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Heart rate variability: Origins, methods, and interpretive caveats
Abstract
Components of heart rate variability have attracted considerable attention in psychology and medicine and have become important dependent measures in psychophysiology and behavioral medicine. Quantification and interpretation of heart rate variability, however, remain complex issues and are fraught with pitfalls. The present report (a) examines the physiological origins and mechanisms of heart rate variability, (b) considers quantitative approaches to measurement, and (c) highlights important caveats in the interpretation of heart rate variability. Summary guidelines for research in this area are outlined, and suggestions and prospects for future developments are considered.
... However, the role of this HRV parameter in depicting sympathovagal balance has recently been discarded, because no real physiological conclusion can be drawn from this finding [64]. Both the low-frequency band of the frequency domain (LF) and heart rate have also often been used, but they do not allow for an accurate interpretation of the autonomic changes found during iVNS, as they reflect mixed inputs from the sympathetic and parasympathetic branches [10,65]. Thus, LF and heart rate cannot be linked specifically to CVA. ...
Electrical vagus nerve stimulation (eVNS) comprises an array of non-pharmacologic techniques used to stimulate afferent fibers of the vagus nerve. Despite the increasing use of eVNS both in clinical settings and in research, there is still a need for a valid biological marker that can be used to indicate the action of eVNS in the central as well as in the peripheral nervous system. The present chapter focuses on one of the most prominent candidates for such a biomarker, namely, heart rate variability (HRV). We provide arguments for the s of specific HRV parameters to this aim, namely, vagally-mediated HRV, which reflects cardiac vagal activity. We describe the mechanism of action underlying the expected effects of eVNS on cardiac vagal activity and perform a literature review, which shows mixed evidence on the increase of cardiac vagal activity due to eVNS. Furthermore, we point out relevant methodological caveats of current literature on eVNS and discuss how to avoid them in a study designed to investigate the relationship between eVNS and cardiac vagal activity. Based on this, we describe what is necessary to properly measure cardiac vagal activity during the use of eVNS, and discuss considerations that need to be observed when it comes to designing studies that aim to address this relationship.
According to the statistics of the world health organization, cardiovascular diseases (CVDs) are the leading cause of death globally and take almost 17.9 million lives per year. The investigations of CVDs rely on cardiovascular health/medical data representation and signal processing techniques. There are some well-known data representations, such as morphology assessment and spectral assessment, but the precision and the expressiveness of those methods are limited due to the mathematical basis and the nonstationarity of physiological signals. Recently, several novel methods were proposed, such as adaptive spectral assessment and multi-dimensional spectral assessment. It had been examined that those techniques are useful tools to explore the nonstationary intrinsic features of physiological signals, not only in blood pulse signal but also in other signals, including EEG signal and MEG signal. It provides a full informational assessment of health/medical data and needs more investigations for the clinical interpretation related to the diseases. This chapter briefly introduces the blood pulse signal representation by using those assessment techniques mentioned above and illustrates the results of the nonstationary intrinsic feature representations.
In sports, physical recovery following exercise‐induced fatigue is mediated via the reactivation of the parasympathetic nervous system (PNS). A non‐invasive way to quantify the reactivation of the PNS is to assess vagally‐mediated heart rate variability (vmHRV), which can then be used as an index of physical recovery. This systematic review and meta‐analysis investigated the effects of physical recovery techniques following exercise‐induced fatigue on vmHRV, specifically via the root mean square of successive differences (RMSSD). Randomized controlled trials from the databases PubMed , WebOfScience, and SportDiscus were included. Twenty‐four studies were part of the systematic review and 17 were included in the meta‐analysis. Using physical post‐exercise recovery techniques displayed a small to moderate positive effect on RMSSD ( k = 22, Hedges’ g = 0.40, 95% confidence interval (CI) = 0.20 to 0.61, p = 0.04) with moderate heterogeneity. In the subgroup analyses, cold water immersion displayed a moderate to large positive effect ( g = 0.75, 95% CI: 0.42 to 1.07) compared to none for other techniques. For exercise type, physical recovery techniques performed after resistance exercise ( g = 0.69, 95% CI: 0.48 to 0.89) demonstrated a larger positive effect than after cardiovascular intermittent ( g = 0.52, 95% CI: 0.06 to 0.97), while physical recovery techniques performed after cardiovascular continuous exercise had no effect. No significant subgroup differences for training status and exercise intensity were observed. Overall, physical post‐exercise recovery techniques can accelerate PNS reactivation as indexed by vmHRV, but the effectiveness varies with the technique and exercise type.
