LF Power Research Articles

Acute impact of cigarette smoking on power spectral measures of HRV

Background: Cigarette smoking is associated with various forms of acute cardiac events such as myocardial infarction and ventricular fibrillation etc.Objective: To observe immediate impact of cigarette smoking on power spectral measures of heart rate variability (HRV) in current apparently healthy male regular cigarette smokers.Methods: This study was carried out on 120 apparently healthy male current regular cigarette smoker aged 20-55 years. To watch the intense impacts, data were recorded 5 and 30 min after completing a full stick of cigarette. Power spectral measures of HRV were recorded by a RMS digital polyrite D. Statistical analysis was done by paired sample t test.Results: LF power, LF nu & LF/HF ratio were significantly increased and HF power & HF nu were significantly decreased from their corresponding baseline value just 5 minutes after smoking and returned close to their baseline value after 30 minutes of smoking.Conclusion: The result of the study concludes that acceleration of sympathetic activity with simultaneous withdrawn of cardiovascular vagal adjustment happens quickly in the wake of smoking a cigarette.J Bangladesh Soc Physiol. 2018, June; 13(1): 8-12

Validation of the Apple Watch for Heart Rate Variability Measurements during Relax and Mental Stress in Healthy Subjects.

Heart rate variability (HRV) analysis is a noninvasive tool widely used to assess autonomic nervous system state. The market for wearable devices that measure the heart rate has grown exponentially, as well as their potential use for healthcare and wellbeing applications. Still, there is a lack of validation of these devices. In particular, this work aims to validate the Apple Watch in terms of HRV derived from the RR interval series provided by the device, both in temporal (HRM (mean heart rate), SDNN, RMSSD and pNN50) and frequency (low and high frequency powers, LF and HF) domain. For this purpose, a database of 20 healthy volunteers subjected to relax and a mild cognitive stress was used. First, RR interval series provided by Apple Watch were validated using as reference the RR interval series provided by a Polar H7 using Bland-Altman plots and reliability and agreement coefficients. Then, HRV parameters derived from both RR interval series were compared and their ability to identify autonomic nervous system (ANS) response to mild cognitive stress was studied. Apple Watch measurements presented very good reliability and agreement (>0.9). RR interval series provided by Apple Watch contain gaps due to missing RR interval values (on average, 5 gaps per recording, lasting 6.5 s per gap). Temporal HRV indices were not significantly affected by the gaps. However, they produced a significant decrease in the LF and HF power. Despite these differences, HRV indices derived from the Apple Watch RR interval series were able to reflect changes induced by a mild mental stress, showing a significant decrease of HF power as well as RMSSD in stress with respect to relax, suggesting the potential use of HRV measurements derived from Apple Watch for stress monitoring.

APPLICATION OF SELF ORGANIZING MAP FOR CORRELATION HUNTING BETWEEN ALPHA BAND POWER OF EEG SIGNALS AND OTHER PHYSIOLOGICAL PARAMETERS DURING MUSLIM PRAYER (SALAT)

This study investigates a new approach to determine the correlations between alpha ([Formula: see text]) electroencephalography (EEG) and other physiological parameters during Muslim prayer (Salat) utilizing the self organizing map (SOM). The powerfulness of SOM in visualizing, understanding, and exploring the complexity in multivariable data can be used to determine the relationships between the input variables. Thirty healthy Muslim male subjects were recruited in the study. Their electroencephalogram (EEG), electrocardiogram (ECG), respiration rate (RSP), and oxygen saturation (SPO2) were continuously recorded using computer-based data acquisition system (MP150, BIOPAC Systems Inc., Camino Goleta, California). Three maps were constructed to determine the correlations in pre-baseline, during Salat, and post-baseline conditions utilizing SOM. The visualized results during Salat indicated that, alpha power (P[Formula: see text]) showed significant positive correlation in the occipital and parietal electrodes with the normalized unit of high-frequency HF (n.u.) power of heart rate variability (HRV) components (as a parasympathetic index), heart rate (HR), and RSP. Significant negative correlation was also observed between P[Formula: see text] with the normalized unit of low-frequency LF (n.u.) power and LF/HF of HRV (as sympathetic indices). SPO2 showed no correlation with P[Formula: see text]. While the results in pre-baseline and post-baseline conditions also did not show any correlation between the variables. The SOM proves that it can be successfully employed as a powerful technique in correlation analysis. The results were presented and compared with a previous study. Thus, it can be applied successfully in various biomedical engineering applications.

