Heart Rate Variability Domains Research Articles

Heart Rate Variability in Military Pilots During Flight: A Scoping Review.

Piloting an aircraft is a complex multitasking activity that involves managing information in a nonautomatic way and generates a high workload (psychological, cognitive, and physical) for the pilot. The excess of these demands can result in decreased performance and may impair flight safety. Heart rate variability (HRV) has been used in recent studies as a method to investigate operator's workload in complex environments. This measure can assess the stress and recovery ability of the autonomic nervous system. However, a better understanding of flight influence on the pilot's autonomic modulation is necessary. Therefore, this scoping review aims to systematically map the studies related to changes in the autonomic modulation in military pilots during flight, in order to characterize their workload at different times and flight profiles. A literature search was conducted using MEDLINE (by PubMed), SCOPUS, and LILACS databases. Recent records (2002-2022) that analyzed HRV in military pilots during flight were included. Meanwhile, studies in which piloting activity was not performed were excluded. The study was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline extension for Scoping Reviews and the Updated Methodological Guidance for the Conduct of Scoping Reviews. A total of 298 records were obtained, of which 19 were included in the scoping review. The studies analyzed flights performed in high- and low-performance aircrafts, helicopters, and flight simulators, using time domain, frequency domain, and nonlinear HRV indices. Real and simulated flights produced significant autonomic changes. Some flights elicited autonomic nervous system responses that persisted up to 5 h after landing. During real flight, the most sensitive indices for identifying variations in pilot workload were root mean square of successive differences between normal heartbeats, standard deviation of interbeat interval of normal sinus beat (SDNN), ratio of low-frequency to high-frequency power, and Poincaré plot standard deviation perpendicular to the line of identity (SD1), whereas the interbeat interval (RR), SDNN, SD1, and Poincaré plot standard deviation along the line of identity (SD2) were the most sensitive indices when comparing segments of simulated flight with different levels of difficulty. This scoping review provided insight into the influence of flight on autonomic modulation in military pilots. Some key themes were highlighted: Increased sympathetic activity during flight, sensibility of different domains of HRV to flight demands, and autonomic changes during recovery time. Future research efforts may allow us to enhance the understanding of pilot's workload limits and to elucidate the optimal postflight recovery time.

Reliability of an "At-Home" Method for Monitoring Resting and Reactive Autonomic Nervous System Activity in Children: A Pilot Study.

Heart rate variability (HRV), an index of the functional status of the autonomic nervous system (ANS), provides an opportunity for early detection of ANS dysfunction. Lower resting, vagally related HRV parameters are associated with increased risk of physical and mental illness. External factors influencing the ANS, such as the testing environment, may impact the interpretation of HRV. This study's main aim was to determine the reliability of HRV resting and reactivity tests performed at home with children aged 4-9 years. Fourteen healthy children (female n = 8) aged 6.8 ± 1.5 years participated. Two HRV tests were performed at home via online supervision 7 days apart using a Polar H10 heart rate monitor. The absolute and relative reliability of the pre-exercise resting (5 min) and sub-maximal exercise step test recovery (4 × 30 s segments) HRV time and frequency domains were calculated. The Pearson correlation coefficients for day 1 versus day 7 for the vagal activity HRV domains (RMSSD log) at rest and in the first 30 s and 30-60 s of recovery indicated good-to-excellent relative reliability (r > 0.8, p < 0.01). Absolute reliability was moderate for the resting RMSSD log, with a coefficient of variation (CV) of 5.2% (90% CI: 3.9, 7.8%), high for the first 30 s of standing recovery, with a CV of 10.7% (90% CI: 8.2, 15.7%), and moderate for 30-60 s of recovery, with a CV of 8.7% (90% CI: 6.6, 12.9%). The findings of this pilot study indicate that the resting and exercise recovery HRV measures of vagal activity can be measured reliably at home in children. This represents a novel "at-home" protocol for monitoring ANS health and development in children.

Study of heart rate and corticosterone variability in the simulation of rhino-surgical interventions in biological objects.

