Ratio Of Heart Rate Variability Research Articles

Thermoregulatory differences in sex and time-of-day within naturally ventilated office environments

Thermal comfort research lacks continuous data collection on thermoregulation and adaptive behavior in real-world environments. This paper presents the findings of a field study that aimed at understanding the temporal and individual differences between humans’ thermoregulation and adaptation within a dynamic thermal environment. The dataset contains a 6-week long summer field study of 2022 observing nine participants in a naturally ventilated office without a cooling system. The data collection comprises a total of 43 measurement days (22,776 data points at 60s frequency). The results indicate that the overall trend in clothing insulation deviates from standard assumptions (0.5 clo), especially above air temperatures of 26 °C. The mean clothing insulation was 0.29 clo ±0.08, overall ranging from 0.20 to 0.73 clo. The data showed significant sex differences in tonic levels of electrodermal activity, the low-frequency to high-frequency heart rate variability ratio, and clothing insulation. Other heart rate variability data, like the root mean square of successive differences and beats per minute, as well as the distal skin temperature of the wrist, show significant sex differences and time-of-day variations in morning-to-afternoon comparisons. The findings indicate a nuanced relationship between air temperature and thermoregulatory responses, highlighting the need for future research with larger, more diverse participant cohorts and enhanced environmental monitoring to strengthen the validity and generalizability of the findings.

Body Water Compartment and Sympathovagal Balance: Association with Visuomotor Retention in Young Adults

Cognitive functions are important for visuomotor learning and are associated with physiological factors such as body fluid compartment and cardiovascular reactivity. Previous studies found that body fluid compartment is associated with brain blood flow, which is regulated via sympathovagal balance. However, more evidence is needed to determine whether body fluid compartment and cardiovascular reactivity are associated with visuomotor learning. The purpose of this study was to explore the relationship of body fluid compartment and cardiovascular reactivity to visuomotor learning. We hypothesized that these physiological factors are associated with overall learning retention using upper extremity (including feedforward, volitional, and feedback conditions). Methods: Thirty young adults (12 males, 24.6 ± 3.9 years, right hand dominant) participated in this study. Participants tracked a sinusoidal wave with left arm at pre-test, learning, and post-test sessions on the first visit and at retention test session on the second visit seven days later. Participants performed one set of nine trials during each test and five sets of three trials during learning. Resistance and wave velocity were different in each trial. Learning error was calculated by the averaged absolute distance between the tracking line and the target line. Heart rate (HR), systolic blood pressure (SBP), and low to high frequency power ratio of heart rate variability (LF/HF) were continuously recorded during baseline before pre-test and during tests and learning. We analyzed participants’ extracellular to intracellular body water ratio (ECW/ICW) using an InBody body composition analyzer and tested their cognitive function with Picture Sequence Memory (PSMT), Pattern Comparison Processing Speed, Dimensional Change Card Sort, Flanker Inhibitory Control and Attention, and List Sorting Working Memory Tests from NIH Cognitive Toolbox. Data were statistically analyzed using linear regression analysis and quartile analysis. Results: ECW/ICW was associated with young adults’ ability to retain visuomotor learning after one week (R2 = 0.138, p = 0.043), whereas HR, SBP, and LF/HF at each session were not significantly associated with visuomotor retention. No differences were found in pre-test error among quartiles of five cognitive tests. Significant differences in retention error among quartiles were only found in PSMT, with participants scoring in the highest quartile of PSMT having lower SBP during the first visit and lower retention error compared to the lowest quartile. This finding suggests that young adults with better episodic memory were less stressed during learning and had better visuomotor retention. Conclusion: These findings support that ECW/ICW is associated with not only cognitive function but also visuomotor retention. In addition, cardiovascular reactivity during visuomotor learning may provide information for retention behavior. Relationship of body water compartment and sympathovagal balance to feedforward and feedback conditions in learning will be further discussed. Research Support: This study was funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development: R01HD084645, R01HD082109. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The impact of outdoor soundscapes at nursing homes on physiological indicators in older adults