Non-stationary Noise Sources in an Optoacoustical Gravitational Antenna

The optoelectronic Pound-Drever-Hall scheme is considered as a registration system of small variations of length and eigenfrequency of reference Fabry-Perot resonator with base of 2 m fixed on the aluminum test body of the GW antenna. In uniform sensitivity analysis shot noise of photoelectrons, intrinsic technical LF laser stochastic frequency deviations and power fluctuations (PF) are considered. Mechanism of PF penetration into the precise feedback chain is pointed out. It is shown that the carrier of PF noise is the quasistatic error signal of the laser frequency tracking system following the drifting frequency of the resonator, since this voltage is formed by synchronous detector from the photodiode current. The frequency discriminator channel of the installation OGRAN can also introduce PF noise, since the output of it’s synchronous detector contains significant LF noise (10÷300 Hz) voltage created by industrial seismic and vibration disturbances.

Carbohydrate ingestion induces differential autonomic dysregulation in normal-tension glaucoma and primary open angle glaucoma

BackgroundIt is reported that glaucoma may be associated with vascular dysregulation. Normal tension glaucoma (NTG) and primary open angle glaucoma (POAG), which feature different intraocular pressure levels, may manifest differential features of systemic autonomic dysregulation.Methods and resultsWe investigated autonomic regulation to carbohydrate ingestion and postural change in 37 glaucoma patients (19 NTG and 18 POAG) and 36 controls. Subjects were age and gender-matched, normotensive, and had normal comparable insulin sensitivity. Continuous finger arterial pressure and ECG was recorded in supine and standing positions before and after carbohydrate ingestion. Low frequency (LF, 0.04–0.15Hz) and high frequency (HF, 0.15–0.4Hz) spectral power of heart rate and systolic blood pressure variability (HRV and SBPV) were calculated to estimate sympathovagal function. Overall comparison glaucoma (N = 37) and controls (N = 36) showed an increased sympathetic excitation, vagal withdrawal and unstable mean arterial pressure after carbohydrate ingestion in glaucoma patients. Glaucoma severity by retinal nerve fibre layer (RNFL) thickness is positively correlated to autonomic responses (HRV LF power and HF power in normalised units (nu), and HRV LF/HF ratio) after carbohydrate ingestion. Early (30 minutes) following carbohydrate ingestion, SBP LF power and HRV parameters remained unchanged in controls; while POAG showed abnormal autonomic responses, with a paradoxical vagal enhancement (increased HRV HF power in nu) and sympathetic inhibition (decreased HRV LF power nu and HRV LF/HF ratio), and associated hypotension. Later (60–120 minutes) following carbohydrate ingestion, HRV parameters remained unaltered in controls; whereas NTG manifested vagal withdrawal (reduced HRV HF power nu) and sympathetic hyper-responsiveness (increased HRV LF power nu and HRV LF/HF ratio), despite increased SBP LF power in both controls and NTG. Both NTG and POAG exhibited attenuated autonomic responses to postural stress.ConclusionsNTG and POAG both manifest some systemic autonomic cardiovascular dysregulation. However, the two forms of glaucoma respond differentially to carbohydrate ingestion, irrespective of insulin resistance.

Effect of long term high altitude exposure on cardiovascular autonomic adjustment during rest and post-exercise recovery

BackgroundDespite the successful adaptation to high altitude, some differences do occur due to long term exposure to the hypoxic environment. The effect of long term high altitude exposure on cardiac autonomic adjustment during basal and post-exercise recovery is less known. Thus we aimed to study the differences in basal cardiac autonomic adjustment and its response to exercise in highlanders and to compare it with lowlanders.MethodsThe study was conducted on 29 healthy highlander males who were born and brought up at altitude of 3000 m and above from the sea level, their cardiac autonomic adjustment was compared with age, sex, physical activity and ethnicity-matched 29 healthy lowlanders using Heart Rate Variability (HRV) during rest and recovery from sub-maximal exercise (3 m step test). Intergroup comparison between the highlanders and lowlanders and intragroup comparison between the rest and the postexercise recovery conditions were done.ResultsResting heart rate and HRV during rest was comparable between the groups. However, heart rate recovery after 3 min step test was faster in highlanders (p < 0.05) along with significantly higher LF power and total power during the recovery phase. Intragroup comparison of highlanders showed higher SDNN (p < 0.05) and lower LF/HF ratio (p < 0.05) during recovery phase compared to rest which was not significantly different in two phases in lowlanders. Further highlander showed complete recovery of RMSSD, NN50, pNN50 and HF power back to resting level within five minutes, whereas, these parameters failed to return back to resting level in lowlanders within the same time frame.ConclusionHighlanders completely recovered back to their resting state within five minutes from cessation of step test with parasympathetic reactivation; however, recovery in lowlanders was delayed.

Measurements of argon metastable density using the tunable diode laser absorption spectroscopy in Ar and Ar/O2**Project supported by the National Natural Science Foundation of China (Grant Nos. 11335004, 11722541, 11675039, and 11747153) and the Important National Science and Technology Specific Project, China (Grant No. 2011ZX02403-001).

