Eva Parrado

Comparison of omega wave system and polar S810i to detect R-R intervals at rest

The present study was performed to compare R-R interval data and heart rate variability indices obtained from the Polar S810i and the Omega Wave Sport System for a total of 96 adults in a supine position. Data were simultaneously recorded with the Polar S810i and the Omega Wave Sport System and processed by unique software. Bland-Altman analysis for the R-R intervals shows minimal bias for free and paced breathing. No significant differences were observed for heart rate variability indices derived from the signal from both devices, except for the power of the high frequency band and the acceleration changes index during either free or paced breathing. Coefficients of correlations were all above 0.96. These data suggest that both systems are valid to record R-R interval signals and to obtain a valid analysis of heart rate variability. However, Omega Wave Sport System enables data to be collected without any artifacts making the analysis of heart rate variability easier than the analysis of Polar S810i. Nevertheless, Polar S810i continues to be more practical in clinical and applied situations due to the affordability of the device.

Facial Video-Based Photoplethysmography to Detect HRV at Rest.

Our aim is to demonstrate the usefulness of photoplethysmography (PPG) for analyzing heart rate variability (HRV) using a standard 5-min test at rest with paced breathing, comparing the results with real RR intervals and testing supine and sitting positions. Simultaneous recordings of R-R intervals were conducted with a Polar system and a non-contact PPG, based on facial video recording on 20 individuals. Data analysis and editing were performed with individually designated software for each instrument. Agreement on HRV parameters was assessed with concordance correlations, effect size from ANOVA and Bland and Altman plots. For supine position, differences between video and Polar systems showed a small effect size in most HRV parameters. For sitting position, these differences showed a moderate effect size in most HRV parameters. A new procedure, based on the pixels that contained more heart beat information, is proposed for improving the signal-to-noise ratio in the PPG video signal. Results were acceptable in both positions but better in the supine position. Our approach could be relevant for applications that require monitoring of stress or cardio-respiratory health, such as effort/recuperation states in sports.

An application of fractional differintegration to heart rate variability time series

Fractional differintegration is used as a new tool to characterize heart rate variability time series. This paper proposes and focuses in two indexes (αc and fnQ) derived from the fractional differintegration operator. Both indexes are applied to fractional Gaussian noise (fGn) and actual RR time series in order to test their behavior. In the analysis of monofractal time series, αc is linearly related with the Hurst exponent and the estimation of the exponent by the proposed index has lower variance than by using Detrended Fluctuation Analysis (DFA) or the periodogram. The other index fnQ quantifies how the time series adjust to a monofractal time series. Age, postural changes and paced breathing cause significant changes on fnQ while αc only shows significant changes due to posture. In the analyzed actual HRV time series, αc shows good correlation with the short term scaling exponent obtained by DFA, LF/HF and RMSSD while no correlations have been found for fnQ.

Perceived Tiredness and Heart Rate Variability in Relation to Overload during a Field Hockey World Cup

The aim of the study was to examine the utility of perceived tiredness to predict cardiac autonomic response to overload among field hockey players during the 2006 World Cup. The French Society for Sports Medicine (SFMS) questionnaire was administered at the start of the Cup to evaluate perception of tiredness. Autonomic function was assessed nine days later at the semifinal match by time and frequency domain analysis of heart rate variability. An anxiety questionnaire was administered so that the effect of precompetitive anxiety on heart rate variability could be controlled. Results showed a negative correlation between perceived tiredness scores and time domain indexes, and a positive correlation of perceived tiredness scores and the high frequency component ratio (LF/HF ratio) of heart rate variability. Anxiety did not influence the precompetitive cardiac response despite somatic anxietys correlation with sympathetic response (LF/HF ratio) and tiredness scores. Perceived tiredness predicted the autonomic cardiac response to competitive overload. Thus, the perceived tiredness assessment would be a good early marker of fatigue and overload states during competition.

HRV based health&sport markers using video from the face

Heart Rate Variability (HRV) is an indicator of health status in the general population and of adaptation to stress in athletes. In this paper we compare the performance of two systems to measure HRV: (1) A commercial system based on recording the physiological cardiac signal with (2) A computer vision system that uses a standard video images of the face to estimate RR from changes in skin color of the face. We show that the computer vision system performs surprisingly well. It estimates individual RR intervals in a non-invasive manner and with error levels comparable to those achieved by the physiological based system.

New indices for quantification of the power spectrum of heart rate variability time series without the need of any frequency band definition

This paper presents a new family of indices for the frequency domain analysis of heart rate variability time series that do not need any frequency band definition. After proper detrending of the time series, a cumulated power spectrum is obtained and frequencies that contain a certain percentage of the power below them are identified, so median frequency, bandwidth and a measure of the power spectrum asymmetry are proposed to complement or improve the classical spectral indices as the ratio of the powers of LF and HF bands (LF/HF). In normal conditions the median frequency provides similar information as the classical indices, while the bandwidth and asymmetry can be complementary measures of the physiological state of the tested subject. The proposed indices seem to be a good choice for tracking changes in the power spectrum in exercise stress, and they can guide in the determination of frequency band limits in other animal species.

A methodology to quantify the differences between alternative methods of heart rate variability measurement

This work proposes a systematic procedure to report the differences between heart rate variability time series obtained from alternative measurements reporting the spread and mean of the differences as well as the agreement between measuring procedures and quantifying how stationary, random and normal the differences between alternative measurements are. A description of the complete automatic procedure to obtain a differences time series (DTS) from two alternative methods, a proposal of a battery of statistical tests, and a set of statistical indicators to better describe the differences in RR interval estimation are also provided. Results show that the spread and agreement depend on the choice of alternative measurements and that the DTS cannot be considered generally as a white or as a normally distributed process. Nevertheless, in controlled measurements the DTS can be considered as a stationary process.