| 研究実績の概要 |
Starting from the previous year, the main focus of this research was to deepen understanding of the PPG dynamics itself and how various factors affect its parameters. Therefore, this FY's first aim was to improve understanding of dynamics changes due to age. Secondly, the effects of the presence of hypertension conditions, a widely spread cardiovascular system disorder, on PPG dynamics were investigated. Results obtained by the recurrence quantification analysis (RQA) clearly demonstrated that the determinism property remains unchanged despite age and hypertension condition, while other dynamical characteristics indicated changes in complexity and predictability with aging or in presence of hypertension conditions. However, the applied analysis could reveal this reliably only in the case of high-quality data measured over a long time. In many cases, contact and especially imaging PPGs can be measured with a good quality only during a short time. Therefore, the effect of data length was additionally investigated to identify indexes useable not only for long but also for short-measured time series. It was detected that certain methods of RQA are applicable even to very short PPG recordings.
Additional attention was paid to the transition of the RQA indexes in different dynamical systems with the change of applied methods parameters. Certain differences in determinism parameter transition was found for chaotic systems compared with noisy periodic systems, which makes it important to confirm PPG analysis results transition with variable parameters.
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