Adapting psychophysiological data collection for COVID-19: The "Virtual Assessment" model.

The COVID-19 pandemic has significantly disrupted research activities globally. Researchers need safe and creative procedures to resume data collection, particularly for projects evaluating infant mental health interventions. Remote research is uniquely challenging for psychophysiological data collection, which typically requires close contact between researchers and participants as well as technical equipment frequently located in laboratory settings. In accordance with public health guidance, we adapted procedures and developed novel protocols for a "virtual assessment" in which women and infants provided behavioral and psychophysiological data from their own homes while researchers coordinated remotely. Data collected at virtual visits included video-recorded parent-child interactions and autonomic nervous system data. Adaptations were designed to optimize safety and data quality while minimizing participant burden. In the current paper, we describe these adaptations and present data evaluating their success across two sites in the United States (University of Delaware and University of Utah), focusing specifically on autonomic nervous system data collected during the well-validated Still-Face Paradigm (SFP). We also discuss advantages and challenges of translating traditional lab procedures into the virtual assessment model. Ultimately, we hope that disseminating these procedures will help other researchers resume safe data collection related to infant mental health during the COVID-19 pandemic and beyond.

La pandemia del COVID-19 ha interrumpido significativamente las actividades de investigación globalmente. Los investigadores necesitan procedimientos seguros y creativos para reasumir la recolección de información, particularmente para proyectos con los que se evalúan intervenciones de salud mental infantil. La investigación remota es particularmente desafiante para recoger información psicofisiológica, lo cual típicamente requiere contacto cercano entre investigadores y participantes, así como también equipo técnico frecuentemente localizado en centros de laboratorio. De acuerdo con las directrices de salud pública, adaptamos procedimientos y desarrollamos protocolos novedosos para una "evaluación virtual," en la cual mujeres e infantes aportaron datos de conducta y psicofisiológicos desde sus propias casas mientras que los investigadores coordinaban remotamente. La información recogida en las visitas virtuales incluyó interacciones progenitor-niño grabadas en video e información del sistema nervioso autónomo. Se diseñaron las adaptaciones para optimizar la seguridad y la calidad de la información mientras que se reducía al mínimo la carga que conlleva la participación. En el presente estudio, describimos estas adaptaciones y presentamos información evaluativa del éxito en dos lugares de Estados Unidos (la Universidad de Delaware y la Universidad de Utah), con enfoque específico en la información obtenida acerca del sistema nervioso autónomo durante el ya bien validado Paradigma del Rostro Inmóvil. Discutimos también las ventajas y retos para transferir los procedimientos tradicionales de laboratorio al modelo de evaluación virtual. En última instancia, esperamos que al diseminar estos procedimientos ayudaremos a otros investigadores a reasumir la segura recolección de información relacionada con la salud mental infantil durante la pandemia del COVID-19 y posteriormente.

La pandémie du COVID-19 a perturbé de manière importante les activités de recherche au niveau global. Les chercheurs ont besoin de procédures sûres et créatives pour reprendre la collecte de données, particulièrement pour des projets évaluant des interventions en santé mentale du nourrisson. Les recherches à distance présentent un défi unique pour la collecte de données psychophysiologiques, qui typiquement exige un contact proche entre les chercheurs et les participants ainsi qu'un équipement technique fréquemment situé en contextes de laboratoire. En accord avec les directives de santé publique nous avons adapté les procédures et développés de nouveaux protocoles pour une « évaluation virtuelle ¼ durant laquelle les femmes et les bébés ont présenté des données comportementales et psychophysiologiques depuis leurs propres domiciles alors que les chercheurs coordonnaient le tout à distance. Les données recueillies durant les visites virtuelles ont inclus des interactions parent-enfant enregistrées à la vidéo et des données liées au système nerveux autonome. Les adaptations ont été conçues afin d'optimiser la sécurité et la qualité des données tout en minimisant le fardeau pour les participants. Dans cet article nous décrivons ces adaptations et présentons les données évaluant leur succès au travers de deux sites aux Etats-Unis (University of Delaware et University of Utah), en s'attachant plus spécifiquement aux données sur le système nerveux autonome obtenues durant le Paradigme de Visage Inexpressif, qui est bien validé. Nous discutons également les avantages et des défis qu'il y a à traduire des procédures traditionnelles de laboratoire en un modèle d'évaluation virtuel. Finalement nous espérons que le fait de disséminer ces procédures aidera d'autres chercheurs à reprendre de manière sûre la collecte de données liées à la santé mentale du nourrisson durant la pandémie du COVID-19 et plus loin.

