An improved method for dual-wavelength photoplethysmography with the ability to extract time difference features

摘要

This study was aimed to present a new approach for obtaining dual-wavelength photoplethismographic (PPG) signals and extracting their time difference features. The new approach was proposed instead of the existing time division multiplex (TDM) method to overcome its disadvantages. An improved sensor system was developed in which drawbacks of previous methods were modified. For performance evaluation and comparison, PPG signals were recorded during bio-physiological challenge experiments by both of the proposed and TDM methods. Peak detection algorithm was applied and the time differences (TDs) were calculated using the obtained peak points. Obtained data were analyzed by two sample t-test, indicating that all measured TDs in the separate phases of the experiments were statistically significant (P<;0.05). Based on the results, the time-difference between PPG signals in two unlike wavelengths obtained by the presented sensor system had very significant variations related to physiological conditions. However in the TDM based system, significant TD variations were not observed. Based on the results, it could be said that the presented method had a suitable potential to evaluate physiological situations and could be used for fast and accurate identification proposes. The outcomes of this project encourage more studies to reach adequate accuracy for clinical applications.