  The 0-1 test distinguishes between regular and chaotic dynamics for a
deterministic system using a time series. Here is presented how to use the test
with biological signals. Between all the biological signals obtained as a times
series, we present the results of applying the test and study with more details
the photoplethysmogram (PPG) from different subjects; different biological
signals of one subject are analyzed also with the test. PPG signal contains
extensive physiological dynamics information; mainly used to heart rate
monitoring and blood oxygen saturation. Based on its understandable statistics,
several indices have been proposed and may apply to some clinical needs.
However, continuous real-time monitoring, of the non-stationary biological
signals, is frequently used on the modern intensive care unit. A deep
understanding of the PPG signal will allow finding algorithms to evaluate other
possible indices that give information about the dynamical system that
constitutes the human body. We demonstrate that the PPG signal, as a time
series, on a healthy individual, is a quasi-periodic signal. The parameters
calculated for the analysis give some ideas of what the quasi-periodic
properties mean. Results are on PPG signals from different healthy young
people. The dynamical analysis of the PPG signal applying the 0-1 test allows
distinguishing a regular dynamic, periodic o quasi-periodic, from a chaotic
dynamics operating directly over the time series. The result obtained is
compared with the results from well known time series that are random, chaotic,
aperiodic, periodic, and quasi-periodic.
