High Frequency Power Research Articles

Adherence to exercise after an acute coronary syndrome: a 6-month randomized controlled trial.

Introduction: Exercise training with well-known health benefits is a key element in the self-management of coronary artery disease (CAD). Although current guidelines for patients with CAD recommend daily exercise training, most of the patients do not follow the guidelines. We tested the hypothesis that an exercise training program guided by a novel technology used at home will improve adherence to exercise training. Methods: One to three weeks after percutaneous coronary intervention (PCI), acute coronary syndrome patients (n = 50) were randomized into traditional (age 65 ± 8years) and novel technology-guided (age 60 ± 8years) exercise rehabilitation groups. The novel technology included a tablet computer with a virtual autonomous physiotherapy agent (VAPA group) for every patient at home; it was used to guide exercise training time, volume, and intensity. Traditional rehabilitation was performed by exercise training prescriptions, phone calls, and diaries (control group). The duration of the rehabilitation program was 6months for both groups. Exercise capacity and 24-h heart rate variability were measured at baseline and at the end of the program. Adherence to exercise was measured over 6months as the percentage of realized training. Results: None of the patients dropped out from the VAPA group, while three patients dropped out from the control group. Adherence to exercise was higher in the VAPA group than in the control group for resistance training (141% ± 56% vs. 50% ± 20%, p < 0.0001), and there were no differences between the groups for aerobic training (144% ± 45% vs. 119% ± 65%, p = 0.22). Exercise capacity increased in both the groups (time p < 0.001, time × group interaction p = ns). High-frequency power of R-R intervals (lnHF) increased in the VAPA group but remained unchanged in the control group (natural logarithm of lnHF power from 5.5 ± 0.7 to 5.8 ± 0.9ms2 and from 5.3 ± 0.8 to 5.2 ± 0.7ms2, respectively, time × group interaction p = 0.014). Conclusion: Compared with the use of traditional methods, the use of novel technology at home results in better adherence to exercise, particularly in resistance training, in acute coronary syndrome patients. Second, the VAPA group showed improved cardiac vagal regulation, documented by increased vagally mediated R-R interval fluctuation, compared with the traditional training group (ClinicalTrials.gov identifier: NCT03704025).

Design a High Frequency Power Inverter Using Ferrite-Core Transformer for Ohmic Heating of Liquid Conducting System

Design a High Frequency Power Inverter Using Ferrite-Core Transformer for Ohmic Heating of Liquid Conducting System

The effects of anesthetic drug choice on heart rate variability and echocardiography parameters in cats

Heart rate variability (HRV) is one of the assessments of cardiovascular risk during general anesthesia. This study aimed to assess the effects of an anesthetic drug on HRV in cats and to provide information for clinical applications. Twenty-four healthy client-owned cats of various breeds, 12 females and 12 males scheduled for elective surgery, were enrolled in this study. The cats were premedicated and induced with 4 protocols: protocol 1, diazepam (0.3 mg/kg) and propofol (2–4 mg/kg) IV; protocol 2, diazepam (0.3 mg/kg) and alfaxalone (1–3 mg/kg) IV; protocol 3, diazepam (0.3 mg/kg) and ketamine (3–5 mg/kg) IV; and protocol 4, xylazine (1 mg/kg) and tiletamine/zolazepam (Zoletil) (5 mg/kg) IM. The heart rate and HRV of the 24 cats were collected before and at least 1 h after administering the anesthetic drugs. Echocardiography was performed to evaluate heart function. Oscillometric blood pressure monitoring was used to obtain the mean blood pressure. After anesthetic drug administration, higher heart rates were found in cats premedicated and induced with alfaxalone (p = 0.045) than in the other protocols. The lowest heart rate (HR) values were found in cats in protocol 4 using xylazine and Zoletil. The HRV low frequency (LF) and high frequency (HF) power ratios increased in all protocols except for cats premedicated and intubated with propofol. The standard deviation of the regular sinus beats (SDNN) was higher in cats premedicated and induced with ketamine than in other anesthetic protocols (p = 0.015). An increase in sympathetic activity and reduced HRV is associated with high blood pressure and left atrial dimension. The percentage of fractional shortening (FS) decreased in cats premedicated with ketamine. The results showed that the anesthesia method using diazepam and propofol caused the least disturbance of HRV compared with other anesthesia methods that were used in this study.