Aims: to assess changes in the time range of heart rate variability (HRV) and plasma corticosterone concentration in rats after simulating septoplasty. Materials and methods: a septoplasty was simulated in 30 mature male Wistar rats weighing 210-290 g. An ECG was recorded with subsequent analysis of the time domain of HRV, as well as blood sampling for changes in the concentration of corticosterone in the blood plasma. Results: SDNN significantly increased in comparison with the control on days 2 and 3 (p &lt;0.001), but decreased on days 4-5 (p &lt;0.001) and 6 days (p &lt;0.01 ). rMSSD changed in waves with two irregular peaks on days 1 and 6. SDNN / rMSSD, in comparison with the 1st day of the postoperative period, increased on the 2nd day and continued to grow (p &lt;0.05), and on the 4th day it began to decrease (p &lt;0.01). The total power of HRV was low throughout the postoperative period (p &lt;0.001), except for the 3rd day, when it was equal to the control data. The increase in the total power indicator fell on the 3rd day after the operation (p &lt;0.01), after which its decline occurred again. The concentration of corticosterone in the blood plasma in rats was significantly higher than before (p &lt;0.001). From the 2nd to the 4th postoperative day, its plateau was determined. Conclusion: Simulation of septoplasty leads to changes in the time range of HRV, an increase in the concentration of corticosterone in the blood plasma in rats with its maximum at the time of surgery and after 24 hours, the formation of a "plateau" from the 2nd to the 4th postoperative days, which coincides with changes of HRV.

Impaired Modulation of the Autonomic Nervous System in Adult Patients with Major Depressive Disorder.

Patients with major depressive disorder (MDD) have an increased risk for cardiac events. This is partly attributed to a disbalance of the autonomic nervous system (ANS) indicated by a reduced vagal tone and a (relative) sympathetic hyperactivity. However, in most studies, heart rate variability (HRV) was only examined while resting. So far, it remains unclear whether the dysbalance of the ANS in patients with MDD is restricted to resting or whether it is also evident during sympathetic and parasympathetic activation. The aim of this study was to compare the responses of the ANS to challenges that stimulated the sympathetic and, respectively, the parasympathetic nervous systems in patients with MDD. Forty-six patients with MDD (female 27 (58.7%), mean age 44 ± 17 years) and 46 healthy controls (female 26 (56.5%), mean age 44 ± 20 years) underwent measurement of time- and frequency-dependent domains of HRV at rest, while standing (sympathetic challenge), and during slow-paced breathing (SPB, vagal, i.e., parasympathetic challenge). Patients with MDD showed a higher heart rate, a reduced HRV, and a diminished vagal tone during resting, standing, and SPB compared to controls. Patients with MDD and controls responded similarly to sympathetic and vagal activation. However, the extent of modulation of the ANS was impaired in patients with MDD, who showed a reduced decrease in the vagal tone but also a reduced increase in sympathetic activity when switching from resting to standing. Assessing changes in the ANS during sympathetic and vagal activation via respective challenges might serve as a future biomarker and help to allocate patients with MDD to therapies like HRV biofeedback and psychotherapy that were recently found to modulate the vagal tone.

Following your heart: Cardiac autonomic modulation as a feature of decision-making under ambiguity and risk

Decision-making requires a bidirectional flow of information from perception, emotion, and bodily behaviour. Heart rate variability (HRV) provides a non-invasive, cost-effective way to assess this connection. 112 healthy participants completed two established decision tasks under ambiguity and risk. Heart rate was continuously recorded at rest, during, and after task performance. To account for differences in cardiac modulation the sample was stratified by sex. Time, frequency, and non-linear HRV domains were selected to assess vagal modulation and sympatho-vagal balance. Vagally meditated HRV showed a pattern corresponding to a replenishment effect by increasing during decision-making in both tasks compared to rest, and then gradually returning to initial levels during recovery. This effect may indicate successful self-regulation, such as enhanced concentration, or emotional regulation. Regarding decision-making, women and men making disadvantageous decisions under ambiguity had higher vagally mediated HRV than those making advantageous decisions. Consistent with this finding are the results for decisions under risk for women. Contrary, men making disadvantageous decisions under risk, showed lower vagally mediated HRV than those making advantageous decisions. The results suggest that there are sex-specific differences to be investigated in the future. HRV analysis is an effective approach for differentiating somatic characteristics associated with decision-making performance.

