Spectral Components Of Heart Rate Variability Research Articles

Effects of green tea and roasted green tea on human responses

Our objective was to elucidate the effects of tea consumption on refreshment and stress reduction/recovery through examining the multiple associations among factors such as various physiological responses and task performance. Participants included 20 healthy young men who performed a mental arithmetic task while 11 physiological responses were measured. The experiments were conducted twice under different beverage consumption conditions on separate days. The mental arithmetic task was executed six times in 1 day; participants ingested hot water, green tea, or roasted green tea (hojicha) before each task. Several subjective assessments: subjective fatigue, stress, mental workload, and flow were evaluated after each task. The R–R intervals, heart rate variability spectral components, the Poincaré plot indices (SD1 and SD2) and plethysmogram amplitude tended to decrease during task periods compared to resting periods. Tissue blood volume/flow (TBV, TBF) and near-infrared spectroscopy responses (NIRS) were lower in the tea condition than in the hot water condition. By scrutinizing various indicators, we found that aromatic stimulation of Japanese tea beverages has the potential to induce positive effects, enhance mental task performance, promote refreshment, and alleviate feelings of fatigue. These positive effects were observed even in small quantities and within a short duration, mirroring responses observed in daily consumption.

Exploration of the physiological response to an online gambling task by frequency domain analysis of the electrodermal activity.

Online gambling has dramatically increased over the last decades, thus the study of the underlying physiological mechanisms could be helpful to better understand related disorders. Specifically, physiological arousal is well-known to play a key role in gambling behavior. In the present study, unconventional frequency feature of the electrodermal activity (EDA) was extracted (EDASympn) and compared to the most common heart rate variability (HRV) spectral parameters (LF, HF, HFn, LF/HF) to measure arousal during an online gambling session. 46 subjects played online slot machines for 30 minutes, while EDA and ECG were recorded. In the analysis the gaming session was divided into three 10-minutes-long phases. A one-way repeated measures analysis of variance was carried out for each spectral parameter, with the game phases as within-subjects factor. All the calculated parameters showed significant differences between the initial phase of the game and the last two (p < 0.001). In particular, EDAsympn displayed a reciprocal trend with respect to HFn: an initial increase (decrease for HFn) was followed by a plateau phase. LF exhibited a significant difference also between the second and the third phases. EDA frequency-domain analysis appears to be a promising method for physiological arousal assessment, by showing the same discriminative power of HRV spectral components. Further research is needed to emphasize these findings.Clinical Relevance-This promotes the use of a new and easy-to-implement method to assess sympathetic activity.

Usefulness of cardiac parasympathetic index in CPAP-treated patients with obstructive sleep apnea: A preliminary study.

Cardiac autonomic indexes, including cardiac parasympathetic index and cardiac sympathetic index, have been reported to accurately identify patients with sleep disorders such as obstructive sleep apnea. Our study aimed to assess cardiac autonomic indexes in patients with obstructive sleep apnea before and during a single full-night continuous positive airway pressure therapy using a combined approach. Our simultaneous heart rate variability-polysomnographic study included 16 never-treated obstructive sleep apnea patients. Two patients dropped out. Patients underwent combined recordings in two consecutive days, at baseline and during a single full-night of acute continuous positive airway pressure treatment. We calculated cardiac parasympathetic index and cardiac sympathetic index as night/day ratio for high-frequency and low-frequency heart rate variability spectral components, respectively. Continuous positive airway pressure treatment significantly reduced cardiac autonomic indexes values in comparison with baseline values (cardiac parasympathetic index: p<.0001; cardiac sympathetic index: p=.001). After acute continuous positive airway pressure treatment, the percentage of decrease of cardiac parasympathetic index was greater than that of cardiac sympathetic index (51.02±15.72 versus 34.64±26.93). A positive statistical correlation was also found between decrease of cardiac parasympathetic index and decrease of apnea-hypopnea index after continuous positive airway pressure (p<.001). This study improves the knowledge on cardiac autonomic modulation during acute continuous positive airway pressure therapy in obstructive sleep apnea. Our results demonstrate that both autonomic indexes decreased significantly after a single-night of acute continuous positive airway pressure therapy. Cardiac parasympathetic index more than cardiac sympathetic index was related to decrease of apnea-hypopnea index after continuous positive airway pressure therapy, thus representing a potential help in everyday clinical practice.

