Active pulse blood constituent monitoring

Abstract

A blood constituent monitoring method for inducing an active pulse in the blood volume of a patient. The induction of an active pulse results in a cyclic, and periodic change in the flow of blood through a fleshy medium under test. By actively inducing a change of the blood volume, modulation of the volume of blood can be obtained to provide a greater signal to noise ratio. This allows for the detection of constituents in blood at concentration levels below those previously detectable in a non-invasive system. Radiation which passes through the fleshy medium is detected by a detector which generates a signal indicative of the intensity of the detected radiation. Signal processing is performed on the electrical signal to isolate those optical characteristics of the electrical signal due to the optical characteristics of the blood.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]Notice: More than one reissue application has been filed for the reissue of U.S. Pat. No. 7,239,905. The reissue applications are application Ser. No. 12 / 497,517 (the present application) and Ser. No. 13 / 047,740 (continuation of present application), both of which are reissues of U.S. Pat. No. 7,239,905.[0002]This application is a continuation of U.S. patent application Ser. No. 09 / 706,965, filed Nov. 6, 2000, now U.S. Pat. No. 6,931,268, issued Aug. 16, 2005, which is a continuation of U.S. patent application Ser. No. 09 / 190,719, filed Nov. 12, 1998, now U.S. Pat. No. 6,151,516, issued Nov. 21, 2000, which is a continuation of U.S. patent application Ser. No. 08 / 843,863, filed Apr. 17, 1997, now U.S. Pat. No. 5,860,919, issued Jan. 19, 1999, which is a continuation of U.S. patent application Ser. No. 08 / 482,071, filed Jun. 7, 1995, now U.S. Pat. No. 5,638,816, issued Jun. 17, 1997. The present application incorporates the foregoing discl...

AI Technical Summary

Benefits of technology

The patent text discusses the difficulties in accurately detecting glucose concentration in a fingertip or earlobe through a fleshy medium, such as blood. The natural heart beat and low signal strength make it difficult to determine the exact path length through the medium. The text proposes a solution by actively inducing a change in the flow of blood in the medium to obtain modulation, which can be used to determine the portion of the attenuated signal due to blood. This approach allows for accurate measurement of glucose concentration in the fingertip or earlobe.

Problems solved by technology

Due to the parameters required by the Beer-Lambert law, the difficulties in detecting glucose concentration arise from the difficulty in determining the exact path length through a medium (resulting from transforming the multi-path signal to an equivalent single-path signal), as well as difficulties encountered due to low signal strength resultant from a low concentration of blood glucose.

Path length through a medium such as a fingertip or earlobe is very difficult to determine, because not only are optical wavelengths absorbed differently by the fleshy medium, but also the signals are scattered within the medium and transmitted through different paths.

Thus, it is often very difficult to determine an exact path length through a fingertip or earlobe for each wavelength.

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