Estimation of blood pressure variability using independent component analysis of photoplethysmographic signal

The maximum cross-correlation coefficient rho_max between blood pressure variability and heart rate variability, whose frequency components are limited to the Mayer wave-related band, is a useful index to evaluate the state of the autonomic nervous function related to baroreflex. However, measurement of continuous blood pressure with an expensive and bulky measuring device is required to calculate rho_max. The present study has proposed an easier method for obtaining rho_max with measurement of finger photoplethysmography (PPG). In the proposed method, independent components are extracted from feature variables specified by the PPG signal by using the independent component analysis (ICA), and then the most appropriate component is chosen out of them so that the rho_max based on the component can fit its true value. The results from the experiment with a postural change performed in 17 healthy subjects suggested that the proposed method is available for estimating rho_max by using the ICA to extract blood pressure information from the PPG signal.