Short-term Heart Rate Variability Research Articles

Shooting Free Throws Under Pressure: A Social Media Self-Talk Intervention

The present study sought to investigate the effects of a self-talk intervention on free-throw performance under pressure. The experimental manipulation was designed using a video from a social media platform. Thirty male college basketball players were randomly assigned into two groups (i.e., control and experimental). The experimental protocol incorporated three trials of three free throws each. Psychophysiological stress was assessed by use of heart rate variability. The illusion of pressure was created using arena recordings of large crowds along with instructions for participants to visualize a high-pressure scenario. The results indicate that the self-talk intervention was sufficient to improve free throw shooting accuracy during the postintervention phase. Short-term heart rate variability reduced significantly for the control group and remained relatively stable for the experimental group. Self-talk appears to influence free throw accuracy during situations of psychosocial stress by inhibiting the influence of negative thoughts on peripheral physiological reactions and movement automaticity.

A Study to Assess Changes in Cortisol Level and Heart Rate Variability between Fixed Duty and Shift Duty Health Care Providers in a Tertiary Care HospitalA Cross-Sectional Study

Introduction: Increased demand of service 24 hours around the clock has divided the workers into 2 domains as “Fixed duty” and “Shift duty”. Personals associated with shift duty are increasing in numbers day by day. Shift duty or more specifically night duty is associated with increased stress which results in high morbidity and decrease in work efficiency. Cortisol hormone and Heart Rate Variability (HRV) are useful parameters to determine the effects of stress. Aim: To find any change in cortisol levels, HRV, Athens score among the fixed duty and shift duty healthcare providers. Materials and Methods: A descriptive cross-sectional comparative study was conducted in a tertiary care hospital at Kolkata between July, 15th to Sept, 15th 2021. Predesigned and pretested questionnaire was made and ethical clearance was taken from institutional IEC. Then after taking consent total 120 (60 fixed duty and 60 shift duty) healthcare providers were recruited for the study. Subjects of the study filled up a questionnaire {including Athens Insomnia Scale (AIS)}. After applying exclusion criteria (any cardiovascular, neurological, psychological, sleep disorder) 120 health individuals were taken five minutes short-term HRV (time and frequency domain) recording in supine posture and 4 PM blood sample (for cortisol) were obtained from the participants which was further analysed in Chemiluminescence Immunoassay (CLI). Data was analysed in SPSS version 20.0. Statistical tests like student t-test, Cron bach’s alpha and chi-square tests were applied significant p<0.05 (95% CI). Results: After analysis, shift duty workers showed a significant (p<0.001, Odd’s 10.706) higher chance of having insomnia (Athens score >6) than fixed duty workers. Blood test showed that shift duty workers had significantly high evening cortisol level than fixed duty workers (p= 0.036). The time domain of HRV showed that the parameters like Standard Deviation all NN interval (SDNN) (p=0.001), Mean HR (p=0.037), RMSSD (p <0.001), NN50 (p=0.006), pNN50 (p=0.002) were significantly different in the two groups. Whereas the frequency domain of HRV showed that HF power was lower and LF power (p=0.002), LF/HF ratio (p <0.001) were significantly higher in shift duty workers. Conclusion: The study showed that shift duty workers had comparatively higher stress levels resulting in significantly high sympathetic drive and increased risk of insomnia. This can be associated with morbidity and ill health in the shifting duty workers.