Oxytocin’s role on the cardiorespiratory activity of endotoxemic rats

BackgroundRecent findings concerning oxytocin indicate its anti-inflammatory, cardioprotective and parasympathetic modulating properties. In this study, we investigated the effects of systemically applied oxytocin on the cardiorespiratory activity in a rodent model of moderate endotoxemia. MethodsTelemetrically recorded electrocardiogram (ECGs) from animals which received lipopolysaccharide (LPS); oxytocin (Ox); lipopolysaccharide+oxytocin (LPS+Ox), or vehicle (V) were analyzed using the ECG-derived respiration (EDR) technique to estimate the respiratory rate. The mean R–R interval and the spectral parameters of heart rate variability (HRV), such as the natural logarithm of the high frequency (lnHF) and low frequency (lnLF) components were also estimated up to 24h after treatment. ResultsThe endotoxemic animals (LPS) showed an elevated respiratory rate as well as a reduced mean R–R interval, lnHF and lnLF components compared to controls (V) from +5 to +12h after the treatment. The administration of oxytocin significantly attenuated the hyperventilation produced by the LPS-induced endotoxemia (LPS+Ox) and restored the values of the mean R–R interval and such spectral parameters at different time points. ConclusionsOur results support the existence of a link among the respiratory, cardiovascular, and immune systems in which oxytocin seems to act as a potential cardioprotective peptide by favoring cardiac cholinergic autonomic coupling. As a result, oxytocin diminished animal’s endotoxemic tachypnea and restored the cardiorespiratory interactions, which was indicated by the spectral components of HRV.

Gender comparison of cardiac autonomic functions as measured by heart rate variability in a tertiary care hospital

Introduction: Heart rate variability (HRV) has been proposed as an indicator of cardiovascular health. Compared to their male counterparts, women are at less risk of coronary heart disease, and of serious arrhythmias, with women lagging behind men in the incidenceof sudden death by 20 years since women have a lower cardiovascular risk, a hypothesis was generated that there exist gender differences in autonomic modulation. Methods: We studied 100 subjects (50 males and 50 females). Anthropometric parameters like age; height; weight and BMI were measured. The baseline characteristics like resting heart rate; systolic blood pressure and diastolic blood pressure were recorded at supine rest for 5 minutes. Using HRV software, recording and analysis of HRV parameters like Total power; Low frequency; Low frequency normalized units; High frequency; High frequency normalized units and Low frequency / High frequency ratio were done. Results: Frequency domain measures of HRV were compared in age-matched populations of 50 males and 50 females. The mean and standard deviation of the low-frequency spectral components of HRV analyzed as absolute units as well as normalised units were high in males as compared to females (p

Effects of moderate-intensity aerobic cycling and swim exercise on post-exertional blood pressure in healthy young untrained and triathlon-trained men and women

Aerobic exercises such as running, walking and cycling are known to elicit a PEH (post-exercise hypotensive) response in both trained and UT (untrained) subjects. However, it is not known whether swim exercise produces a similar effect in normotensive individuals. The complex acute physiological responses to water immersion suggest swimming may affect BP (blood pressure) differently than other forms of aerobic exercises. We tested the hypothesis that an acute bout of swimming would fail to elicit a PEH BP response compared with an equivalent bout of stationary cycling, regardless of training state. We studied 11 UT and ten triathlon-trained young healthy normotensive [SBP/DBP (systolic BP/diastolic BP) <120/80 mmHg)] men and women (age 23±1 years) who underwent 30 min of intensity-matched cycling and swimming sessions to assess changes in BP during a 75-min seated recovery. CO (cardiac output), SV (stroke volume), TPR (total peripheral resistance), HR (heart rate), HRV (HR variability) and core and skin temperature were also assessed. In UT subjects, PEH was similar between cycling (-3.1±1 mmHg) and swimming (-5.8±1 mmHg), with the greater magnitude of PEH following swimming, reflecting a significant fall in SV between modalities (P<0.05). Trained individuals did not exhibit a PEH response following swimming (0.3±1 mmHg), yet had a significant fall in SBP at 50 min post-cycling exercise (-3.7±1 mmHg) (P<0.05). The absence of PEH after swimming in the trained group may reflect a higher cardiac sympathetic outflow [as indicated by the LF (low-frequency) spectral component of HRV) (25 and 50 min) (P<0.05)] and a slower return of vagal tone, consistent with a significant increase in HR between modalities at all time points (P<0.05). These results suggest that training may limit the potential for an effective post-exertional hypotensive response to aerobic swimming.