This research explores the impact of outdoor soundscapes at nursing homes on the physiological health of older adults. Using virtual reality, the study recreated the outdoor environments at nursing homes for 57 seniors in a lab setting, continuously monitoring physiological indicators such as skin conductance level, heart rate, low to high-frequency heart rate variability ratio, respiratory frequency, blink frequency, and pupil diameter. The comparison of these indicators with corresponding soundscapes revealed the diverse effects of different nursing home outdoor scenarios on the physiological health of older adults. Furthermore, analysis of the temporal marginal effects of these indicators highlighted the significant influence of time on the physiological responses of seniors in various soundscapes, showing fluctuations in each indicator at different times. Finally, to understand the channels of impact, the study examined how acoustic features at nursing homes affect seniors' physiological indicators. The findings suggest that increased loudness and roughness in soundscapes elevate seniors' heart rates and cardiovascular risks, while a moderate increase in LAeq and fluctuation strength in dynamic scenarios might have positive stimulative effects on the physiological functions of the older adults.

Virtual Reality Adaptive Training for Personalized Stress Inoculation.

To evaluate a personalized adaptive training program designed for stress prevention using graduated stress exposure. Astronauts in the high-risk space mission environment are prone to performance-impairing stress responses, making preemptive stress inoculation essential for their training. This work developed an adaptive virtual reality-based system that adjusts environmental stressors based on real-time stress indicators to optimize training stress levels. Sixty-five healthy subjects underwent task training in one of three groups: skill-only (no stressors), fixed-graduated (prescheduled stressor changes), and adaptive. Psychological (subjective stress, task engagement, distress, worry, anxiety, and workload) and physiological (heart rate, heart rate variability, blood pressure, and electrodermal activity) responses were measured. The adaptive condition showed a significant decrease in heart rate and a decreasing trend in heart rate variability ratio, with no changes in the other training conditions. Distress showed a decreasing trend for the graduated and adaptive conditions. Task engagement showed a significant increase for adaptive and a significant decrease for the graduated condition. All training conditions showed a significant decrease in worry and anxiety and a significant increase in the other heart rate variability metrics. Although all training conditions mitigated some stress, the preponderance of trial effects for the adaptive condition supports that it is more successful at decreasing stress. The integration of real-time personalized stress exposure within a VR-based training program not only prepares individuals for high-stress situations by preemptively mitigating stress but also customizes stressor levels to the crew member's current state, potentially enhancing resilience to future stressors.

Coping und vegetative Reaktivität bei Aderhautmelanomen

Summary Background We aimed to assess coping and vegetative reactivity in uveal melanoma (UM) patients compared to controls with benign nevi of the uvea. Material and methods In total, 20 patients with recently diagnosed uveal melanoma were recruited and matched for age and gender to 20 controls with benign nevi of the uvea. Heart rate variability (HRV) and blood pressure variability (BPV) were monitored throughout an initial period of rest (POR1), a mental stress test (DT), and another period of rest (POR2). Coping strategies were assessed for both groups using a stress-coping questionnaire. Results The LF/HF ratio (low-/high-frequency component of total spectral power) of HRV showed decreasing values in the UM group and increasing values in controls throughout the measurement sequence (p = 0.025). Diastolic BPV revealed declining values of the low-frequency component in normalized units (LFnu) between POR1 and DT in UM patients compared to rising values between POR1 and DT in controls (p = 0.006). There were no intergroup differences in coping strategies (p > 0.05). Conclusions Coping mechanisms are unaltered in patients with uveal melanoma compared to controls, but vegetative reactivity may show a different pattern once patients are diagnosed.

Parental History of Hypertension: A Risk for Autonomic Dysfunction and Metabolic and Vascular Derangement in Normotensive Male Offspring.

