Patent ID: 6480729
Filing Date: 2002-11-12
Classification: A61B

Abstract:
A method for determining blood constituents of a patient, said patient having a tissue region, said tissue region including venous and arterial blood, comprising;coupling an oximeter sensor arrangement to said tissue region of said patient; passing first and second lights through said patient's tissue region while said venous blood in said tissue region has a first volume for a first period of time and said venous blood in said tissue region has a second volume for a second period of time, said first light being substantially in a red light range and said second light being substantially in an infrared light range; detecting light absorbed by said tissue region and providing a first signal corresponding to said absorbed light; processing said first signal to provide a second signal corresponding to a red light signal component and a third signal corresponding to an infrared light signal component, each of said second and third signals having at least first and second frequencies, wherein said first frequency comprises approximately the reciprocal of the sum of said first and second periods; computing a first ratio of said second and third signals at said first frequency; computing a second ratio of said second and third signals at said second frequency; comparing said first and second ratios to determine a first blood constituent.