P-1352 - Improvement of the link between cardiac vagal influence and delta sleep in sahs by long-term nCPAP treatment

Introduction Numerous cardiovascular events are related to sleep apnea-hypopnea syndrome (SAHS). Several studies reported, in SAHS patients, increased cardiac sympathic influence and altered link between cardiac vagal activity and delta sleep EEG. Nevertheless, short-term nasal CPAP (nCPAP) treatment regulates cardiac sympatho-vagal balance and sleep architecture. Objectives We tested that long-term nCPAP treatment improves the link between cardiac vagal influence and delta sleep EEG across the night. Aims Long-term nCPAP treatment could improve the link between heart rate variability (HRV) and sleep to prevent occurrence of cardiovascular events. Methods Cardiac activity and sleep of 8 middle-aged men suffering from SAHS were recorded before and after at least 6 months of nCPAP treatment. They were matched for sex, age, caffeine, nicotine and alcohol consumption with 14 healthy men. All subjects were free of somatic and psychiatric disorders as well as medication. Sleep architecture, spectral components of HRV and delta power band were calculated across the first three NREM-REM cycles as well as a coherence analysis between cardiac vagal influence and delta sleep EEG. Results AHI was 63.5 ± 22.9 vs 5.5 ± 4.4 events/hour after 47 ± 34 months of nCPAP treatment (mean± standard deviation). Awake, NREM and REM sleep durations were similar between groups as well as spectral HRV components. Coherence analysis revealed decreased gain value for untreated patients in comparison to controls while difference disappeared with nCPAP treatment. Conclusions Long-term nCPAP treatment improves the link between cardiac vagal influence and delta sleep even in the absence of altered HRV.

P-1353 - ADHD does not affect cardiac vagal activity during sleep

Introduction Several studies reported increased cardiac sympathic activity in ADHD patients and increased mortality with treatment. In contrast, others did not find differences for heart rate variability (HRV) in comparison to healthy controls. Sleep disorders were often associated to ADHD. Objectives We tested whether HRV components and the link between cardiac vagal activity and delta sleep EEG were altered in patients suffering from ADHD but without sleep disorders. Aims ADHD without sleep disorders did not affect cardiac vagal activity. Methods 10 men, diagnosed ADHD by a psychiatrist and using Conners and Wender-Utah rating scales, were matched for age and BMI with healthy men. All subjects were medication-free and did not suffer from somatic or psychiatric conditions. Sleep was recorded across three successive nights. ECG and EEG of the three first NREM-REM cycles were computed to obtain spectral components of HRV and sleep delta power. Coherence analysis was applied to measure the link between cardiac vagal activity and delta. Results Patients demonstrated lower sleep efficiency and larger REM duration. During the first 3 cycles, NREM, REM and awake durations were similar between groups. RR-Intervals decreased from NREM to REM and awake for controls and from NREM to awake for patients. The spectral cardiac vagal components of HRV were similar between groups and decreased from NREM to REM and awake. ADHD patients did not demonstrate differences for coherence analysis in comparison to controls. Conclusions Patients suffering from ADHD without sleep disorder did not show altered cardiac sympatho-vagal influence across the night.

Heart rate variability may identify patients who will develop severe bradycardia during spinal anaesthesia

The reported incidence of cardiac arrest during spinal anaesthesia is 6.4+1.2 per 10,000 patients. Many of these arrests occurred in healthy young patients during minor surgery. This raises the question of whether some of them were avoidable. We investigated the value of Heart Rate Variability (HRV) to identify patients prone to developing severe bradycardia during spinal anaesthesia. Eighty ASA I-II patients, 21-60 years of age, undergoing elective surgery under spinal anaesthesia were studied. The HRV was assessed for 25 min before the spinal block. Two spectral components of HRV were calculated: a low-frequency (LF) and a high-frequency (HF) component. Patients were grouped according to whether bradycardia did or did not develop during spinal anaesthesia. Nineteen patients developed severe bradycardia (<45 b.p.m.). The mean value of HF before spinal anaesthesia was significantly increased in the bradycardic group (P<0.05). The correlation between baseline heart rate (HR(baseline)) and minimum heart rate and LF, HF during spinal anaesthesia was significant (P<0.01). A receiver operator curve characteristic analysis showed a sensitivity and specificity of HF and HR(baseline) of 65% and 74%, respectively, to predict bradycardia <45 b.p.m. after spinal anaesthesia. The present study shows that HF and clinical factors such as patient's HR(baseline) could identify patients prone to developing severe bradycardia during spinal anaesthesia.