AN EFFECTIVE DEEP LEARNING BASED APPROACH TO MEASURE INTERDEPENDENCE OF HEART RATE VARIABILITY ANALYSIS AND R-PEAKS


 
 
 Heart rate variability (HRV) is the physiological phenomenon to measure variations between consecutive heartbeats. HRV analysis has been used to analyse and detect different cardiac diseases that rely on R-peaks' reliability and accurate detection. Myocardial infarction (MI) is a main cardiac disease that causes irregularity in heartbeats and some non-specific abnormalities occur in the recorded ECG, including ST changes and T-wave alternans. These abnormalities may be ignored by considering minor changes that can lead to delayed diagnosis. Therefore, the analysis of these abnormalities is a challenging task. This study investigated these non-specific abnormalities to recognize MI patterns based on HRV analysis highlighting the importance of R-peaks detection accuracy. Short-term HRV analysis of two publicly available datasets, MIT-BIH ST Changes and European ST-T changes was performed based on R-peaks detected from ECG signals. R-peaks detection achieved an averaged 99.77% sensitivity, 99.49% positive predictability and 99.32% accuracy for MIT-BIH ST changes dataset whereas for European ST-T changes dataset, 99.85% sensitivity, 99.41% positive predictability, and 99.28% accuracy was achieved. Subsequently, HRV parameters were computed from both datasets and data fusion was performed followed by a deep learning model to find out the most accurate pattern recognition results. For pattern recognition, a finely tuned artificial neural network was applied to HRV parameters, in two scenarios. For both scenarios, an accuracy greater than 99% was achieved. Furthermore, linear regression was also performed on computed HRV measures in both scenarios that observed a similarity of 97% between both datasets. The importance of reliable and accurate R-peaks detection for HRV analysis to analyse and detect different cardiovascular diseases was elaborated in the end.
 
 

Validity and reliability of short-term heart-rate variability from disposable electrocardiography leads.

Single-use electrocardiography (ECG) leads have been developed to reduce healthcare-associated infection. This study compared the validity and reliability of short-term heart rate variability (HRV) obtained from single-use disposable ECG leads. Thirty healthy subjects (33 ± 10 years; 9 females) underwent 5-minresting HRV assessments using disposable (single use) ECG cable and wire system (Kendall DL™ Cardinal Health) and a standard, reusable ECG leads (CardioExpress, Spacelabs Healthcare). Intraclass correlation coefficient (ICC) with 95% confidence interval (CI) between disposable and reusable ECG leads was for the time domain [R-R interval (ms); 0.99 (0.91, 1.00)], the root mean square of successive normal R-R interval differences (RMSSD) (ms); 0.91 (0.76, 0.96), the SD of normal-to-normal R-R intervals (SDNN) (ms); 0.91 (0.68, 0.97) and frequency domain [low-frequency (LF)normalized units (nu); 0.90 (0.79, 0.95), high frequency (HF) nu; 0.91 (0.80, 0.96), LF power (ms2); 0.89 (0.62, 0.96), HF power (ms2); 0.90 (0.72, 0.96)] variables. The mean difference and upper and lower limits of agreement between disposable and reusable leads for time- and frequency-domain variables were acceptable. Analysis of repeated measures using disposable leads demonstrated excellent reproducibility (ICC 95% CI) for R-R interval (ms); 0.93 (0.85, 0.97), RMSSD (ms); 0.93 (0.85, 0.97), SDNN (ms); 0.88 (0.75, 0.95), LF power (ms2); 0.87 (0.72, 0.94), and HF power (ms2); 0.88 (0.73, 0.94) with coefficient of variation ranging from 2.2% to 5% (p > 0.37 for all variables). Single-use Kendall DL™ ECG leads demonstrate a valid and reproducible tool for the assessment of HRV.

Obstructive Sleep Apnea Detection Scheme Based on Manually Generated Features and Parallel Heterogeneous Deep Learning Model Under IoMT.

