SD2 Indices Research Articles

HEMODIALYSIS EFFECTS ON AUTONOMIC FUNCTION: RESULTS OF LINEAR AND NON-LINEAR ANALYSIS OF HEART-RATE-VARIABILITY AT REST AND IN RESPONSE TO PHYSICAL AND MENTAL STRESS TESTS

Objective: Cardiac arrhythmias are the most common cause of death in hemodialysis. Autonomic dysfunction plays a central role in this arrhythmogenic background. Previous studies on hemodialysis-related changes in heart-rate-variability(HRV) give contradictory results. This study investigated HRV indices both at rest and in response to physical and mental stimulation maneuvers at multiple time-points around and during the hemodialysis procedure. Design and method: Autonomic function was assessed by linear and non-linear HRV indices at pre-dialysis, during-dialysis(3 equal time-periods), post-dialysis, and on the non-dialysis day in 36 hemodialysis patients. Continuous measurement of beat-by-beat heart-rate was recorded with Finometer-PRO(The Netherlands) at rest and after orthostatic, sit-to-stand, handgrip and mental-arithmetic test. Results: The RMSSD, SD1, and SD2 indices significantly increased during dialysis(early-HD, mid-HD, late-HD periods) compared with the pre-dialysis levels(p<0.05) and returned to baseline post-dialysis(RMSSD: 54.39±83.73 vs 137.98±109.53* vs 119.85±97.34* vs 144.47±88.74* vs 85.82±121.43msec, *p<0.05 vs pre-dialysis and post-dialysis). No differences were detected in the above indices between the pre-dialysis and non-dialysis day. However, post-dialysis, the HRV responses to orthostatic and sit-to-stand tests were more exaggerated than in the pre-dialysis measurements (p<0.05). The HRV responses both at resting and physical tests in the non-dialysis day were similar to the pre-dialysis levels. HRV indices in mental-arithmetic test during hemodialysis were much higher than at the non-dialysis day(RMSSD: 77.05 (180.41) vs 19.75 (105.47)msec; p = 0.031) were detected. Conclusions: Hemodialysis causes marked changes in autonomic function. Resting HRV indices return to baseline post-dialysis, but HRV responses to physical stress remain exaggerated and return to baseline on the non-dialysis day. Detecting patients with significant autonomic dysfunction may help towards reduction of arrhythmia risk through individualized approaches.

Hemodialysis Effects on Autonomic Function: Results of Linear and Nonlinear Analysis of Heart Rate Variability at Rest and in Response to Physical and Mental Stress Tests

Introduction: Cardiac arrhythmias are the most common cause of death in hemodialysis. Autonomic dysfunction plays a central role in this arrhythmogenic background. Previous studies on hemodialysis-related changes in heart rate variability (HRV) give contradictory results. This study investigated HRV indices both at rest and in response to physical and mental stimulation maneuvers at multiple time-points around and during the hemodialysis procedure. Methods: Autonomic function was assessed by linear and nonlinear HRV indices at predialysis, during dialysis (3 equal time-periods), postdialysis, and on the nondialysis day in 36 hemodialysis patients. Continuous measurement of beat-by-beat heart rate was recorded with Finometer-PRO (The Netherlands) at rest and after orthostatic, sit-to-stand, handgrip, and mental-arithmetic test. Results: The RMSSD, SD1, and SD2 indices significantly increased during dialysis (early-HD, mid-HD, late-HD periods) compared with the predialysis levels (p < 0.05) and returned to baseline postdialysis (RMSSD: 54.39 ± 83.73 vs. 137.98 ± 109.53* vs. 119.85 ± 97.34* vs. 144.47 ± 88.74* vs. 85.82 ± 121.43msec, *p < 0.05 vs. predialysis and postdialysis). No differences were detected in the above indices between the predialysis and nondialysis day. However, postdialysis, the HRV responses to orthostatic and sit-to-stand tests were more exaggerated than in the predialysis measurements (p < 0.05). The HRV responses both at resting and physical tests in the nondialysis day were similar to the predialysis levels. HRV indices in the mental arithmetic test during hemodialysis were much higher than at the nondialysis day (RMSSD: 77.05 [180.41] versus 19.75 [105.47] msec; p = 0.031). Conclusions: Hemodialysis causes marked changes in the autonomic function. Resting HRV indices return to baseline postdialysis, but HRV responses to physical stress remain exaggerated and return to baseline on the nondialysis day. Detecting patients with significant autonomic dysfunction may help towards reduction of arrhythmia risk through individualized approaches.

