Robust accurate non-invasive analyte monitor

• US 5,830,132 A
• Filed: 02/03/1997
• Issued: 11/03/1998
• Est. Priority Date: 08/24/1993
• Status: Expired due to Fees

• Current Assignee: Mark R. Robinson
• Original Assignee: Mark R. Robinson
• Inventors: Robinson, Mark R.
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US08/794,677
• Time in Patent Office: 638 Days
• Field of Search: 600/310-324
• US Class Current: 600/310
• CPC Class Codes: A61B 2562/0233 Special features of optical sensors or probes classified in A61B5/00
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence
• CPC Class Codes: G01N 21/359 using near infrared light
• CPC Class Codes: G01N 21/49 within a body or fluid
• CPC Class Codes: G01N 2201/0621 Supply

Abstract

An improved method and apparatus for determining noninvasively and in vivo one or more unknown values of a known characteristic, particularly the concentration of an analyte in human tissue. The method includes: (1) irradiating the tissue with infrared energy (400 nm-2400 nm) having at least several wavelengths in a given range of wavelengths so that there is differential absorption of at least some of the wavelengths by the tissue as a function of the wavelengths and the known characteristic, the differential absorption causeing intensity variations of the wavelengths incident from the tissue; (2) providing a first path through the tissue; (3) optimizing the first path for a first sub-region of the range of wavelengths to maximize the differential absorption by at least some of the wavelengths in the first sub-region; (4) providing a second path through the tissue; and (5) optimizing the second path for a second sub-region of the range, to maximize the differential absorption by at least some of the wavelengths in the second sub-region. In the preferred embodiment a third path through the tissue is provided for, which path is optimized for a third sub-region of the range. With this arrangement, spectral variations which are the result of tissue differences (e.g., melanin and temperature) can be reduced. At least one of the paths represents a partial transmission path through the tissue. This partial transmission path may pass through the nail of a finger once and, preferably, twice. Also included are apparatus for: (1) reducing the arterial pulsations within the tissue; and (2) maximizing the blood content i the tissue.

Claims

1. In a method of determining noninvasively and in vivo one or more unknown values of a known characteristic, including the steps of irradiating human tissue with at least one source of infrared energy having at least several wavelengths in a given range of wavelengths so that there is differential absorption of at least some of said wavelengths by said tissue as a function of said wavelengths and said characteristic, said differential absorption causing intensity variations of said wavelengths, collecting with at least one detector at least some of said wavelengths that have traversed through said tissue, and calculating said one or more unknown values of said known characteristic, the improvement comprising:

positioning said at least one source and said at least one detector relative to said tissue to provide at least first and second average optical paths through said tissue, said first path being for a first sub-region of said wavelengths, said second path being for a second sub-region of said wavelengths, said first path being different in length from said second path, and using said intensity variations from said second subregion of said wavelengths to compensate said intensity variations from said first subregion of said wavelengths.

2. The method as set forth in claim 1, further including the step of compensating for those intensity variations that adversely influence the quantitative measurement of said known characteristic.

3. The method as set forth in claim 2, wherein said compensation step reduces said intensity variations which are the result of tissue differences.

4. In a method of determining noninvasively and in vivo one or more unknown values of a known characteristic, including the steps of irradiating human tissue with at least one source of infrared energy having at least several wavelengths in a given range of wavelengths so that there is differential absorption of at least some of said wavelengths by said tissue as a function of said wavelengths and said characteristic, said differential absorption causing intensity variations of said wavelengths, collecting with at least one detector at least some of said wavelengths that have traversed through said tissue, and calculating said one or more unknown values of said known characteristic, the improvement comprising:

a. positioning said at least one source and said at least one detector relative to said tissue to provide at least first and second average optical paths through said tissue, said first path being different in length from said second path; and

b. compensating said intensity variations of said wavelengths collected from said first path with said intensity variations of said wavelengths collected from said second path.

5. The method as set forth in claim 4, wherein said collected wavelengths from said first and second paths are different.

6. The method as set forth in claim 4, wherein at least some of said collected wavelengths from said first and second paths are the same.

7. The method as set forth in claim 4, wherein said first path is for a first sub-region of said wavelengths, and said second path is for a second sub-region of said wavelengths.

8. The method as set forth in claim 4, further including the step of compensating for those intensity variations that adversely influence the quantitative measurement of said known characteristic.

9. The method as set forth in claim 8, wherein said compensation step reduces said intensity variations which are the result of tissue differences.