Water temperature affects heart rate and core body temperature during whole body immersion

Background Whole body immersion (WI) is one of the oldest therapeutic concepts of medicine and still constitutes a significant role in the area of CAM as well as in rehabilitation facilities. Medical baths have strong effects on the cardiovascular regulation and the autonomic nervous system, mainly mediated by buoyancy, hydrostatic pressure and water temperature. However, scientific literature with respect to this medical practice is limited. In particular, little is known about the effects of different water temperatures on heart rate, heart rate variability (HRV) and body core temperature. Hence, we investigated the effects of WI with water temperatures of 33 and 36 °C (indifferent temperature) and 39 °C on heart rate, HRV and core body temperature before, during and after bathing. Methods In total 21 healthy subjects (average age: 24.3±2.3 years, 11 female, 10 male) underwent WI with water temperatures of 33 °C (WI33), 36 °C (WI36), 39 °C (WI39). “Dry-bath”(DB; bathtub without water to assure same body position as during WI) was used as a control. The procedure consisted of three successive intervals: 30 min resting in a supine position, 20 min WI and 30 min rest in the supine position. The recording of an electrocardiogram was started after 20 min of rest before WI. It was continued throughout the rest of the procedure. In addition, core body temperature was recorded using a rectal sensor. Here, we report on the effects with respect to the last 60 s at the end of each interval. Results During WI33, WI36 and DB the average heart rate was not affected (70.2, 74.2, and 67.2 beats/min) compared to baseline before WI. Correspondingly, the standard deviation of normal-to-normal heartbeats (SDNN) did not change (68, 63, 62 ms). Furthermore, the core body temperature was not affected (36.9, 37.0, 37.0 °C). However, during WI39 the heart rate increased to 97 beats/min and SDNN decreased to 24 ms. At the same time the core body temperature increased to 37.5 °C. During rest after WI39 the core body temperature stayed at 37.5 °C, but the heart rate decreased to 73.9 beats/min and SDNN increased to 60 ms. Conclusion WI with a water temperature of 39 °C increased heart rate and core body temperature and decreased HRV. Hence, WI at this temperature induces moderate cardiovascular stress and moderate hyperthermia. Spectral components of HRV and more specific analysis of temperature regulation may reveal more subtle changes during WI at different water temperatures.

Influence of the menstrual cycle on nonlinear properties of heart rate variability in young women

This study was designed to assess the changes in nonlinear properties of heart rate (HR) variability (HRV) during the menstrual cycle by means of complexity measures, including sample entropy (SampEn) and correlation dimension (CD), and explore probable physiological interpretations for them. In 16 healthy women (mean age: 23.8 +/- 2.7 yr), complexity measures along with the spectral components of HRV (sympathovagal markers) were analyzed over 1,500 R-R intervals recorded during both the follicular phase (day 11.9 +/- 1.4) and the luteal phase (day 22.0 +/- 1.4) of each woman's menstrual cycle. Simultaneously, serum ovarian hormone (estradiol-17 and progesterone) and thyroid-related hormone [free triiodothyronine, free thyroxine (T(4)), and thyroid-stimulating hormone] concentrations were measured. With regard to HRV measures, SampEn, CD, and high-frequency (HF) components decreased from the follicular phase to the luteal phase, whereas normalized low-frequency (LF) components and the LF-to-HF ratio as well as resting HR increased. In regard to hormone levels, whereas progesterone was increased, the other hormone concentrations were unchanged. Furthermore, across the menstrual cycle, both SampEn and CD were well correlated with the spectral indexes and free T(4) concentrations, and SampEn also showed significant correlations with the ratio of estradiol-17 to progesterone concentrations. These results suggest that the nonlinear properties in HRV are altered during the regular menstrual cycle and that the autonomic nervous system, ovarian hormone balance, and free T(4) may be involved in nonlinear HR control in healthy women. All of these factors may enrich the physiological meanings of complexity measures.

