Date Published: June 5, 2019
Publisher: Public Library of Science
Author(s): Guangjun Wang, Shuyong Jia, Hongyan Li, Xiaojing Song, Weibo Zhang, Yih-Kuen Jan.
Our previous study employed the classic laser Doppler flux (LDF) to explore the complexity of local blood flow signals and their relationship with heart rate variability (HRV). However, microcirculation blood flow is composed of different velocity components. To investigate the complexity of local speed-resolved perfusion and HRV following stimulation with different temperatures in healthy subjects, multiscale entropy (MSE) and multiscale fuzzy entropy (MFE) were used to measure the complexity of local speed-resolved perfusion signals. MSE was also used to evaluate the complexity of HRV. The results indicated that thermal stimulation increased all components of local speed-resolved perfusion and that stimulation with different temperatures resulted in different changes in the complexity area index. However, the same stimulation had no effect on the MSE of HRV. Further research showed that 44°C thermal stimulation resulted in a weak correlation between the composite speed-resolved perfusion and the HRV complexity. The current study provides a new approach for studying the relationship between speed-resolved perfusion signals and cardiac function.
There is increasing evidence that microcirculation can be used to evaluate vascular disorders at the systemic level[1, 2], and there is a close relationship between cardiac and vessel functions[3, 4]. In general, the functional status of vessels can be assessed by laser Doppler flowmetry (LDF). However, it is difficult to differentiate between different vascular compartments using the classical LDF approach. Recently, a multiparameter model based on the Monte Carlo algorithm has provided the possibility of further distinguishing the different velocity components in microcirculation perfusion[5–8]. This new method may provide further insight into evaluating vascular dysfunction at the systemic level[9, 10].
A total of 60 subjects were recruited in the current study. Detailed information on the participants receiving thermal stimulation (TS group, n = 30) and the blank control subjects (BC group, n = 30) is summarized in Table 1. In the thermal stimulation group, the stimulation order was randomly generated for each subject, which is detailed in S1 Table. The experimental design is shown in Fig 1A. The blood flux recording positions are shown in Fig 1B. The different thermal stimulation conditions, the related speed-resolved perfusion and the classic LDF are shown in Fig 1C. The time for each subject to participate in the measurement was not fixed in the current study. To exclude the influence of circadian rhythm from the analysis results, we compared the heart rates of the subjects before each intervention, and there was no significant difference between the groups (S2 Table).
In our previous study, classic LDF changes that were caused by stimulation with different temperatures were explored from the perspective of complexity. Furthermore, the relationship between the local blood flux and HRV was investigated. However, local blood flow after stimulation with different temperatures from the perspective of blood flow distribution in different speed regions has not been evaluated previously. In the current study, the complexity of different velocity components was analyzed, which is an extension of our previous research. To the best of our knowledge, this is the first study to explore the relationship between speed-resolved perfusion and HRV complexity.
Different complexity area indexes of speed-resolved blood perfusion were observed following different thermal stimulations. A monotonic correlation of the complexity area index between HRV and both the high-velocity and the composite local blood components was found after 44°C thermal stimulation. The current study provides an approach to explore the relationship between the heart function and the acupoint velocity-resolved perfusion via a complexity analysis.