Children of hypertensive parents have an increased propensity of developing hypertension, at an age very much prior to their parents. Understanding the pathophysiology of hypertension in such young individuals, especially baroreflex sensitivity (BRS), is necessary. Reduced heart rate variability (HRV), insulin resistance (IR), dyslipidemia, and decreased vasodilatory adipokines, namely, apelin and relaxin, in normotensives may predispose to the onset of hypertension. Thus, this study compared autonomic functions, vascular markers, and metabolic profiles between normotensive male offspring with and without parental hypertension. This analytical cross-sectional study comprised 40 male normotensive offspring of hypertensive parents, aged 18-35 years, recruited as the study group and 40 age- and body mass index (BMI)-matched normotensive male offspring with non-hypertensive parents enrolled as controls. Cardiovascular autonomic functions, including BRS, HRV, diastolic blood pressure response to isometric handgrip test (ΔDBPIHG), Valsalva ratio, and metabolic and vascular markers, were assessed. The study group exhibited reduced BRS, HRV, and Valsalva ratio and higher ΔDBPIHG compared to controls, indicating impaired autonomic functions. The study group had higher IR and triglyceride levels and reduced apelin and relaxin levels. BRS showed significant correlations with HRV, Valsalva ratio, ΔDBPIHG, and metabolic and vascular markers. Normotensive male offspring of hypertensive parents exhibit impaired autonomic functions, as evidenced by reduced BRS, HRV, and Valsalva ratio. Additionally, they have higher IR, dyslipidemia, and decreased levels of vasodilatory adipokines, indicating an increased risk for future hypertension development. These findings signify that early identification of hypertensive potential in this high-risk population is warranted, which would enable taking necessary preventive measures.

Stress reappraisal improves the autonomic nervous system response of test anxious individuals: Evidence from heart rate variability

BackgroundStress belief plays an important role in stress response. This study investigated whether individuals with high test anxiety/low test anxiety (HTA/LTA) held different stress belief, and tested the effect of stress reappraisal on reducing test anxiety related autonomic nervous system (ANS) response. Methods51 HTA students and 49 LTA students were recruited using the Test Anxiety Scale (TAS). They completed a 10-min intelligence test (including preparation, test, and recovery phases), then were randomly assigned to reappraisal group and control group to complete the test again. Heart rate variability (HRV) was recorded throughout the protocol. Beliefs about Stress Scale was obtained before and after the experiment. Stress belief were manipulated using a 2-min film clip that orienting participant to the enhancing nature of stress. Emotional changes were assessed. ResultsHTA individuals held more negative stress beliefs and showed greater emotional arousal during the test than the LTA individuals. Their negative stress belief was associated with higher TAS score and worse HRV response. (2) When facing an exam, LTA individuals exhibited increased low-frequency HRV and stable high-frequency HRV, while HTA individuals showed stable low-frequency HRV and decreased high-frequency HRV. (3) HTA individuals who underwent reappraisal showed a reduction in test anxiety and in low-frequency/high-frequency HRV ratio. ConclusionsThe ANS activity of HTA individuals is imbalanced in the test situations. Stress belief is a meaningful variable in anxiety related ANS activity. Stress reappraisal can effectively reduce test anxiety and improve the balance of ANS activity of HTA individuals.

Effects of exposure to carbon dioxide and human bioeffluents on sleep quality and physiological responses

Twenty-four subjects were exposed to two levels of occupant pollution in a thermally neutral sleeping environment, as indicated with average carbon dioxide (CO2) concentrations of 800 ppm and 2000 ppm during the night. Sleep quality was measured by polysomnography and a wrist-type actigraphy sensor simultaneously, and also assessed by a questionnaire. Physiological parameters indicating responses of cardiovascular and pulmonary function were measured repeatedly prior to sleep and after waking up in the morning. The results show that when exposed to the high level of occupant pollution with the average CO2 concentration being 2000 ppm, subjects reported lower satisfaction on sleep and less easiness of awakening, and experienced a shorter duration of total sleep and deep sleep stage, which indicates a worse sleep quality. Furthermore, fractional CO2, end-tidal CO2 and systolic blood pressure measured in the morning were significantly higher. The change of LF/HF ratio of heart rate variability was significantly more at the onset of sleep and less during arousal. This suggests that when sleeping in an occupant-polluted environment, subjects experienced a slower automatic nervous system transition from a sympathetically dominated state to a parasympathetically dominated state at night, and vice versa in the morning.