Densities of Ar metastable states 1s5 and 1s3 are measured by using the tunable diode laser absorption spectroscopy (TDLAS) in Ar and Ar/O2 mixture dual-frequency capacitively coupled plasma (DF-CCP). We investigate the effects of high-frequency (HF, 60 MHz) power, low-frequency (LF, 2 MHz) power, and working pressure on the density of Ar metastable states for three different gas components (0%, 5%, and 10% oxygen mixed in argon). The dependence of Ar metastable state density on the oxygen content is also studied at different working pressures. It is found that densities of Ar metastable states in discharges with different gas components exhibit different behaviors as HF power increases. With the increase of HF power, the metastable density increases rapidly at the initial stage, and then tends to be saturated at a higher HF power. With a small fraction (5% or 10%) of oxygen added in argon plasma, a similar change of the Ar metastable density with HF power can be observed, but the metastable density is saturated at a higher HF power than in the pure argon discharge. In the DF-CCP, the metastable density is found to be higher than in a single frequency discharge, and has weak dependence on LF power. As working pressure increases, the metastable state density first increases and then decreases, and the pressure value, at which the density maximum occurs, decreases with oxygen content increasing. Besides, adding a small fraction of oxygen into argon plasma will significantly dwindle the metastable state density as a result of quenching loss by oxygen molecules.

LF HRV power as an index of sympathetic inhibition

Although the spectral power of HF HRV oscillations is widely accepted as a measure of the cardiovagal activity, the interpretation of LF HRV power is more controversial. It was suggested that LF HRV power provides information about the sympathetic or/and parasympathetic outflow, baroreflex modulation of cardiac autonomic outflows, vasomotor tone modulation, and mechanisms of central autonomic outflow. As follows from these contradictory hypotheses, till now there is no widely accepted interpretation of LF power. We hypothesize that LF HRV power is an index of sympathetic inhibition.The participants, 150 men, and 149 women were enrolled from V.N. Karazin Kharkiv National University student population. The ECG recording, HRV analysis, and blood pressure (BP) measurements were performed four times with an hour interval. The average values were included in the analysis. The stepwise multiple linear regression analysis with centered variables was performed to evaluate a contribution of LnLF and LnHF power in heart rate (HR), systolic and diastolic BP (SBP and DBP), adjusted also for sex, BMI, height, two‐way, three‐way, four‐way interactions, and in addition, for presence of hypertension. Statistical analysis was performed with the SPSS statistical program, version 22.The multiple linear regression analysis revealed that resting HR was negatively associated with LnHF at high significant level (P&lt;0.001) and with LnLF at lower significant level (P=0.021) (Table 1). The negative association between HR and LnHF power was expected, as it is widely accepted that HF power represents a cardiovagal outflow which predominates at rest. As it follows from the positive association between HR and LnHF by LnLF interaction (LnHF*LnLF) (Table 1), the LnHF and LnLF work in a reciprocal manner: either LnLF or LnHF can reduce HR at a higher degree with a predominance of LnHF in apparently healthy individuals. There are at least three variants of interpretation of the negative association between HR and LnLF power such as the LF power represents: 1) both sympathetic and parasympathetic activities with predominance of the cardiovagal outflow; 2) inhibitory influences of a variety of peripheral reflexes on the medullary presympathetic neurons; 3) the central hyporeactive immobility and sympathoinhibition.The SBP and DBP were positively associated with gender (men) and BMI and negatively with LnLF power in men with high values of BMI (Table 1) indicating the negative feedback control of blood pressure. Since there are no parasympathetic nerves directly influencing blood pressure, the second possibility was accepted in congruence with idea that LF power is an index of the baroreflex modulation of cardiac autonomic outflows specifically of the sympathetic limb of this negative feedback controlling mechanism.The introduction of one more variable and number of interactions increases the complexity of the linear regression model but may give more information. The model including also presence of prehypertension (51 independent centered variables and interactions) indicates that SBP was negatively associated with LnLF in normotensive participants only (not shown), demonstrating according to our hypothesis lack of sympathoinhibition in prehypertensives.In conclusion, from HRV and stepwise multiple regression analysis with centered independent variables and interactions, it is suggested that LnLF power represent sympathoinhibitory negative feedback controlling mechanisms.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Muscle Metaboreflex Modulation of Spontaneous Cardiac Baroreflex Sensitivity: Does Sex Matter?