Neuromuscular electrical stimulation but not photobiomodulation therapy improves cardiovascular parameters of rats with heart failure.

The aim of the present study was to analyze the effect of neuromuscular electrical stimulation (NMES) and photobiomodulation (PBMT) on the cardiovascular parameters, hemodynamic function, arterial baroreflex sensitivity (BRS), and autonomic balance (ANS) of rats with heart failure (HF). Male Wistar rats (220-290 g) were organized into five groups: Sham (n = 6), Control-HF (n = 5), NMES-HF (n = 6), PBMT-HF (n = 6), and NMES + PBMT-HF (n = 6). Myocardial infarction (MI) was induced by left coronary artery ligation. Animals were subjected to an eight-week NMES and PBMT protocol. Statistical analysis included the General Linear Model (GLM) followed by a Bonferroni post-hoc test. Rats of the NMES-HF group showed a higher MI area than the Control-HF (P = 0.003), PBMT-HF (P = 0.002), and NMES + PBMT-HF (P = 0.012) groups. NMES-HF and NMES + PBMT-HF showed higher pulmonary congestion (P = 0.004 and P = 0.02) and lower systolic pressure (P = 0.019 and P = 0.002) than the Sham group. NMES + PBMT-HF showed lower mean arterial pressure (P = 0.02) than the Sham group. Control-HF showed a higher heart rate than the NMES-HF and NMES + PBMT-HF (P = 0.017 and P = 0.013) groups. There was no difference in the BRS and ANS variables between groups. In conclusion, eight-week NMES isolated or associated with PBMT protocol reduced basal heart rate, systolic and mean arterial pressure, without influence on baroreflex sensibility and autonomic control, and no effect of PBMT was seen in rats with HF.

An updated normative data set from the autonomic reflex screen representative of Southwestern Ontario.

In evaluating autonomic dysfunction, the autonomic reflex screen (ARS) is an established set of standardized tests to evaluate the presence and severity of autonomic dysfunction. Our laboratory previously reported normative data on 121 healthy individuals; however, the sample size in older individuals was reduced compared with other age groups. Therefore, the objective of the current study was to provide updated normative values representative of young, middle-aged, and older individuals from Southwestern Ontario. Two hundred and fifty-two healthy individuals completed quantitative sudomotor axon reflex testing, heart rate responses to deep breathing (HRDB), and Valsalva maneuver using standard protocols of the ARS. All 4 sweat sites demonstrated a significant effect of sex (p < 0.001). In addition, the proximal leg, distal leg, and foot were all significantly affected by age (p < 0.001). Cardiovagal parameters, measured via HRDB and Valsalva ratio revealed a significant regression with age (p < 0.001). These results show similar trends with previously reported normative data sets. All normative data as a function of age and sex, where appropriate, are expressed as percentiles (2.5th, 5th, 95th, 97.5th). The current study provides updated normative data describing autonomic functioning in healthy individuals obtained from the sudomotor and cardiovagal components of the ARS.

Improved cardiovascular autonomic modulation in transgenic rats expressing an Ang-(1-7)-producing fusion protein.

Angiotensin-(1-7) counterbalances angiotensin II cardiovascular effects. However, it has yet to be determined how cardiovascular autonomic modulation may be affected by chronic and acute elevation of Ang-(1-7). Hemodynamics and cardiovascular autonomic profile were evaluated in male Sprague-Dawley (SD) rats and transgenic rats (TGR) overexpressing Ang-(1-7) [TGR(A1-7)3292]. Blood pressure (BP) was directly measured while cardiovascular autonomic modulation was evaluated by spectral analysis. TGR received A-779 or vehicle and SD rats received Ang-(1-7) or vehicle and were monitored for 5 h after i.v. administration. In another set of experiments with TGR, A-779 was infused for 7 days using osmotic mini pumps. Although at baseline no differences were observed, acute administration of A-779 in TGR produced a marked long-lasting increase in BP accompanied by increased BP variability (BPV) and sympathetic modulation to the vessels. Likewise, chronic administration of A-779 with osmotic mini pumps in TGR increased heart rate, sympathovagal balance, BPV, and sympathetic modulation to the vessels. Administration of Ang-(1-7) to SD rats increased heart rate variability values in 88% accompanied by 8% of vagal modulation increase and 18% of mean BP reduction. These results show that both acute and chronic alteration in the Ang-(1-7)-Mas receptor axis may lead to important changes in the autonomic control of circulation, impacting either sympathetic and (or) parasympathetic systems.