Effects of using different algorithms and fiducial points for the detection of interbeat intervals, and different sampling rates on the assessment of pulse rate variability from photoplethysmography

ObjectivePulse Rate Variability (PRV) has been widely used as a surrogate of Heart Rate Variability (HRV). However, there are several technical aspects that may affect the extraction of PRV information from pulse wave signals such as the photoplethysmogram (PPG). The aim of this study was to evaluate the effects of changing the algorithm and fiducial points used for determining inter-beat intervals (IBIs), as well as the PPG sampling rate, from simulated PPG signals with known PRV content. MethodsPPG signals were simulated using a proposed model, in which PRV information can be modelled. Two independent experiments were performed. First, 5 IBIs detection algorithms and 8 fiducial points were used for assessing PRV information from the simulated PPG signals, and time-domain and Poincaré plot indices were extracted and compared to the expected values according to the simulated PRV. The best combination of algorithms and fiducial points were determined for each index, using factorial designs. Then, using one of the best combinations, PPG signals were simulated with varying sampling rates. PRV indices were extracted and compared to the expected values using Student t-tests or Mann-Whitney U-tests. ResultsFrom the first experiment, it was observed that AVNN and SD2 indices behaved similarly, and there was no significant influence of the fiducial points used. For other indices, there were several combinations that behaved similarly well, mostly based on the detection of the valleys of the PPG signal. There were differences according to the quality of the PPG signal. From the second experiment, it was observed that, for all indices but SDNN, the higher the sampling rate the better. AVNN and SD2 showed no statistical differences even at the lowest evaluated sampling rate (32 Hz), while RMSSD, pNN50, S, SD1 and SD1/SD2 showed good performance at sampling rates as low as 128 Hz. ConclusionThe best combination of IBIs detection algorithms and fiducial points differs according to the application, but those based on the detection of the valleys of the PPG signal tend to show a better performance. The sampling rate of PPG signals for PRV analysis could be lowered to around 128 Hz, although it could be further lowered according to the application. SignificanceThe standardisation of PRV analysis could increase the reliability of this signal and allow for the comparison of results obtained from different studies. The obtained results allow for a first approach to establish guidelines for two important aspects in PRV analysis from PPG signals, i.e. the way the IBIs are segmented from PPG signals, and the sampling rate that should be used for these analyses. Moreover, a model for simulating PPG signals with PRV information has been proposed, which allows for the establishing of these guidelines while controlling for other variables, such as the quality of the PPG signal.

Effects of 12-week Pilates training program on cardiac autonomic modulation: a randomized controlled clinical trial.

Aim: To evaluate the effects of 12-week Pilates training program on cardiac autonomic modulation. Materials& methods: A randomized controlled trial of a 12-week Pilates training program was conducted. A total of 54 men were randomly allocated to either a control or a Pilates group. Initially, the RR intervals were captured for 20min for later analysis of heart rate variability (HRV). The training protocol was then initiated, in which the Pilates group performed 36 sessions of the Pilates method for approximately 60min each session, three-times a week, totaling 12 weeks. The control group was instructed to maintain their normal activities during this period. One week after the end of the training, the final evaluations were performed with the capture of RR intervals in both the groups. Linear indices in the time (SDNN and rMSSD) and frequency (low frequency [LF] and high frequency [HF]) domains, and the Poincaré plot (SD1 and SD2) were used. Nonlinear indices were also analyzed (approximate entropy and detrended fluctuation analysis). Descriptive statistics and generalized mixed models were performed. Results: There was a group effect for LF (ms2) and a time effect for SD2. There was a training effect observed by the time*group interactions in which an increase in global HRV indices was found for the Pilates group after 12weeks (SDNN: mean difference [MD] =9.82; standard deviation [SD] =18.52; ES=-0.514; LF [ms2]: MD=334.23; SD=669.43; ES=-0.547; SD2: MD=14.58; SD=24.28; ES=-0.693). Conclusion: A 12-week Pilates training program promotes significant improvement in global modulation of HRV in the Pilates group considering the significant increase in SDNN, LF (ms2) and SD2 indices. Trial registration number: NCT03232866.