It is well established that during exercise, the arterial baroreflex is reset to operate around the prevailing blood pressure in an exercise intensity‐dependent manner. This exercise‐induced modulation of baroreflex function is mediated by central signals and by afferent signals arising from working skeletal muscle that are composed of mechanically and metabolically sensitive afferents. Previous studies in humans examining the influence of metabolically sensitive skeletal muscle afferents (i.e., muscle metaboreflex) on cardiac baroreflex sensitivity (cBRS) have found equivocal results reporting increases, decreases, or no change in sensitivity. The reason behind these discrepancies could be attributable to variation in the methods used to assess baroreflex function, exercise modality and intensity, size of exercising muscle mass, and, less discussed, but also relevant, the inclusion of both men and women. This becomes important given a plethora of studies indicating that sex plays a pivotal role when it comes to blood pressure regulation. Given this, the aim of the present study was to investigate the effect of isolated muscle metaboreflex activation on cBRS and the potential sex‐related differences in this interaction. Forty healthy and physically active volunteers (20 men), aged 18–30 years were recruited. All women were non‐oral contraceptives users and performed experiments in the early follicular phase of the menstrual cycle. After 10 minutes rest period, the subjects performed 90s of isometric handgrip (IHG) at 40% of maximal voluntary contraction followed by 3‐min of post exercise ischemia (PEI) to isolate the muscle metaboreflex. Beat‐to‐beat heart rate (HR ‐ electrocardiography) and arterial blood pressure (finger photopletysmography) were continuously measured. Spontaneous cBRS was assessed for all combined sequences (Gainall), and also separately upward (Gainup) and downward (Gaindown) using the sequence technique. HR variability was measured in time (RMSSD ‐ standard deviation of the RR intervals) and frequency domains (LF – low and HF – high frequency power). Resting MBP was lower in women than men (P &lt; 0.01). MBP increased from rest during IHG and remained elevated during PEI in both men and women. However, the magnitude of these responses was greater in men. Resting cBRS was similar between men and women. During PEI, men exhibited an increase in cBRS (Gainall: Δ3.0 ± 1.1 ms mmHg‐1, P = 0.03; Gainup: Δ4.4 ± 2.1 ms mmHg‐1, P = 0.04; and Gaindown: Δ3.3 ± 1.4 ms mmHg‐1, P = 0.03). In contrast, cBRS was unchanged during PEI in women (Gainall: Δ0.6 ± 0.7 ms mmHg‐1, P = 0.10; Gainup: Δ0.3 ± 0.7 ms mmHg‐1, P = 0.27; and Gaindown: Δ0.2 ± 1.1 ms mmHg‐1, P = 0.43). At rest, HF and LF power were lower in women compared with men, whereas RMSSD and LF/HF ratio were similar. During PEI, men exhibited a highest increase in RMSSD and HF compared to women, while LF power was unchanged in both groups. In addition, LF/HF ratio decreased in men and was unchanged in women. These findings indicate that the muscle metaboreflex activation modulates spontaneous cBRS in a sex dependent manner.Support or Funding InformationBrazilian National Council of Scientific and Technological Development (CNPq); Foundation for Research Support of Federal District (FAPDF); Brazilian Federal Agency for Support and Evaluation of Graduate Education (CAPES).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Responses of cerebral blood flow and tissue oxygenation to low frequency oscillations during simulated hemorrhagic stress in humans

IntroductionHemorrhage is a leading cause of death from traumatic injury in both the military and civilian populations. Use of lower body negative pressure (LBNP) as a model of hemorrhage in humans has revealed that there is a spectrum of tolerance to this stress. Recent evidence from our laboratory suggests that low frequency (LF; ~0.1 Hz) oscillations in mean arterial pressure (MAP) and middle cerebral artery velocity (MCAv) play a role in this tolerance; high tolerant subjects exhibit greater LF power in MAP and MCAv when compared to low tolerant subjects. We hypothesize that exogenously inducing LF oscillations via oscillatory LBNP (OLBNP) will attenuate reductions in cerebral blood flow and oxygenation during simulated hemorrhagic stress.Methods11 young, healthy subjects (9M/2F) were exposed to two LBNP profiles with an average chamber pressure of −60 mmHg in a randomized and counterbalanced design: 1) static LBNP (0 Hz) and, 2) oscillatory LBNP (0.1 Hz). During both profiles, chamber pressure was gradually reduced to −60 mmHg over 1‐min after which pressure remained at −60 mmHg (0 Hz) for 9‐min or oscillated between −30 mmHg and −90 mmHg (0.1 Hz) for 9‐min. Profiles were separated by a 5‐min recovery. Physiological measurements included arterial pressure and stroke volume via finger photoplethysmography, MCAv via transcranial Doppler ultrasound, and regional cerebral oxygenation of the frontal lobe (ScO2) via near infrared spectroscopy. Hemodynamic data was analyzed using a paired t‐test. Tolerance was assessed with a Fischer's exact test.ResultsNo differences were observed between profiles for MAP (0 Hz, 79.8±2.5 mmHg vs. 0.1 Hz, 80.0±1.9 mmHg; P=0.93) and MCAv (0 Hz, 42.4±3.3 cm/s vs. 0.1 Hz, 43.5±3.7 cm/s P=0.43). The reduction in ScO2 was attenuated (P=0.05) during the 0.1 Hz profile (−4.1±1.2 %) compared to the 0 Hz profile (−6.1±1.1 %). A similar attenuation was observed in the stroke volume response (0 Hz, −42.6±2.5 % vs. 0.1 Hz, −30.6±2.5 %; P&lt;0.001). Importantly, 8/11 subjects completed the 0.1 Hz profile compared with just 5/11 subjects for the 0 Hz profile (P=0.048).DiscussionIn partial support of our hypothesis, cerebral oxygenation was protected during the 0.1 Hz OLBNP profile. While MCAv was similar between conditions, we propose that the oscillatory pattern of cerebral blood flow may elicit a shear‐stress induced vasodilation, so assessment of velocity may be masking an increase in flow. This possibility is further supported by the finding that stroke volume was also protected during the 0.1 Hz profile, which may reflect an increase in venous return during the upstroke period of the OLBNP profile. Importantly, more subjects were able to tolerate the 0.1 Hz profile compared to the static 0 Hz profile, despite similar arterial pressure responses. These findings emphasize the potential importance of hemodynamic oscillations in maintaining perfusion and oxygenation of cerebral tissue during a hemorrhagic stress.Support or Funding InformationUNTHSC ICMD Junior Faculty Seed GrantThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Increment in Systolic Blood Pressure During Cold Pressure Test Is Associated with Baseline LF Power in Young Prehypertensive Men

