Heart Rate Variability Measures Research Articles

Effects of Bhramari and Sheetali Pranayama on Cardio Respiratory Function in Post-COVID Patients: A Randomised Controlled Study.

The COVID-19 pandemic has led to a range of long-term health issues in recovered patients, collectively known as "post-COVID syndrome." This study aimed to investigate the effects of combined pranayama techniques, specifically Sheetali and Bhramari, on pulmonary function and heart rate variability in post-COVID patients. A randomised controlled trial was conducted with 90 post-COVID patients (aged 19-40). Participants were divided into three groups of 30 each: control, Bhramari Pranayama and Sheetali Pranayama. The intervention groups practiced their respective pranayama techniques for 15 minutes twice daily for 6 months. Outcome measures included Pulmonary Function Tests (PFT) and Heart Rate Variability (HRV), assessed at baseline, 3 months and 6 months. At 3 months, both pranayama groups showed moderate improvements in pulmonary function and HRV compared to baseline. By 6 months, these improvements were significantly enhanced. The Bhramari group showed increased FVC from 3.2 ± 0.5 L to 3.5 ± 0.4 L at 3 months, and to 3.7 ± 0.4 L at 6 months (P < .001). Similarly, the Sheetali group reflected improved FVC from 3.3 ± 0.4 L to 3.5 ± 0.3 L at 3 months, reaching 3.7 ± 0.3 L at 6 months (P < .001). HRV measures showed a similar trend, with SDNN and RMSSD in the Bhramari group and Sheetali pranayama group. This study provides novel insights into the combined effects of Bhramari and Sheetali Pranayama on post-COVID patients. The findings suggest significant improvements in respiratory function and autonomic nervous system balance.

Acute Effects of Slow-Paced Breathing on Measures of HRV in Hospitalized Patients With Bilateral COVID-19 Pneumonia: A Secondary Analysis of a Randomized Clinical Trial.

Slow-paced breathing (SPB) with prolonged exhalation is assumed to stimulate vagal reflexes, which is represented by increased heart rate variability (HRV) values. However, most trials were conducted in healthy participants. We sought to evaluate the feasibility of SPB in hospitalized patients with confirmed bilateral COVID-19 pneumonia with major respiratory impairment and to investigate if SPB shows acute increasing effects on HRV measures in these severely ill patients with distinctly reduced vagal tone. This single-center randomized controlled clinical trial enrolled 23 patients in the intervention (4-second inhalation, 6-second exhalation for 20 minutes 3× daily) and 23 patients in the control group (IG/CG). The effects of SPB on HRV were calculated using post-hoc likelihood ratio tests. Baseline HRV measures between the groups over time were compared using multilevel mixed-effect linear regression models with random slope including the covariates relevant comorbidities, COVID-19 medication, and age. HRV values at baseline were significantly decreased in all patients. During SPB, HRV parameters increased significantly (ln(SDNN), ln(LF), ln(TP); all p < .001). Higher breathing rate at baseline correlated with lower LF during SPB (p < .045). IL-6 morning levels were associated with lower HRV measures (p < .001). Resting HRV measures as well as subjective health increased over hospitalization time with no differences between IG and CG (comparing random slope with random slope interaction models: all LR χ2(5) < 4.5; p > .48). SPB is feasible and safe in patients with bilateral COVID-19 pneumonia and appears to be an effective self-performed intervention to acutely increase HRV measures. This observation was independent of comorbidities and comedication. Further trials should corroborate these findings and extend it to other severely ill populations. German Clinical Trials Register under ID DRKS00023971 (https://drks.de/search/en/trial/DRKS00023971), with a Universal Trial Number (UTN) U1111-1263-8658.

Exploring the efficacy of sense of Okayness (SOK) as an antidote for stress in older adults: the role of SOK elevation intervention, heart rate variability (HRV), and cognitive performance in stressful and relaxing situations