Association of diabetic autonomic neuropathy with red blood cell aldose reductase activity.

OBJECTIVE: Activation of polyol pathway based on increased activity of aldose reductase (AR) has been implicated in the development of diabetic complications including diabetic autonomic neuropathy (DAN). The relationship between DAN and hyperglycemia-induced activation of polyol pathway is still uncertain. In the present study, we investigate the association between aldose reductase activity and diabetic autonomic neuropathy by measuring AR level in red blood cells (RBC). METHOD: In this study, 145 subjects with diabetes with or without DAN and 32 subjects without diabetes have been included. All subjects have been investigated for autonomic function tests and RBC aldose reductase activity. DAN was defined if results of any 2 of the tests of parasympathetic function were abnormal. RBC aldose reductase level was determined spectrophotometrically and expressed as unit/g of hemoglobin. The values were expressed as mean ± standard deviation, and ANOVA test has been applied for comparison between groups. RESULTS: RBC aldose reductase activity was found to be significantly higher in people with diabetes with autonomic neuropathy in comparison to people with diabetes without autonomic neuropathy and healthy individuals without diabetes. Aldose reductase (AR) level ranges from 0.8 units/g Hb to 14.2 units/g Hb. The mean AR level was 8.6±2.95 units in subjects of DM with autonomic neuropathy, while mean AR level was 4.1±1.78 units and 2.0±0.89 units in people with diabetes without neuropathy and normal healthy individuals, respectively (p<0.001). CONCLUSIONS: High aldose reductase activity is associated with the presence of autonomic neuropathy in subjects of type 2 DM.

Is critical illness polyneuropathy associated with decreased heart rate variability?

INTRODUCTION: This pilot study assessed the association between critical illness polyneuropathy (CIP) and decreased heart rate variability (HRV) in intensive care patients. METHODS: All patients admitted to the intensive care unit and expected to be ventilated for at least 72 hours were included and underwent weekly electromyograms and HRV analyses for three weeks. HRV was assessed by time domain analysis of 24h recording electrocardiograms, and alterations in HRV were assessed as the square root of the mean squared differences of successive RR intervals (RMSSD) ≤ 15. RESULTS: We evaluated 26 patients, 12 men and 14 women, median age 64 years. During follow-up, 12 patients died and 9 developed CIP. CIP was not associated with age, sex, simplified acute physiology score II and treatment agents. Altered RMSSD tended to be associated with onset of CIP (P=0.06). Altered RMSSD occurred earlier or at the same time as electromyogram abnormalities in all CIP patients, but the difference was not significant. CONCLUSION: Altered HRV, may be associated with the onset of CIP in ICU patients. Although not statistically significant (P=0.06), altered RMSSD may be a surrogate marker of CIP in ICU patients undergoing mechanical ventilation. The physiological pathway linking HRV and CIP remains uncertain.

Impaired Cardiovagal Activity as a Link Between Hyperglycemia and Arterial Stiffness in Adults With Type 2 Diabetes Mellitus Among an Eastern Indian Population: A Cross-sectional Study.

OBJECTIVES: Cardiac autonomic neuropathy (CAN) is one of the most common yet overlooked complications of type 2 diabetes mellitus (T2DM). Individuals with T2DM with CAN have a 5-fold higher rate of cardiovascular morbidity and mortality. The presence of CAN in T2DM could potentially lead to arterial stiffness. However, only sparse data are available suggesting any association between autonomic dysfunction and arterial stiffness in T2DM. METHODS: We recruited 80 people with T2DM and 74 healthy controls for our study. Heart rate variability (HRV) testing was performed to assess autonomic function. Assessment of arterial stiffness was done by measuring the brachial pulse wave velocity (baPWV) and augmentation index (AI). RESULTS: The time-domain parameters were significantly decreased (p<0.001) and frequency-domain parameters, such as total power and high-frequency band expressed as a normalized unit, were found to be significantly reduced in people with T2DM (p<0.001). Both baPWV and AI were significantly higher in people with T2DM compared with healthy controls (p<0.001). We observed a moderate correlation between standard deviation of normal to normal interval (SDNN) and baPWV (r=-0.437, p=0.002) and AI (r=-0.403, p=0.002). A multiple linear regression model showed an association between SDNN and arterial stiffness parameters, such as baPWV and AI, which were statistically significant (p<0.05) in a fully adjusted model that included the conventional risk factors for atherosclerosis. CONCLUSIONS: Impaired cardiovagal activity is an independent risk factor for the development of arterial stiffness. Incorporation of HRV testing into the diabetes management protocol would have potential benefits for identifying individuals at high risk of developing cardiovascular events. Hence, preventive measures can be taken as early as possible to improve patient outcomes.