The cold pressor test (CPT) is commonly used as a sympathoexcitatory maneuver to provoke an increment in arterial pressure and heart rate and to measure cardiovascular reactivity to stress. However, use of the CPT as a predictor test of future hypertension is still debatable. We investigated whether exaggerated blood pressure responsiveness to CPT is observed in young prehypertensive men and determined baseline HRV indices and autonomic nervous system contribution into the elevation of blood pressure.CPT was performed in 81 normotensive and 72 prehypertensive men enrolled from V.N. Karazin Kharkiv National University student population. All participants gave written informed consent. After 5 min resting stage subjects placed their right hand into ice‐cold water for 1 minute. ECG was continuously recorded and resting HRV indices were interpreted (CardioLab 2010). Blood pressure was measured at the end of each stage (Nissei WS‐1011). GLM one‐way MANOVA and MANCOVA with height and BMI were used to test for possible effects of prehypertension on heart rate (ΔHR) and blood pressure (ΔSBP and ΔDBP) responses. The stepwise multiple linear regression analysis was carried out to assess the relative importance of baseline LnLF (LnLFrest) and LnHF (LnHFrest) power in HR, SBP, and DBP increments, adjusted also for the presence of prehypertension, BMI, height, and two‐way interactions.In the current study, prehypertensive subjects did not demonstrate higher cardiovascular reactivity to CPT (Table 1). Moreover, normotensives had higher SBP response to CPT (Table 1). When height and BMI were taken into account this difference was even more significant (not shown). Previous studies have yielded inconsistent results with some showing higher and some showing the same and even lower blood pressure reactivity to CPT in prehypertensive subjects or in persons with family history of hypertension.The stepwise multiple regression analysis revealed that ΔSBP in prehypertensives and ΔDBP in all subjects were negatively associated with LnLFrest possibly indicating, according to our hypothesis, activity of the inhibitory interneurons projected to the presympathetic neurons in the rostral ventrolateral medulla. The central inhibition of sympathetic activity reduced the increment of SBP in subjects developing hypertension and controlled increment of DBP in all subjects (Table 2).It was shown that increments in both SBP and DBP were associated with ΔHR only in the prehypertensive subjects and in persons with increased BMI (Table 2). These findings may be partially explained by blunting of baroreceptor reflex sensitivity and/or resetting of the baroreceptor reflex to a higher control point.in prehypertensives and in subjects with increased BMI. The increments in SBP and DBP associated also with ΔHR in subjects with a high level of baseline parasympathetic activity as shown by the positive association between LnHFrest by ΔHR interaction and ΔSBP or ΔDBP (Table 2) possibly because high LnHFrest reduces HR and increases atrioventricular delay which may contribute to a ventricular filling.In conclusion, young prehypertensive subjects demonstrated lower SBP response to CPT than normotensives possibly due to their increment in SBP was associated with resting LnLF power, indicating according to our hypothesis, inhibition of the presympathetic medullary neurons; ΔSBP and ΔDBP were associated with ΔHR only in prehypertensives and in persons with high baseline parasympathetic activity.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Vascular and autonomic changes in adult cancer patients receiving anticancer chemotherapy.