Sense of Okayness (SOK) is an emerging concept that describes a person’s ability to remain stable and unshaken in the face of life transitions and hardships. This quality enables effective stress regulation and heightened tolerance to uncertainty. To investigate the possible role of the parasympathetic nervous system (PNS) in mediating the relationship between SOK and stress regulation among older individuals, an analytical sample of N = 69 participants (74% women) with a mean age of 78.75 years (SD age = 6.78) was recruited for a standardized cognitive assessment and stress induction. Baseline heart rate variability (HRV), measured via electrocardiogram (ECG), and SOK assessments were conducted prior to stress induction, along with a baseline cognitive evaluation. Subsequently, participants were subjected to a psychosocial stress paradigm, followed by either a 30-minute SOK elevation intervention (n = 40) or a control condition with nature sounds (n = 29). A second cognitive assessment was administered post-intervention, with continuous HRV measurement through ECG. The results revealed significant HRV changes due to the experimental intervention, though no significant differences were observed between the SOK intervention and control groups. Interestingly, individuals with high trait SOK displayed more stable HRV trajectories, exhibiting a smaller decline during the stress intervention and a milder increase during both the stressor and SOK intervention phases. Overall, these findings do suggest a significant association between SOK, parasympathetic activity, and stress reactivity. These results prompt further investigation into whether personality patterns, such as a strong SOK, may be linked to reduced vagal reactivity and better coping in old age.

Heart rate variability in biophilic design: A systematic literature review

The use of Virtual Reality as a representation of biophilic design has been commonly used for design evaluations on human perception and performance before the actual construction. Biophilic design is known for the relaxing effects on human physiological responses; particularly cardiac activity indexed by Heart Rate Variability (HRV), representing human’s relaxation or stress conditions. How virtual biophilic design affects HRV, and what research protocols are most effective in assessing these physiological effects remains unclear. This literature review clarify research protocols and outline the trends of HRV in virtual biophilic design and to propose guidelines for improving the accuracy and reliability of HRV measurements. Most of the reviewed studies found an equal trend of the increased parasympathetic activity correlating with a reduced anxiety, during exposure to specific virtual biophilic designs. Studies with insignificant HRV effects may be due to the inadequate measurement protocol. The clearer effects on HRV may be observed by limiting virtual exposure to 15 minutes, avoiding virtual sickness, maintaining consistent subject positions, incorporating paced breathing in all conditions during HRV recordings, and evaluating short-term HRV measures for a minimum of 5 minutes. Virtual biophilic exposure holds promise for pre-construction design assessment, depending on appropriate methodologies.

Diagnostic accuracy of heart rate variability as a screening tool for mild neurocognitive disorder.

Mild neurocognitive disorder (mNCD) is recognized as an early stage of dementia and is gaining attention as a significant healthcare problem due to current demographic changes and increasing numbers of patients. Timely detection of mNCD provides an opportunity for early interventions that can potentially slow down or prevent cognitive decline. Heart rate variability (HRV) may be a promising measure, as it has been shown to be sensitive to cognitive impairment. However, there is currently no evidence regarding the diagnostic accuracy of HRV measurements in the context of the mNCD population. This study aimed to evaluate the diagnostic accuracy of vagally-mediated HRV (vm-HRV) as a screening tool for mNCD and to investigate the relationship between vm-HRV with executive functioning and depression in older adults who have mNCD. We retrospectively analyzed data from healthy older adults (HOA) and individuals with a clinical diagnosis of mNCD with a biomarker-supported characterization of the etiology of mNCD. Diagnostic accuracy was evaluated using receiver operating characteristic curve analysis based on the area under the curve. Sensitivity and specificity were calculated based on the optimal threshold provided by Youden's Index. Multiple linear regression analyses were conducted to investigate the relationship between vm-HRV and executive functioning and depression. This analysis included 42 HOA and 29 individuals with mNCD. The relative power of high frequency was found to be increased in individuals with mNCD. The greatest AUC calculated was 0.68 (with 95% CI: 0.56, 0.81) for the relative power of high frequency. AUCs for other vm-HRV parameters were between 0.53 and 0.61. No consistent correlations were found between vm-HRV and executive functioning or depression. It appears that vm-HRV parameters alone are insufficient to reliably distinguish between HOA and older adults with mNCD. Additionally, the relationship between vm-HRV and executive functioning remains unclear and requires further investigation. Prospective studies that encompass a broad range of neurocognitive disorders, HRV measurements, neuroimaging, and multimodal approaches that consider a variety of functional domains affected in mNCD are warranted to further investigate the potential of vm-HRV as part of a multimodal screening tool for mNCD. These multimodal measures have the potential to improve the early detection of mNCD in the future.

Sleep Stage Classification Through HRV, Complexity Measures, and Heart Rate Asymmetry Using Generalized Estimating Equations Models.