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The objective of this work is to describe guidelines for measuring degraded human performance
based on driver state and competences from a real-time driver monitoring perspective. The
guidelines integrate state-of-the-art knowledge from the literature with knowhow from the industry
and practical results from the Mediator project. The formulated guidelines are defined based on
functionality, technological possibilities, safety relevance and feasibility.
Before and after Trier Social Stress Test, 91 participants (18–50 years, 67% women) inhaled one odor during 10 min: Scots pine, grass (=cis-3-hexenol), or control (=demineralized water). Group differences were tested on repeated measurements of stress (affect reports, salivary cortisol and heart rate variability) and eating behavior (food choice and craving). Both nature olfactory exposures improved some stress outcomes. Both were associated with lower cortisol in non-stress conditions, but only grass odor was more beneficial for negative affect decrease after stress. No effect on heart rate variability was seen. Some contradictory findings were present for eating behavior. In non-stress situations, grass odor increased vegetable preference, while the pine odor group had higher sweet high-fat snack preference. Grass odor was also reported to induce healthier food choices. During stress recovery, both pine and grass odor groups had higher preference to sweet high-fat snacks.
Introduction
To protect against infection, individuals have evolved context‐dependent pathogen‐avoidant strategies, including selective social behaviors aimed at avoiding foreign individuals who may possess greater risk of infection. Parasympathetic nervous system (PNS) activity is associated with social engagement and regulation of the classical immune system but has not been widely investigated in relation to changes in intergroup perception and the behavioral immune system.
Method
The current research investigated the relationship between parasympathetic activity and perceived foreignness of in and outgroup speakers during exposure to a pathogen‐relevant odor (butyric acid). High‐frequency heart rate variability was measured at rest and while participants rated foreignness of speakers with and without the odor present.
Results
Findings show that exposure to the odor was associated with higher foreignness perceptions of outgroup speakers and lower foreignness perceptions of ingroup speakers. This effect was especially evident among individuals with higher resting parasympathetic activity.
Conclusion
These results suggest that the PNS may play a role in changes in social perceptions during a behavioral immune response.
We have demonstrated previously that transfer function analysis can be used to precisely characterize the respiratory sinus arrhythmia (RSA) in normal humans. To further investigate the role of the autonomic nervous system in RSA and to understand the complex links between respiratory activity and arterial pressure, we determined the transfer functions between respiration, heart rate (HR), and phasic, systolic, diastolic, and pulse arterial pressures in 14 healthy subjects during 6-min periods in which the respiratory rate was controlled in a predetermined but erratic fashion. Pharmacological autonomic blockade with atropine, propranolol, and both, in combination with changes in posture, was used to characterize the sympathetic and vagal contributions to these relationships, as well as to dissect the direct mechanical links between respiration and arterial pressure from the effects of the RSA on arterial pressure. We found that 1) the pure sympathetic (standing + atropine) HR response is characterized by markedly reduced magnitude at frequencies greater than 0.1 Hz and a phase delay, whereas pure vagal (supine + propranolol) modulation of HR is characterized by higher magnitude at all frequencies and no phase delay; 2) both the mechanical links between respiration and arterial pressure and the RSA contribute significantly to the effects of respiration on arterial pressure; 3) the RSA contribution to arterial pressure fluctuations is significant for vagal but not for sympathetic modulation of HR; 4) the mechanical effects of respiration on arterial pressure are related to the negative rate of change of instantaneous lung volume; 5) the mechanical effects have a higher magnitude during systole than during diastole; and 6) the mechanical effects are larger in teh standing than the supine position. Most of these findings can be explained by a simple model of circulatory control based on previously published experimental transfer functions from our laboratory.