Immediate effects of the high-velocity low-amplitude thrust on the heart rate autonomic modulation of judo athletes

IntroductionThere is controversy about the repercussions of high speed-low amplitude thrust (HVLAT) manipulation in the thoracic region on the autonomic nervous system. Objective: To evaluate the immediate effects of the HVLAT in the high thoracic region on the heart rate autonomic modulation of judo athletes. MethodsIn the experimental study, thirty-eight healthy men divided into 2 groups (Judo athletes and non-athletes) having heart rate variability (HRV) collected beat-to-beat using a cardio-pacemater during all stages of the manipulation: i) rest, ii) time 1 (participant positioning), iii) time 2 (positioning of the participant together with the therapist), iv) HVLAT manipulation, v) post 5min, vi) post 10min and vii) post 15min HVLAT. Systolic blood pressure (SBP), diastolic blood pressure (DBP), breath frequency (BF), and HRV were also analyzed. ResultsA higher sympathetic modulation was observed with an increase in the standard deviation of successive normal R-R intervals (SDNN) and SD2 indices representing the total variability, however, there was no significant statistical difference in the root mean square of the mean squared differences (RMSSD), percentual of interval differences of successive NN intervals greater than 50 ms (pNN50), and SD1 variables, which represent the parasympathetic nervous system. ConclusionHVLAT manipulation was able to decrease HRV during manipulation, reflecting sympathetic hyperactivity. However, the return of the HRV indices to the baseline conditions in the first minutes of recovery in Judo athletes and non-athletes reflected the safety of the application of the manipulation in these conditions studied.

Parkinson's disease effect on autonomic modulation: an analysis using geometric indices.

Parkinson's disease (PD) produces autonomic changes, indicating lower parasympathetic modulation and global variability, but these changes need further studying regarding geometric methods. To investigate the autonomic modulation in individuals with PD using heart rate variability (HRV) indices obtained through geometric methods. This is a cross-sectional study that assessed 50 individuals, split into two groups: PD group (PDG; n=26; 75.36±5.21 years) and control group (CG; n=24; 75.36±5.21 years). We evaluated the autonomic modulation by measuring the heart rate beat-to-beat for 30 min with the individual in supine rest using a heart rate monitor and assessed geometric indices (RRtri, TINN, SD1, SD2, SD1/SD2 ratio, and qualitative analysis of the Poincaré plot). Significant reductions were found in RRtri, TINN, SD1, and SD2 indices among PDG compared to CG. Regarding the SD1/SD2 ratio, no significant changes were detected between the groups. The Poincaré plot demonstrated that individuals with PD had lower beat-to-beat dispersion in RR intervals, in addition to greater long-term dispersion of RR intervals compared to CG. The results suggest a reduction in the parasympathetic autonomic modulation and global variability in individuals with PD compared to controls, regardless of sex, age, and body mass index.

Effects of Breakfast Omission on Resting, Exercise, and Postexercise Autonomic and Hemodynamic Profile in Men

ABSTRACT Purpose: The acute effects of fasting interventions on metabolic dynamics have been widely investigated. However, knowledge about the acute effect of overnight fasting on hemodynamic and cardiac autonomic modulation is limited, especially during and after exercise. Our objective was to investigate the effects of breakfast omission on hemodynamic and cardiac autonomic modulation during different stress conditions. Method: Twenty-one young men [age: 20.3 (20.1, 26.5 years); body mass index: 22.7 (21.4, 24.4 kg/m2)] underwent resting and postexercise blood pressure assessments and heart rate variability (HRV) analysis, using the SD1 and SD2 indices of Poincaré plots, at rest in supine and standing positions, every 10 minutes during moderate cardiorespiratory training and every 10 minutes throughout the postexercise recovery phase, for a total of 30 minutes for each phase (exercise and recovery). All measurements were performed in a randomized order after overnight fasting or 60 minutes after a breakfast containing ~20% of the total recommended daily calories. The normality hypothesis was rejected, and the Wilcoxon test was conducted to compare the interventions (p < .05). Results: No differences between interventions were observed for resting and postexercise blood pressures (p = .21 to 0.87) or for resting, exercise, and postexercise SD1 (p = .10 to 0.82) and SD2 indices (p = .14 to 0.71). Conclusions: We concluded that overnight fasting does not promote significant changes in resting and postexercise blood pressures or cardiac autonomic modulation in young men at rest (in supine and standing positions), during 30 minutes of moderate cardiorespiratory training and throughout a 30-minute postexercise recovery phase.