Metabolic syndrome and short‐term heart rate variability in young adults

Heart rate variability (HRV) can be used to estimate autonomic nervous control of the cardiovascular system. In middle-aged subjects, the metabolic syndrome (MetS) is associated with lower HRV. We hypothesized that alterations in autonomic balance are already present in young adults with the MetS, and analysed the association of short-term HRV with the MetS (using the National Cholesterol Education Program definition), in 1889 subjects aged 24-39 years. Short-term (3 min) HRV analysis included high-frequency (HF), low-frequency (LF) and total (TP) spectral components of HRV and LF/HF ratio. The presence of the MetS was associated with lower HF, LF and TP in men and women, and with higher LF/HF ratio in women. In men, waist circumference was the strongest individual MetS component that associated with HRV. After adjustments for age and heart rate, MetS was associated with lower HF and higher LF/HF ratio in women, but only with a lower TP in men (all P < 0.05). MetS is associated with lower HRV in young adults. The individual components of MetS are differentially associated with HRV in men and in women. Our results are consistent with lower vagal activity and a possible increase in sympathetic predominance in women with the MetS. This sex difference in vagal activity and sympathovagal balance may partly explain the greater increase in cardiovascular risk associated with MetS in women than in men.

Discordance between microneurographic and heart-rate spectral indices of sympathetic activity in pulmonary arterial hypertension

Objectives:To determine, in patients with pulmonary arterial hypertension (PAH), whether there is a relationship: (1) between sympathetic nerve firing rate and spectral indices of sympathetic neural heart rate modulation; and...

Does Paced Breathing Improve the Reproducibility of Heart Rate Variability Measurements?

The effects of paced breathing (PB) on the reproducibility of heart rate variability (HRV) measurements were examined in 55 male subjects (age range: 20-54 years). Spectral components of HRV were measured under a combination of two respiratory conditions (spontaneous and 4s PB) and two postures (standing and supine). The procedures were repeated 3 weeks after the first measurement. Log-transformed low-frequency (lnLF) and high-frequency (lnHF) components of HRV were calculated from a 205s electrocardiography (ECG) recording. The coefficients of interindividual variations of lnHF and lnLF (ca. 13-16%) and the intraindividual variations of the frequency components (5-6%) were not significantly affected by PB. The coefficients of intraindividual variation of heart rate, ln HF and ln LF did not correlate with age in either posture. Effect sizes of PB on the intraindividual variation ranged from -0.04 to 0.13. Although intraclass correlation coefficients (ICCs) were slightly improved by PB in some cases, the differences were negligible. The above results suggest that PB provides a limited improvement in the reproducibility of HRV measurements, and metronome-guided respiration is not necessarily required for HRV measurement if subjects are reminded to avoid irregular respiration.

Autonomic control of the respiratory-hemodynamic system in 8-to 11-year-old children with different baroreflex sensitivities

The efficiency of baroreflex control depends on the baroreflex sensitivity (BRS), which is defined as the ratio of the change in the heart rate (HR) to the change in the blood pressure (BP). The BRS value may be used for assessing the autonomic control of the cardiovascular system and the degree of autonomic dysfunction. Until recently, the baroreflex had not been assessed in a large population of healthy subjects. In this study, the BRS was estimated by the ratio of the low-frequency component of the HR spectrum and the low-frequency component of the rhythm of the systolic BP. For assessing the arterial baroreflex in children, the BRSs for spontaneous and induced baroreflexes were compared. Sex-and age-related differences in BRS were found in 8-to-11-year-old children, and correlations between BRS and some spectral components of HR variability (HRV) and BP rhythm variability were determined. Cluster analysis of the BRS calculated for the spontaneous baroreflex at rest was used to distinguish three clusters of subjects (with high, medium, and low BRSs). These clusters differed in the variability of the basic parameter and size and showed sex-related differences.

Hypnotizability-dependent modulation of the changes in heart rate control induced by upright stance

Subjects with high (Highs) and low (Lows) susceptibility to hypnosis show differences in the sensory–motor integration for postural control and in the cardiovascular response to stress and experimental pain. Aim of the experiment was to assess whether the cardiac response to gravity-related stimulation depending on changes in the body position were different in the two groups. Thus, heart rate (HR) and heart rate variability (HRV) were evaluated in sitting and upright position in Highs and Lows. Position-related HRV changes were studied in the time (statistical indexes, Poincaré Plot) and frequency (spectral analysis) domain. Results indicated that upright stance was associated with similar changes in heart rate and different modulation of HRV in the two groups. The association of time and frequency domain analyses allowed hypothesizing different control mechanisms as responsible for the cardiac response to upright stance in Highs and Lows, likely due to a different role of the Very Low Frequency (VLF) spectral component of HRV in the two groups. The results are in line with previous findings indicating a natural protection of Highs against cardiovascular events and suggest that the Highs’ cardiac function might be less impaired by microgravity than the Lows’ one.