Analysis of the factors of heart rate variability affected after a hypoxia tolerance test as a function of gender

Heart rate variability (HRV), the variation of time intervals between heartbeats, reflects the result of the interaction between the autonomic nervous system and the cardiovascular system. Hypoxia is a stressor that causes changes in HRV and a decrease in arterial oxygen saturation (SaO2). The aim of our study is to analyse if the time and frequency domains of HRV are affected after a hypoxia tolerance test in healthy participants as a function of gender. Material and methods: 23 healthy volunteers (11 women and 12 men) with a mean age of 23.08±2.99 performed a hypoxia tolerance test (11%, 5050 m) with the iAltitude simulator. Heart rate and SaO2 were monitored during the test and HRV frequency domain (FD) and time domain (TD) data were obtained. We analysed the five minutes before and after each session. Outcomes: Simulated altitude-induced hypoxia can cause changes in HRV in a group of healthy individuals. Statistically significant differences were also found between before and after the normobaric hypoxia test in the time-domain variables RRm, SDNN, HRm, HR STD, pNN50. In addition, in women statistically significant differences were found in RMSSD, and in the frequency-domain variables HF and LF/HF. While in males, statistically significant differences were found in SDNN. In both men and women, significant differences were observed in RRm, HRm and pNN50. Conclusion: The differences found in HRV after the hypoxia tolerance test indicate that females show a greater activation of the parasympathetic nervous system compared to males. While males showed greater sympathetic activation. Keywords: Heart rate variability, normobaric hypoxia, stress, autonomic nervous system.

Changes in heart rate variability over time from symptom onset of transient global amnesia

Transient global amnesia (TGA) often involves precipitating events associated with changes in autonomic nervous system (ANS), and heart rate variability (HRV) reflects the ANS state. This study aimed to investigate HRV changes after TGA. A retrospective analysis of HRV included patients diagnosed with TGA between January 2015 and May 2020. The time and frequency domains of HRV were compared among three groups: early (< 1 week after TGA, n = 19), late (1–4 weeks after TGA, n = 38), and healthy control (HC, n = 19). The Pearson’s correlation between time and time-domain HRV was also examined. The standard deviation of NN intervals (SDNN) (early, 47.2; late, 35.5; HC, 41.5; p = 0.033) and root mean square of successive RR interval differences (RMSSD) (early, 38.5; late, 21.3; HC, 31.0; p = 0.006) differed significantly among the three groups. Post-hoc analysis showed statistically significant differences only in the early and late groups in both SDNN (p = 0.032) and RMSSD (p = 0.006) values. However, the frequency domain with total power, low-frequency and high-frequency powers, and low-frequency/high-frequency ratio did not differ. SDNN (Pearson correlation coefficient =− 0.396, p = 0.002) and RMSSD (Pearson correlation coefficient =− 0.406, p = 0.002) were negatively correlated with time after TGA. Changes in HRV occurred over time after the onset of TGA, with the pattern showing an increase in the first week and then a decrease within 4 weeks.

Cardiac remodeling in patients with heart failure with mildly reduced ejection fraction and metabolic disorders: association with biomarkers and autonomic nervous system parameters