Cerebral Hemodynamics and Vagally Mediated HRV Associated with High- and Low-frequency Yoga Breathing: An Exploratory, Randomized, Crossover Study.

Volitionally modifying respiration leads to changes in middle cerebral arterial (MCA) blood flow. The effect of changes in breath rate on MCA blood flow has not been reported. To determine the effect of slow (bumblebee yoga breathing) and fast (high frequency yoga breathing) yoga breathing techniques on MCA blood flow and vagally mediated heart rate variability. Thirty participants (mean age ± standard deviation, 27.3 ± 4.2 years) were assessed on 2 separate days practicing either high frequency yoga breathing (HFYB, breath frequency 54.2/min) or slow frequency bumblebee yoga breathing (BBYB, breath frequency 3.8/min) in random order to determine the effects of changes in breath frequency on MCA hemodynamics. Assessments included transcranial Doppler sonography, vagally mediated heart rate variability (VmHRV), and respiration. Both HFYB and BBYB (i) reduced MCA flow velocities, i.e., peak systolic, end diastolic, and mean flow velocities, and (ii) increased MCA pulsatility indices. There was an increase in VmHRV during BBYB based on increased power in high frequency (HF) and low frequency (LF). LF reflects VmHRV for slow breath frequencies. In BBYB the average breath rate was 3.8 breaths/min. In contrast, VmHRV decreased during HFYB (based on reduced HF power; repeated measures analysis of variance, P < 0.05, all cases). Hence, irrespective of the differences in breath frequency, both HFYB and BBYB appear to reduce MCA flow velocities and increase the resistance to blood flow bilaterally, although the VmHRV changed in opposite directions. MCA velocity and pulsatility changes are speculated to be associated with low global neural activity during yoga breathing.

Cardiac Autonomic Dysfunction Measured as Reduced Heart Rate Variability, in the Intermediate Post-Covid State in Men

Abstract Background: A critical illness such as severe coronavirus disease 2019 (COVID-19) activates autonomic, endocrine, and emotional stress responses. Whether the manifestations of excessive stress experience persist beyond full recovery into the intermediate post-COVID period (3–6 months after recovery) is not known and was the question we addressed in the current study. Methods: An analytical observational cross-sectional study compared the heart rate variability (HRV), 8 AM serum cortisol concentration, and the Depression, Anxiety, and Stress Scale–21 (DASS-21) scores between COVID-19 recovered participants and their age-matched control subjects (21 male participants, 30–70 years of age, in each group). Results: The median (Q1–Q3) of low frequency (LF), high frequency (HF), and total powers of HRV was significantly reduced in those who recovered from severe COVID-19, compared to control subjects (respectively LF power: 410.871 [245.10–861.94], 947.57 [536.11–1778.55], P = 0.011; HF power: 192.916 [87.66–564.43], 705.18 [248.67–1192.19] P = 0.013; Total power: 646.33 [308.72–1518.28], 1613.33 [956.14–4022.55] P = 0.015, Mann–Whitney U-test). Serum cortisol and DASS-21 scores were not different from the control group. Conclusions: Impaired cardiac autonomic function, evidenced by reduced HRV, was observed in the intermediate period following recovery from severe COVID-19. However, psychological stress and elevated serum cortisol were not noted. Our result that exposes the effect of COVID-19 on cardiac autonomic responsiveness is important as diminished HRV increases the vulnerability of COVID-19 survivors to diseases. These findings may also suggest a focus of therapy in them, as specific interventions are known to improve HRV and cardiac autonomic functioning.