Post-exercise Cardiac Autonomic Modulation: Comparison Between Triathlon And High-intensity Functional Training Athletes.

PURPOSE: To verify if athletes submitted to volume overload display differences in the cardiac autonomic function throughout the post-exercise recovery phase comparatively to athletes submitted to resistance overload. METHODS: 30 men were divided into three equal groups (p>0,05): non-athlete group (n=10 30.8±3.0 year, BMI: 24.6±2.7 kg/m2), high-intensity functional training athletes (n=10, 31.4±2.9 year, BMI: 31.4±2.2 kg/m2), and triathlon athletes (n=10, 31.2±2.8 year, BMI: 23.1±1.8 kg/m2). Participants underwent a maximal graded treadmill exercise test followed by a five-minute of active recovery protocol (2,4km/h 2,5%). During the post-exercise recovery phase, a valid R-R intervals series were recorded (5min) using a valid and reliable heart rate monitor. The data were processed off-line using the Kubios HRV - Heart Rate Variability Software. A Kruskal-Wallis test was used to determine differences in SD1 and SD2 indices between all groups. The SD1 and SD2 indices were used to assess the degree of parasympathetic reactivation and global cardiac modulation, respectively over the recovery phase. Heart rate variability, by means, SD1 and SD2 indexes of Poincaré Plot were recorded during the 30s; 1stmin; 3rdmin and 5thmin of recovery to evaluate the cardiac autonomic function (CAF). RESULTS: No significant differences were found in parasympathetic and global cardiac modulation between groups, There were no difference between 3 groups in SD1-30s (2.66-3.15; p = 0.29), SD1-1st min (2.52-3.24; p = 0.23), SD1-3rd min (2.87-3.72; p = 0.58), SD1-5th min (3.08-4.29; p = 0.44), SD2-30s (2.22-2.88; p = 0.21), SD2-1st min (2.57-2.92; p = 0.39), SD2-3rd min (4.36-5.78; p = 0.58), SD2-5th min (5.34-6.79; p = 0.53). Possibly, the magnitude of differences is small, which warrants a larger sample size than used in our study to detect statistical differences. CONCLUSIONS: In our study, no significant differences in parasympathetic and global cardiac modulation were found between groups. These initials results show that individuals submitted to resistance and volume overload training have similar abilities of the autonomic branches (sympathetic and parasympathetic) on the modulation of the heart throughout the post-exercise recovery.

Does the number of sets in a resistance exercise session affect the fast and slow phases of post-exercise cardiac autonomic recovery?

Abstract Aims: The purpose of this study was to evaluate the acute effects of different resistance exercise (RE) volumes on postexercise cardiac autonomic modulation in men. Methods: Ten young men (25.5 ± 4.9 years, 24.8 ± 2.1 kg/m2) performed 3 trials of RE with 1, 2 or 3 sets (48-72 h between each trial) of 10-12 repetitions (70% of the one-maximum repetition) of bench press, leg press, and barbell row. Heart rate variability (HRV) was assessed at the 1st and 5th minutes of recovery (fast phase) and 3 consecutive 5-minute intervals from the 5th to 20th minute of recovery (slow phase). Parasympathetic and global modulations were assessed using the SD1 and SD2 indices of HRV, respectively. The comparison of the interventions was performed using the Friedman and Wilcoxon tests (p<0.05). Results: Lower parasympathetic modulation was identified after 2 and 3 sets compared to 1 set in both the fast and slow recovery phases (p= 0.004-0.05). Lower global modulation was identified after 3 sets compared to 1 set in both fast and slow recovery phases (p= 0.005-0.01). No differences in post-exercise parasympathetic and global modulation were observed between 2 and 3 sets. Conclusion: We concluded that 2 and 3 sets of RE compared to 1 set promoted higher autonomic reduction on the post-exercise phase, which should be considered by coaches when prescribing an RE program for untrained participants or intend to manipulate the postexercise organic recovery.

Cardiovascular risk in scuba divers.