The effect of exercise using incentive spirometry on heart rate variability in patients after COVID-19 infection

Background: COVID-19 infection causes various sequelae and complications after recovery. Changes in heart rate variability (HRV) were found in patients with COVID-19 infection, suggesting a disturbance in the autonomic system. Breathing exercises with diaphragmatic breathing and incentive spirometry have been shown to increase HRV by increasing lung capacity, respiratory muscle strength, and pulmonary O2 pressure, which can affect baroreflex signals. Incentive spirometry is one of the easy-to-use, safe, inexpensive pulmonary rehabilitation exercises that can be done at home without supervision and are accompanied by a visual display as a guide to the patient. The purpose of the study was to determine the effect of giving breathing exercises using Incentive Spirometry for four weeks on Heart Rate Variability in patients post COVID-19 infection Method: This research is an experimental study with a pre-post-test control group design. The treatment group was given breathing exercises using Incentive Spirometry, while the control group used diaphragmatic breathing five times a day, seven times per week, for four weeks in each group. HRV measurement was performed before and after four weeks of intervention, using the parameter Root Mean Square of Successive Differences between normal heartbeats (RMSSD), Standard Deviation of N-N intervals (SDNN), and LF/HF ratio of Heart Rate Variability (HRV). Result: There subject of this study was 20 post-COVID-19 patients divided into a treatment group (n=10) and a control group (n=10). There was no significant increase in RMSSD, SDNN, and LF/HF ratio pre and post-intervention in both groups, suggesting no significant increase in HRV. Conclusion: Exercise with Incentive Spirometry and Diaphragmatic Breathing for four weeks did not increase the Heart Rate Variability value in post-COVID-19 patients.

Autonomic modulation by low-intensity focused ultrasound stimulation of the vagus nerve

Objective. Our previous study has shown that low-intensity focused ultrasound stimulation (FUS) of the vagus nerve could modulate blood pressure (BP), but its underlying mechanisms remain unclear. We hypothesized that low-intensity FUS of the vagus nerve would regulate autonomic function and thus BP. Approach. 17 anesthetized spontaneously hypertensive rats were treated with low-intensity FUS of the left vagus nerve for 15 min each trial. Continuous BP, heart rate, respiration rate (RR), and core body temperature were simultaneously recorded to evaluate the effects on BP and other physiological parameters. Heart rate variability (HRV), systolic BP variability, and baroreflex sensitivity were computed to evaluate the autonomic modulation function. A Control-sham group without stimulation and another Control-FUS group with non-target stimulation were also examined to exclude the influence of potential confounding factors on autonomic modulation. Main results. A prolonged significant decrease in BP, pulse pressure, RR, the normalized low-frequency power of HRV, and the low-to-high frequency power ratio of HRV were found after the low-intensity FUS of the left vagus nerve in comparison with the baseline and those of the control groups, demonstrating that activities of the sympathetic nervous system were inhibited. The prolonged significant increase of the normalized high-frequency power of HRV suggested the activation of parasympathetic activity. Significance. Low-intensity FUS of the left vagus nerve effectively improved the autonomic function by activating parasympathetic efferent and inhibiting sympathetic efferent, which contributes to BP reduction. The findings shed light on the hypotensive mechanism underlying FUS.

Variability of autonomic nerve activity in dry eye with decreased tear stability

The autonomic nervous system plays a crucial role in the maintenance of homeostasis. Neurogenic inflammation due to decreased stability of tear film may induce changes in autonomic nerve activity, which could be associated with symptom expression.This study aimed to measure biological parameters that represent autonomic nerve activity in dry eye (DE)s caused by tear film dysfunction and investigate their relationship with symptom intensity. This prospective, cross-sectional, comparative study evaluated 34 eyes of 34 participants (mean age: 52.5 ± 13.4 years; range: 20-81 years) without keratoconjunctival damage. Nineteen eyes in the DE group showed DE symptoms and tear break-up time (TBUT) of ≤5 seconds (short TBUT DE); the 15 eyes in the non-DE group showed no DE symptoms. Autonomic nerve activity was measured for 10 minutes-starting and ending 5 minutes before and after instilling ophthalmic solution-and evaluated using the low-frequency component (LF) to the high-frequency component (HF) ratio of heart rate variability (autonomic balance). The pre-ophthalmic solution administration LF/HF ratio was not significantly different (P = 0.59) between the two groups, however, the standard deviation of the LF/HF ratio (LF/HF-SD) tended to be higher in the DE group than that in the non-DE group (P = 0.086). The DE symptom intensity was significantly related to LF/HF-SD (P = 0.005), which significantly decreased after ophthalmic solution administration in the DE group (P = 0.04). The large fluctuations in autonomic balance may be key for the understanding of the mechanism underlying DE symptoms.