This study investigates whether heart rate asymmetry (HRA) parameters offer insights into sleep stages beyond those provided by conventional heart rate variability (HRV) and complexity measures. Utilizing 31 polysomnographic recordings, we focused exclusively on electrocardiogram (ECG) data, specifically the RR interval time series, to explore heart rate dynamics associated with different sleep stages. Employing both statistical techniques and machine learning models, with the Generalized Estimating Equation model as the foundational approach, we assessed the effectiveness of HRA in identifying and differentiating sleep stages and transitions. The models including asymmetric variables for detecting deep sleep stages, N2 and N3, achieved AUCs of 0.85 and 0.89, respectively, those for transitions N2-R, R-N2, i.e., falling in and out of REM sleep, achieved AUCs of 0.85 and 0.80, and those for W-N1, i.e., falling asleep, an AUC of 0.83. All these models were highly statistically significant. The findings demonstrate that HRA parameters provide significant, independent information about sleep stages that is not captured by HRV and complexity measures alone. This additional insight into sleep physiology potentially leads to a better understanding of hearth rhythm during sleep and devising more precise diagnostic tools, including cheap portable devices, for identifying sleep-related disorders.

Sex differences in the reactivity of gastric myoelectrical activity and heart rate variability as putative psychophysiological markers in human pain research.

This study explored the potential of electrogastrography (EGG) and heart rate variability (HRV) as psychophysiological markers in experimental pain research related to the gut-brain axis. We investigated responses to the experience of pain from the visceral (rectal distension) and somatic (cutaneous heat) pain modalities, with a focus on elucidating sex differences in EGG and HRV responses. In a sample of healthy volunteers (29 males, 43 females), EGG and ECG data were collected during a baseline and a pain phase. Data were analyzed for changes in gastric myoelectrical activity and cardiac autonomic regulation, with special attention to sex-specific patterns and correlations with perceptual responses to visceral and somatic pain stimuli, assessed by visual analogue scale ratings. Acute pain induced significant instability in EGG slow-wave frequency and amplitude, increased tachygastria, and decreased normogastric spectral power, without evidence of sex differences. HRV analyses revealed increases in SDNN, RMSSD, and pNN50 during pain, indicating sympathovagal regulation changes. While there were no significant sex differences in EGG responses, only female participants exhibited significant correlations between visceral pain unpleasantness and EGG alterations. HRV measures, particularly time-domain parameters, showed sex differences, independent of pain-induced autonomic reactivity. The experience of pain in the lower abdominal region may induce impaired gastric motility. EGG and HRV are sensitive to acute pain and offer insight into pain mechanisms along the gut-brain axis. While EGG responses were consistent across sexes, HRV revealed sex-specific differences, suggesting that autonomic regulation and gastric motility may be modulated differently by pain and psychosocial factors. Further research in patients with chronic visceral pain is warranted.

Impact of exhaustive exercise on autonomic nervous system activity: insights from HRV analysis.

Exhaustive exercise is a common training method in sports, but its impact on the autonomic nervous system of the human body remains unclear. Understanding the effects of exhaustive exercise on the body and its connection with the autonomic nervous system and central nervous system is crucial for guiding healthy training methods. Twenty-three participants were selected, and exhaustive exercise intervention was performed using the Bruce Protocol. By measuring heart rate variability (HRV), the effects of exhaustive exercise on the autonomic nervous system function were analyzed. After exhaustive exercise, time-domain indices SDNN, RMSSD, and PNN50 all significantly decreased, with changes reaching significant levels (p < 0.01). Among them, the decrease in pNN50 was particularly pronounced, with a change rate of -94.55%. Frequency-domain indices VLF, LF, and HF also showed significant decreases (p < 0.01), but the ratio of LF to HF showed an upward trend (p < 0.01), with LF showing a greater decrease. Nonlinear indices SD1 and SD2 showed extremely significant decreases (p < 0.01), and the SD2/SD1 ratio showed a significant increase (p < 0.01), indicating significant changes in HRV nonlinear characteristics after exercise. Exhaustive exercise leads to a decrease in autonomic nervous system activity and an increase in sympathetic nervous system activity. These findings underscore the profound impact of exhaustive exercise on the autonomic nervous system, with implications for understanding the physiological responses to intense physical exertion. Further research is warranted to explore the long-term effects of exhaustive exercise on autonomic regulation and its potential implications for training methodologies and athlete health.