Role of the autonomic nervous system and premature atrial contractions in short-term paroxysmal atrial fibrillation forecasting: Insights from machine learning models.

BACKGROUND: Machine learning and deep learning techniques are now used extensively for atrial fibrillation (AF) screening, but their use for AF crisis forecasting has yet to be assessed in a clinical context. AIMS: To assess the value of two machine learning algorithms for the short-term prediction of paroxysmal AF episodes. METHODS: We conducted a retrospective study from an outpatient clinic. We developed a deep neural network model that was trained for a supervised binary classification, differentiating between RR interval variations that precede AF onset and RR interval variations far from any AF. We also developed a random forest model to obtain forecast results using heart rate variability variables, with and without premature atrial complexes. RESULTS: In total, 10,484 Holter electrocardiogram recordings were screened, and 250 analysable AF onsets were labelled. The deep neural network model was able to distinguish if a given RR interval window would lead to AF onset in the next 30 beats with a sensitivity of 80.1% (95% confidence interval 78.7-81.6) at the price of a low specificity of 52.8% (95% confidence interval 51.0-54.6). The random forest model indicated that the main factor that precedes the start of a paroxysmal AF episode is autonomic nervous system activity, and that premature complexes add limited additional information. In addition, the onset of AF episodes is preceded by cyclical fluctuations in the low frequency/high frequency ratio of heart rate variability. Each peak is itself followed by an increase in atrial extrasystoles. CONCLUSIONS: The use of two machine learning algorithms for the short-term prediction of AF episodes allowed us to confirm that the main cause of AF crises lies in an imbalance in the autonomic nervous system, and not premature atrial contractions, which are, however, required as a final firing trigger.

Higher blood glucose impairs cardiac autonomic modulation in fasting and after carbohydrate overload in adults.

This study aimed to assess whether the blood glucose levels influence cardiac autonomic modulation under fasting and after carbohydrate overload conditions. Participants (n = 108) were separated into lower blood glucose and higher blood glucose groups, based on the median (90.5 mg·dL-1) of fasting glucose assessed. The SD2, SDNN, LF indices, and LF/HF increased, and HF decreased after dextrose overload compared with fasting (p < 0.05). Body mass (78.9 vs 69.7 kg), abdominal circumference (90.2 vs 82.2 cm), systolic (113 vs 108 mm Hg) and diastolic (72 vs 67 mm Hg) blood pressure were higher (p < 0.05) in the higher blood glucose group. Heart rate variability (HRV) indices (SD1: 21.0 vs 26.5; SD2: 76.8: vs 86.1; RMSSD: 28.7 vs 37.5; SDNN: 56.1 vs 62.5 ms; pNN50: 10.6 vs 18.9%, HF: 328.4 vs 506.0; LF: 982.8 vs 1259.0 ms2), and the area under the curve of these indices after dextrose overload were lower in the higher blood glucose group (p < 0.05). Additionally, glycemia after dextrose overload was correlated with HRV indices (ρ = -0.216 to -0.273, p < 0.05). Individuals with higher blood glucose, even in the normality range, showed impairment in the cardiac autonomic modulation both at fasting and after carbohydrate overload. Novelty: Higher fasting blood glucose impairs cardiac autonomic modulation. Carbohydrate overload impairs cardiac autonomic modulation.

[Improving parasympathetic functioning to contain the inflammatory response of COVID-19 infection]. / Améliorer le fonctionnement parasympathique pour contenir l'effet inflammatoire de la Covid-19.

COVID-19 infection results in an unrestrained inflammatory reaction in serious cases. The autonomic nervous system (ANS), in particular the parasympathetic branch, helps to regulate the inflammatory response. A dysfunction of this branch, frequent in people at risk of developing COVID-19, favours a pro-inflammatory effect. Reinforcing and stimulating the parasympathetic ANS is possible and accessible to paramedical and medical professionals.