Analysis of Heart Rate Variability in Young Male Adults with Depression and Anxiety during Warm-water Footbath

Abstract Background: Heart rate variability (HRV) modulates both the sympathetic nervous system and the parasympathetic nervous system (PNS) of the autonomic nervous system. Mood disorder is one of the contributing factors to influence HRV. The warm-water footbath as a relaxing way is used to enhance the PNS. In this study, we intended to explore the association between HRV and a footbath in the mood disorder group. Methods: We recruited 14 young male study participants to receive a 30-minute warm-water footbath three times a week. Furthermore, we monitored the heart rates electrocardiographically before, during, and after the intervention. Results: This study showed that the footbath not only significantly enhanced standard deviation of NN (SDNN) intervals, high-frequency (HF) power, and low-frequency (LF) power during the first five minutes footbath (p &lt; 0.01) but also increased all the parameters in five minutes after finishing the footbath. SDNN intervals, HF power, and LF power remained significantly upward in the next five minutes (p &lt; 0.05). Conclusion: In line with previous studies, this study showed that a footbath elevated the PNS-related HRV parameters. We suggest that a warm-water footbath improves the PNS modulation possibly through baroreflex. In addition, those with cardiac conditions and depression should be particularly attentive to their condition during and following a footbath.

Vagal predominance correlates with mood state changes of winter-over expeditioners during prolonged Antarctic residence.

Winter-over expeditioners in Antarctica are challenged by various environmental and psycho-social stress factors, which may induce psychophysiological changes. The autonomic nervous system (ANS) plays a crucial role in the adaptation process under stress. However, the relationship between ANS activity and the mood states of expeditioners remains largely unexplored. This study aims to uncover the pattern of ANS adjustment under extreme Antarctic environments and provide new insights into the correlations between ANS activity and mood state changes, which may provide scientific data for medical interventions. Fourteen expeditioners at Zhongshan Station participated in this study. The study was conducted during four representative periods: pre-Antarctica, Antarctica-1 (pre-winter), Antarctica-2 (winter), and Antarctica-3 (summer). The heart rate variability (HRV) of the expeditioners was continuously measured for 24 hours to evaluate ANS activity. Plasma levels of catecholamines were tested by ELISA. Mood states were assessed by the Profile of Mood States (POMS) scale. HRV analysis showed a disturbance of ANS during winter and summer periods. For frequency domain parameters, very low frequency (VLF), low frequency (LF), high frequency (HF), and total power (TP) significantly increased during the second half of the mission. Especially, LF/HF ratio decreased during summer, indicating the predominance of vagal tone. Results of the time domain analysis showed increased heart rate variability during the austral winter and summer. Plasma epinephrine (E) significantly increased during residence in Antarctica. Compared with pre-Antarctica, the vigor, depression, and anger scores of the expeditioners decreased significantly during the austral summer. Notably, the depression score showed a moderate positive correlation with LF/HF, while weak negative correlations with other HRV indicators, including TP, VLF, and LF. Anger score showed a moderate positive correlation with LF/HF and weak negative correlations with the average normal-to-normal (NN) interval, and the root mean square of differences between adjacent RR intervals (RMSSD). Plasma E level weakly correlated with the average NN interval. Prolonged residence in Antarctica increased the ANS activities and shifted the cardiac autonomic modulation towards vagal predominance. The alteration of HRV correlated with mood states and plasma epinephrine levels.

Multirate Modeling and Predictive Control for WBG-Device-Based High-Switching-Frequency Power Converters

With the growth of wide bandgap devices, it is necessary to exploit the high switching frequency benefits to improve the power converter's performance, thus requiring a higher sampling/interrupt frequency in digital signal processors. However, such a short interrupt time duration imposes big computational difficulty in the execution of programming code, especially using the model predictive control (MPC). Thus, most of the existing MPCs are applied with switching frequencies below 20 kilohertz, which cannot exploit the full potential of the wide bandgap device-based power converters. To solve this challenge, this article proposes a multi-rate MPC scheme, where the trigger of interrupt and switching device transition can be performed at different rates. Compared to conventional MPCs, the main uniqueness of the proposed multi-rate MPC is that the high-dimension control sequence is solved and applied within each interrupt interval. Therefore, the increased switching frequency objective can be easily achieved with a low sampling/interrupt frequency configuration, which also significantly relieves the digital execution of the heavy interrupt tasks. The proposed method shows a more optimized control input and higher computational efficiency over the multi-rate finite-control-set MPC counterpart. A silicon carbide inverter-fed AC motor drive system is used to verify the proposed multi-rate MPC. The results show the improved system performance with the combined advantages of both the high switching frequency and MPC strategy.