Obstructive sleep apnea (OSA) syndrome is a common sleep disorder and a key cause of cardiovascular and cerebrovascular diseases that seriously affect the lives and health of people. The development of Internet of Medical Things (IoMT) has enabled the remote diagnosis of OSA. The physiological signals of human sleep are sent to the cloud or medical facilities through Internet of Things, after which diagnostic models are employed for OSA detection. In order to improve the detection accuracy of OSA, in this study, a novel OSA detection system based on manually generated features and utilizing a parallel heterogeneous deep learning model in the context of IoMT is proposed, and the accuracy of the proposed diagnostic model is investigated. The OSA recognition scheme used in our model is based on short-term heart rate variability (HRV) signals extracted from ECG signals. First, the HRV signals and the linear and nonlinear features of HRV are combined into a one-dimensional (1-D) sequence. Simultaneously, a two-dimensional (2-D) HRV time-frequency spectrum image is obtained. The 1-D data sequences and 2-D images are coded in different branches of the proposed deep learning network for OSA diagnosis. To validate the performance of the proposed scheme, the Physionet Apnea-ECG public database is used. The proposed scheme outperforms the existing methods in terms of accuracy and provides a novel direction for OSA recognition.

The Autonomic Imbalance of Myocardial Ischemia during Exercise Stress Testing: Insight from Short-Term Heart Rate Variability Analysis.

Exercise stress testing (EST) has limited power in diagnosing obstructive coronary artery disease (CAD). The heart rate variability (HRV) analysis might increase the sensitivity of CAD detection. This study aimed to evaluate the correlation between short-term HRV and myocardial ischemia during EST, including the acceleration, maximum, and recovery stages of heart rate (HR). The HRV during EST from 19 healthy (RHC) subjects and 35 patients with CAD (25 patients with insignificant CAD (iCAD), and 10 patients with significant CAD (sCAD)) were compared. As a result, all HRV indices decreased at the maximum stage and no significant differences between iCAD and sCAD were found. The low-frequency power of heart rate signal (LF) of the RHC group recovered relatively quickly from the third to the sixth minutes after maximum HR, compared with that of the sCAD group. The relative changes of most HRV indices between maximum HR and recovery stage were lower in the sCAD group than in the RHC group, especially in LF, the standard deviation of all normal to normal intervals (SDNN), and the standard deviation in the long axis direction of the Poincaré plot analysis (SD2) indices (p < 0.05). The recovery slope of LF was significantly smaller in the sCAD group than in the RHC group (p = 0.02). The result suggests that monitoring short-term HRV during EST provides helpful insight into the cardiovascular autonomic imbalance in patients with significant CAD. The relative change of autonomic tone, especially the delayed sympathetic recovery, could be an additional marker for diagnosing myocardial ischemia.

Abstract 14985: Artificial Intelligence Based Heart Rate Variability Analysis for Sudden Cardiac Arrest Risk Prediction

Introduction: Sudden Cardiac Arrest (SCA) is an unexpected life-threatening loss of cardiac function potentially leading to sudden cardiac death (SCD). It accounts for a half of cardiac mortality, posing a major public health problem. While SCA can be treated with implantable cardioverter defibrillators (ICD), most (80%) SCDs occur in relatively low risk patients, for whom risk benefit ratio of an ICD is unfavorable. Therefore, novel methods to identify high risk individuals and the time on which their risk is high may facilitate prevention of SCD. Methods : Long (~24h) ECG recordings from individuals who had an SCA on record (n=20), patients with other arrhythmias (n=84) and from healthy individuals (n=17) from PhysioNet databases were analyzed to extract inter beat intervals (IBI). For each step in the IBI series, 120 last IBIs were used to calculate 19 indices that quantify short term heart rate variability (HRV). An artificial intelligence model named temporal convolutional network (TCN) was used to continuously assess the risk of a future VF event based on the current HRV estimate combined with few hours of history of previous HRV estimates. Training and testing of the TCN was done using Leave One Out testing done twice. Patients being classified at any point in the record as high risk were considered high risk. Results : Only patients from the SCA population, and none from the other arrythmia and healthy patients, were classified as high risk (PPV=100%). On average, sensitivity and specificity were 62.5% and 100% respectively Conclusions : In this preliminary retrospective analysis, artificial intelligence based HRV analysis identified risk for a SCA event in the following 24 hours with high specificity. Larger cohort and prospective testing are needed to assess the clinical utility of such systems.