Aim. The high prevalence of obesity in a cohort of patients with heart failure and mildly reduced ejection fraction (HFmrEF) determines the relevance of clarifying the role of biomarkers and autonomic imbalance in myocardial remodeling, taking into account metabolic risk factors.Material and methods. We examined 19 men with postinfarction cardiosclerosis and class II HFmrEF (median age 62 years), overweight/class I-II obesity, type 2 diabetes in 53/47%, 48% of cases, respectively, who received therapy. The biomarker panel included N-terminal pro-brain natriuretic peptide (NT-proBNP), galectin-3, pro-collagen I C-terminal propeptide (PICP), N-terminal propeptide of procollagen type III (PIIINP), C-terminal telopeptide of type I collagen, matrix metalloproteinase-9 (MMP-9), tissue inhibitor of matrix proteinase-1 (TIMP-1), leptin and adiponectin. Heart rate variability (HRV) and turbulence were obtained using 24-hour Holter monitoring. We assessed the time and frequency domains of HRV (24 h) and 5 min recordings of wakefulness at rest, calculated TO (turbulence onset) and TS (turbulence slope).Results. Significant positive associations of leptin and TIMP-1 levels with left ventricular hypertrophy markers were confirmed. Positive correlations of peak e' with following HRV indicators were revealed: SDNN (r=0,68; p=0,02) and RMSSD (r=0,69; p=0,003). Lower TS values were associated with higher index parameters of left ventricular mass (p&lt;0,05 for all). Associations of biomarkers with autonomic nervous system (ANS) were observed: MMP-9 with RMSSD (r=0,54) and pNN50 (r=0,51); TIMP-1 with TO (r=0,46); PICP/PIIINP ratio with HFn (5 min) (r=-0,49); NT-proBNP/adiponectin ratio with SDNN (r=-0,49); leptin level with TS (r=-0,54) (p&lt;0,05 for all).Conclusion. In patients with HFmrEF of ischemic origin and additional metabolic risks, serum biomarkers of fibrosis, adipokines, and ANS parameters are associated mainly with markers of increased left ventricular filling pressure. The study results predetermine the further search for potential risk-stratification markers of unfavorable myocardial remodeling and prognosis in large samples of patients with metabolic deviations and HF with EF &gt;40% against the background of modern drug therapy.

Mood Disorder Severity and Subtype Classification Using Multimodal Deep Neural Network Models.

The subtype diagnosis and severity classification of mood disorder have been made through the judgment of verified assistance tools and psychiatrists. Recently, however, many studies have been conducted using biomarker data collected from subjects to assist in diagnosis, and most studies use heart rate variability (HRV) data collected to understand the balance of the autonomic nervous system on statistical analysis methods to perform classification through statistical analysis. In this research, three mood disorder severity or subtype classification algorithms are presented through multimodal analysis of data on the collected heart-related data variables and hidden features from the variables of time and frequency domain of HRV. Comparing the classification performance of the statistical analysis widely used in existing major depressive disorder (MDD), anxiety disorder (AD), and bipolar disorder (BD) classification studies and the multimodality deep neural network analysis newly proposed in this study, it was confirmed that the severity or subtype classification accuracy performance of each disease improved by 0.118, 0.231, and 0.125 on average. Through the study, it was confirmed that deep learning analysis of biomarker data such as HRV can be applied as a primary identification and diagnosis aid for mental diseases, and that it can help to objectively diagnose psychiatrists in that it can confirm not only the diagnosed disease but also the current mood status.

Field Investigations on Subjective Perception, Physiological Responses, and Cognitive Performance under Increasing CO2 Concentration in an Underground Confined Space

The objective of this research was to explore the impacts of heightened CO2 concentrations on human health and wellness in an underground confined space. A total of 180 participants were subjected to CO2 concentrations ranging from 1000 to 10000 ppm within a confined underground environment. The study assessed not only subjective perceptions and physiological responses but also cognitive performance, integrating novel measures such as emotion, skin conductance (SC), and heart rate variability (HRV). The findings demonstrated a notable variation in thermal sensation votes (TSV) and perceived air quality acceptability with the change in CO2 concentration. A significant increase in total mood disturbance (TMD) of 1.5 units was observed at a CO2 concentration of 8500 ppm, compared to 1000 ppm. Cognitive performance remained consistent for concentrations below 8500 ppm; however, a substantial alteration was noted at 10000 ppm. In terms of task difficulty, numerical calculations were perceived to require 0.74 units more effort than letter searches. As CO2 concentration exceeded 7500 ppm, significant variances were noted in physiological parameters such as diastolic blood pressure (DBP), heart rate (HR), LF/HF, MF/HF ratios, PNN 50, and frequency domains of HRV (LF, MF, and HF) in comparison to the parameters at 1000 ppm. At 8500 ppm, the LF and HF parameters were found to be 780 and 452.3 units, respectively, higher than at 7000 ppm. These findings suggest that high humidity, low temperature, and elevated CO2 concentrations collectively contribute to the significant human stress responses. This study is of interest as there are limited reported researches on the air quality in underground confined space.