We evaluated the role of scuba diving on cardiovascular risk in a small group of divers. We have enrolled 14 subjects (12 males and 1 female, mean age 49±12.2 years) undergone to scuba diving (one patient did not complete the period of observation due to the b-blocker treatment). We evaluated electrocardiographyc trace and we have measured QT and RR interval to calculate the QTc index (Bazzet, Fridericia, Hodges and Framingam index) and the Tpeak to Tend index and heart rate variability index before and after scuba diving activity. The results of our study confirm that there is a statistically significant improvement of the RR and QT index but there is not a statistically significant increase of the QTc index (QT interval normalized by heart rate) evaluated before and after scuba diving. In the same cohort of subjects, we have noted a not statistically significant improvement of Tpeak to Tend index. Our study has underlined a statistically significant modification of the SD1 and SD2 indices representative of parasympathetic and orthosympathic activity. Scuba diving activity seems to not be associated with a statistically significant variation of the cardiovascular risk. Our data confirm that non-linear analysis is characterized by a statistically significant variation of the neurovegetative tone mainly linked to an increased parasympathetic activity. However, further studies are necessary to elucidate these preliminary findings.

Effects of High Intensity Resistance Training on Cardiac Autonomic Modulation in Hypertensive Women

Individuals with arterial hypertension often have an autonomic nervous system (ANS) imbalance with predominance of sympathetic ANS. This predominance can lead to injury of several organs affecting its functioning. There is evidence that performing high intensity resistance training (RT) with heavier loads and a lower number of repetitions results in lower cardiovascular stress when compared with lighter loads and a higher number of repetitions. However, the effects of different protocols of RT in autonomic modulation are not known specially using nonlinear analyses methods. PURPOSE: Analyze and compare the effects of different protocols of high intensity of effort RT on autonomic cardiac modulation of hypertensive women using nonlinear methods. METHODS: A randomized crossover design clinical trial was conducted with 15 postmenopausal hypertensive women who underwent a control session and two high intensity RT protocols involving 6 and 15 repetition maximum (RM). The nonlinear variables that compose Heart Rate Variability (HRV) were collected pre, immediately post, 1 h post, and 24 h post each protocol. Repeated-measures ANOVA were used. RESULTS: The SD1 indices that represent parasympathetic activity in the system were lower in 15RM protocol immediately after the exercise (9.32±11.40) when compared with 6RM (16.38±13.15) and control (19.39±13.40) (p<0.05). The SD2 indices that represent a global variability in the system also were lower in 15RM protocol especially immediately after (13.84±9.57) the exercise when compared with 6RM (24.19±17.50) and control (29.32±17.41) (p<0.05). For the 6RM protocol no relevant clinical changes were observed. CONCLUSIONS: Performing high intensity RT with lower loads and a higher number of repetitions decreases parasympathetic ANS activity, which may be related to an increased cardiovascular stress. On the other hand, heavier load and lower repetition RT did not have a significant impact upon autonomic modulation when compared to a control session.

Sensitivity, Specificity and Predictive Value of Heart Rate Variability Indices in Type 1 Diabetes Mellitus.

BackgroundHeart rate variability (HRV) indices may detect autonomic changes with good diagnostic accuracy. Type diabetes mellitus (DM) individuals may have changes in autonomic modulation; however, studies of this nature in this population are still scarce.ObjectiveTo compare HRV indices between and assess their prognostic value by measurements of sensitivity, specificity and predictive values in young individuals with type 1 DM and healthy volunteers.MethodsIn this cross-sectional study, physical and clinical assessment was performed in 39 young patients with type 1 DM and 43 young healthy controls. For HRV analysis, beat-to-beat heart rate variability was measured in dorsal decubitus, using a Polar S810i heart rate monitor, for 30 minutes. The following indices were calculated: SDNN, RMSSD, PNN50, TINN, RRTri, LF ms2, HF ms2, LF un, HF un, LF/HF, SD1, SD2, SD1/SD2, and ApEn.ResultsType 1 DM subjects showed a decrease in sympathetic and parasympathetic activities, and overall variability of autonomic nervous system. The RMSSD, SDNN, PNN50, LF ms2, HF ms2, RRTri, SD1 and SD2 indices showed greater diagnostic accuracy in discriminating diabetic from healthy individuals.ConclusionType 1 DM individuals have changes in autonomic modulation. The SDNN, RMSSD, PNN50, RRtri, LF ms2, HF ms2, SD1 and SD2 indices may be alternative tools to discriminate individuals with type 1 DM.