Meditative-based diaphragmatic breathing vs. vagus nerve stimulation in the treatment of fibromyalgia—A randomized controlled trial: Body vs. machine

Vagus nerve innervation via electrical stimulation and meditative-based diaphragmatic breathing may be promising treatment avenues for fibromyalgia. Explore and compare the treatment effectiveness of active and sham transcutaneous vagus nerve stimulation (tVNS) and meditative-based diaphragmatic breathing (MDB) for fibromyalgia. Participants enrolled from March 2019-October 2020 and randomly assigned to active tVNS (n = 28), sham tVNS (n = 29), active MDB (n = 29), or sham MDB (n = 30). Treatments were self-delivered at home for 15 min/morning and 15 min/evening for 14 days. Follow-up was at 2 weeks. Outpatient pain clinic in Oslo, Norway. 116 adults aged 18-65 years with severe fibromyalgia were consecutively enrolled and randomized. 86 participants (74%) had an 80% treatment adherence and 107 (92%) completed the study at 2 weeks; 1 participant dropped out due to adverse effects from active tVNS. Active tVNS is placed on the cymba conchae of the left ear; sham tVNS is placed on the left earlobe. Active MDB trains users in nondirective meditation with deep breathing; sham MDB trains users in open-awareness meditation with paced breathing. Primary outcome was change from baseline in ultra short-term photoplethysmography-measured cardiac-vagal heart rate variability at 2 weeks. Prior to trial launch, we hypothesized that (1) those randomized to active MDB or active tVNS would display greater increases in heart rate variability compared to those randomized to sham MDB or sham tVNS after 2-weeks; (2) a change in heart rate variability would be correlated with a change in self-reported average pain intensity; and (3) active treatments would outperform sham treatments on all pain-related secondary outcome measures. No significant across-group changes in heart rate variability were found. Furthermore, no significant correlations were found between changes in heart rate variability and average pain intensity during treatment. Significant across group differences were found for overall FM severity yet were not found for average pain intensity. These findings suggest that changes in cardiac-vagal heart rate variability when recorded with ultra short-term photoplethysmography in those with fibromyalgia may not be associated with treatment-specific changes in pain intensity. Further research should be conducted to evaluate potential changes in long-term cardiac-vagal heart rate variability in response to noninvasive vagus nerve innervation in those with fibromyalgia. https://clinicaltrials.gov/ct2/show/NCT03180554, Identifier: NCT03180554.

Validity of Ultra-Short-Term HRV Analysis Using PPG-A Preliminary Study.

Continuous measurement of heart rate variability (HRV) in the short and ultra-short-term using wearable devices allows monitoring of physiological status and prevention of diseases. This study aims to evaluate the agreement of HRV features between a commercial device (Bora Band, Biosency) measuring photoplethysmography (PPG) and reference electrocardiography (ECG) and to assess the validity of ultra-short-term HRV as a surrogate for short-term HRV features. PPG and ECG recordings were acquired from 5 healthy subjects over 18 nights in total. HRV features include time-domain, frequency-domain, nonlinear, and visibility graph features and are extracted from 5 min 30 s and 1 min 30 s duration PPG recordings. The extracted features are compared with reference features of 5 min 30 s duration ECG recordings using repeated-measures correlation, Bland–Altman plots with 95% limits of agreements, Cliff’s delta, and an equivalence test. Results showed agreement between PPG recordings and ECG reference recordings for 37 out of 48 HRV features in short-term durations. Sixteen of the forty-eight HRV features were valid and retained very strong correlations, negligible to small bias, with statistical equivalence in the ultra-short recordings (1 min 30 s). The current study concludes that the Bora Band provides valid and reliable measurement of HRV features in short and ultra-short duration recordings.

Normative values of short-term heart rate variability in a cross-sectional study of a Danish population. The DanFunD study.