A pilot study of the effects of suboccipital fascial release on cortisol levels in workers in the clothing industry - randomized clinical trial.

INTRODUCTION: Repetitive and time sensitive demands of clothing workers has been associated with higher salivary cortisol levels that may reflect the stress experienced by the worker. OBJECTIVE: This trial evaluates if suboccipital fascial release (SFR) is associated with reduced salivary cortisol levels. METHODS: Randomized controlled trial with 40 workers, divided into: untreated group (UG, n = 15) and treated group (TG, n = 25). Both were removed from the work environment. The TG received the above technique and the UG remained lying at rest, both for five minutes. Salivary cortisol levels were measured by a commercial enzyme-linked immunosorbent assay (ELISA) kit. Statistical analysis of data distribution, intragroup and intergroups, were performed with α adjusted to 0.05. RESULTS: Pre / post intragroup analyses showed significant differences in cortisol levels in both groups, as well as intergroup analyses with lower values in favor of TG (p = 0.014). CONCLUSION: The reduction in salivary cortisol levels in TG suggests that SFR may be more effective than rest in reducing stress. Future studies with increased experimental rigor are necessary to confirm this conclusion. CLINICAL TRIAL REGISTRATION NUMBER: REBEC - RBR - 56yk9m.

INTRODUCTION: Les exigences aiguës imposées aux travailleurs de l'industrie du vêtement ont été associées à de fortes concentrations de cortisol salivaire pouvant traduire le stress vécu par ces travailleurs. OBJECTIF: Cet essai vise à savoir si le relâchement des fascias des muscles sous-occipitaux est associé à une réduction des concentrations de cortisol salivaire. MÉTHODOLOGIE: Essai comparatif avec répartition aléatoire mené auprès de 40 travailleurs répartis en deux groupes: groupe non traité (GNT, n = 15) et groupe traité (GT, n = 25). Les sujets des deux groupes ont été retirés de leur milieu de travail. La technique ci-haut mentionnée a été utilisée sur les sujets du GT alors que les sujets du GNT sont restés au repos: pour les deux groupes, l'intervention a duré cinq minutes. Les concentrations de cortisol salivaire ont été mesurées à l'aide d'une trousse pour dosage d'immunoabsorption par enzyme liée (ELISA) offerte dans le commerce. L'analyse statistique de la distribution des données intra-groupes et inter-groupes a été effectuée avec α ajusté à 0.05. RÉSULTATS: L'analyse des données prétraitement et post-traitement à l'intérieur des groupes a révélé des différences appréciables de concentration de cortisol dans les deux groupes, les analyses entre les groupes montrant des concentrations plus faibles dans le GT (p = 0.014). CONCLUSION: La réduction des concentrations de cortisol salivaire dans le GT semble indiquer que le relâchement des fascias de muscles sous-occipitaux peut être plus efficace que le repos pour réduire le stress. Il faut mener d'autres études expérimentales plus rigoureuses pour confirmer cette conclusion. NUMÉRO D'ENREGISTREMENT DE L'ESSAI CLINIQUE: REBEC ­ RBR ­ 56yk9m.

Heart rate variability mediates motivation and fatigue throughout a high-intensity exercise program.

High-intensity exercise interventions are often promoted as a time-efficient public health intervention to combat chronic disease. However, increased physical effort and subsequent fatigue can be barriers to long-term maintenance of high-intensity exercise programs. The purpose of the present study was to determine if heart rate variability (HRV) mediated state traits related to exercise program adherence. Fifty-five healthy men and women (ages 19-35 years) used a commercially available smartphone application to monitor daily HRV status throughout a 6-week high-intensity exercise intervention. Participants reported state motivation to exercise and global physical fatigue immediately prior to each exercise session. Temporary shifts toward increased parasympathetic reactivation (p = 0.030) resulted in significant increases in daily fatigue (p < 0.001) and decreases in motivation to exercise (p = 0.028). Through modulation of exercise volume, in response to these temporary shifts in HRV, these effects were reversed (p < 0.001) via increased parasympathetic withdrawal (p = 0.018). For the first time, these data demonstrate a mediating effect of HRV on adherence-related trait states throughout a high-intensity exercise program. Applied strategies, such as appropriately timed exercise volume moderation, may be able to leverage this effect and help facilitate long-term exercise program maintenance. Novelty These data establish a link between expected shifts in HRV throughout high-intensity exercise programs with motivation to participate and physical fatigue. Modulation of training volume, in response to these shifts, can optimize adherence-related behavioral responses during high-exercise programs.