Involvement of rest diastolic arterial pressure in autonomic heart rate recovery from exercise in normotensive men

OBJECTIVE: Rest arterial pressure has been shown to be associated with cardiovascular mortality. Autonomic heart rate control during recovery from exercise is estimated to detect changes in cardiovascular system, which may lead to cardiovascular diseases. We assessed the involvement of rest diastolic arterial pressure (DAP) on heart rate dynamics after exercise in normotensive physically active men. METHOD: We evaluated healthy physically active men aged 18 to 22 years old divided into two unequal groups: G1- rest DAP between 80 and 90 mmHg (N=11) and G2- rest DAP < 80mmHg (N=24). Volunteers performed physical exercise on a treadmill with intensity equivalent to 60% of Vmax. Heart rate recovery in the first (HRR1) and third (HRR3) minute after exercise were measured and heart rate variability (HRV) was examined in the time and frequency domain. Additionally, we performed the quantitative analysis of the Poincare plot. HRV was recorded in the following phases: the 10-minute period before exercise, during exercise and the 60 minute period after exercise. RESULTS: We found no significant difference between G1 and G2 concerning HRV changes during exercise. The G2 group exhibited a delayed recovery of SDNN, RMSSD, RRTri, LF, HF, LF/HF, SD1 and SD2 indices during recovery from exercise. HRR1 and HRR3 was greater in the G2 group. CONCLUSION: Normotensive physically active men with DAP between 80 and 90 mmHg presented faster heart rate recovery and an accelerated recovery of heart rate autonomic control after aerobic exercise.

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ABSTRACT Introduction: Overweight and obesity have increased their prevalence worldwide; these factors relate to different pathologies, among them, alteration in cardiac autonomic function with a possible development of cardiovascular disease. Objective: To describe and compare the relation between normal anthropometric indices to parameters of heart rate variability. Materials and methods: An ex post-facto correlational study was carried out. It was analyzed data from a sample of 30 young men between 18 and 22 years old, medical students, who collaborated voluntarily, whom body mass index and waist-hip ratio was determined, and also, blood pressure and an electrocardiogram was performed for each one. For the analysis of electrocardiogram heart rate variability, the NN intervals obtained were converted into geometric figures and, from them, we calculated the triangular index, triangular interpolation of NN intervals, SD1 and SD2 indices of Poincare’s diagram, standard deviation of every NN interval, the square root of the average of the addition of squares of differences between NN intervals, frequency domain as low frequency bands, high frequency bands and relation LF/HF. Results: Subjects had an average age of 19.5±0.9 years old; weight of 66.3±7.6 Kg, body mass index of 22±2.3 Kg/m2 and waist-hip ratio of 0.86±0.1.We found a statistically significant inverse relation between the triangular interpolation of NN intervals and waist-hip ratio (r= -0.396, p<0.05). Conclusion: Changes in anthropometric indices affect heart modulation, being central obesity measured by waist- hip ratio, a better predictor of heart nervous control and sympathovagal balance. MED UIS. 2015;28(3):301-8. Keywords: Heart Function Tests. Obesity. Anthropometry. Heart Rate. Overweight.

Responses of the geometric indices of heart rate variability to the active orthostatic test in women

OBJECTIVES: The effects of the orthostatic test on the cardiovascular system have been investigated, but there are no data on the behavior of the geometric indices of heart rate variability. We evaluated the effects of the active orthostatic test on the geometric indices of heart rate variability in women. METHOD: The study was performed on 12 healthy women between ages 18 and 30. For the analysis of heart rate variability, heart rate was recorded beat-to-beat. The RR intervals were transformed into geometric figures, and from these we calculated the triangular index, the triangular interpolation of RR intervals, the SD1, SD2 indexes and the SD1/SD2 ratio, which were obtained from the Poincare´ plot. Visual analysis of the plot was also performed. For the test, participants quickly stood up from a seated position in 3 seconds or less, and remained standing still for 15 minutes. Heart rate variability samples were collected at four moments: rest, 0-5 minutes, 5- 10 minutes and 10-15 minutes at standing position. RESULTS: The triangular index, the triangular interpolation of RR intervals, the SD1 and SD2 indices were reduced (p < 0.05) at 10-15 minutes after the volunteers stood up from seated position. The SD1/SD2 ratio was decreased at 0-15 minutes after the subjects changed from seated to orthostatic position. CONCLUSION: The geometric indices of heart rate variability decreased in response to the active orthostatic test in healthy women.

Auditory stimulation with music influences the geometric indices of heart rate variability in men.