Reference values for heart rate variability in older adults: A systematic review.

Heart rate variability (HRV) is an early marker of risk for various health conditions, and its analysis serves as a valuable tool for assessing older adults. This study aimed to describe the reference values of HRV parameters in older adults through a systematic review of the literature. The review included searches in MEDLINE (via PubMed®), EMBASE, Latin American and Caribbean Health Literature, Scopus, and Web of Science (WOS). Studies presenting reference values for at least one HRV linear analysis measure in older adults were considered eligible. Out of 1618 studies identified, only 11 met the inclusion criteria. Sample sizes of older adults ranged from 21 to 6250 subjects. The HRV measures assessed (mean RR intervals, SDNN, RMSSD, PNN50, LF, HF, and LF/HF ratio) varied significantly between studies, with no standardized methods for HRV analysis. We concluded that reference values for HRV measures in older adults vary widely between studies. The scientific literature on HRV reference values in older adults is still limited, and future studies should standardize assessment methods for HRV measures in this population.

Mental stress analysis by measuring heart rate variability during learning programming: Comparison of visual- and text-based languages

Visual-based programming languages that facilitate block-based coding have gained popularity as introductory methods for learning programming. Conversely, programming experts typically use text-based programming languages like C and Java. Nevertheless, a seamless method for transitioning from a visual- to text-based language has yet to be developed. Therefore, our research project aims to develop a methodology that facilitates this transition by bridging the gap between the two languages and verifying the variations in the biometric information of learners of both languages. In this study, we measured the participants’ heart rate variability (HRV) and evaluated variations in mental stress experienced while learning visual- and text-based languages. The experimental results confirmed that participants proficient in text-based languages experienced lower HRV (indicating higher stress levels) when learning visual-based languages. Conversely, those poorly proficient in text-based languages exhibited higher HRVs (indicating more favorable stress levels) while learning text-based languages. This study successfully observed differences in stress levels while learning both language types using experimental methods. These findings serve as a preliminary step toward clarifying the impact of stress experienced during learning outcomes and identifying the factors that constitute beneficial stress. This study establishes a foundation for an intermediate language that can enhance transitions between the two types of languages.

Interdisciplinary Fascia Therapy: A Proof-of-Concept Pilot Study for a New Myofascial Approach for Chronic Low Back Pain.

Background/Objectives: Chronic low back pain (CLBP) is highly prevalent and relevant in all medical fields. This study evaluated the safety and effectiveness of interdisciplinary fascia therapy (IFT) for CLBP, focusing on its potential to reduce pain intensity, disability, and regulate autonomic nervous system (ANS) activity. Methods: Nine participants with CLBP each underwent nine sessions of IFT, twice weekly. The intervention involved a 12-grip manual sequence targeting deep paravertebral myofascial structures, complemented by heart rate variability (HRV) biofeedback training twice daily for 15 min. Pain and quality-of-life measures were assessed using the Brief Pain Inventory (BPI) questionnaire at baseline, mid-treatment (4th session), and post-treatment (9th session). HRV metrics were monitored with a 24 h ECG Holter device before and after the treatment period. Statistical analyses included paired t-tests, Wilcoxon signed-rank tests, and Cohen's d for effect size. Results: Significant reductions in pain levels were observed across all subjective BPI measures, including momentary, strongest, minimal, and average pain scores (p < 0.001), with 83% and 87% reductions in pain intensity and disability, respectively. Quality-of-life indicators such as mood, sleep, and enjoyment of life showed significant improvements (p < 0.001). While only one HRV metric (rMSSD) achieved statistical significance, other HRV measures indicated medium to large effect sizes, suggesting favorable trends in ANS regulation. Conclusions: IFT demonstrated significant effects on subjective BPI pain reduction and quality of life, alongside potential regulatory impacts on ANS activity in individuals with CLBP. These results support the use of IFT as an effective intervention for pain management in CLBP and ANS regulation, meriting further exploration.

Prognostic Value of Ultra-Short Heart Rate Variability Measures Obtained from Electrocardiogram Recordings of Hospitalized Patients Diagnosed with Non-ST-Elevation Myocardial Infarction.