Chemotherapy is associated with acute and long-term cardiotoxicity. To date, risk assessment has primarily focused on the heart; however, recent findings suggest that vascular and autonomic function may also be compromised. Whether this occurs during chemotherapy treatment remains unknown. Therefore, the present study evaluated carotid artery stiffness, cardiovagal baroreflex sensitivity (cBRS), and heart rate variability (HRV) in cancer patients currently being treated with adjuvant chemotherapy. Eleven current cancer patients receiving adjuvant chemotherapy and 11 matched (1:1) controls were studied. Carotid artery stiffness was assessed via two-dimensional ultrasonography. cBRS was assessed from the spontaneous changes in beat-to-beat time series of R-R interval and systolic blood pressure via the cross-correlation technique. HRV was assessed using the standard deviation of R-R intervals (SDNN) and low (LF) and high (HF) power frequencies. Carotid artery β-stiffness was significantly higher in the cancer patients compared with control participants (8.0 ± 0.8 vs. 6.3 ± 0.6 U, respectively; P = 0.02). cBRS was lower in the cancer patients compared with controls (4.3 ± 0.7 vs. 10.7 ± 1.9 ms/mmHg, respectively; P = 0.01), and all indices of HRV were lower in the cancer patients (SDNN, P = 0.02; LF, P = 0.01; HF, P = 0.02). There was no significant correlation between β-stiffness and cBRS ( P = 0.4). However, LF power was significantly correlated with cBRS (r = 0.66, P < 0.001). Compared with matched healthy controls, cancer patients undergoing chemotherapy demonstrated a significantly higher arterial stiffness and lower cBRS. The previously reported adverse effects of chemotherapy on the heart appear to also influence other aspects of cardiovascular health. NEW & NOTEWORTHY Patients treated with anticancer chemotherapy exhibit an impaired baroreflex control of arterial blood pressure and increased arterial stiffness. These findings hold significant value, in particular as part of a risk-stratification strategy in current cancer patients receiving chemotherapy. This is the first investigation, to our knowledge, to demonstrate an attenuated spontaneous baroreflex control of arterial blood pressure in cancer patients currently undergoing chemotherapy.

Comparing the cardiac autonomic activity profile of daytime naps and nighttime sleep

Heart rate variability (HRV) is a reliable technique to evaluate autonomic activity and shows marked changes across a night of sleep. Previous nighttime sleep findings report changes in HRV during non-rapid eye movement sleep (NREM), which have been associated with cardiovascular health benefits. Daytime sleep, however, has been linked with both positive and negative cardiovascular outcomes. Yet, no studies have directly compared HRV profiles during an ecologically-valid daytime nap in healthy, well-rested adults to that of nighttime sleep. Using a within-subjects design, 32 people took a daytime nap and slept overnight in the lab at least one week apart; both sleep sessions had polysomnography, including electrocardiography (ECG), recorded. We measured inter-beat intervals (RR), total power (TP), low frequency power (LF; .04–.15 Hz), and high frequency power (HF; .15–.40 Hz) components of HRV during NREM and rapid eye movement (REM) sleep. Compared to the nap, we found longer RR intervals and decreased heart rate during the night for both Stage 2 and SWS and increased TP, LF and HF power during nighttime Stage 2 sleep only; however, no differences in the LFHF ratio or normalized HF power were found between the nap and the night. Also, no differences in REM sleep between the nap and night were detected. Similar relationships emerged when comparing the nap to one cycle of nighttime sleep. These findings suggest that longer daytime naps, with both SWS and REM, may provide similar cardiovascular benefits as nocturnal sleep. In light of the on-going debate surrounding the health benefits and/or risks associated with napping, these results suggest that longer daytime naps in young, healthy adults may support cardiac down-regulation similar to nighttime sleep. In addition, napping paradigms may serve as tools to explore sleep-related changes in autonomic activity in both healthy and at-risk populations.

Autonomic Nervous System Measurement in Hyperbaric Environments Using ECG and PPG Signals.

The main aim of this paper was to characterize the Autonomic Nervous System response in hyperbaric environments using electrocardiogram (ECG) and pulse-photoplethysmogram (PPG) signals. To that end, 26 subjects were introduced into a hyperbaric chamber and five stages with differentatmospheric pressures (1atm; descent to 3 and 5atm; ascent to 3 and 1atm) were recorded. Respiratory information was extracted from the ECG and PPG signals and a combined respiratory rate was studied. This information was also used to analyze Heart Rate Variability (HRV) and Pulse Rate Variability (PRV). The database was cleaned by eliminating those cases where the respiratory rate dropped into the low frequency band (LF: 0.04-0.15Hz) and those in which there was a discrepancy between the respiratory rates estimated using the ECG and PPG signals. Classical temporal and frequency indices were calculated in such cases. The ECG results showed a time-related dependency, with the heart rate and sympathetic markers (normalized power in LF and LF/HF ratio) decreasing as more time was spent inside the hyperbaric environment. A dependence between the atmospheric pressure and the parasympathetic response, as reflected in the high-frequency band power (HF: 0.15-0.40Hz), was also found, with power increasing with atmospheric pressure. The combined respiratory rate also reached a maximum in the deepest stage; thus, highlighting a significant difference between this stage and the first one. The PPG data gave similar findings and also allowed the oxygen saturation to be computed; therefore, we propose the use of this signal for future studies in hyperbaric environments.