Effects of hyperventilation length on muscle sympathetic nerve activity in healthy humans simulating periodic breathing

Background: Periodic breathing (PB) is a cyclical breathing pattern composed of alternating periods of hyperventilation (hyperpnea, HP) and central apnea (CA). Differences in PB phenotypes mainly reside in HP length. Given that respiration modulates muscle sympathetic nerve activity (MSNA), which decreases during HP and increases during CA, the net effects of PB on MSNA may critically depend on HP length. Objectives: We hypothesized that PB with shorter periods of HP is associated with increased MSNA and decreased heart rate variability. Methods: 10 healthy participants underwent microelectrode recordings of MSNA from the common peroneal nerve along with non-invasive recording of HRV, blood pressure and respiration. Following a 10-min period of tidal breathing, participants were asked to simulate PB for 3 min following a computed respiratory waveform that emulated two PB patterns, comprising a constant CA of 20 s duration and HP of two different lengths: short (20 s) vs long (40 s). Results: Compared to (3 min of) normal breathing, simulated PB with short HP resulted in a marked increase in mean and maximum MSNA amplitude (from 3.2 ± 0.8 to 3.4 ± 0.8 µV, p = 0.04; from 3.8 ± 0.9 to 4.3 ± 1.1 µV, p = 0.04, respectively). This was paralleled by an increase in LF/HF ratio of heart rate variability (from 0.9 ± 0.5 to 2.0 ± 1.3; p = 0.04). In contrast, MSNA response to simulated PB with long HP did not change as compared to normal breathing. Single CA events consistently resulted in markedly increased MSNA (all p < 0.01) when compared to the preceding HPs, while periods of HP, regardless of duration, decreased MSNA (p < 0.05) when compared to normal breathing. Conclusion: Overall, the net effects of PB in healthy subjects over time on MSNA are dependent on the relative duration of HP: increased sympathetic outflow is seen during PB with a short but not with a long period of HP.

Mechanisms for blood pressure reduction following isometric exercise training: a systematic review and meta-analysis.

Isometric exercise training (IET) is established as an effective antihypertensive intervention. Despite this, the physiological mechanisms driving blood pressure (BP) reductions following IET are not well understood. Therefore, we aimed to perform the first meta-analysis of the mechanistic changes measured following IET. PubMed, Cochrane library and SPORTDiscus were systematically searched for randomized controlled trials published between January 2000 and December 2021 reporting the effects of IET on resting BP and at least one secondary mechanistic parameter following a short-term intervention (2-12 weeks). Eighteen studies with a pooled sample size of 628 participants were included in the final analysis. IET produced significant reductions in resting systolic and diastolic BP of 9.35 mmHg (95% confidence interval [CI] = -7.80 to -10.89, P < 0.001) and 4.30 mmHg (CI = -3.01 to -5.60, P < 0.001), respectively. Mechanistically, IET produced a statistically significant reduction in resting heart rate (mean difference [MD]: -1.55 bpm, CI = -0.14 to -2.96, P = 0.031) and a significant increase in stroke volume (MD: 6.35 ml, CI = 0.35 to 12.60, P = 0.038), with no significant change in cardiac output. Conversely, total peripheral resistance (TPR) significantly decreased following IET (MD: -100.38 dyne s -1 cm 5 , CI = -14.16 to -186.61, P = 0.023), with significant improvements in the low frequency to high frequency heart rate variability ratio (MD: -0.41, CI = -0.09 to -0.73, P = 0.013) and baroreceptor reflex sensitivity (MD: 7.43 ms/mmHg, P < 0.001). This work demonstrates that a reduction in TPR, potentially mediated through enhanced autonomic vasomotor control, is primarily responsible for BP reductions following IET. Furthermore, this novel analysis suggests wall squat interventions to be the most effective IET mode, with clinically relevant differences in BP reductions compared to handgrip and leg extension IET; although future direct comparative research is required.

