Assessing determinism of photo-plethysmographic signal

A study was performed to analyze the signal obtained from a noninvasive photo-plethysmographic device from four subjects in different clinical conditions. With the help of the theory of nonlinear dynamics, it is verified that the cardiovascular dynamics is dominated by an underlying chaotic attractor. A new robust and computationally efficient method is presented for the detection of the hidden deterministic structure of a time series. It is shown that the degree of chaos as well as the underlying determinism is directly related to the subject's clinical stability.