Human fetuses have nonlinear cardiac dynamics
1 Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of South Alabama, Mobile, Alabama 36604; 2 Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock 72205; and 3 Department of Applied Sciences, University of Arkansas at Little Ro...
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Veröffentlicht in: | Journal of applied physiology (1985) 1999-08, Vol.87 (2), p.530-537 |
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Zusammenfassung: | 1 Division of Maternal-Fetal
Medicine, Department of Obstetrics and Gynecology, University of
South Alabama, Mobile, Alabama 36604;
2 Department of Pediatrics,
University of Arkansas for Medical Sciences, Little Rock 72205; and
3 Department of Applied
Sciences, University of Arkansas at Little Rock, Little Rock, Arkansas
72204
Approximate
entropy (ApEn) is a statistic that quantifies regularity in time series
data, and this parameter has several features that make it attractive
for analyzing physiological systems. In this study, ApEn
was used to detect nonlinearities in the heart rate (HR) patterns of 12 low-risk human fetuses between 38 and 40 wk of gestation. The fetal
cardiac electrical signal was sampled at a rate of 1,024 Hz by using
Ag-AgCl electrodes positioned across the mother's abdomen, and fetal R
waves were extracted by using adaptive signal processing techniques. To
test for nonlinearity, ApEn for the original HR time series was
compared with ApEn for three dynamic models: temporally uncorrelated
noise, linearly correlated noise, and linearly correlated noise with
nonlinear distortion. Each model had the same mean and SD in HR as the
original time series, and one model also preserved the Fourier power
spectrum. We estimated that noise accounted for 17.2-44.5% of the
total between-fetus variance in ApEn. Nevertheless, ApEn for the
original time series data still differed significantly from ApEn for
the three dynamic models for both group comparisons and individual fetuses. We concluded that the HR time series, in low-risk human fetuses, could not be modeled as temporally uncorrelated noise, linearly correlated noise, or static filtering of linearly correlated noise.
chaos |
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ISSN: | 8750-7587 1522-1601 |
DOI: | 10.1152/jappl.1999.87.2.530 |