Role of the autonomic nervous system and premature atrial contractions in short-term paroxysmal atrial fibrillation forecasting: Insights from machine learning models

Machine learning and deep learning techniques are now used extensively for atrial fibrillation (AF) screening, but their use for AF crisis forecasting has yet to be assessed in a clinical context. To assess the value of two machine learning algorithms for the short-term prediction of paroxysmal AF episodes. We conducted a retrospective study from an outpatient clinic. We developed a deep neural network model that was trained for a supervised binary classification, differentiating between RR interval variations that precede AF onset and RR interval variations far from any AF. We also developed a random forest model to obtain forecast results using heart rate variability variables, with and without premature atrial complexes. In total, 10,484 Holter electrocardiogram recordings were screened, and 250 analysable AF onsets were labelled. The deep neural network model was able to distinguish if a given RR interval window would lead to AF onset in the next 30 beats with a sensitivity of 80.1% (95% confidence interval 78.7-81.6) at the price of a low specificity of 52.8% (95% confidence interval 51.0-54.6). The random forest model indicated that the main factor that precedes the start of a paroxysmal AF episode is autonomic nervous system activity, and that premature complexes add limited additional information. In addition, the onset of AF episodes is preceded by cyclical fluctuations in the low frequency/high frequency ratio of heart rate variability. Each peak is itself followed by an increase in atrial extrasystoles. The use of two machine learning algorithms for the short-term prediction of AF episodes allowed us to confirm that the main cause of AF crises lies in an imbalance in the autonomic nervous system, and not premature atrial contractions, which are, however, required as a final firing trigger.

Anti‐depressant lithium compounds reliefs cardiorespiratory disturbances and improves cardiac function in experimental non‐ischemic heart failure

Non‐ischemic heart failure (HF) is a complex medical problem with a high incidence among the older population. While several efforts have been made to improve HF outcomes there is an urgent need for new strategies to reduce mortality rates. Sympathoexcitation and disordered breathing are both considered hallmarks of HF and are closely related to disease progression. Lithium salts has been largely used as anti‐depressants; however, lithium compounds also showed several pleiotropic effects some of them linked to the origin of cardiorespiratory disorders in HF (i.e. oxidative stress). Accordingly, using drug repurposing strategy we aimed to define whether lithium treatment improve cardiorespiratory function in experimental HF. Male Sprague‐Dawley rats underwent volume overload to induce non‐ischemic HF. Four weeks after HF induction, an osmotic minipump containing lithium chloride (Li+, 2 meq/Kg/day) was subcutaneously implanted for drug delivery. Cardiac autonomic and baroreflex function, ventilatory chemoreflex drive and disordered breathing were evaluated after 4 weeks of Li+ treatment in freely moving rats. In addition, cardiac function was determine using PV‐loops. Compared to Sham rats, HF animals displayed autonomic imbalance, reduced baroreflex sensitivity, higher incidence of cardiac arrhythmias, enhanced central chemoreflex and breathing disorders. Cardiac diastolic dysfunction was evident in HF animals compared to Sham animals. HF rats that underwent Li+ treatment showed significant (p&lt;0.05) improvements in cardiac autonomic function as evidenced by reduced low‐to‐high frequency ratio of heart rate variability (LF/HF: 2.8 ± 0.3 vs. 0.9 ± 0.4; HF+Veh vs. HF+Li+), baroreflex sensitivity (BRS: 2.0 ± 0.5 vs. 5.8 ± 1.0 ms/mmHg; HF+Veh vs. HF+Li+) and reduced cardiac arrhythmogenesis (PVC: 220 ± 50 vs. 30 ± 10 events/h; HF+Veh vs. HF+Li+). Furthermore, Li+ treatment in HF completely normalized central chemoreflex drive. Indeed, hypercapnic ventilatory responses obtained in HF+Li+ rats were undistinguishable from the ones obtained in Sham rats (HCVR: 1.7 ± 0.4 vs. 2.0 ± 0.4 DVe/FiCO2; HF+Veh vs. HF+Li+). Also, breathing disorders (i.e. apneas/hypopneas) were markedly reduced by Li+ treatment in HF (AHI: 8.5 ± 1.0 vs. 3.7 ± 0.8; HF+Veh vs. HF+Li+). Lastly, HF+Li+ treated rats displayed marked improvements in cardiac diastolic function (~2.5‐fold reduction in EDPVR) compared to HF+Veh treated rats. We found that the beneficial effects of Li+were partially associated with upregulation of the Nrf2 pathway and related antioxidant genes (i.e. SOD2), reductions in tissue oxidative stress and decreases in the expression of pro‐inflammatory cytokines (i.e. TNF‐a) in HF rats. Our results support the notion that lithium compounds may offer new avenues for the treatment of cardiorespiratory disorders and cardiac diastolic dysfunction in non‐ischemic HF.