Impact of plasma operating conditions on the ion energy and angular distributions in dual-frequency capacitively coupled plasma reactors using CF4 chemistry

A two-dimensional hybrid model is used to simulate an industrial dual-frequency capacitively coupled plasma reactor working at closely spaced frequencies (13.56–40.68 MHz) in pure CF4 chemistry. The goal is to understand how plasma operating conditions (pressure, low-frequency and high-frequency RF powers, and chamber wall conditions) influence critical etching parameters such as the ion energy and angular distribution (IEAD) and the ion flux at the wafer. In base case conditions, the ionic and radical composition at the center of the plasma is analyzed, revealing CF3+ and F− as the primary ions, and F, CF, CF3, CF2, and F2 as the predominant radicals (by decreasing density). The impact of the surface recombination coefficient of F radicals into F2 at the reactor walls, γ(rec,F &amp;gt; F2), is then explored; it is found that increasing γ(rec,F &amp;gt; F2) has a strong impact on the final plasma composition, decreasing CF and F densities while increasing CF3, CF2, and F densities, which highlights the importance of properly considering wall conditions in CF-based plasmas simulation. The IEAD at the wafer is then characterized, showing that the total IEAD shape is affected by the plasma ion composition: heavy ions such as CF3+ (69 amu) form the core of the distribution while lighter species such as F+ (19 amu) form the wing of the distribution due to their lower mass. The low frequency (LF) power (100–900 W) is shown to substantially modify the ion energy distribution function (IEDF) owing to sheath voltage changes, but to also marginally increase the ion flux at the wafer. Conversely, the high-frequency (HF) power (100–1500 W) strongly impacts the ion flux at the wafer due to HF voltage fluctuations, while the IEDF remains mostly unaffected. This study also reveals some coupling between the effects of the LF (13.56 MHz) and HF (40.68 MHz) power, a phenomenon attributable to their proximity in frequency which should not be neglected. Finally, increasing the pressure from 30 to 200 mTorr is found to increase the electronegativity by a factor 4 and to strongly impact the plasma structure, primarily due to variations in ion mobility; it also widens the ion angular spread, potentially influencing etch uniformity. Notably, higher pressures exceeding 100 mTorr result in a decrease in the average ion density and the emergence of a low-energy peak in the ion energy distribution, attributed to charge exchange collisions.

A Monolithic GaN Power Stage with Common-Mode Transient Immunity and Negative Voltage Operation Design for High Frequency Power Converters

A Monolithic GaN Power Stage with Common-Mode Transient Immunity and Negative Voltage Operation Design for High Frequency Power Converters

Effects of different winter paddock management of Thoroughbred weanlings and yearlings in the cold region of Japan on physiological function, endocrine function and growth.

Effects of different winter paddock management of Thoroughbred weanlings and yearlings in Hokkaido, Japan, which is extremely cold in winter, on physiological function, endocrine function and growth were investigated. They were divided into two groups; those kept outdoors for 22 hr in the paddock (22hr group) and those kept outdoors for 7 hr in daytime with walking exercise for 1 hr using the horse-walker (7hr+W group), and the changes in daily distance travelled, body temperature (BT), heart rate (HR), HR variability (HRV), endocrine function and growth parameters were compared between the two groups from November at the year of birth to January at 1 year of age. The 7hr+W group could travel almost the same distance as the 22hr group by using the horse-walker. The 22hr group had a lower rate of increase in body weight than the 7hr+W group in January. In addition, lower in BT and HR were observed, and HRV analysis showed an increase in high frequency power spectral density, indicating that parasympathetic nervous activity was dominant. And also, changes in circulating cortisol and thyroxine were not observed despite cold environment. On the other hand, the 7hr+W group had higher prolactin and insulin like growth factor than the 22hr group in January, and cortisol and thyroxine were also increased. Physiological and endocrinological findings from the present study indicate that the management of the 7hr+W group is effective in promoting growth and maintaining metabolism during the winter season.