Association between Sleep Quality and Cardiac Autonomic Modulation in Adolescents: A Cross Sectional Study.

Objective To analyze the impact of sleep quality/duration on cardiac autonomic modulation on physically active adolescents with obesity. Materials and Methods The present cross-sectional study included 1,150 boys with a mean age of 16.6 ± 1.2 years. The assessment of cardiac functions included the frequency domain of heart rate variability (HRV; low frequency - LF; high frequency - HF; and the ratio between these bands -LF/HF -, defined as the sympathovagal balance), and each parameter was categorized as low / high . Physical activity levels and sleep quality/duration were obtained by questionnaires. Abdominal obesity was assessed and defined as waist circumference > 80 th percentile. Results Poor sleep quality resulted in lower HF (odds ratio [OR]: 1.8; 95% confidence interval [95%CI]: 1.01-3.21]) regardless of physical activity and abdominal obesity. Moreover, the study found no association between sleep duration and HRV parameters in adolescents. Conclusion Sleep quality, not sleep duration, reduces parasympathetic cardiac modulation apart from other factors such as physical activity and abdominal obesity in adolescents.

Chronic Sacral Nerve Stimulation Inhibits Visceral Hypersensitivity in Diarrhea–Predominant Irritable Bowel Syndrome Rats Model

ObjectiveSacral nerve stimulation (SNS) is emerging as a novel treatment for irritable bowel syndrome (IBS). However, its effects are limited, and the underlying mechanisms remain largely unknown. Materials and MethodsIn this study, rats were divided into three groups (n = 12 rats per group): 1) the SNS group; 2) the sham SNS group (the sham group for short); and 3) the control group. The SNS and sham groups were exposed to chronic and acute stress to establish an IBS model. Electrode implantation surgery was performed in rats with the IBS model. The SNS group received electrical stimulation for 30 minutes every day for seven days. Abdominal withdrawal reflex (AWR) was used to evaluate the effect of SNS on visceral sensitivity in diarrhea-predominant IBS (IBS-D) rats. The frequency domain of heart rate variability (HRV) was analyzed to assess the effect of SNS on regulating the autonomic function. The expression of transient receptor potential vanilloid 1 (TRPV1) in the colon, spinal cord, and hippocampus was detected by immunohistochemistry to explore the mechanism of SNS in IBS-D rats. ResultsCompared with the sham group, AWR scores were significantly decreased under different gas volumes of stimulation of 0.4, 0.6, and 0.8 ml for rectal distention in the SNS group (all p < 0.05). However, there was no significant difference <1.0 ml between the two groups (p > 0.05). Compared with the sham group, the frequency domain indexes of HRV were significantly altered. Normalized low-frequency power and low frequency-to-high frequency ratio were significantly decreased, and normalized high-frequency power was significantly increased in the SNS group (all p < 0.05). Moreover, the expression of TRPV1 in the spinal cord and colon in the SNS group was significantly decreased compared with the sham group (both p < 0.05). These results suggested that chronic SNS not only improved the visceral sensitivity and autonomic dysfunction but also decreased the expression of TRPV1 in the spinal cord-gut tissue in IBS-D rats. ConclusionChronic SNS was found to have an inhibitory effect on visceral hypersensitivity in IBS-D rats, providing experimental evidence for its potential clinical application in IBS.

Sound stimulation using the individual's heart rate to improve the stability and homeostasis of the autonomic nervous system.

