Autonomic neuroscience : basic & clinical
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Comparative Study
Nonlinear and chaos characteristics of heart period time series: healthy aging and postural change.
In this study we investigated nonlinear and linear characteristics of heart period variability with aging in supine and standing posture. Sixty healthy subjects (8-61 years) divided in three age groups participated in the study. Heart period variability was assessed by measurement of short-term scaling exponent, sample entropy, largest Lyapunov exponent and spectral low-frequency and high-frequency power. ⋯ In standing both low-frequency and high-frequency powers are correlated with short-term scaling exponent and sample entropy. These results show that posture, standing compared to supine, has significant effect on nonlinear properties of heart period variability in healthy subjects while the influence of healthy aging is less pronounced. The findings indicate that intrinsic properties of heart period dynamics, reflected on nonlinear measures, are altered only by robust changes of autonomic modulation of heart rate.
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Comparative Study
Acute pain increases heart rate: differential mechanisms during rest and mental stress.
The main aim was to investigate if acutely stressed subjects have abnormal heart rate variability responses to acute pain. Efferent cardiac autonomic activity was assessed by analyzing RR interval variation in 26 male volunteers. Heart rate variability was measured as mean and standard deviation of normal RR intervals (mean RR, SDNN) and by power spectral analysis where high frequency (HF) and low frequency (LF) power were used as indexes of vagal function and of sympatho-vagal interaction, respectively. ⋯ We conclude that acute pain induced efferent cardiac sympathetic activation during rest and during attention to pain as LF power and CCV-LF increased without alterations of pure vagal heart rate variability measures. During mental stress, pain inhibited mean RR without changing heart rate variability measures suggesting that pain does not increase efferent cardiac sympathetic activity during mental stress. Pain induced decrease of mean RR during mental stress may be caused by the release of catecholamines into the systemic circulation.