Exploring factors associated with heart rate variability in newly injured traumatic cervical spinal cord injury patients

Background: Assessment of heart rate variability (HRV) in traumatic cervical spinal cord injury (SCI) patients is widely reported, but few studies have examined the HRV in the newly injured. Further, there is paucity of data relating HRV to factors that might have a bearing on the extent of variability in them. Aim and Objectives: The current study explored the factors associated with the HRV of newly injured cervical SCI American Spinal Injury Association (ASIA) Impairment Scale (AIS) grade A/B patients. Materials and Methods: A secondary analysis of HRV data acquired from 24 newly injured tetraplegic patients in a previously published study compared the HRV between AIS grade A and B patients, and across cervical levels of lesion. In addition, the correlation of HRV indices with duration since injury and the patients’ age was examined. Results: The ratio of low to high frequency power was significantly lower in AIS B compared to AIS A patients, and significantly negatively correlated with duration since injury. Conclusion: The ratio of modulations of cardiac sympatho-vagal supply was lower in AIS B patients and reduced with increasing duration since injury. AIS grade and duration since injury need to be considered when interpreting the HRV data of newly injured tetraplegic patients.

Experimental Variable Band Hybrid Current Mode Control for High Power High Frequency Inverter in Electro Surgical Applications

Experimental Variable Band Hybrid Current Mode Control for High Power High Frequency Inverter in Electro Surgical Applications

Artificial Intelligence-Enhanced Peak Current Mode Control for Enhanced Power Regulation in High Power High Frequency Electrosurgical Generators

Artificial Intelligence-Enhanced Peak Current Mode Control for Enhanced Power Regulation in High Power High Frequency Electrosurgical Generators

A Spatial Electromagnetic Field Analysis Method for Estimating the Dynamic Positions of Multiple Mobile High-frequency Power Supplies

A Spatial Electromagnetic Field Analysis Method for Estimating the Dynamic Positions of Multiple Mobile High-frequency Power Supplies