Heart Rate Variability in Healthy Non-Concussed Youth Athletes: Exploring the Effect of Age, Sex, and Concussion-Like Symptoms.

Heart rate variability (HRV) is a non-invasive neurophysiological measure of autonomic nervous system regulation emerging in concussion research. To date, most concussion studies have focused on the university-aged athlete with no research examining healthy active youths. Corroborating changes in HRV alongside traditional subjective self-report measures (concussion symptoms) in the non-concussed state provides a foundation for interpreting change following concussion. The objectives were to (1) explore the influence of age and sex on HRV and (2) examine the relationship between HRV and baseline/pre-injury concussion symptom domains (physical, cognitive, emotional, and fatigue) in healthy youth athletes. Healthy, youth athletes 13-18 years of age [N = 294, female = 166 (56.5%), male = 128 (43.5%)] participated in this cross-sectional study. Age, sex, and concussion-like symptoms were collected as part of a baseline/pre-injury assessment. The Post-Concussion Symptom Inventory-SR13 (PCSI-SR13) was used to collect domain scores for physical, cognitive, emotional, and fatigue symptoms. HRV was collected for 24 h. HRV measures included time (SDNN, RMSSD, and pNN50) and frequency (HF, HFnu, LF, LFnu, and total power) domain HRV measures. Variables were logarithmically transformed to increase robustness of linear regression models. Older youth participants displayed significantly higher HRV compared to younger participants (p < 0.05). Females displayed significantly lower HRV compared to males (p < 0.05). A significant interaction effect between concussion-like symptoms and HRV indicated differential patterns as a function of sex (p < 0.05). Youth athletes who reported more cognitive symptoms had lower HRV (p < 0.05). HRV was found to have a significant relationship with a traditional clinical measure (subjective self-report of concussion-like symptoms) utilized in concussion assessment and management. Baseline/pre-concussion trends in HRV were significantly associated with age and sex, highlighting the value in understanding key demographic factors within the context of concussion-like symptoms.

ХВИЛЬОВА СТРУКТУРА ПОКАЗНИКІВ ГЕМОДИНАМІКИ ПРИ РІЗНОМУ ВИХІДНОМУ РІВНІ ЧАСТОТИ ДИХАННЯ У ЧОЛОВІКІВ

Introduction . It is expedient to investigate the features of wave structure of the oscillations of the stroke volume (SV) and duration of R-R interval by the different level of the main vegetative indicators such as respiratory rate and volume of cardiac output which are considered to be constant for each person according to the data of many studies. Purpose . To find out the features of the wave structure of oscillations of SV and duration of R-R interval in healthy young men with a different level of respiratory rate. Methods. The measurements are carried out on 120 healthy young men aged from 17 to 23 years. By the distribution of the initial value of the Mo duration of respiratory cycle men were divided into 3 groups: tachypnea (39 men) – with abnormally rapid breathing, normopnea (62 men) – with normal respiratory rate and bradypnea (19 men) - with abnormally slow breathing. Time series were analyzed with five-minutes implementations of successive stroke volume and R-R duration in the “Caspico” program. For the duration of cardiocycles were distinguished 3 main spectral components: HF (0,15-0,4 Hz), LF (0,04-0,15 Hz), VLF (0-0,04 Hz) and total power of the spectrum (TP), the power of high frequency oscillations in normalized units (HFnorm). These indicators for SV were respectively HF sv , LF sv , VLF sv , ТР sv and HFnorm sv . Results . People with low and high frequency of breathing in a state of rest are characterized by the relatively higher amplitude of oscillations of duration of R-R interval and stroke volume in the range of 0,04-0,15 Hz than normopnea. By bradypnea it is stipulated by a violation of respiratory periodicals in this frequency range and higher level of activation of parasympathetic link of the vegetative nervous system, by tachypnea it is stipulated by a number of factors: relatively higher level of blood-filling of organs in thorax, increase of sympathetic effects on the heart and increase of spontaneous baro-reflex sensitivity. By dosed load it is vice verse – relatively larger sympathetic activation is observed by bradypnea. Conclusion. Taking into account the output frequency of breathing can significantly improve the diagnostic value of the methods for analyzing of the variability of the stroke volume and heart rate.