1 Stationary Time Series.- 2 Hilbert Spaces.- 3 Stationary ARMA Processes.- 4 The Spectral Representation of a Stationary Process.- 5 Prediction of Stationary Processes.- 6* Asymptotic Theory.- 7 Estimation of the Mean and the Autocovariance Function.- 8 Estimation for ARMA Models.- 9 Model Building and Forecasting with ARIMA Processes.- 10 Inference for the Spectrum of a Stationary Process.- 11 Multivariate Time Series.- 12 State-Space Models and the Kalman Recursions.- 13 Further Topics.- Appendix: Data Sets.
Carotid baroreceptors of nine healthy young men and women were stretched or compressed with neck suction or pressure, before and after beta-adrenergic and cholinergic blockade, to evaluate several nonlinearities of sinus node baroreflex responses. Sinus node inhibition was related linearly to the intensity of brief baroreceptor stimuli over a range extending from carotid-distending pressures of about 101 +/- 5 (mean +/- SE) to 160 +/- 6 mm Hg (the subject's average systolic pressure was 108 +/- 2 mm Hg). Sinus node response to sustained (5 seconds) neck suction or pressure were strikingly asymmetrical. Responses were abolished by atropine, or by atropine and propranolol. Propranolol alone augmented sinus node responses to both neck suction and pressure. These results suggest that, in normal human subjects, sinus node responses to abrupt alterations of afferent baroreceptor traffic are nonlinear and are mediated by fluctuations of efferent cholinergic activity. Most of the observed nonlinear behavior of the integrated reflex can be explained on the basis of known properties of afferent and central portions of the baroreflex arc.
The heart period (R-R) variability power spectrum presents two components, at low (LF; similar to 0.10 Hz) and high (similar to 0.25 Hz) frequencies, whose reciprocal powers appear to furnish an index of sympathovagal interaction modulating heart rate. In addition, the LF component of the systolic arterial pressure variability spectrum furnishes a marker of sympathetic modulation of vasomotor activity. The contribution of spinal and supraspinal neural circuits to the genesis of these rhythmic oscillatory components remains largely unsettled. Therefore we performed spectral analysis of R-R and systolic arterial pressure variabilities in 15 chronic neurologically complete quadriplegic patients (QP) and in 15 control subjects during resting conditions, controlled respiration, and head-up tilt. At rest, in seven QP the LF component was undetectable in both cardiovascular variability spectra; in two QP this component was present only in R-R variability spectrum, whereas the remaining six showed a significantly reduced LF in both signals. In QP, the LF component, when present, underwent paradoxical changes with respect to controls, decreasing during tilt and increasing during controlled respiration. In five QP in whom the recording session was repeated after 6 mo, a significant increase in LF was observed in both variability spectra. These data confirm the finding that a disconnection of sympathetic outflow from supraspinal centers can cause the disappearance of the LF spectral component. However, LF presence in some QP supports the hypothesis of a spinal rhythmicity likely to be modulated by the afferent sympathetic activity.
The general intention of this study was empirically to evaluate the selection of cardiovascular parameters that are suited for the assessment of individual differences in haemodynamics and for multivariate pattern analysis of stimulus and individual specific responses. Multiple cardiovascular recordings in 42 male student subjects included measurements of electrocardiogram, impedance cardiogram, phonocardiogram, ear densitogram, carotid pulse curve, upper and lower arm rheograms, calibrated finger pulse, finger temperature, respiration, and intermittent automatic blood pressure. Experimental conditions were mental arithetic under distracting noise, maximal handgrip, and rest. Parametrization was performed on a beat-to-beat basis and resulted in about 200 measures for each cardiac cycle as well as a considerable number of indices. The selection of relevant parameters was performed according to a set of rational criteria. Findings are presented concerning the consistency of various measures, e.g. pulse-wave velocity, systolic time intervals, parameters from the electrocardiogram and impedance cardiogram. Aspects of within-subject and between subjects correlation are discussed, as well as specific issues regarding standardization.
Spectral analysis of spontaneous heart rate fluctuations were assessed by use of autonomic blocking agents and changes in posture. Low-frequency fluctuations (below 0.12 Hz) in the supine position are mediated entirely by the parasympathetic nervous system. On standing, the low-frequency fluctuations increase and are jointly mediated by the sympathetic and parasympathetic nervous systems. High-frequency fluctuations, at the respiratory frequency, are decreased by standing and are mediated solely by the parasympathetic system. Heart rate spectral analysis is a powerful noninvasive tool for quantifying autonomic nervous system activity.