1. A method for determining arterial and venous side oximetry based upon full arterial pressure pulse waveform and arterio-venous pressure pulse waveform, comprising the steps of: measuring of plethysmography waveforms of red and infra-red lights which are representative of arterial pulses measured by any of optical absorption or transmission by using a non-invasive sensor device configured to be disposed on a portion of the body of a patient, the measured arterial pulses containing mixed interactions of arterial and venous pulsations with the effect of atrial diastolic blood flow demand; determining an estimated full arterial pulse waveform representing only a supply side pulse of the left ventricle and defined as the measured arterial pulse signal without the effect of atrial diastolic blood flow demand that reduces the ventricular supply causing a dicrotic notch, and an estimated arterio-venous pulse waveform representing only a demand side pulse of the right atrium and estimating the atrial diastolic blood flow demand as sensed from the arterial side and defined by subtracting the measured arterial pulse signal from the estimated full arterial pulse waveform, for each of the red and infra-red light plethysmography waveforms by way of a processor unit having its input coupled via an A/D converter to the non-invasive sensor device; determining further an arterial side and a venous side pulse variable component and a pulse constant component in the processor unit for each of the red and infra-red light plethysmography waveforms by using the estimated full arterial pulse waveform for the arterial side and the estimated arterio-venous pulse waveform for the venous side; determining further an arterial side and a venous side normalized ratio of pulse variable component to pulse constant component in the processor unit for each of the red and infra-red light plethysmography waveforms by using the estimated full arterial pulse waveform for the arterial side and the measured arterio-venous pulse waveform for the venous side; determining still further the arterial oxygen saturation as a function of a first ratio of the normalized ratio of the full arterial pulse variable component to the full arterial pulse constant component in the processor unit for the arterial side for the red light plethysmography waveform to the normalized ratio of the full arterial pulse variable component to the full arterial pulse constant component for the arterial side for the infra-red light plethysmography waveform; determining still further the venous oxygen saturation as a function of a second ratio of the normalized ratio of the arterio-venous pulse variable component to the arterio-venous pulse constant component in the processor unit for the venous side for the red light plethysmography waveform to the normalized ratio of the arterio-venous pulse variable component to the arterio-venous pulse constant component for the venous side for the infra-red light plethysmography waveform; and coupling a display station to an output of the processor unit for receiving the arterial oxygen saturation and the venous oxygen saturation and for providing visual and audio monitoring of the patient's health condition and for alerting medical personnel of changes in the patient's health condition.