The autonomic nervous system includes parasympathetic and sympathetic components that monitor and regulate most of the bodily functions and play a central role in the physiology and homeostasis of the human body. Heart rate variability is a non-invasive tool for quantification of rhythmic fluctuations in heart rate that reflects the function of the autonomic nervous system. The study aims to describe the heart rate variability distribution in the general population, stratified in sex and age groups, which is currently insufficiently described. A cross-sectional population-based study recruited participants in 10 municipalities in the western part of the greater Copenhagen area in Denmark, including 6891 men and women aged 18-72 years (participation rate was 29.5%). Short-term heart rate variability measures were obtained and related to age and gender. Both time and frequency domain measures showed a huge variation in the different sex and age groups. Women had a higher median heart rate than men, and the association with age was U-shaped. Measures indicating a predominance of the parasympathetic component in relation to the sympathetic component were more frequent in women and younger age groups. Both sex and age influence the heart rate variability in this adult Danish population. Therefore, our age- and sex-related reference values of heart rate variability in the time and frequency domain should be used in further epidemiological and clinical research.

Alterations in heart rate variability before and after percutaneous coronary intervention in patients with ischaemic heart disease

Objectives: Heart rate variability (HRV) is the beat-to-beat variation of heart rate and an important non-invasive tool to study the cardiac autonomic nervous system activity. Ischaemic heart disease (IHD) patients are often considered to have a state of sympathetic predominance. Elimination of myocardial ischaemia with percutaneous coronary intervention (PCI) could restore autonomic balance. Hence, this study aimed to evaluate HRV measures, after successful revascularisation among IHD patients. Materials and Methods: A total of 145 male IHD patients planned for coronary angiography were recruited. Fifteen minutes of electrocardiogram recording was done. Short-term HRV analyses of all the patients were acquired and time-domain indices (standard deviation of normal-to-normal intervals [SDNN], root-mean-squared differences of successive R-R intervals [rMSSD]) and frequency-domain indices (low-frequency [LF] power, high-frequency [HF] power and total power [TP]) were analysed. Before and after PCI, all measurements were made. Results: This study included 145 male IHD patients with the mean age of 54.57 ± 10.81 years. There was a significant decrease in SDNN, rMSSD, LF, HF and TP whereas increase in LF/HF ratio following revascularisation. These changes in measures of neurocardiac regulation correlated with risk factors and medication on regression analysis. Conclusion: Increase in LF/HF ratio with the decrease in SDNN, rMSSD, LF, HF and TP in patients with IHD who underwent coronary intervention infers changed cardiac autonomic balance with this surgical procedure. These measures could be potentially used as prognostic measures in the future studies.

Short term Heart Rate Variability in Rats

Objective: A sustainable animal model is needed to detect Cardiovascular autonomic dysfunctions, which can be assessed by recording electrocardiogram and analysis of heart rate variability (HRV). Therefore, the present study tried to find out the duration for HRV analysis for reliable results.Material and methods: Recording of Electroencephalogram (ECG) is reported in many articles. However, there is no information regarding the duration of ECG to be considered for the HRV analysis. Adult Wistar rat were used for a recording of ECG and HRV analysis. A combination of Ketamine 50 mg/kg and Xylazine 10 mg/kg was used for anesthésia in all the recordings. We analyzed the HRV parameters for all the records with 10 different durations starting from 1 minute to 10 minutes and compared.Results and Discussion: It was observed that, ECG parameters were within normal range while the data from HRV analysis from different duration showed wide discrepancies depending on the duration of ECG recording used for HRV analysis.Conclusion: The minimum duration of eight minutes of recording is likely to produce acceptable data for HRV parameters.

A simple version of resting-state heart rate variability interpretation for patients with affective disorders: A four-pattern perspective.