Nerve Conduction and Heart Rate variability in Patients with Hypothyroidism at a Tertiary Care Centre in Eastern Nepal

Thyroid hormone effects on many organs including central and peripheral nervous systems. However, these hormones do not affect all systems/organs to a similar extent. Thus, we conducted this study to explore the effect of thyroid hormones on somatic nervous system assessed by Nerve conduction study and cardiac autonomic activity assessed by heart rate variability. The study included newly diagnosed hypothyroid patients and healthy controls. In all subjects NCS were performed in median, ulnar, tibial and sural nerves using Nihonkohden machine Cardiac autonomic control was assessed using Short-term Heart Rate Variability and parameters were analyzed by Time Domain and Frequency Domain methods. Both the groups were comparable in term of age, Body Mass Index, Pulse Rate, Systolic Blood Pressure and Diastolic Blood Pressure. Sensory parameters of NCS showed significant decrease in left median nerve SNAP amplitude (38.24±10.23 Vs 31.59±14.06, P=0.048) and nerve conduction velocity of bilateral median nerve in hypothyroid patients. In motor parameters of NCS, onset latencies of bilateral median nerves and right ulnar nerve were significantly increased in hypothyroid patients. All Time Domain measures of HRV and Frequency Domain measures; LF Power, HF Power and Total Power were significantly decreased (P<0.05) in hypothyroid patients. These HRV parameters are indicators of parasympathetic activity. In newly diagnosed hypothyroid patients, especially median nerve functions (both sensory and motor) and parasympathetic activity were decreased. It reflects that in hypothyroidism both autonomic nervous system and other somatic nerves are not affected in a similar extent.

Parachuting training improves autonomic control of the heart in novice parachute jumpers

This study aimed to investigate the acute effect of skydiving and the chronic effect of parachute jump training on the cardiac response in novice and trained parachuters.The study included 11 experienced skydivers (expert group), aged 35.9±7.2 years, and 12 students (novice group), aged 27.9±7.2 years. Participants underwent 10-unit training in accelerated freefall (AFF) from an altitude of 4000m.In experts, the highest HR was noted during the phase of opening of the parachute and during the landing phase, and in pre-training novices during the phase of exit from the plane and the descent by parachute. Mean standard deviation of NN intervals (SDNN) was higher in experts than pre-training novices.In novices, post-training values of SDNN, root mean square of successive differences (RMSSD), and the low/high frequency oscillation ratio (LF/HF) were higher, and HF and LF were lower, than pre-training values. In experts the values of SDNN, RMSSD, LF, HF, and total power spectrum (TP) were significantly higher and LF/HF significantly lower than in pre-training novices.Novice compared to experienced skydivers are characterized by higher modulation of the sympathetic, and lower modulation of the parasympathetic autonomic nervous system (ANS). Chronic effects of 10-unit AFF training are characterized by decreased modulation of the sympathetic nervous system, increased total power spectrum of HRV, and increased activity of the parasympathetic nervous system. The changes in ANS modulation suggest that parachute training leads to a reduction of the stress response and improves autonomic control of cardiovascular function in novice skydivers.

Evaluation of autonomic functions of patients with multiple system atrophy and Parkinson's disease by head-up tilt test.

The aim of this study was to evaluate the autonomic neural function in Parkinson's disease (PD) and multiple system atrophy (MSA) with head-up tilt test and spectral analysis of cardiovascular parameters. This study included 15 patients with MSA, 15 patients with PD, and 29 healthy control (HC) subjects. High frequency power of the RR interval (RR-HF), the ratio of low frequency power of RR interval to RR-HF (RR-LF/HF) and LF power of systolic BP were used to evaluate parasympathetic, cardiac sympathetic and vasomotor sympathetic functions, respectively. Both patients with PD and MSA showed orthostatic hypotension and lower parasympathetic function (RR-HF) at tilt position as compared to HC subjects. Cardiac sympathetic function (RR-LF/HF) was significantly high in patients with PD than MSA at supine position. RR-LF/HF tended to increase in MSA and HC, but decreased in PD by tilting. Consequently, the change of the ratio due to tilting (ΔRR-LF/HF) was significantly lower in patients with PD than in HC subjects. Further analysis showed that compared to mild stage of PD, RR-LF/HF at the supine position was significantly higher in advanced stage. By tilting, it was increased in mild stage and decreased in the advanced stage of PD, causing ΔRR-LF/HF to decrease significantly in the advanced stage. Thus, we demonstrated that spectral analysis of cardiovascular parameters is useful to identify sympathetic and parasympathetic disorders in MSA and PD. High cardiac sympathetic function at the supine position, and its reduction by tilting might be a characteristic feature of PD, especially in the advanced stage.

Development and Evaluation of Neonate Physiological Index at Parental Contact

Rooming-in is an arrangement that allows mothers and newborn babies in the same room during the postpartum hospital stay. This practice gives an opportunity for the parents to have more affectionate touching with their infants. However, the influence of intimate contact on a neonate’s physiological changes has not been studied. Our study develops an evaluation system of neonate physiological changes during parental contact. The system recorded an electrocardiogram (ECG) in real-time and analyzed the heart rate variability (HRV). Thirty healthy neonates were recruited for this study. The paired t-test was performed for statistical analysis. The HRV of a baby with and without parental hold was compared. The HF power and HF/LF ratio are significant (P<0.05). However, there is no considerable difference in LF power. In conclusion, this research has developed a system to evaluate the neonate physiological index. The system can make available the long-term monitoring and recording of neonate physiological information for parents.