System and method for measuring blood urea nitrogen, blood osmolarity, plasma free hemoglobin and tissue water content

• US 6,246,894 B1
• Filed: 02/24/1998
• Issued: 06/12/2001
• Est. Priority Date: 02/01/1993
• Status: Expired due to Term

• Current Assignee: Fresenius Medical Care Holdings Incorporated (Fresenius Medical Care AG)
• Original Assignee: In-Line Diagnostics Corp.
• Inventors: Miller, David R., Steuer, Robert R.
• Primary Examiner(s): Nasser, Robert L.
• Application Number:
  US09/028,809
• Time in Patent Office: 1,204 Days
• Field of Search: 600/300, 600/310, 600/322-327
• US Class Current: 600/322
• CPC Class Codes: A61B 5/14535 for measuring haematocrit
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/14557 specially adapted to extracorporeal circuits
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure
• CPC Class Codes: A61M 1/361 before treatment
• CPC Class Codes: A61M 1/3612 after treatment
• CPC Class Codes: G01N 2021/036 transformable, modifiable
• CPC Class Codes: G01N 21/0303 Optical path conditioning in cuvettes, e.g. windows; adapted optical elements or systems; path modifying or adjustment G01N21/031 - G01N21/15 take precedence

Abstract

Systems and methods are provided for noninvasively measuring the levels of urea, blood osmolarity (or Na⁺), plasma free hemoglobin and tissue water content in a patient'"'"'s blood or tissue. Light of selected wavelengths is passed through blood or body tissue and the transmitted or reflected light is detected and the detected signals can be electronically compared and manipulated to provide the non-invasive, continuous and quantitative display of a patient'"'"'s blood urea, blood osmolarity (or Na⁺), plasma free hemoglobin and tissue water content.

Claims

1. A system for determining a plurality of different constituents of the blood or tissue of a patient, the blood flowing in a pulsatile fashion in a body part of the patient or in an extracorporeal passageway in communication with the circulatory system of the patient so as to be subjectable to transcutaneous examination in the body part or to noninvasive examination in the extracorporeal passageway, the body part or the extracorporeal passageway defining a blood conduit, the system comprising:

blood conduit receiving means for receiving a blood conduit containing the flowing blood of the patient;

a plurality of emitters positioned on said conduit receiving means for emitting a plurality of different radiation wavelengths;

directing means for directing said plurality of radiation wavelengths into the flowing blood in the blood conduit;

detecting means for detecting the amount of radiation for each of said plurality of wavelengths after passing through the blood conduit, said detected amounts of radiation each having different extinction characteristics; and

a plurality of determining means each receiving the same one of said plurality of radiation wavelengths from said first detecting means and at least one of said remaining plurality of wavelengths for determining a respective constituent, said plurality of determining means being four and said plurality of constituents being BUN, tissue water content, osmolarity, and Na+.

2. The system of claim 1, wherein said one radiation wavelength is 1300 nm.

3. The system of claim 1, wherein said blood and tissue constituents are selected from the group consisting of BUN, PFH, tissue water content, hematocrit, hemoglobin, osmolarity, and Na⁺.

4. The method of claim 1, wherein said first radiation wavelength is 2190 nm.

5. The method of claim 1, wherein said first radiation wavelength is 810 nm.

7. The method of claim 5, wherein the one radiation wavelength is 1300 nm.

6. A method for determining BUN of a patient, the blood flowing in a pulsatile fashion in a body part of the patient or in an extracorporeal passageway in communication with the circulatory system of the patient so as to be subjectable to examination in the extracorporeal passageway, in the body part or the extracorporeal passageway defining a blood conduit, the method comprising the steps of:

flowing the blood of a patient through a blood conduit;

placing a first emitter emitting a first radiation wavelength on the blood conduit;

directing the first radiation wavelength through the blood on the blood conduit;

detecting the amount of first radiation after passing through the blood in the blood conduit, the detected amount of first radiation having at least one extinction characteristic; and

determining a plurality of blood constituents based on the detected amount of first radiation in accordance with the equation I=I_oe<sup>[−

E(x)d+B(d, E(x))]</sup>, where B(d, Ex) is an optical pathlengthening function, I_o is the intensity of the incident source radiation, I is the transmitted intensity of the source radiation through the sample, E is the extinction coefficient of the sought for constituent, x is the concentration of the BUN and d is the optical separation distance.

8. A system for determining BUN of a patient, the blood flowing in a pulsatile fashion in a body part of the patient or in an extracorporeal passageway in communication with the circulatory system of the patient so as to be subjectable to transcutaneous examination in the body part or to noninvasive examination in the extracorporeal passageway, the body part or the extracorporeal passageway defining a blood conduit, the system comprising:

blood conduit receiving means for receiving a blood conduit containing the flowing blood of the patient;

a first emitter positioned on said conduit receiving means for emitting a first radiation wavelength;

directing means for directing the first radiation wavelength into the flowing blood in the blood conduit;

first detecting means for detecting the amount of first radiation after passing through the blood conduit, said detected amount of first radiation having at least one extinction characteristic; and

determining means receiving said first radiation from said first detecting means for determining BUN by solving the equation log [I/I_o)₂₁₉₀/(I/I_o1300]•

[F[log (I/I_o)₈/log (I/I_o)₁₃]], where E₂₁₉₀ equals the extinction coefficent at 2190 nm wavelength, E₁₃₀₀ equals the extinction coefficient at 1300 nm wavelength, F equals a function of hematocrit, I equals the transmittal intensity of source radiation, I_o equals the intensity of incident source radiation;

log (I/I_o)₈ is the log value at 810 nm wavelength and log (I/I_o)₁₃ is the log value at 1300 nm wavelength.