (p < 0.01), when examining the correlation between the SUDEP-7 inventory and HRVHV parameters. This correlation between RMSSDHV and the SUDEP-7 Risk Inventory in patients with DRE represents a novel and consequential finding, suggesting its potential as an indicator of SUDEP risk.

Hypertension and its correlation with autonomic nervous system dysfunction, heart rate variability and chronic inflammation

Objective This study investigates the relationship between hypertension, dysregulation of the autonomic nervous system, heart rate variability (HRV), and chronic inflammation. Methods We analysed a cohort of 50 hypertensive patients treated at the affiliated Hospital of Jianghan University. The average systolic and diastolic blood pressures (BPs) in this group were 155.26 and 95.32 mmHg, respectively. A control group of 50 healthy volunteers, undergoing routine physical examinations at the same hospital, was also analysed. Results The average systolic BP of the control group was 115.64 ± 10.27 mmHg, and the average diastolic BP was 75.33 ± 8.25 mmHg. In contrast, the experimental group exhibited an average systolic BP of 155.26 ± 20.13 mmHg and an average diastolic BP of 95.32 ± 12.16 mmHg. Both systolic and diastolic BPs were significantly higher in the hypertensive group (p < 0.05). The experimental group also demonstrated reduced HRV and skin conductance response, alongside increased BP variability (BPV), urinary epinephrine levels and prolonged pupillary light reaction time compared to controls (p < 0.05). Notably, Standard Deviation of Normal to Normal Intervals (SDNN) and Root Mean Square of Successive Differences (RMSSD) values were significantly lower in the experimental group (p < 0.05). Furthermore, levels of inflammatory markers such as CRP, TNF-α, IL-6 and IL-1β were markedly elevated in hypertensive patients (p < 0.05). Negative correlations were observed between systolic and diastolic BP with HRV metrics, while positive correlations were found between BP and BPV as well as urinary adrenaline levels. Conclusions The findings indicate that hypertension is closely associated with autonomic nervous system dysfunction, reduced HRV and increased chronic inflammation. A comprehensive approach to hypertension management should integrate these interrelated physiological and pathological mechanisms, with potential therapeutic interventions targeting autonomic function and inflammatory states.

Elevated correlations in cardiac–neural dynamics: An impact of mantra meditation on stress alleviation

Mantra meditation is a widely practiced technique with a demonstrated ability to promote relaxation and alleviate stress. This study aims to evaluate the impact of regular mantra meditation practice on electroencephalogram (EEG) patterns and heart rate variability (HRV) in young adults grappling with increased stress levels. Furthermore, the study explored possible correlations between these two physiological markers. Thirty-eight participants practiced mantra meditation for eight weeks, and their EEG and HRV were recorded before and after. The pre-post analysis evaluated brain activity and autonomic nervous system regulation alterations by examining EEG and HRV in the time, frequency, and nonlinear domains. Data analysis revealed significant correlations between EEG patterns and HRV indices following mantra meditation, suggesting a potential interconnection between neural and cardiovascular regulation. A notable increase in Root Mean Square of Successive Differences (RMSSD) and Standard Deviation of NN intervals (SDNN) within HRV, along with a decrease in Heart Rate (HR) and Stress Index (SI) and an increase in EEG alpha and theta power, accompanied by a reduction in their ratio, was observed. Three pivotal correlations consistently increased during eight weeks: Alpha/Theta Ratio (ATR) with Low-Frequency/High-Frequency Ratio (LHR), ATR with SD2/SD1 Ratio (SDR), and Relaxation Index (RI) with Stress Index (SI). After eight weeks, these correlations attained statistical significance, optimizing the balance between calmness and vigilance, boosting parasympathetic activity, and reducing chaos between the parasympathetic and sympathetic systems. The study elucidates the scientific mechanisms of mantra meditation, enriching research on its stress-reducing effects and emphasizing mental and physical well-being.

Breathing variability during running in athletes: The role of sex, exercise intensity and breathing reserve

Highly trained aerobic athletes progressively use most of their breathing reserve with increased exercise intensity during whole-body exercise. Additionally, females typically present proportionally smaller lungs than males. Therefore, sex, exercise intensity, and breathing reserve use likely influence the volume and time in which respiratory parameters vary between consecutive breaths during whole-body exercise. However, breath-by-breath variability has been scarcely investigated during exercise. Accordingly, we sought to investigate breath-by-breath pulmonary ventilation (V̇E), tidal volume (VT), and respiratory frequency (fR) variability during a maximal treadmill incremental exercise test in 17 females and 18 males highly trained professional endurance runners. The breath-by-breath variability was analyzed by root mean square of successive differences (RMSSD) within 1-minute windows. Females had lower absolute and percent predicted forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) than males, as well as lower height-adjusted absolute FVC than males. V̇E and VT reserve use were similar between the sexes at peak exercise. While RMSSDV̇E and RMSSDfR did not change over exercise (P > 0.05), RMSSDVT progressively decreased (P < 0.001). RMSSDVT was negatively correlated with VT reserve use only in males. Females showed lower RMSSDV̇E than males during the entire exercise test (P < 0.001). At iso-V̇E reserve use, between-sex differences in RMSSDV̇E persisted (P = 0.003). Our findings indicate that exercise intensity decreases VT variability in professional runners, which is linked to VT reserve use in males but not females. Additionally, the female sex lowers V̇E variability regardless of exercise intensity and V̇E reserve use.