Determination of minimal recording period to assess resting heart rate variability during pregnancy.

Traditionally, resting heart rate variability (rHRV) is measured for 10 min using the last 5 min for analyses (e.g., criterion period). It is unknown whether the measurement period can be shortened in pregnant women as there are currently no established standards. We aimed to compare shorter time segments (e.g., from the 1st to 10th minutes) of the parasympathetic index natural logarithm transformation of root mean square of successive R-R differences (Ln rMSSD) with the criterion period in pregnant and nonpregnant women. Twelve pregnant (age: 30.8 ± 3.4 years; gestational age: 20.1 ± 5.0 weeks) and 15 nonpregnant women (age: 29.8 ± 4.0 years) were included. rHRV was measured using a portable heart rate monitor for 10 min while sitting. Ln rMSSD difference/agreement between shorter time segments and criterion period was analyzed. The result observed between the 4th-5th minutes was the shortest time segment not different from/highly agreed with the criterion period in pregnant women (difference [95% confidence interval (CI)]: -0.10 [-0.22 to 0.02]/bias ± 1.96 × SD: -0.06 [-0.38 to 0.25]). In nonpregnant women, the 2nd-3rd-minute segment was the shortest with similar results (difference [95% CI]: -0.04 [-0.15 to 0.07]/bias ± 1.96 × SD: -0.03 [-0.39 to 0.32]). The Ln rMSSD was found to be stable from the 5th-10th minutes and the 3rd-10th minutes in pregnant and nonpregnant women, respectively. A shortened rHRV assessment can increase its applicability in clinical/exercise-training settings. Novelty Ln rMSSD can be measured for 5 min in pregnant women, with the last 1-min segment analyzed. The last 1-min segment from 3 min can be used for rHRV measurement in nonpregnant women. The shortened rHRV assessment can facilitate its applicability in clinical/exercise-training settings.

Effects of high-intensity intervals and moderate-intensity exercise on baroreceptor sensitivity and heart rate variability during recovery.

Numerous studies have examined heart rate variability (HRV) and cardiac baroreceptor sensitivity (BRS) variables during recovery both acutely (under 3 h) and long-term (24, 48, and 72 h) postexercise. However, there is little literature examining HRV and BRS measures between these timepoints. Spontaneous short-term HRV and cardiac BRS measures were collected in 9 participants before and at zero, 1, 2, 4, 6, and 8 h after 3 separate conditions: moderate-intensity continuous exercise (MICE; 45 min at 50% heart rate reserve), high-intensity interval exercise (HIIE; 25 min including ten 1-min intervals at 85% heart rate reserve), and control (30 min quiet rest). HRV measures in the time domain were only affected immediately following HIIE and MICE at hour zero (all p < 0.043), whereas frequency-domain metrics were unaltered (all p > 0.102). These measures were highly consistent across the control day (all p > 0.420). Cardiac BRS was assessed via low-frequency (LF) gain, and revealed reductions following HIIE at hour zero (p < 0.012). Cardiac BRS LF gain remained consistent following MICE and control interventions (all p > 0.280). The common practice of waiting 12 to 24 h is overly conservative as the current findings demonstrate measures return to baseline at ∼60 min after exercise. Moreover, these metrics demonstrated high levels of within- and between-day reliability. Novelty Previously a 12-h minimum restriction from exercise was required before participation in HRV/BRS studies. Recovery from moderate-intensity exercise for HRV and BRS metrics was <60 min; whereas, high-intensity intervals led to alterations for approximately 60 min. Spontaneous HRV and cardiac BRS demonstrated high levels of within-day reproducibility.

[Heart Rate Variability - State of Research and Clinical Applicability]. / Herzfrequenzvariabilität ­ Stand der Forschung und klinische Anwendbarkeit.

