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; determining a full arterial pulse waveform, defined as the arterial pulse signal without the effect of atrial diastolic blood flow demand, and an arterio-venous pulse waveform, defined by subtracting the arterial pulse signal from the full arterial pulse waveform, for each of the red and infra-red light plethysmography waveforms; determining an arterial side and a venous side normalized pulse variable component to pulse constant component for each of the red and infra-red light plethysmography waveforms by using the full arterial pulse waveform for the arterial side and the arterio-venous pulse waveform for the venous side; determining an arterial side and a venous side normalized ratio of pulse variable component to pulse constant component for each of the red and infra-red light plethysmography waveforms by using the full arterial pulse waveform for the arterial side and the arterio-venous pulse waveform for the venous side; determining 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 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 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 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 optionally calculating arterial and venous oxygen content using Fick's equation.