Resting Heart Rate Variability is Independently Associated with Visceral Fat Rating Scores in Saudi Adult Males.

Visceral adipose tissue (VAT) may be a specific modifiable contributor to body composition-related autonomic impairment. To compare heart rate variability (HRV) between groups stratified by visceral fat rating (VFR) and compare associations between HRV and body composition metrics. A cross-sectional study was conducted on healthy men (n=99,age=37.8±13.4 years, body mass index [BMI]=26.9±4.6 kg/m2). HRV was derived from 5-minute electrocardiographic recordings. Body composition (body fat percentage, VFR, and muscle mass to visceral fat ratio [MMVFR]) was estimated using tetrapolar bioelectrical impedance analysis. Participants were categorized into groups according to VFR: G1 (VFR=1-8); G2(VFR=9-12); and G3(VFR>12). Age-adjusted comparisons were made between groups. Independent associations were quantified with multiple linear regressions. P <0.05 was significant. Root-mean square of successive differences (RMSSD) and standard deviation of normal RR intervals (SDNN) were higher for G1 vs. G2 and G3 (p<0.05). Low-frequency power (LF) was higher in G1 than in G2 (p<0.05). VFR and MMVFR were negatively associated with SDNN, RMSSD, LF, and HF (p<0.05). After adjusting for age, BMI, and systolic and diastolic blood pressure, VFR was significantly predictive of RMSSD, SDNN, and HF (p=0.002,-0.027), and MMVFR was significantly predictive of RMSSD and SDNN (p=0.020,-0.023). Men in the lowest VFR category had the highest HRV. VFR was more strongly associated with HRV than body fat percentage and MMVR. Time domain parameters were more sensitive to VAT than frequency domain parameters. HRV parameters could be the primary parameters of interest in tracking cardiac-autonomic status in response to interventions targeting VAT reduction.

A Comparative Analysis of Heart Rate Variability Indices in Patients with Liver Cirrhosis.

Cardiac autonomic dysfunction (AD) in reference to chronic liver disease (CLD) has become widely accepted as a symptomatic burden. This study will be undertaken to measure heart rate variability (HRV) indices and detect the severity of cardiac autonomic dysfunction in CLD patients. This study was conducted on 150 patients with liver cirrhosis and compared with 110 healthy controls. Information concerning medical history, radiological and laboratory findings was extracted for interpretation and association among both groups. The HRV was assessed by recording with a polygraph (RMS Polyrite D, version 1.0), which was based on the principle of electrocardiography. Heart rate variability indices like standard deviation of each interval normal-to-normal (SDNN), percentage of successive RR intervals that differ by >50 ms (pNN50%), high frequency (HF), low frequency (LF), and the LF/HF ratio were found to be remarkably low in cases with CLD in comparison to the healthy control group (p < 0.05). The Child-Pugh (CP) score was class C (10-15) in 52%, class B (7-9) in 30%, and class A (5-6) in 18% of patients. The CP score in CLD patients had a statistically significant negative correlation with SDNN (r = -0.5429, p < 0.001), root mean square of successive differences (RMSSD) (r = -0.375, p < 0.001), pNN50% (r = -0.6037, p < 0.001), HF (r = -0.2033, p = 0.0125), and LF (r = -0.3674, p < 0.001). SDNN, pNN50%, and LF parameters were lowest in alcohol-related CLD, highest in hepatitis C virus (HCV)-related CLD, and intermediate in hepatitis B virus (HBV)-related CLD. Our study concluded that liver cirrhosis patients have reduced HRV compared to healthy individuals. A decrease in HRV highlights people at risk of death. This is a variable that can be used to track patients over time and aid in transplant selection.

Intra- and Inter-Rater Reliability of Linear and Nonlinear Measures of Short-Term Heart Rate Variability Following Combat-Related Traumatic Injury.

