Assessing skin blood flow dynamics in older adults using a modified sample entropy approach.
Assessing skin blood flow dynamics in older adults using a modified sample entropy approach.
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DOI：
10.1109/embc.2014.6943692
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发表时间：
2014-01-01
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影响因子：
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通讯作者：
Jan, Yih-Kuen
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文献类型：
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作者：
Liao, Fuyuan;Jan, Yih-Kuen
老化过程可能导致响应于环境刺激的微血管反应性减弱，这可以通过分析皮肤血流（SBF）信号来评估。在分析生理信号的各种方法中，样本熵（SE）通常用于量化时间序列的规律性程度。然而，我们发现，对于时间相关的数据，SE值取决于采样率。当数据过采样时，SE可能会给出误导性的结果。为了解决这个问题，我们建议修改SE的定义，通过使用时间滞后的向量在计算条件概率，连续数据点的任何两个向量在公差r内的m个点保持在下一个点的公差内。可以选择滞后作为自动互信息函数的第一最小值。我们使用模拟信号和SBF数据测试了改进的SE的性能。结果表明，改进的SE是能够量化的程度的规律性的信号，而不管采样率。使用这种方法，我们观察到与基线相比，年轻人和老年人在局部加热诱导的最大血管舒张期内的血流振荡（BFO）行为更有规律，而与年轻人相比，老年人的BFO行为更有规律。这些结果表明，修改后的SE可能是有用的SBF动力学的研究。
The aging process may result in attenuated microvascular reactivity in response to environmental stimuli, which can be evaluated by analyzing skin blood flow (SBF) signals. Among various methods for analyzing physiological signals, sample entropy (SE) is commonly used to quantify the degree of regularity of time series. However, we found that for temporally correlated data, SE value depends on the sampling rate. When data are oversampled, SE may give misleading results. To address this problem, we propose to modify the definition of SE by using time-lagged vectors in the calculation of the conditional probability that any two vectors of successive data points are within a tolerance r for m points remain within the tolerance at the next point. The lag could be chosen as the first minimum of the auto mutual information function. We tested the performance of modified SE using simulated signals and SBF data. The results showed that modified SE is able to quantify the degree of regularity of the signals regardless of sampling rate. Using this approach, we observed a more regular behavior of blood flow oscillations (BFO) during local heating-induced maximal vasodilation period compared to the baseline in young and older adults and a more regular behavior of BFO in older adults compared to young adults. These results suggest that modified SE may be useful in the study of SBF dynamics.