Background: Myocardial infarction (MI) is a common emergency with high rates of morbidity and mortality. Current risk stratification scores for non-ST-elevation MI (NSTEMI) use subjective or delayed information. Heart rate variability was shown to correlate with prognosis following MI. This study aimed to evaluate ultra-short heart rate variability (usHRV) as a prognostic factor in NSTEMI patients. Methods: A retrospective analysis was performed on 183 NSTEMI patients admitted to Rambam Health Care Campus in 2014. usHRV measures, including the standard deviation of normal-to-normal intervals (SDNN) and root mean square of successive differences (RMSSD), were calculated. Logistic regression assessed whether clinical, laboratory, or usHRV parameters predicted severe in-hospital complications like heart failure (HF), atrial flutter/fibrillation (AFL/AF), ventricular tachycardia/fibrillation (VT/VF), and atrioventricular block (AVB). Both Cox and logistic regression were used for survival analysis. Results: Of 183 patients (71.6% male, mean age 67.1), 35 (19%) died within 2 years. In-hospital complications included 39 cases (21.3%) of HF, 3 cases (1.6%) of VT/VF, and 9 cases (4.9%) of AVB. Lower usHRV was significantly associated with higher mortality at 2 years and showed marginal significance at 90 days and 1 year. Increased usHRV was linked to a higher risk of in-hospital ventricular arrhythmia (VT/VF). Conclusions: Overall, this study is in agreement with previous research, showing a correlation between low usHRV and a higher mortality risk. However, the association between usHRV and the risk of VT/VF demands further investigation. More expansive prospective studies are needed to strengthen the observed associations.

Autonomic function and change in functional capacity in older adults: a longitudinal investigation

Functional capacity is an important objective health metric, and relies on the maintenance of physiological homeostasis. Autonomic nervous system is known to coordinates the maintenance of multi-organ homeostasis. The objective of this study was to examine the association of autonomic nervous system function with functional capacity in adults aged 55 years and older. A cohort of 542 adults (mean age of 70.1 years) received repeated measurements of heart rate variability, an autonomic nervous system function marker, and chair rise time, a functional capacity measure. Linear mixed models analysis showed that 1 SD lower powers in low-frequency range at baseline was associated with a 0.11 (95% CI 0.01–0.21) s/year faster increase in chair rise time during the follow-up, whereas 1 SD increase in powers in high-frequency range and 1 SD decrease in the ratio of powers in low-frequency range to powers in high-frequency range during the follow-up were associated with a 0.22 (95% CI 0.06–0.39) s and 0.17 (95% CI 0.01–0.33) s increase in chair rise time. In conclusion, autonomic nervous system function and its changes were longitudinally associated with changes in functional capacity in older adults.

Deriving Accurate Nocturnal Heart Rate, rMSSD and Frequency HRV from the Oura Ring.

Cardiovascular diseases are a major cause of mortality worldwide. Long-term monitoring of nighttime heart rate (HR) and heart rate variability (HRV) may be useful in identifying latent cardiovascular risk. The Oura Ring has shown excellent correlation only with ECG-derived HR, but not HRV. We thus assessed if stringent data quality filters can improve the accuracy of time-domain and frequency-domain HRV measures. 92 younger (<45 years) and 22 older (≥45 years) participants from two in-lab sleep studies with concurrent overnight Oura and ECG data acquisition were analyzed. For each 5 min segment during time-in-bed, the validity proportion (percentage of interbeat intervals rated as valid) was calculated. We evaluated the accuracy of Oura-derived HR and HRV measures against ECG at different validity proportion thresholds: 80%, 50%, and 30%; and aggregated over different durations: 5 min, 30 min, and Night-level. Strong correlation and agreements were obtained for both age groups across all HR and HRV metrics and window sizes. More stringent validity proportion thresholds and averaging over longer time windows (i.e., 30 min and night) improved accuracy. Higher discrepancies were found for HRV measures, with more than half of older participants exceeding 10% Median Absolute Percentage Error. Accurate HRV measures can be obtained from Oura's PPG-derived signals with a stringent validity proportion threshold of around 80% for each 5 min segment and aggregating over time windows of at least 30 min.

Clinical characteristics and autonomic balance in patients with burning mouth syndrome: A retrospective chart review.