Heart Rate Variability - State of Research and Clinical Applicability Abstract. Heart rate variability is considered a marker of autonomous nervous system activity. Autonomic imbalance is found as a common component in a wide range of pathologies. It has been found to precede the onset of pathologic states and correlates with therapy response. In addition, heart rate variability at rest is a psychophysiological phenomenon with broad significance. Psychological experience affects physiological homeostasis, including immune processes, via the autonomous nerve system, which biologically underpins psychosomatic effects and makes them measurable by heart rate variability. The autonomous nerve system as the interface of this psychophysiological regulation is becoming increasingly important in heart rate variability research and allows a better understanding of the interactions between psyche, lifestyle, autonomous regulation and chronic illness. It requires a systemic, cross-organ view as well as an orientation towards long-term processes. The assessment and normalization of autonomic imbalance thus represents a novel therapeutic strategy from which numerous interventions and lifestyle modifications can be derived. Interventions that strengthen the vagal tone (aerobic or moderate physical training, relaxation techniques, vagus nerve stimulation, etc.) are becoming increasingly important. Despite the simple non-invasive measurement and popularity as a research instrument, interpretation is complex, and clinical implementation has been reluctant so far. Nevertheless, guidelines and data sets of reference values exist for users to apply.

Maternal cardioautonomic responses during and following exercise throughout pregnancy.

Blood pressure regulation during pregnancy is poorly understood. Cardiovagal baroreflex gain (BRG) is an important contributor to blood pressure regulation through its influence on heart rate. Heart rate fluctuations occur in response to various physiological stimuli and can be measured using heart rate variability (HRV). It is unclear how these mechanisms operate during pregnancy, particularly with regard to exercise. We examined BRG and HRV prior to, during, and following prenatal exercise. Forty-three pregnant (n = 10 first trimester (TM1), n = 17 second trimester (TM2), n = 16 third trimester (TM3)) and 20 nonpregnant (NP) women underwent an incremental peak exercise test. Beat-by-beat blood pressure (photoplethysmography) and heart rate (lead II electrocardiogram) were measured throughout. BRG (the slope of the relationship between fluctuations in systolic blood pressure and the R-R interval) and HRV (root mean square of the successive differences; RMSSD) were assessed at rest, during steady-state exercise (EX), and during active recovery. BRG decreased with gestation and was lower in the TM3 group than in the NP group (17.9 ± 6.9 ms/mm Hg vs 24.8 ± 7.4 ms/mm Hg, p = 0.017). BRG was reduced during EX in all groups. Resting HRV (RMSSD) also decreased with gestation and was lower in the TM3 group than in the NP group (29 ± 17 ms vs 48 ± 20 ms, p < 0.001). RMSSD was blunted during EX in all groups compared with rest. During active recovery, RMSSD was further blunted compared with EX in the NP group but not during pregnancy (TM1, TM2, and TM3). Compared with the nonpregnant controls, the pregnant women had lower BRG and HRV at rest, but comparable cardioautonomic control during both exercise and active recovery following peak exercise.

Peripheral chemoreceptor deactivation attenuates the sympathetic response to glucose ingestion.

Acute increases in blood glucose are associated with heightened muscle sympathetic nerve activity (MSNA). Animal studies have implicated a role for peripheral chemoreceptors in this response, but this has not been examined in humans. Heart rate, cardiac output (CO), mean arterial pressure, total peripheral conductance, and blood glucose concentrations were collected in 11 participants. MSNA was recorded in a subset of 5 participants via microneurography. Participants came to the lab on 2 separate days (i.e., 1 control and 1 experimental day). On both days, participants ingested 75 g of glucose following baseline measurements. On the experimental day, participants breathed 100% oxygen for 3 min at baseline and again at 20, 40, and 60 min after glucose ingestion to deactivate peripheral chemoreceptors. Supplemental oxygen was not given to participants on the control day. There was a main effect of time on blood glucose (P < 0.001), heart rate (P < 0.001), CO (P < 0.001), sympathetic burst frequency (P < 0.001), burst incidence (P = 0.01), and total MSNA (P = 0.001) for both days. Blood glucose concentrations and burst frequency were positively correlated on the control day (r = 0.42; P = 0.03) and experimental day (r = 0.62; P = 0.003). There was a time × condition interaction (i.e., normoxia vs. hyperoxia) on burst frequency, in which hyperoxia significantly blunted burst frequency at 20 and 60 min after glucose ingestion only. Given that hyperoxia blunted burst frequency only during hyperglycemia, our results suggest that the peripheral chemoreceptors are involved in activating MSNA after glucose ingestion.

Nonlinear analyses of heart rate variability in hypertension.