(Invited) Characteristics of GaN/High-k Capacitors Under Positive Bias Stress

Vertical GaN-based trench gate metal-oxide-semiconductor field-effect transistors (MOSFETs) have been widely investigated to suppress leakage currents for applications associated with high power and high frequency. Various materials with high dielectric constant (High-k) such as Al2O3, HfO2, AlSiO x , HfSiO x , and HfAlOx have been studied as gate insulator to obtain high gm value of GaN MOSFET [1-6]. The structure of High-k gate insulator and interface between GaN and High-k is well known to affect characteristics of GaN MOS capacitor. An amorphous HfAlOx film could be fabricated by forming (HfO2)/(Al2O3) nanolaminate films via plasma-enhanced atomic layer deposition and post-deposition annealing at 800°C. Al2O3 and HfAlOx gate insulators with an amorphous structure found to exhibit superior fundamental electrical properties including no frequency dispersion, a high breakdown voltage and a low interface state density [3,5,6]. However, reliability characteristics under high voltage sweep and positive bias stress (PBS) conditions are not currently well understood.In this paper, we investigate flatband voltage (Vfb) shift of the Al2O3 and HfAlOx capacitors by varying effective electric field (Eeff) from Vfb under PBS. We also compare Vfb shift behavior among Al2O3, HfAlOx and reported High-k gate insulators.Here, to understand influence of the thermal budget at 800°C on electrical property, two n-GaN/Al2O3(10nm)/Pt MOS capacitors were prepared: One was fabricated by thermal budget at 300°C (AlO). The other was fabricated by the same capacitor fabrication process, with the GaN substrate annealed at 800°C before Al2O3 film deposition (Pre800C-AlO). To examine interface properties of the n-GaN/HfAlOx, n-GaN/interfacial layer (IL)/HfAlOx(10nm)/Pt capacitor with a 0.5nm-thick-Al2O3-IL (AlO/HfAlO) and a 0.5nm-thick-HfO2-IL (HfO/HfAlO) and without IL (HfAlO) were prepared.All High-k gate insulators had an amorphous structure. The k-values of Al2O3 and HfAlOx gate insulators estimated from C-V measurement were 8 and 17.2, respectively [3,6]. All capacitors exhibited the smooth J-Eeff properties due to an amorphous structure regardless of the 800°C pre-annealing of the GaN substrate and IL of HfAlOx case. All capacitors also exhibited no frequency dispersion in the range of 1k-1MHz. However, the Pre800C-AlO capacitor showed a large hump due to the electrical defects in the C-V curve. The Vfb shift behavior of the capacitor was examined by varing Eeff from Vfb of PBS. The Eeff was estimated from the applied voltage divided by capacitanc equivalent thickness. The Eeff from Vfb of Al2O3 and HfAlOx capacitors were varied from 4.1-8.7 and 6.5-15.4MVcm-1, respectively. The stress time was varied from 0 to 300s . The sweep voltage range of C-V measurement for obtaining Vfb in each stress time was always applied smaller than the PBS voltage. The positive Vfb shift was observed in all capacitors after PBS, indicating the presence of some electron trapping sites. The positive Vfb increased siginificantly up to a stress time of 10s, gradually increased up to 200s, and saturated above 200s in all Eeff from Vfb regions. The positive Vfb value of all capacitors reached to around 0.2V when the Eeff from Vfb was applied to 6.5MVcm-1 at 300s. Above 6.5MVcm-1, different Vfb shift profiles were observed for two Al2O3 and three HfAlOx capacitors. The positive Vfb value of the Al2O3 capacitors increased drastically to 0.5V as the Eeff from Vfb increased from 6.5 to 8.7MVcm-1. Furthermore, the Pre800C-AlO capacitor became larger Vfb shift than the AlO capacitor because the Pre800C-AlO capacitor is due to the introduction of some defects on the GaN surface by pre-annealing at 800°C. On the other hand, for the HfAlO, AlO/HfAlO and HfO/HfAlO capacitors, the positive Vfb shift value was suppressed to 0.3V even when the Eeff from Vfb was applied to 15.4 MVcm-1. Furthermore the Vfb shift showed similar behavior regardless of Al2O3- and HfO2-IL. Based on these experimental data, we conclude that the HfAlOx capacitors have a high reliability under PBS condition.This work was supported by the MEXT Program for Creation of Innovative Core Technology for Power Electronics Grant Number JPJ009777. This work was supported in part by JSPS KAKENHI Grant No. JP20H02189.[1] J. T. Asubar et al., J. Appl. Phys. 129, 121102 (2021). [2] Y. Ando et al., Appl. Phys. Lett. 117, 102102 (2020). [3] K. Yuge et al., Semicond. Sci. Technol. 34, 034001 (2019). [4] D. Kikuta et al., Appl. Phys. Express 13, 026504 (2020). [5] T. Nabatame et al., Appl. Phys. Express 12, 011009 (2019). [6] T. Nabatame et al., ECS Trans. 104 113 (2021).