In this study, we explain the role of enhancing the stability and homeostasis of the autonomic nervous system (ANS) by proposing the average heart rate sound resonance (aHRSR), a sound stimulation to prevent imbalance of ANS due to dynamic movement. The effect of aHRSR on ANS was analyzed through the time and frequency domain of heart rate variability (HRV) using the photoplethysmogram data (PPG) of 22 participants (DUIRB-202109-12). When the subjects performed dynamic movements that could cause changes in the ANS, HRV indicators using PPG data for 5 min before and after the movements were analyzed according to the presence or absence of aHRSR. The standard deviation of the NN intervals (SDNN), the square root of the mean squared differences of the NN intervals (RMSSD), low-frequency band (LF), and high-frequency band (HF), which represent sympathetic and parasympathetic nerve activity, were used as indicators, where SNDD and LF represent total ANS and sympathetic activity, while RMSSD and HF represent parasympathetic activity. As the effects of aHRSR on dynamic movement, the recovery time of RR interval was advanced by about 15 s, SDNN increased from ([44.16 ± 13.11] to [47.85 ± 15.16]) ms, and RMSSD increased from ([23.73 ± 9.95] to [31.89 ± 12.48]) ms (p < 0.05), increasing the stability of the ANS and reducing instability. The effect of homeostasis of the ANS according to aHRSR is also shown in reducing the change rate of LF from (-13.83 to -8.83) %, and the rate of change of HF from (10.59 to 3.27) %. These results suggest that aHRSR can affect the cardiovascular system by assisting physiological movements that occur during dynamic movement.

Effect of acupuncture-moxibustion stimulation of combined "Biao-Ben" acupoints on autonomic nervous activity and related factors in rats with irritable bowel syndrome diarrhea

To observe the effect of acupuncture and moxibustion of the combined "Biao-Ben" acupoints on autonomic nervous function and related factors in rats with irritable bowel syndrome diarrhea (IBS-D). Female SD rats were randomly divided into normal control, IBS-D model, "Biao-Ben" acupoint combination, and conventional acupoint combination groups, with 10 rats in each group. The IBS-D model was established by repeated chronic stress stimulation (water or food deprivation, painful tail pinching, exposure to a 43 ℃ environment, forced swimming in 4 ℃ water, day-night inversion and horizontal vibration) for 28 d, and followed by acute restraint stress (wrapping of shoulders, forelimbs and trunk) for 1 h and gavage of senna fluid, once daily for 28 d. For rats of the "Biao-Ben" acupoint combination group, acupuncture and moxibustion were applied to "Guanyuan" (CV4), bilateral "Zusanli" (ST36), and "Neiguan" (PC6), and for rats of the conventional acupoint combination group, acupuncture and moxibustion were applied to bilateral ST36, "Tianshu"(ST25), and "Shangjuxu"(ST37). Both acupuncture and suspension moxibustion treatment were conduced for 15 min, once daily for 21 days. The fecal water content was calculated, and the spontaneous activity behaviors (total distance of crossing and the number of squares crossed in 5 min) were evaluated by open-field tests. The abdominal withdrawal reflex (AWR) was detected. H.E. staining was used to observe the histopathological changes of colon tissue. The domains of heart rate variability (HRV) including low frequency (LF), high frequency (HF), and LF/HF were analyzed using an electrophysiological recorder. The contents of calcitonin gene-related peptide (CGRP) in serum and noradrenaline (NE) in plasma were detected using ELISA. The expression level and immunoactivity of 5-hydroxytryptamine (5-HT) in colon tissues were detected by Western blot and immunofluorescence histochemistry, separately. Compared with the normal group, the model group had a striking increase in fecal water content, AWR scores at 20, 40, 60, and 80 mm Hg, NE and CGRP contents, LF, LF/HF, and 5-HT protein expression and immunoactivity (P<0.01), and an obvious decrease in the total distance of crossing, the number of squares crossed, and HF of HRV (P<0.01). In comparison with the model group, the fecal water content, AWR scores at 20, 40, 60, and 80 mm Hg, NE and CGRP contents, LF, LF/HF, and 5-HT protein expression and immunoactivity were significantly decreased (P<0.01,P<0.05), while the total distance of cros-sing, number of squares crossed, HF of HRV were considerably increased (P<0.01, P<0.05) in both "Biao-Ben" acupoint combination and conventional acupoint combination groups. The effects of the "Biao-Ben" acupoint combination were apparently superior to those of conventional acupoint combination in down-regulating the fecal water content, AWR score at 20, 40, 60 and 80 mm Hg, NE and CGRP contents, LF, LF/HF, and 5-HT expression and immunoactivity, and in increasing the number of squares crossed, and HF of HRV (P<0.01, P<0.05). HE staining showed no pathological changes in colonic mucosa in all groups. Acupuncture and moxibustion stimulation of combined "Biao-Ben" acupoints can effectively improve the symptoms (spontaneous activities, visceral hypersensitivity) of IBS-D model rats, which may be related to its functions in regulating autonomic nervous activities, and down-regulating blood NE and CGRP contents and colonic 5-HT protein expression and immunoactivity, and the effects of "Biao-Ben" acupoint combination are superior to those of conventional acupoint combination.

