Apparatus and method for in-vivo measurements of chemical concentrations

• US 4,622,974 A
• Filed: 03/07/1984
• Issued: 11/18/1986
• Est. Priority Date: 03/07/1984
• Status: Expired due to Fees

• Current Assignee: The University Of Tennessee Research Corporation (University of Tennessee)
• Original Assignee: The University Of Tennessee Research Corporation (University of Tennessee)
• Inventors: Coleman, Jerry T., Sepaniak, Michael J.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): Hanley, John C.
• Application Number:
  US06/587,234
• Time in Patent Office: 986 Days
• Field of Search: 128/633, 128/634, 128/665, 128/666, 356/432, 356/436, 356/440
• US Class Current: 600/342
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: A61B 5/6848 Needles

Abstract

A method and apparatus in which a blunt interior needle is positioned within a larger external needle and a sample cavity is formed at the blunt end of the interior needle. An optical fiber extends from the sample cavity up the interior needle and to a light source and light detector. A reflective surface is placed at the end of the sample cavity reflects light back to the optical fiber. A beam splitter separates the incident and reflected light.

To make an in-vivo measurement of chemical concentrations in a body, the needle is inserted into the body and fluids are aspirated into the sample cavity. Light is then transmitted to the cavity by the optical fiber and is transmitted from the cavity to a detector by the same fiber. By measuring the amount of light reflected, one can determine the amount of light absorbed in the cavity and may thus determine concentrations of selected chemicals.

Claims

1. An apparatus for use in making in-vivo determinations of light absorbance of biological fluid of a body comprising:

an insertion needle with a needle point for penetrating the body to a region of the biological fluid to be tested;

a reflective surface disposed within the needle and adjacent to the needle point in an orientation generally perpendicular to the longitudinal axis of the needle;

a sample cavity disposed within said needle for receiving and containing samples of the biological fluid, said reflective surface being disposed between said needle point and at least a portion of said sample cavity;

ingress means for providing a pathway from the biological fluids from outside the needle to said sample cavity within said needle to allow ingress of fluid into said sample cavity;

a source of light;

optical fiber having a first end disposed within said needle and a second end receiving light from said light source and transmitting light to said first end, said first end of said optical fiber being disposed at said sample cavity in an opposed generally parallel relationship with said reflective surface so that light is transmitted from the first end, through said sample cavity, and reflected by said reflective surface back through said sample cavity and into said first end, the distance between said reflective surface and said first end of said optical fiber defining one-half of the length of the sample light path through the sample cavity;

means for detecting the intensity of light transmitted from said second end of said single optical fiber simultaneously with the transmission of light into said second end by said light source whereby the biological fluid is determined by transmitting light into said sample cavity through said optical fiber and measuring the intensity of light is reflected by said reflective surface that passes through said sample cavity, and reenters said first end of said optical fiber to determine the amount of light that was absorbed by the light absorbing constituents of the biological fluid in said sample cavity; and

means for adjusting the distance between said reflective surface and the first end of said optical fiber to change the length of said sample light path,

said means for adjusting the distance between said reflective surface and the first end of said optical fiber comprising a micrometer mechanically linked to said optical fiber and mechanically linked to said needle to change and indicate the position of the first end of said fiber with respect to said reflective surface.