Synchrotron X-Ray Topography Studies for Defect Formation at the Early Stage of PVT-Grown 4H-SiC Crystals

Silicon Carbide (SiC), typically 4H-SiC, is replacing conventional silicon materials for high power and high frequency applications due to its excellent electrical and thermal properties [1]. However, high quality SiC wafers with low defect density are still in urgent need for automotive and energy saving applications. SiC wafers are obtained from bulk growth by physical vapor transport (PVT) method and considerable efforts have been expended to optimize growth process to lower defect densities. One major approach is the study of initial stages of crystal growth as most defects are nucleated at this stage and propagate into the boule. Ailihumaer et al [2] demonstrated the behaviors of threading edge dislocations (TEDs), threading screw dislocations (TSDs)/threading mixed dislocations (TMDs), and basal plane dislocations (BPDs) across the seed/newly grown layer interface in PVT-grown 4H-SiC. Sanchez et al [3] revealed the nucleation of TEDs and TSDs at the initial growth stage in PVT-grown SiC.However, more detailed investigations are still in demand for PVT grown 4H-SiC crystals during initial stage of growth. This study investigates 4° off-axis 4H-SiC wafers with several hundred microns of initial-stage growth PVT method. Synchrotron X-ray topography (SXRT) technique is employed and shows dramatically modified defect distribution across the seed/newly grown layer interface (Figure 1). The formation of Shockley stacking fault starting at initial stage of crystal growth is suggested as partial dislocations running along <11-20> directions on basal plane are observed to form rhombus shapes (Figure 2). Prismatic slip is observed to take place near the wafer edges and prismatic dislocations undergo cross slip to form unique dislocation configurations. A statistical analysis on defect changes across the seed/newly grown layer is being carried out and the results will be reported. These results will be complemented by observations from Nomarski optical microscopy (NOM) and Raman Spectroscopy studies to propose the formation mechanism of defects across the seed/newly grown layers.

Differences in heart rate responses to upright posture are associated with variations in the high-frequency power of heart rate variability.

High resting heart rate is a cardiovascular risk factor, but limited data exist on the underlying hemodynamics and reproducibility of supine-to-upright increase in heart rate. We recorded noninvasive hemodynamics in 574 volunteers [age, 44.9 yr; body mass index (BMI), 26.4 kg/m2; 49% male] during passive head-up tilt (HUT) using whole body impedance cardiography and radial artery tonometry. Heart rate regulation was evaluated using heart rate variability (HRV) analyses. Comparisons were made between quartiles of supine-to-upright heart rate changes, in which heart rate at rest ranged 62.6-64.8 beats/min (P = 0.285). The average upright increases in heart rate in the quartiles 1-4 were 4.7, 9.9, 13.5, and 21.0 beats/min, respectively (P < 0.0001). No differences were observed in the low-frequency power of HRV, whether in the supine or upright position, or in the high-frequency power of HRV in the supine position. Upright high-frequency power of HRV was highest in quartile 1 with lowest upright heart rate and lowest in quartile 4 with highest upright heart rate. Mean systolic blood pressure before and during HUT (126 vs. 108 mmHg) and the increase in systemic vascular resistance during HUT (650 vs. 173 dyn·s/cm5/m2) were highest in quartile 1 and lowest in quartile 4. The increases in heart rate during HUT on three separate occasions several weeks apart were highly reproducible (r = 0.682) among 215 participants. To conclude, supine-to-upright increase in heart rate is a reproducible phenotype with underlying differences in the modulation of cardiac parasympathetic tone and systemic vascular resistance. As heart rate at rest influences prognosis, future research should elucidate the prognostic significance of these phenotypic differences.NEW & NOTEWORTHY Subjects with similar supine heart rates are characterized by variable increases in heart rate during upright posture. Individual heart rate increases in response to upright posture are highly reproducible as hemodynamic phenotypes and present underlying differences in the modulation of cardiac parasympathetic tone and systemic vascular resistance. These results indicate that resting heart rate obtained in the supine position alone is not an optimal means of classifying people into groups with differences in cardiovascular function.

Reliability of five-minute vs. one-hour heart rate variability metrics in individuals with spinal cord injury.