The Retinal Nerve Fiber Layer Thickness Is Associated with Systemic Neurodegeneration in Long-Term Type 1 Diabetes.

To determine whether the retinal nerve fiber layer thickness can be used as an indicator for systemic neurodegeneration in diabetes. We used existing data from 38 adults with type 1 diabetes and established polyneuropathy. Retinal nerve fiber layer thickness values of four scanned quadrants (superior, inferior, temporal, and nasal) and the central foveal thickness were extracted directly from optical coherence tomography. Nerve conduction velocities were recorded using standardized neurophysiologic testing of the tibial and peroneal motor nerves and the radial and median sensory nerves, 24-hour electrocardiographic recordings were used to retrieve time- and frequency-derived measures of heart rate variability, and a pain catastrophizing scale was used to assess cognitive distortion. When adjusted for hemoglobin A1c, the regional thickness of the retinal nerve fiber layers was (1) positively associated with peripheral nerve conduction velocities of the sensory and motor nerves (all P < 0.036), (2) negatively associated with time and frequency domains of heart rate variability (all P < 0.033), and (3) negatively associated to catastrophic thinking (all P < 0.038). Thickness of the retinal nerve fiber layer was a robust indicator for clinically meaningful measures of peripheral and autonomic neuropathy and even for cognitive comorbidity. The findings indicate that the thickness of the retinal nerve fiber layer should be studied in adolescents and people with prediabetes to determine whether it is useful to predict the presence and severity of systemic neurodegeneration.

The Validity of Heart Rate Variability Obtained from Electrocardiography and Blood Pressure in Rats Subjected to Isoproterenol-Induced Heart Ischemia.

Heart rate variability (HRV) is calculated by electrocardiography (ECG-HRV) or blood pressure (BP-HRV). The purpose of this study was to determine the validity of the above methods in rats with normal and ischemic hearts during the baroreflex maneuver. The study was conducted at Shiraz University of Medical Sciences, Shiraz, Iran, in 2021. Sprague-Dawley rats were divided into a sham group and an isoproterenol-mediated cardiac ischemia (ISO) group. Saline and isoproterenol (150 mg/kg) injected subcutaneously for 2 consecutive days in the sham and ISO groups, respectively. Then, the animals were anesthetized with an intraperitoneal injection of sodium thiopental (60 mg/kg), and the femoral artery and vein were cannulated. Baroreflex was activated using an intravenous injection of phenylephrine (10 μg/100 μL saline). ECG, BP, and heart rate (HR) were recorded, and the time domain of HRV and baroreflex gain were calculated. Baroreflex gain in the ISO group (male, weight=275.8±2.8 g, n=8) was lower than that in the sham group (male, weight=258±2.3 g, n=8) (P<0.05). ECG-HRV indicated an increase in the standard deviation of the RR interval (SDRR), the index of overall HRV, and the parasympathetic index of the root mean square of successive differences (RMSSD) in both groups. However, the rise in SDRR and RMSSD in the ISO group was less than that in the sham group (P<0.05). SDRR and RMSSD obtained from BP did not show a difference between the sham and ISO groups, nor did they correspond with the results seen in baroreflex gain. BP-HRV was not as valuable as ECG-HRV in assessing cardiac ischemia.