This study aimed to identify the clinical characteristics of patients with burning mouth syndrome (BMS) according to the low frequency/high frequency (LF/HF) ratio in the heart rate variability test and to evaluate the potential of the LF/HF ratio as an indicator for the diagnostic or predictive assessment of patients with BMS. A total of 469 patients with BMS who visited the Oral Diseases Clinic of Kyung Hee University Korean Medicine Hospital between January 1, 2018, and December 31, 2022, were included in the study. The patients were asked to rate their tongue pain on a visual analog scale before and after treatment. Heart rate variability testing and measurement of the unstimulated and stimulated salivary flow rates were conducted. The patients were divided into 3 groups according to their LF/HF ratios. Clinical characteristics, including tongue pain, salivary secretion, and concomitant symptoms, were compared between the groups. Spearman correlation analysis was performed to determine any significant correlation between the LF/HF ratio and the clinical symptoms. The patients were also classified into 2 groups according to psychological factors to analyze their effects on the clinical characteristics of BMS. The pretreatment pain score (PRPS), posttreatment pain score (POPS), and incidence rate of dry mouth symptoms were higher in the parasympathetically activated group than in the other groups. Spearman correlation analysis revealed a negative correlation between the LF/HF ratio and the PRPS. The PRPS and POPS were higher and the unstimulated salivary flow rate, stimulated salivary flow rate, and LF/HF ratio were lower in the group with psychological factors than in the group without psychological factors. The parasympathetic group reported higher PRPS and POPS and a higher incidence of dry mouth symptoms. This may be attributable to the role of psychological factors in BMS, which is a functional pain disorder. The different clinical characteristics based on the LF/HF ratio indicate that the LF/HF ratio may serve as a significant indicator for diagnosing or predicting the prognosis of patients with BMS.

Heart rate variability is not associated with multiple chemical sensitivity in a cross-sectional population-based study - The Danish study of functional disorders

ObjectiveMultiple chemical sensitivity (MCS), a functional somatic disorder (FSD), is a multisystem, polysymptomatic disease, characterized by various individual symptoms attributed to low level of volatile chemical exposures. Symptoms relate to the autonomic nerve system (ANS) among others which is mandatory in the MCS delimitations. An accepted measure of ANS is heart rate variability (HRV). The aim was to explore associations between HRV and MCS in the general Danish population. MethodsIn the Danish Study of Functional Disorders, 7493 adults filled in questionnaires and participated in a physical health examination (2012–2015). The “E motion” heart rate monitor device assessed time and frequency measures of HRV. For this study, 143 were categorized with MCS of which, 84 were subcategorized as MCS without comorbid FSD. The remaining population (n = 5525) was used as comparison group. Logistic regression models to assess odds ratio (OR) with 95 % confidence intervals (95 % CI) of MCS, and MCS without comorbid FSD for each HRV exposure adjusted for age, sex, and chronic stress. ResultsCompared to the general population, median resting heart rate was higher (64.7 vs 63.1 bpm, p = 0.007) and median normal-to-normal intervals was lower (930 vs 952 ms, p = 0.007) in MCS individuals. Resting heart rate was associated with MCS (OR: 1.019, 95 %CI: 1.003; 1.037); but not after adjustment for chronic stress. No other associations with other HRV measures nor in MCS without comorbid FSD were found. ConclusionHRV was not associated with MCS. The magnitude of the differences between groups was small and of uncertain clinical significance.

Examining the practical importance of nonstationary cardio-respiratory coupling detection in breathing training: a methodological appraisal.

This study investigates changes in cardiorespiratory coupling during clinic breathing training and its impact on autonomic nervous functioning compared with heart rate variability (HRV). A total of 39 subjects undergoing dynamic electrocardiogram-recorded breathing training were analyzed. Subjects were divided into early- and late-training periods, and further categorized based on changes in HRV indexes. Subtypes were identified using time-frequency cardiorespiratory coupling diagrams. Significant differences were observed in the high-frequency (HF) index between training stages in the subgroup with increasing HF-HRV (p=0.0335). Both unimodal and bimodal subtypes showed significant high-frequency coupling (HFC) in the mid-training period compared with early and late stages (both p<0.0001), suggesting improved parasympathetic cardiac regulation or reduced sympathetic control. This study highlights the potential of nonstationary cardiorespiratory coupling analysis alongside traditional HRV in evaluating the therapeutic effect of breathing training on autonomic nervous function. Cardiorespiratory coupling analysis could provide valuable adjunctive information to HRV measures for assessing the impact of breathing training.

Cardiovascular responses as predictors of mortality in children with acute brain injury.