Binge drinking‐like behavior in juvenile rats causes long‐lasting cardiorespiratory dysfunction that persists until adulthood

Harmful alcohol abuse is associated with serious psychosocial and health damage, including cardiac and neurological morbidities. Americans drink 40% more than the global average and adolescents are the heaviest drinkers, displaying a pathological consumption pattern termed “binge drinking”, consisting in short episodes of heavy alcohol intake followed by long withdrawal periods. Despite adolescent binge drinking (ABD) drives severe impairments in neurological and cardiorespiratory function, there are no current health policies to prevent ABD or its physiological consequences. Indeed, little is known about the long‐term consequences of ABD in adulthood physiology. Therefore, we aimed to investigate the potential harmful effects of ABD on cardiac and respiratory (patho)physiology in the adult life. Sixteen male juvenile Sprague‐Dawley rats underwent ABD‐like alcohol administration protocol or control treatment, consisting of 2‐days “ON” and 2‐days “OFF” doses of ethanol (3.0 g/kg, 25% w/v in saline administered i. p.) beginning on post‐natal day (PND) 25 until PND 38. Once rats reached adulthood (PND80), respiratory and cardiac function were respectively assessed by whole‐body plethysmography and intraventricular pressure‐volume loops. Compared to controls, adult rats exposed to ABD displayed no differences in resting blood pressure, heart rate and pulmonary ventilation, but they showed a significant (p&lt;0.05) increase in the breath‐to‐breath interval variability (40.8 ± 2.8 vs. 25.6 ± 2.3 ms; ABD vs. Control, respectively) and in the incidence of apneas/hypoapneas (AHI: 5.83 ± 0.40 vs. 2.50 ± 0.37 events/h; ABD vs. Control, respectively). Intraventricular cardiac function analysis using PV‐loops revealed a reduction in left ventricular compliance in ABD animals, evidenced by the augmented slope of the end diastolic pressure‐volume relationship (EDPVR: 0.0303 ± 0.006 vs. 0.009 ± 0.001 mmHg/µL; ABD vs. Control). Also, we found that ABD induced cardiac autonomic imbalance estimated by low/high frequency ratio of heart rate variability (LFHRV/HFHRV: 1.59 ± 0.23 vs. 1.01 ± 0.08) and increased arrhythmia incidence (53.6 ± 12.7 vs. 21.7 ± 5.7 events/h; ABD vs. Control). Our results shows that binge drinking in adolescence causes long‐lasting cardiorespiratory dysfunction that includes at least cardiac diastolic dysfunction, autonomic imbalance, and generation of irregular breathing all of them persisting until the adulthood.1Laboratory of Cardiorespiratory Control, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile. 2Biomedical Department, Facultad of Health Science, Universidad de Antofagasta. 3Centro de Excelencia de Biomedicina en Magallanes (CEBIMA), Universidad de Magallanes, Punta Arenas, Chile. 4Centro de Envejecimiento y Regeneración CARE‐UC, Pontificia Universidad Católica de Chile, Santiago, Chile.

Investigation of the use of a sensor bracelet for the presymptomatic detection of changes in physiological parameters related to COVID-19: an interim analysis of a prospective cohort study (COVI-GAPP)

ObjectivesWe investigated machinelearningbased identification of presymptomatic COVID-19 and detection of infection-related changes in physiology using a wearable device.DesignInterim analysis of a prospective cohort study.Setting, participants and interventionsParticipants from a national...

Psychophysiological impact of spinal cord injury: Depression, coping and heart rate variability