Cardiac Autonomic Control in Patients with Refractory Epilepsy before and during Vagus Nerve Stimulation Treatment: A One‐Year Follow‐up Study

To elucidate possible effect of vagus nerve stimulation (VNS) therapy on interictal heart rate (HR) variability in patients with refractory epilepsy before and after 1-year VNS treatment. A 24-hour electrocardiogram (ECG) was recorded at the baseline and after 12 months of VNS treatment in 14 patients with refractory epilepsy, and once in 28 healthy age- and sex-matched control subjects. Time and frequency domain measures, along with fractal and complexity measures of HR variability, were analyzed from the ECG recordings. The mean value of the RR interval (p=0.008), standard deviation of N-N intervals (SDNN) (p<0.001), very-low frequency (VLF) (p<0.001), low-frequency (LF) (p=0.001), and high-frequency (HF) (p=0.002) spectral components of HR variability, and the Poincaré components SD(1) (p=0.005) and SD(2) (p<0.001) of the patients with refractory epilepsy were significantly lower than those of the control subjects before VNS implantation. The nocturnal increase in HR variability usually seen in the normal population was absent in patients with refractory epilepsy. VNS had no significant effects on any of the HR-variability indexes despite a significant reduction in the frequency of seizures. HR variability was reduced, and the nocturnal increase in HR variability was not present in patients with refractory epilepsy. One-year treatment with VNS did not have a marked effect on HR variability, suggesting that impaired cardiovascular autonomic regulation is associated with the epileptic process itself rather than with recurrent seizures.

Effects of local arteriosclerosis on carotid baroreflex sensitivity and on heart rate and arterial pressure variability in humans

The study examined whether the alterations in heart rate variability (HRV) and baroreflex sensitivity (BRS) observed in patients with coronary artery disease can also be discerned in otherwise healthy subjects with mild-to-moderate arteriosclerosis in the carotid artery bifurcation. Based on the results of carotid duplex ultrasonography, subjects were designated as either having no arteriosclerotic lesions (n = 18), unilateral (n = 19) or bilateral lesions (n = 18) in the bifurcation. Electrocardiograms were recorded and simultaneous and continuous records of arterial pressure were obtained. Resting HRV was determined by calculating the spectral power density in three frequency bands: 0-0.05 Hz [very low frequency (VLF) band], 0.05-0.15 [low frequency (LF) band] and 0.15-2 Hz (high frequency band), whereas the arterial pressure variability (APV) was determined from spectral power density of the VLF and LF bands. Carotid BRS was evaluated by measuring R-R intervals during application of pulse-synchronous graded pressures (40 to -65 mmHg) in a neck-chamber device. Analysis of variance revealed no effect of mild-to-moderate carotid arteriosclerosis on the spectral components of HRV and APV or on BRS. It thus appears that mild-to-moderate asymptomatic carotid arteriosclerosis does not affect carotid BRS, APV or HRV at rest.

Effects of Extreme Endurance Running on Cardiac Autonomic Nervous Modulation in Healthy Trained Subjects

This study examined spectral components of heart rate variability (HRV) during endurance mountain running in 8 healthy trained subjects. The data showed that during this type of mountain running, all spectral components of HRV may severely decrease, particularly very-low-frequency and low-frequency (LF) power, suggesting extreme activation of the sympathetic nervous system. The physiologic response of the heart in this situation was the downregulation of the beta-adrenergic receptors to protect myocardial function, with a subsequent increase in parasympathetic tone, reflected by an increase in high-frequency (HF) power and a decrease in the LF/HF ratio.

Assessment of Heart Autonomic Control on the Basis of Spectral Analysis of Heart Rate Variability

An orthostatic test with frequency-controlled breathing (with a respiration period of 10 s) or spontaneous breathing was used to analyze frequency estimates of the heart rate variability (HRV) in the low-frequency (LF) and high-frequency (HF) ranges in young men and women. It was demonstrated that the spectral components of HRV bear no signs of sex differentiation, suggesting a uniform structural organization of the system of autonomic nervous control of the heart (SANCH) in humans. The LF component of the HRV spectrum is a marker of the functional state of the SANCH; it should be studied under conditions of controlled breathing at a frequency of 0.1 Hz. The HF and LF components of the HRV characterize the state of the SANCH at a given moment and do not reflect directly its adaptation reserve. The HF component of the HRV is interesting as a parameter that may be used for estimating the changes in the adaptation reserve of heart autonomic control. It is preferable to analyze this component in the absence of external disturbances in the LF range of the spectrum.