Heart rate variability (HRV) is often considered as a biomarker reflecting well-being, but the clinical meaning of short-term resting-state HRV is not sufficiently defined. We assume that combining several common HRV indices as "HRV patterns" and using the patterns for screening purposes are meaningful approaches. Resting-state 5-min HRV data of 424 subjects were analyzed. Four of the most commonly used HRV indices were considered: standard deviation of normal-to-normal RR intervals, low-frequency power, high-frequency power and the ratio of low-frequency to high-frequency power. According to these indices, four HRV patterns were defined: normal pattern, low HRV pattern, relatively high sympathetic pattern, and relatively high vagal pattern. The associations between the demographics, lifestyles, personality traits, psychological states, and HRV patterns were explored: the low HRV pattern was positively associated with age, body mass index, and depression; the relatively high sympathetic pattern was positively associated with age and negatively associated with exercise habit; and the relatively high vagal pattern was negatively associated with having a steady job and novelty seeking. The pattern perspective may provide a convenient and evidence-based way to interpret resting-state HRV for patients with affective disorders.

Association of fetal heart rate short term variability pattern during term labor with neonatal morbidity and small for gestational age status

ObjectiveTo assess the association of fetal heart rate short-term variability (STV) pattern during term labor with both neonatal composite morbidity (cord blood pH ≤ 7.10 and/or neonatal intensive care unit admission and/or Apgar score at 5 min <7) and small for gestational age (SGA) status. Study designRetrospective cohort in a single academic institution between January 2016 and December 2018. A total of 1896 women that delivered a singleton during labor in cephalic presentation after 37 weeks of gestation were included (948 women with SGA neonates and 948 women with appropriate weight for gestational age (AGA) neonates that were matched to women with SGA neonates based on maternal age, parity, induction of labor, gestational diabetes, gestational age at delivery and a history of one cesarean section using propensity score matching). STV was compared at labor onset (cervical dilation ≤ 4 cm), in the first stage of labor (cervical dilation = 6 cm) and in the second stage of labor (cervical dilation = 10 cm). A generalized linear mixed model was used to assess the association between SGA status, neonatal composite morbidity and STV. ResultsAfter adjustment for maternal origin, term, gestational diabetes, labor length, SGA status was not associated with any change in STV during labor (mean adjusted STV: −0.20 ms, 95 %CI[-0.58–0.17], p = 0.284 at labor onset, 0.29 ms, 95 %CI[-0.1– 0.68], p = 0.155, in the first stage of labor and 0.36 ms, 95 %CI[-0.02–0.74], p = 0.065 in the second stage of labor). In case of neonatal composite morbidity mean adjusted STV was lower in the first stage of labor (mean adjusted STV: −1.29 ms, 95 %CI[-2.1 – −0.43], p = 0.003) and in the second stage of labor (mean adjusted STV: −1.15 ms, 95 %CI[-1.96 – −0.34], p = 0.005). The results were similar with the addition of delivery mode and meconium-stained amniotic fluid in the model or non-reassuring fetal heart rate and meconium-stained amniotic fluid. ConclusionsThis work suggests that STV decrease during term labor is associated with fetal well-being, independently of fetal weight. This suggests that further prospective studies should consider the evaluation of this parameter in the prediction of neonatal compromise.

Effects of a Combined Intradialytic Exercise Training Program and Music on Cardiac Autonomic Nervous System Activity in Hemodialysis Patients.

