A system for measuring of arterial and venous blood constituent concentration based first on measuring cardiac blood flow balance parameter between the right chamber of the heart and the left chamber of the heart, which includes a sensor device for measuring one of blood pressure and blood flow rate and blood constituent concentration of a patient so as to generate an arterial pulse signal. A processing unit is responsive to the arterial pulse signal for generating full arterial pulse plethysmography waveforms, arterio-venous pulse plethysmography waveforms, and balance parameters. A computational device that is responsive to plethysmography waveforms generating a plurality of state space linear transfer functions by applying system identification between plethysmography waveforms at various wavelengths representing a plurality of models of the blood constituent concentration, including oxygen, carbon dioxide, hemoglobin, and glucose, and displaying related useful information.