Patent ID: 7608045

Claim:
A method for noninvasively determining physiological parameters of a patient, comprising the steps of: providing a first tissue probe, said first tissue probe including a first radiation emitter adapted to emit first radiation having a first wavelength and a first radiation detector adapted to receive said first radiation after absorbance through a first radiation path length of the patient's blood; providing a second tissue probe, said second tissue probe including a second radiation emitter adapted to emit second radiation having a second wavelength and a second radiation detector adapted to receive said second radiation after absorbance through a second radiation path length; varying the volume and pressure of the patient's blood at first and second patient sites, said first patient site being proximate said first tissue probe, said second patient site being proximate second tissue probe; measuring first absorbance of the patient's blood at said first patient site as said blood volume and pressure are varied by transmitting said first radiation at said first wavelength through the patient's blood and detecting said first radiation after passage through the patient's blood; measuring second absorbance of the patient's blood at said second patient site as said blood volume and pressure are varied by transmitting said second radiation at said second wavelength through the patient's blood and detecting said second radiation after passage through the patient's blood; timing the arrival of pulse and flow waves at said first and second patient sites by comparing said first and second absorbances measured at said first and second patient sites; and determining a cardiac characteristic based on said arrival times of said pulse and flow waves.