This study aimed to examine the effect of an intradialytic exercise program in combination with music on heart rate variability (HRV) indices and functional capacity in patients on maintenance hemodialysis (HD). Methods: Forty HD patients were randomized to four training groups for six months: the combined music and exercise group (Group A), the exercise group (Group B), the music group (Group C), and the control group (Group D). At baseline and after 6 months, all participants underwent both short- (for 30 min) and long- (for 24 h) term measurements of HRV and functional capacity assessment with a 6 min walking test (6MWT). Patients of groups A and C listened to preferred music. Results: Long-term HRV analysis showed that standard deviation of all normal-to-normal RR intervals (SDNN) and the square root of the mean squared differences of successive RR intervals (rMSSD) were significantly higher at the end of the study in groups A (by 13.2% and 47.3%), B (by 15.1% and 50%), and C (by 9.0% and 30.1%), compared to group D (p < 0.05). Values of rMSSD and percentage of RR intervals differing by more than 50 ms from the preceding RR interval (pNN50) were elevated in groups A (by 35.6% and 142.9%), B (by 36.1% and 75%), and C (by 15.2% and 28.6%), compared to baseline measurements (p < 0.05). Also, pNN50 was increased in group A compared to groups B (by 21.4%), C (by 88.9%), and D (by 142.9%) (p < 0.05). Similar results were noted by short-term HRV analysis. Functional capacity was improved at the end of the 6-month study in groups A (by 20.3% and 25.7%) and B (by 15.8% and 21.1%) compared to groups C and D (p < 0.05). Conclusions: Intradialytic exercise combined with music-listening can improve the functional capacity and cardiac autonomic nervous system activity in hemodialysis patients.

Association of the Heart Rate Variability Response to Active Standing with the Severity of Calcific Aortic Valve Disease: Novel Insights of a Neurocardiovascular Pathology.

The aim of this work was to obtain insights of the participation of the autonomic nervous system in different stages of calcific aortic valve disease (CAVD) by heart rate variability (HRV) analysis. Studying subjects with no valve impairments and CAVD patients, we also sought to quantify the independent contribution or explanatory capacity of the aortic valve echocardiographic parameters involved in the HRV changes caused by active standing using hierarchical partitioning models to consider other variables or potential confounders. We detected smaller adjustments of the cardiac autonomic response at active standing caused specifically by the aortic valve deterioration. The highest association (i.e., the highest percentage of independent exploratory capacity) was found between the aortic valve area and the active standing changes in the short-term HRV scaling exponent α1 (4.591%). The valve’s maximum pressure gradient echocardiographic parameter was present in most models assessed (in six out of eight models of HRV indices that included a valve parameter as an independent variable). Overall, our study provides insights with a wider perspective to explore and consider CAVD as a neurocardiovascular pathology. This pathology involves autonomic-driven compensatory mechanisms that seem generated by the aortic valve deterioration.

Obstructive sleep apnoea-related respiratory events and desaturation severity are associated with the cardiac response.

BackgroundObstructive sleep apnoea (OSA) causes, among other things, intermittent blood oxygen desaturations, increasing the sympathetic tone. Yet the effect of desaturations on heart rate variability (HRV), a simple and noninvasive method for assessing sympathovagal balance, has not been comprehensively studied. We aimed to study whether desaturation severity affects the immediate HRV.MethodsWe retrospectively analysed the electrocardiography signals in 5-min segments (n=39 132) recorded during clinical polysomnographies of 642 patients with suspected OSA. HRV parameters were calculated for each segment. The segments were pooled into severity groups based on the desaturation severity (i.e. the integrated area under the blood oxygen saturation curve) and the respiratory event rate within the segment. Covariate-adjusted regression analyses were performed to investigate possible confounding effects.ResultsWith increasing respiratory event rate, the normalised high-frequency band power (HFNU) decreased from 0.517 to 0.364 (p<0.01), the normalised low-frequency band power (LFNU) increased from 0.483 to 0.636 (p<0.01) and the mean RR interval decreased from 915 to 869 ms (p<0.01). Similarly, with increasing desaturation severity, the HFNU decreased from 0.499 to 0.364 (p<0.01), the LFNU increased from 0.501 to 0.636 (p<0.01) and the mean RR interval decreased from 952 to 854 ms (p<0.01). Desaturation severity-related findings were confirmed by considering the confounding factors in the regression analyses.ConclusionThe short-term HRV response differs based on the desaturation severity and the respiratory event rate in patients with suspected OSA. Therefore, a more detailed analysis of HRV and desaturation characteristics could enhance OSA severity estimation.