OBJECTIVE: The autonomic nervous system plays an important role in blood pressure regulation and in the development of hypertension. Heart rate variability (HRV) may be of importance in identifying subjects at higher risk of developing hypertension. In the present study, comparative analysis of HRV for normal and hypertension subjects using nonlinear indices has been carried out. PATIENTS AND METHODS: We analyzed the data from 24 patients with essential hypertension aged 45-55 (HG). All the subjects in this group had a confirmed diagnosis of the first- or second-stage essential hypertension. The control group for these subjects included 32 healthy volunteers of the same age group (CG). We analyzed the whole 5minutes of the ECG recording. Nonlinear indices D2, K2 and lagged Poincaré plot indices were calculated. RESULTS: Values of D2 and K2 in hypertension state is statistically significantly lower than in healthy. Poincaré plot indices SD1 and SD2 in healthy volunteers are statistically higher than in hypertensive patients for all lags (P<0,05). SD1/SD2 ratio is also higher in healthy subjects, but the difference is statistically significant only for l=5 and 6. CONCLUSION: The heart rhythm in groups with hypertension is more regular, its dynamics are less complex and less "chaotic," compared to healthy ones. This is expressed in lower values of entropy and correlation dimension. The HR stabilization is observed at both short and long time intervals, but mainly due to the decrease in the difference of the "neighboring" R-R intervals.

A new conceptual framework for the integrated neural control of locomotor and sympathetic function: implications for exercise after spinal cord injury.

All mammals, including humans, are designed to produce sustained locomotor movements. Many higher centres are involved in movement, but ultimately these centres act upon a core "rhythm-generating" network within the brainstem-spinal cord. In addition, endurance-based locomotor exercise requires sympathetic neural support to maintain homeostasis and to provide needed metabolic resources. This review focuses on the roles and integration of these 2 neural systems. Part I reviews the cardiovascular, thermoregulatory, and metabolic functions under spinal sympathetic control as revealed by spinal cord injury at different levels. Part II examines the integration between brainstem-spinal sympathetic pathways and the neural circuitry producing motor rhythms. In particular, the rostroventral medulla (RVM) contains the neural circuitry that (i) integrates heart rate, contractility, and blood flow in response to postural changes; (ii) initiates and maintains cardiovascular adaptations for exercise; (iii) provides direct descending innervation to preganglionic neurons innervating the adrenal glands, white adipose tissue, and tissues responsible for cooling the body; (iv) integrates descending sympathetic drive for energy substrate mobilization (lipolysis); and (v) is the relay for descending locomotor commands arising from higher brain centres. A unifying conceptual framework is presented, in which the RVM serves as the final descending supraspinal "exercise integration centre" linking the descending locomotor command signal with the metabolic and homeostatic support needed to produce prolonged rhythmic activities. The role and rationale for an ascending sympathetic and locomotor drive from the lower to upper limbs within this framework is presented. Examples of new research directions based on this unifying framework are discussed.

Heart rate variability responses to acute and repeated postexercise sauna in trained cyclists.

Short- to medium-term (i.e., 4-14 days) heating protocols induce physiological adaptations including improved cardiac autonomic modulations, as assessed using heart rate variability, which may contribute to greater exercise performance. Whether similar cardiac autonomic changes occur during an intense heating protocol (sauna) reported to increase plasma volume in athletes remains to be confirmed. This study examined changes in heart rate and its variability during a single extreme heat (sauna) exposure and repeated exposures in athletes. Six well-trained male cyclists undertook sauna bathing (30 min, 87 °C, 11% relative humidity) immediately after normal training over 10 consecutive days. Heart rate recordings were obtained during each sauna bout. Heart rate and its variability (natural logarithm of root mean square of successive differences, lnRMSSD) were analysed during 10-min periods within the first bout, and changes in heart rate and lnRMSSD were analysed during each bout via magnitude-based inferences. During the first sauna bout, heart rate was almost certainly increased (∼32%, effect size 1.68) and lnRMSSD was almost certainly reduced (∼62%, effect size -5.21) from the first to the last 10-min period, indicating reduced parasympathetic and (or) enhanced sympathetic modulations. Acute exposure to extreme heat stress via sauna produced alterations in heart rate and cardiac autonomic modulations with successive postexercise heat exposures producing unclear changes over a 10-day period. The physiological benefits of intense heating via sauna on cardiac control in athletes remain to be elucidated.