Objectives: The aim was to examine the association of post-injury heart rate variability (HRV), coping with injury (fighting-acceptance), and depression symptoms in individuals with spinal cord injury (SCI). Study Design: Cross-sectional study. Setting: Tertiary care spinal cord injury hospital. Participants: Ninety-one individuals with SCI. Methods: All participants were assessed for HRV using polar heart rate monitor RS 800 CX and completed the Patient Health Questionnaire and Spinal Cord Lesion Coping Strategy questionnaire. Participants were grouped based on level of injury (tetraplegic, high paraplegia, and low paraplegia) and injury duration (early vs. late). Odds ratio calculated the risk of depression using HRV and coping as factors for early and late duration groups. Spearman rho estimated the correlation between three ratios: HRV (LF vs. HF), depression (somatic vs. cognitive), and coping (fighting spirit vs. acceptance) for each level of injury group for early and late duration. Results: Individuals with SCI with high HRV had lower odds of depression (OR = 0.14, CI = 0.03–0.78) than individuals with SCI with low HRV in the early duration group. Individuals with SCI with high acceptance had lower odds of depression (OR = 0.19, CI = 0.44–0.79) than individuals with SCI with low acceptance in the later duration group. In the later duration, HRV ratio negatively correlated with coping ratio in individuals with low paraplegia and depression ratio in individuals with high paraplegia. Conclusion: The aftermath of spinal cord injury might reflect a close association between the physiological response of autonomic variability and psychological response of coping and depression with implications for the level of injury and post-injury duration.

The differences between daytime and nighttime heart rate variability may usefully predict the apnea-hypopnea index in patients with obstructive sleep apnea.

The association between daytime/nighttime heart rate variability (HRV) and the apnea-hypopnea index (AHI) remains unclear. We sought a relationship between AHI and the daytime-to-nighttime HRV ratio as measured by 24-hour Holter monitoring in patients with obstructive sleep apnea. We prospectively enrolled 66 patients who visited our sleep clinic complaining of habitual snoring or sleep apnea. All underwent 24-hour Holter monitoring (to measure HRV) combined with full-night polysomnography. Sixty-two met our enrollment criteria. We evaluated the associations between HRV frequency domains and the polysomnography indices. We also considered medical histories and anthropometric data. The nighttime very-low-frequency (VLF), low-frequency (LF), and high-frequency HRVs were significantly higher than the daytime values. On correlation analysis, the day/night VLF (r = .550, P < .001), LF (r = .556, P < .001), and high-frequency (r = .303, P = .017) HRVs were significantly related to the AHI. Of the day/night HRV ratios, the VLF (P for trend = .003) and LF (P for trend = .013) ratios decreased significantly by obstructive sleep apnea severity. Multivariable analysis showed that the day/night VLF (β = 16.387, P < .001) and day/night LF (β = 25.248, P < .001) were independently (and significantly) associated with the AHI. Twenty-four-hour Holter monitoring may usefully predict AHI. The day/night VLF and day/night LF ratios tended to decrease by obstructive sleep apnea severity and were independently associated with the AHI. Nam E-C, Chun KJ, Won JY, Kim J-W, Lee WH. The differences between daytime and nighttime heart rate variability may usefully predict the apnea-hypopnea index in patients with obstructive sleep apnea. J Clin Sleep Med. 2022;18(6):1557-1563.

Relationship between untreated obstructive sleep apnea and breath hydrogen and methane after glucose load.

Patients with sleep disturbances have gastrointestinal symptoms. Breath hydrogen (H2) and methane (CH4) indicating small intestinal bacterial overgrowth (SIBO) might be related with these symptoms. The study was conducted to assess the link between breath profiles and untreated obstructive sleep apnea (OSA). : This prospective study enrolled consecutive patients with OSA using polysomnography. Heart rate variability (HRV) was used as a measurement for the balance of autonomic nervous system during polysomnography. Glucose breath test (GBT) to evaluate breath H2 and CH4 and bowel symptom questionnaire to investigate associated intestinal symptoms were performed. Among 52 patients with OSA, 16 (30.8%) showed positivity to GBT. Although no significant difference was shown in GBT positivity between patients with healthy controls and patients with OSA (13.3% vs 30.8%, P = 0.109), breath H2 and CH4 levels in the OSA group were significantly higher than those in controls (P < 0.05). Flatulence was significantly common in OSA groups with GBT positivity than those without GBT positivity. Multivariate analysis demonstrated that waist-to-hip ratio (odds ratio = 12.889; 95% confidence interval (CI): 1.257-132.200; P = 0.031) and low-to-high-frequency ratio of HRV (odds ratio = 1.476; 95% CI: 1.013-2.151, P = 0.042) are independently related to GBT positivity in patients with OSA. : Elevated breath H2 or CH4 after glucose load might not be an uncommon finding in patients with untreated OSA. Abdominal obesity and autonomic imbalance dysfunction are significantly associated with GBT positivity in OSA patients. SIBO could be considered as target for therapeutic management in OSA patients.