COMPARISON OF THE EFFECTS OF MODELING SEPTOPLASTY AND DEPRIVATION OF THE OLFACTORY ANALYZER IN RATS ON CHANGES IN HEART RATE VARIABILITY

The effect of modeling septoplasty and modeling sensory deprivation of the olfactory analyzer in rats on changes in the frequency domain of heart rate variability was compared. Bulbectomy provokes more pronounced changes in heart rate variability in rats, compared with septoplasty simulation.

Study of heart rate and corticosterone variability in the simulation of experimental rhino-surgical interventions.

Aims: to assess changes in the time range of heart rate variability (HRV) and plasma corticosterone concentration in rats after simulating septoplasty. Materials and methods: a septoplasty was simulated in 30 mature male Wistar rats weighing 210-290 g. An ECG was recorded with subsequent analysis of the time domain of HRV, as well as blood sampling for changes in the concentration of corticosterone in the blood plasma. Results: SDNN significantly increased in comparison with the control on days 2 and 3 (p &lt;0.001), but decreased on days 4-5 (p &lt;0.001) and 6 days (p &lt;0.01 ). rMSSD changed in waves with two irregular peaks on days 1 and 6. SDNN / rMSSD, in comparison with the 1st day of the postoperative period, increased on the 2nd day and continued to grow (p &lt;0.05), and on the 4th day it began to decrease (p &lt;0.01). The total power of HRV was low throughout the postoperative period (p &lt;0.001), except for the 3rd day, when it was equal to the control data. The increase in the total power indicator fell on the 3rd day after the operation (p &lt;0.01), after which its decline occurred again. The concentration of corticosterone in the blood plasma in rats was significantly higher than before (p &lt;0.001). From the 2nd to the 4th postoperative day, its plateau was determined. Conclusion: Simulation of septoplasty leads to changes in the time range of HRV, an increase in the concentration of corticosterone in the blood plasma in rats with its maximum at the time of surgery and after 24 hours, the formation of a "plateau" from the 2nd to the 4th postoperative days, which coincides with changes of HRV.

MODELING SEPTOPLASTY AND SENSORY DEPRIVATION IN RAT OLFACTORY ANALYZER AND ITS IMPACT ON THE RESPONSES OF THE AUTONOMIC NERVOUS SYSTEM

Experimental septoplasty and sensory deprivation in rat olfactory analyzer was conducted to study changes in the frequency domain of heart rate variability. Bulbectomy provokes more pronounced changes in heart rate variability in rats, compared with septoplasty simulation. After bulbectomy, there is an increase in the high frequencies, low frequencies, very low frequencies, and the LF/HF ratio.

Drowsiness Transitions Detection Using a Wearable Device

Due to a reduction in reaction time and, consequently, the driver’s concentration, driving when fatigued has become an issue throughout time. Consequently, the likelihood of having an accident and it being fatal increases. In this work, we aim to identify an automatic method capable of detecting drowsiness transitions by considering the time, frequency, and nonlinear domains of heart rate variability. Therefore, the methodology proposed considers the multivariate statistical process control, using principal components analysis, with accelerometer and time, frequency, and nonlinear domains of the heart rate variability extracted by a wearable device. Applying the proposed approach, it was possible to improve the results achieved in the previous studies, where it was able to remove points out-of-control due to signal noise, identify the drowsy transitions, and, consequently, improve the drowsiness classification. It is important to note that the out-of-control points of the heart rate variability are not influenced by external noise. In terms of limitations, this method was not able to detect all drowsiness transitions, and in some individuals, it falls far short of expectations. Regarding this, is essential to understand if there is any pattern or similarity among the participants in which it fails.