Heart rate variability (HRV) is a marker of autonomic function. However, the reliability of short-term HRV measurement in individuals with combat-related traumatic injury (CRTI) remains undetermined. An intra- and inter-rater reliability study was conducted using a subsample (n = 35) of British servicemen with CRTI enrolled in the ongoing ADVANCE study. A five-minute epoch of single-lead electrocardiogram data collected during spontaneous breathing was used to measure HRV. HRV analyses were independently performed by two examiners using Kubios. Intraclass correlation coefficient (ICC), standard error of measurement (SEM), minimum detectable change (MDC), and coefficient of variance were calculated for linear [root mean square of successive difference (RMSSD), standard deviation of NN interval, low-frequency, high-frequency, total power] and nonlinear (SD1-2, acceleration and deceleration capacities, sample entropy) measures. Bland-Altman %plots were used to assess bias in intra- and inter-rater HRV data. The mean age of participants was 39.3 ± 6.3 years. An excellent ICC score of 0.9998 (95% CI 0.9997, 0.9999) was observed for intra-rater analyses of RMSSD, and similar excellent ICC scores were seen for all other HRV measures. The inter-rater reliability analyses produced an excellent ICC score (range 0.97-1.00). Comparatively, frequency-domain measures produced higher MDC% and SEM% scores than time-domain and nonlinear measures in both inter- and intra-rater analyses. The Bland-Altman plots revealed relatively higher bias for frequency-domain and nonlinear measures than time-domain measures. ECG-related short-term HRV measures were reliable in injured servicemen under spontaneous breathing. However, the reliability appeared better with the time-domain measure than frequency-domain and nonlinear measures in this sample.

The level of partial pressure of carbon dioxide affects organ perfusion in respiratory failure patients undergoing pressure support ventilation with venovenous extracorporeal membrane oxygenation: a prospective study

BackgroundWe evaluated the influence of different partial carbon dioxide pressure (PaCO2) levels on organ perfusion in patients with respiratory failure receiving pressure-support ventilation with veno-venous extracorporeal membrane oxygenation (V-V ECMO).MethodsIn this twelve patients prospective study, ECMO gas-flow was decreased from baseline (PaCO2 < 40 mmHg) until PaCO2 increased by 5–10 mmHg (High-CO2 phase). Resistance indices of gut, spleen, and snuffbox artery, the peripheral perfusion index (PPI), and heart rate variability were measured at baseline and High-CO2 phase.ResultsWhen PaCO2 increased from 36 (36–37) mmHg at baseline to 42 (41–43) mmHg in the High-CO2 phase (p < 0.001), PPI decreased significantly (p = 0.026). The snuffbox artery (p = 0.022), superior mesenteric artery (p = 0.042), and spleen (p = 0.012) resistance indices increased significantly. The root mean square of successive differences (RMSSD) decreased from 19.5(18.1–22.7) to 15.9(14.4–18.6) ms (p = 0.034), and the ratio of low-frequency to high-frequency components(LF/HF) increased from 0.47 ± 0.23 to 0.70 ± 0.38 (p = 0.013).ConclusionsHigh PaCO2 might cause decreased peripheral tissue and visceral organ perfusion through autonomic nervous system in patients with respiratory failure undergoing PSV with V-V ECMO.

Evaluation of low vagally-mediated heart rate variability as an early marker of depression risk

BackgroundBoth low vagally-mediated heart rate variability (HRV) and depression have been shown to be risk factors for cardiovascular disease (CVD). We recently identified an HRV cutpoint below which persons have an increased risk for several cardiometabolic disorders. However, no cutpoint exists to identify those at risk for depression. MethodsThe association between daytime HRV and diagnostically validated depression cutoffs using the five-item World Health Organization Well-being Index (WHO-5) was examined in adults from the Mannheim Industrial Cohort Study (n = 9973; Mage = 41.9[10.9]; 20 % women [n = 1934]). The aim was to identify HRV cutpoints for individuals who may have clinical depression. ResultsRegression adjusting for age, sex, and linear trend showed a significant quadratic association between depression, indexed by WHO-5 scores and HRV, indexed by the root mean square successive differences (RMSSD) in milliseconds (ms) (p < 0.001). Logistic regression models adjusting for age, sex, and heart period (i.e., inter-beat intervals) compared the clinically depressed (WHO-5 ≤ 28) and those with a screening diagnosis of depression (WHO-5 ≤ 50) to the rest of the population. Significant odds ratios suggested two RMSSD values 25 ± 2 ms (OR = 1.39 [1.17, 1.64]) and 35 ± 2 ms (OR = 1.17 [1.02, 1.34]) that may be used to identify those with an elevated risk for depression. LimitationsThe sample was primarily German men. Fitness and anti-depressant use were not available. ConclusionsAs HRV is a brief measure that can be used in clinical settings, our HRV cutpoints have implications for the early detection of those at risk for psychological and cardiometabolic disorders.