A previous study showed low reliability of 1-h HRV outcomes in participants with spinal cord injury (SCI), but it was not certain whether the low reliability was due to the unrestricted activity of participants. We aimed to investigate test-retest reliability of HRV metrics in individuals with SCI using a 1-h measurement in a supine position. Individuals with SCI underwent two sessions of 1-h recording of the time between consecutive R waves (RR-intervals) in a supine position. HRV outcomes were obtained from a single 5-min data segment and for the full 1-h recording. HRV parameters of interest were: standard deviation of all normal-to-normal R-R intervals (SDNN) and square root of the mean of the squared differences between successive R-R intervals (RMSSD) (time domain); and high frequency power (HF), low frequency power (LF), very low frequency power (VLF), ultra-low frequency power (ULF) and total power (TP) (frequency domain). Relative reliability was assessed by intraclass correlation coefficient (ICC). Absolute reliability was assessed by coefficient of variation (CV) and Bland-Altman limits of agreement (LoA). Data from 37 individuals (14 with tetraplegia and 23 with paraplegia) were included. Relative reliability was higher for the 1-h (ICCs ranged from 0.13-0.71) than for the 5-min duration (ICCs ranged from 0.06-0.50) in the overall SCI group for all HRV metrics. Participants with tetraplegia had lower relative reliability compared to participants with paraplegia in all HRV metrics for the 5-min duration (ICCs ranged from -0.01-0.34 vs. 0.21-0.57). For the 1-h duration, participants with paraplegia showed higher relative reliability than participants with tetraplegia in all HRV metrics (ICCs ranged from 0.18-0.79 vs. 0.07-0.54) except TP (ICC 0.69 vs. 0.82). In terms of absolute reliability, the CVs and LoAs for the 1-h duration were better than for the 5-min duration. In general, time domain metrics showed better reliability than frequency domain metrics for both durations in participants with tetraplegia and paraplegia. The lowest CV and narrowest 95% LoA were found for SDNN in 5-min and 1-h durations overall and in both lesion levels. The supine position did not provide better reliability compared to unrestricted activity in participants with SCI. HRV analysis using a 5-min duration is of limited value in SCI due to poor reliability. For the 1-h analysis duration, interpretation of the reliability of HRV varies according to lesion level: it is recommended to take lesion level into account when interpreting reliability measures.

Autonomic nervous system function assessed by heart rate variability and the presence of symptoms affecting activities of daily living in community-dwelling residents with chronic pain: The Hisayama Study.

Autonomic nervous system dysfunction has been reported to be associated with impaired activities of daily living (ADL) among patients with chronic pain, but the association has not been fully addressed in general populations. This study cross-sectionally investigated the association between autonomic nervous system function and the presence of subjective symptoms affecting ADL in community-dwelling residents with chronic pain. A total of 888 residents with chronic pain, aged 40-79 years, who underwent a health examination in 2017-2018 were included. Based on heart rate variability measured by fingertip pulse wave, the standard deviation of normal-to-normal intervals (SDNN), root mean square of successive RR interval differences (RMSSD), low frequency (LF) power, and high frequency (HF) power were calculated. Symptoms affecting ADL were defined as those scoring ≥1 on the modified Rankin Scale. Odds ratios (ORs) and their 95% confidence intervals (CIs) for symptoms affecting ADL were estimated using a logistic regression analysis. The overall prevalence of symptoms affecting ADL was 39.4%. The ORs for symptoms affecting ADL increased significantly per 1-standard-deviation decrement in log-transformed SDNN (OR 1.23 [95% CI 1.06-1.44]), RMSSD (1.25 [1.08-1.45]), LF power (1.29 [1.11-1.52]), and HF power (1.29 [1.11-1.51]) after adjusting for age, sex, education, hypertension, diabetes, serum total cholesterol level, body mass index, past medical history, current smoking, current drinking, exercise, depressive symptoms, and pain intensity. Decreased heart rate variability was associated with the presence of symptoms affecting ADL among individuals with chronic pain in a Japanese community. Decrease in heart rate variability was associated with the presence of symptoms affecting ADL among individuals with chronic pain in a Japanese community. This article could help scientists understand the significance of autonomic nervous system dysfunction in the pathology of chronic pain. Approaches that target autonomic nervous system dysfunction may be an option to relieve or prevent symptoms affecting ADL for chronic pain sufferers.