Method and apparatus for in vitro calibration of oxygen saturation monitor

• US 4,796,633 A
• Filed: 06/25/1985
• Issued: 01/10/1989
• Est. Priority Date: 06/25/1985
• Status: Expired due to Fees

• Current Assignee: Baxter International Inc.
• Original Assignee: American Hospital Supply Corp. (Baxter International Inc.)
• Inventors: Zwirkoski, Lori J.
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): Hanley, John C.
• Application Number:
  US06/748,485
• Time in Patent Office: 1,295 Days
• Field of Search: 128/633, 128/634, 128/665, 128/666, 73/1 G, 250/252.1, 356/39-42, 356/243
• US Class Current: 600/332
• CPC Class Codes: A61B 2560/0233 Optical standards
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes

Abstract

A calibration reference apparatus comprising an elongated peripheral tubular wall open at one end and an end wall closing the other end of the tubular wall. The tubular wall and the end wall are integrally molded. The end wall defines a curved cavity opening toward the open end of the tubular wall. The calibration reference apparatus is adapted to receive a light guide through the tubular wall and in the cavity. A stop limits the extent to which the light guide can be advanced into the cavity whereby an end face of the light guide is spaced from a region of the surface to define a gap. The end wall and the gap are adapted to return a known ratio of the light directed into the gap from the end face of the light guide.

Claims

1. A calibration reference apparatus for use with a light guide having an end portion which terminates in an end face, said apparatus comprising:

a calibration element having a surface defining a cavity, said cavity having an opening at one end and otherwise being essentially optically closed, said opening being sized to receive the end portion of a light guide;

means for releasably positioning the end portion of a light guide in the cavity with the end face of the light guide spaced from said surface opposite said opening to define a gap whereby a light guide can direct light at least at one wavelength from the end face thereof across the gap and against said surface opposite said opening;

said calibration element having means for returning some of the light at said one wavelength which is directed against said surface opposite said opening;

said means for returning having similar light returning properties as blood; and

said positioning means and said calibration element being fixed with respect to each other.

2. An apparatus as defined in claim 1 wherein said surface is part spherical.

3. An apparatus as defined in claim 1 wherein said positioning means includes a portion of said surface, said portion of said surface being rigid and adapted to form a friction fit with the end portion of a light guide.

4. An apparatus as defined in claim 1 wherein the calibration element is constructed of a material that essentially allows no light of said one wavelength directed against said surface opposite said opening to be transmitted completely through the calibration element.

5. An apparatus as defined in claim 1 including an essentially opaque optical barrier element at least partially receiving the calibration element.

6. An apparatus as defined in claim 1 wherein said means for returning includes a matrix and a plurality of light scattering particles distributed in said matrix.

7. An apparatus as defined in claim 1 including an elongated tubular wall integral with the calibration element for guiding a light guide into said cavity.

8. A calibration reference apparatus as defined in claim 1 wherein said surface has homogeneous optical properties.

9. A calibration reference apparatus for use with a light guide having an end portion which terminates in an end face, said apparatus comprising:

a matrix;

a plurality of light scattering particles dispersed in said matrix;

means for holding the end portion of a light guide in predetermined spaced relationship with a region of the matrix to define a gap between the end face of the light guide and said region of the matrix whereby the light guide can direct light at least at one wavelength into the gap and toward the matrix;

said matrix being adapted to return some of the light at said one wavelength directed into the gap from the end face of the light guide;

means surrounding the gap to essentially prevent transmission of the light at said one wavelength directed into the gap from the end face of the light guide radially of the gap to the outside of the calibration reference device; and

said matrix and said surrounding means being fixed with respect to each other.

10. An apparatus as defined in claim 9 wherein said matrix is constructed of plastic and includes dye.

11. A calibration cup comprising:

an elongated peripheral tubular wall open at one end and an end wall closing the other end of the tubular wall, said tubular wall and said end wall being integrally molded;

said end wall defining a curved cavity opening toward the open end of the tubular wall, said calibration cup being adapted to receive a light guide through the tubular wall and in the cavity;

said end wall having light-scattering, absorption and reflection properties which in the aggregate are similar to blood;

said end wall including a matrix of plastic material and a plurality of light scattering particles distributed in said matrix and said cavity is part spherical; and

a stop means for limiting the extent to which a light guide can be advanced into said cavity whereby an end face of the light guide can be spaced from a region of the end wall to define a gap and said end wall is adapted to return a ratio of the light directed into the cavity from the end face of the light guide.

12. A calibration cup as defined in claim 11 including an essentially opaque barrier element at least partially receiving the calibration element.

13. An assembly comprising:

an elongated peripheral tubular wall open at one end and an end wall closing the other end of the tubular wall, said tubular wall and said end wall being integrally molded;

an optical catheter having an end portion which terminates in an end face and light-conducting means for conducting light along the length of the catheter to and from said end face;

said end wall defining a curved cavity opening toward the open end of the tubular wall, said tubular wall receiving the end portion of the optical catheter; and

a stop for limiting the extent to which the end portion can be advanced into the cavity whereby the end face of the optical catheter is spaced from a region of the end wall to define a gap and said end wall and the gap being adapted to return some of the light directed into the cavity from the end face.

14. An assembly comprising:

a calibration reference apparatus including a calibration element having a curved surface defining a cavity, said cavity having an opening at one end and otherwise being optically closed, at least a portion of said curved surface being generally opposite said opening;

an optical catheter having an end portion which terminates in an end face and light-conducting means for conducting light along the length of the catheter to and from said end face;

said opening of said cavity being sized to receive the end portion of the optical catheter;

means for positioning the end portion of the optical catheter in the cavity with the end face of the optical catheter being spaced from said surface opposite said opening to define a gap whereby the optical catheter can direct light at least at one wavelength from the end face thereof into the gap;

said calibration element being adapted to return some of the light at said one wavelength directed into the gap from the end face of the optical catheter; and

said positioning means including means for preventing the optical catheter from being advanced into the cavity far enough to eliminate said gap between said end face and said surface.

15. A method of calibrating a light guide having an end portion which terminates in an end face and light-conducting means for conducting light along the length of the catheter to and from the end face, said method comprising:

providing a calibration element having a surface defining a cavity, said cavity having an opening at one end and otherwise being closed, and said opening being sized to receive the end portion of the light guide;

inserting the end portion of the light guide into the cavity to a position in which the end face of the light guide is spaced from said surface opposite said opening to define a gap;

directing light at least at one wavelength through the light-conducting means and said gap and against said surface;

allowing the calibration element and the air gap to return a known ratio of the light at said one wavelength directed into the gap from the light-conducting means back through the light-conducting means;

measuring the intensity of the light returned through the light-conducting means; and

utilizing the information obtained in said step of measuring in the calibration of the light guide.