Investigate the utility of cardiovascular responses such as heart rate (HR), blood pressure (BP), and heart rate variability (HRV) in the prognosis of children with acute acquired brain injury (ABI). Children under 18 years with severe acute acquired brain injury (ABI) who survived at least 12 h after PICU admission were included in a prospective observational cohort in a tertiary academic PICU. Physiological variables, neurological data, laboratory tests (chemistry and hematology), and medications were recorded within 12 h of admission. Linear and nonlinear HRV indices, CT scans, PICU scores, and survival rates were evaluated. Seventy-two children, median age 10.7 years (IQR 4.1-13.6), were eligible for the study; 28 (38.9%) were diagnosed with brain death (BD). Tachycardia, SBP and MBP < 5th percentile, and MBP and DBP> 99th percentile were significantly associated with mortality. Poincaré SD1/SD2 was significantly associated with mortality after adjusting for age, sex and ongoing medication. Tachycardia, systolic hypotension and median hypo and hypertension were associated to mortality in children with severe ABI. While further validation through larger, multicenter studies is necessary, the Poincaré SD1/SD2 ratio has shown promise as a prognostic tool for predicting mortality in children with severe ABI. This study explores cardiovascular changes, including heart rate and blood pressure, and linear/nonlinear HRV measures using ECG at 1000 Hz, and compare them with other prognostic factors like brain tomography and PICU scores. Tachycardia, hypo/hypertension in the early hours after admission are linked to early mortality in children with severe traumatic and non-traumatic brain injury. Linear/non-linear measures of HRV were also related to survival. Higher HRV values indicating better survival chances. We identified Poincaré SD1/SD2 ratio as a promising tool for predicting mortality in children with severe ABI.

Influence of an inspiratory muscle fatigue protocol on older adults on respiratory muscle strength and heart rate variability. A randomized controlled trial.

Inspiratory muscle fatigue has been shown to have effects on the autonomic nervous system and physical condition. This study aimed to evaluate the influence of an inspiratory muscle fatigue protocol on respiratory muscle strength and heart rate variability in older adults. A randomized controlled clinical trial with double-blinding was carried out involving 24 individuals over 60 years old who demonstrated physical independence in walking and movement. Participants were distributed randomly into three groups: Inspiratory muscle fatigue, activation and control. Measurements of heart rate variability, diaphragmatic ultrasound, and maximum inspiratory pressure were taken at two stages: prior to the intervention (T1) and directly after treatment (T2). The inspiratory muscle fatigue group exhibited decrease scores in respiratory and heart rate variability subsequent to undergoing the diaphragmatic fatigue intervention compared to both the activation and control groups (p < 0.05). Conversely, the activation group demonstrated higher values in heart rate variability and respiratory capacity variables following the inspiratory muscle activation training (p < 0.05). Fatigue of the inspiratory musculature appears to negatively impact heart rate variability and inspiratory muscle strength in older adults. https://clinicaltrials.gov/study/NCT06269042, identifier: NCT06269042.

Is Greener Better? Quantifying the Impact of a Nature Walk on Stress Reduction Using HRV and Saliva Cortisol Biomarkers.

The physiological impact of walking in nature was quantified via continuous heart rate variability (HRV), pre- and post-walk saliva cortisol measures, and self-reported mood and mindfulness scores for N = 17 participants who walked "The Green Road" at Walter Reed National Military Medical Center in Bethesda, Maryland. For N = 15 of the participants, HRV analysis revealed two main groups: group one individuals had a 104% increase (mean) in the root mean square standard deviation (RMSSD) and a 47% increase (mean) in the standard deviation of NN values (SDNN), indicating an overall reduction in physiological stress from walking the Green Road, and group two individuals had a decrease (mean) of 42% and 31% in these respective HRV metrics, signaling an increase in physiological stresses. Post-walk self-reported scores for vigor and mood disturbance were more robust for the Green Road than for a comparable urban road corridor and showed that a higher HRV during the walk was associated with improved overall mood. Saliva cortisol was lower after taking a walk for all participants, and it showed that walking the Green Road elicited a significantly larger reduction in cortisol of 53%, on average, when compared with 37% of walking along an urban road. It was also observed that the order in which individuals walked the Green Road and urban road also impacted their cortisol responses, with those walking the urban road before the Green Road showing a substantial reduction in cortisol, suggesting a possible attenuation effect of walking the Green Road first. These findings provide quantitative data demonstrating the stress-reducing effects of being in nature, thus supporting the health benefit value of providing access to nature more broadly in many settings.