BackgroundChronic classical music was reported to increase parasympathetic activitywhen evaluating heart rate variability (HRV). It is poor in the literature investigation of the acute effects of baroque and heavy metal styles of musical auditory stimulation on HRV. In this study we evaluated the acute effects of relaxant baroque and excitatory heavy metal music on the geometric indices of HRV in healthy men.MethodThe study was performed in 12 healthy men between 18 and 30 years old. We excluded persons with previous experience with music instrument and those who had affinity with the song styles. We analyzed the following indices: RRtri, TINN and Poincaré plot (SD1, SD2 and SD1/SD2 ratio). HRV was recorded at rest for ten minutes. Subsequently they were exposed to relaxant baroque or excitatory heavy metal music for five minutes through an earphone. After the first music exposure they remained at rest for more five minutes and them they were exposed again to Baroque or Heavy Metal music (65–80 dB). The sequence of songs was randomized for each individual.ResultsThe RRTri and SD2 indices were reduced during the heavy metal musical auditory stimulation (p < 0.05). No changes were observed regarding TINN, SD1 and SD1/SD2 ratio (p > 0.05).The qualitative Poincaré plot analysis indicated that during relaxant classical baroque music there was observed a higher beat-to-beat dispersion of RR intervals compared with no music exposure and during excitatory heavy metal musical auditory stimulation, showing higher HRV.ConclusionWe suggest that excitatory heavy metal music acutely decreases global HRV.

Heart Rate Variability in Novice Pilots During and After a Multi-Leg Cross-Country Flight

A pilot's workload induces autonomic nervous system modulations which could be related to a decrease of vigilance that could impair safety. Kinetics during flight and recovery are not well known. The aim of this study was to assess linear and nonlinear heart rate variability (HRV) modulations and vigilance during a high mental workload induced by a complex flight and subsequent recovery. There were 10 novice pilots (37.8 +/- 4.4 yr, 115.8 +/- 15.7 h flight experience) who performed a 3 h 30 min (09:30-13:00) multi-leg cross-country flight (Piper Pa28 airplane: 160 hp). We recorded electrocardiogram (ECG) during the flight and performed tests during the 24 h before and after the flight (13:30, 16:00, 18:30, 21:00, and 06:45). Tests included a stand test (10 min supine, 10 min standing), a Mackworth 'clock' vigilance test, and a Karolinska Sleepiness Scale questionnaire. We assessed HRV components by time and frequency domains in parallel with the Poincaré plot analysis. The flight induced a progressive decrease of RR intervals, standard deviation between normal-to-normal intervals (SDNN), Poincaré SD1 and SD2 indices, and an increase of the low-frequency to high-frequency ratio (LF/HF). During recovery, vigilance remained depressed for 2 h 30 min after the flight. The decreased RR intervals and SD1 persisted for 5 h postflight both in supine and standing positions. LF/HF stayed elevated for 2 h 30 min after the flight. A multi-leg cross-country flight involves a vagal withdrawal and an increase of sympathetic activity lasting 5 h after landing. This delay could be recommended as a safety period.

Characterization of Heart Rate Variability Changes Following Asphyxia in Rats

A non-invasive method to monitor the functioning of the autonomous nervous system consists in heart rate variability (HRV) analysis. The aim of this study was to investigate the changes on HRV after an asphyxia experiment in rats, using several linear (time and frequency domain) and nonlinear parameters (approximate entropy, SD1 and SD2 indices derived from Poincare plots). The experiments involved the study of HRV changes after cardiac arrest (CA) resulting from 5 min of hypoxia and asphyxia, followed by manual resuscitation and return of spontaneous circulation. 5 min stationary periods of RR intervals were selected for further analysis from 5 rats in following distinct situations: 1) baseline, 2) 30 min after CA, 3) 60 min after CA, 4) 90 min after CA, 5) 120 min after CA, 6) 150 min after CA. The ANS contribution has been delineated based on time and frequency domain analysis. The results indicate that the recovery process following the asphyxia cardiac arrest reflects the impaired functioning of the autonomic nervous system. Both linear and nonlinear parameters track the different phases of the experiment, with an increased sensitivity displayed by the approximate entropy (ApEn). After 150 min the ApEn RRI parameter recovers to its baseline value. The results forward the ApEn as a more sensitive parameter of the recovery process following the asphyxia.