Desaturation severity affects OSA-related changes in short-term heart rate variability

Desaturation severity affects OSA-related changes in short-term heart rate variability

Measuring effects of height on the autonomic nervous system in middle-aged adolescents using the very low frequency band of heart rate variability

Previous studies have revealed the association between falling accidents and stress, measured via heart rate variability (HRV). However, none have studied this association using the very low frequency (VLF) band of HRV in adolescent populations. This study aimed to fill this gap by recruiting 90 adolescents to perform a light physical task at varying heights. Heart rates were used to calculate short-term HRV. The results showed a positive correlation between VLF bands and parasympathetic indices and a negative correlation with sympathetic indices, demonstrating the balancing effects of the autonomic modulation associated with height. The lowest VLF bands were obtained as 79.25 ms2 at 10 m (p < 0.001) and 62.87 ms2 at 9 m (p < 0.001) for the experienced and non-experienced male groups, respectively, and 28.09 ms2 at 6 m (p = 0.001) for the female group. The results also suggested the need for a relatively lower height restriction for female adolescents than for males. Practitioner summary: Increased working heights can cause stress, which leads to falling accidents. The very low frequency band was shown to be associated with parasympathetic and sympathetic indices. Furthermore, the results suggested that the height limit necessary for providing a safe working environment may be lower for female adolescents than for males. Abbreviations: HRV: heart rate variability; VLF: very low frequency; ms2: absolute power; ANS: autonomic nervous system; PNS: parasympathetic nervous system; SNS: sympathetic nervous system; RR: intervals between two successive peaks of R waves; RMSSD: root mean square of successive RR interval differences; SD1: Poincaré plot index of standard deviation 1; SD2: Poincaré plot index of standard deviation 2; HF: high frequency; LF: low frequency; BMI: body mass index; ECG: electrocardiography; HR: heart rate; FFT: fast Fourier transformation; IQR: interquartile range; r: non-parametric partial correlation coefficient; η2: eta-squared; EM: experienced males; NM: non-experienced males; NF: non-experienced females; EEG: electroencephalogram

Respiratory Sinus Arrhythmia is Mainly Driven by Central Feedforward Mechanisms in Healthy Humans.

Heart rate variability (HRV) has prognostic and diagnostic potential, however, the mechanisms behind respiratory sinus arrhythmia (RSA), a main short-term HRV, are still not well understood. We investigated if the central feedforward mechanism or pulmonary stretch reflex contributed most to RSA in healthy humans. Ventilatory support reduces the centrally mediated respiratory effort but remains the inspiratory stretch of the pulmonary receptors. We aimed to quantify the difference in RSA between spontaneous breathing and ventilatory support. Nineteen healthy, young subjects underwent spontaneous breathing and non-invasive intermittent positive pressure ventilation (NIV) while we recorded heart rate (HR, from ECG), mean arterial pressure (MAP) and stroke volume (SV) estimated from the non-invasive finger arterial pressure curve, end-tidal CO2 (capnograph), and respiratory frequency (RF) with a stretch band. Variability was quantified by an integral between 0.15–0.4 Hz calculated from the power spectra. Median and 95% confidence intervals (95%CI) were calculated as Hodges–Lehmann’s one-sample estimator. Statistical difference was calculated by the Wilcoxon matched-pairs signed-rank test. RF and end-tidal CO2 were unchanged by NIV. NIV reduced HR by 2 bpm, while MAP and SV were unchanged in comparison to spontaneous breathing. Variability in both HR and SV was reduced by 60% and 75%, respectively, during NIV as compared to spontaneous breathing, but their interrelationship with respiration was maintained. NIV reduced RSA through a less central respiratory drive, and pulmonary stretch reflex contributed little to RSA. RSA is mainly driven by a central feedforward mechanism in healthy humans. Peripheral reflexes may contribute as modifiers of RSA.