Optical probe

• US 5,251,633 A
• Filed: 08/08/1991
• Issued: 10/12/1993
• Est. Priority Date: 08/13/1990
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Company (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Rupp, Lothar, Guenther, Martin, Wunderling, Martin
• Primary Examiner(s): Green, Randall L.
• Assistant Examiner(s): GUALTIERI, GINA
• Application Number:
  US07/742,596
• Time in Patent Office: 796 Days
• Field of Search: 128/634, 128/637, 128/635, 356/39-41
• US Class Current: 600/311
• CPC Class Codes: A61B 5/14539 for measuring pH
• CPC Class Codes: A61B 5/1459 invasive, e.g. introduced into the body by a catheter A61B5/1464 takes precedence

Abstract

An improved optical probe for the invasive measurement of partial carbon dioxide pressures is disclosed that minimizes pCO₂ reading drift. An optical probe for the invasive measurement of the partial carbon dioxide pressure comprises an optical fiber and a pCO₂ sensor. The pCO₂ sensor comprises a diffusion zone with a dye-containing gel that is optically sensitive to H⁺ ions and a semi-permeable membrane that is permeable to CO₂ molecules, but is substantially nonpermeable to hydrogen ions Components of the pCO₂ sensor, such as the part of the optical fiber extending into the sensor or a reflector, are covered with a substance--preferably with a coating--that is substantially nonpermeable to hydrogen ions. This prevents the hydrogen ions from diffusing into the sensor components, which otherwise would cause an imbalance of hydrogen ions and, therefore, a drift in the pCO₂ reading.

Claims

1. An optical probe for the invasive measurement of at least the pCO₂ of a biologic circulatory system comprising:

a pCO₂ sensor including

(a) a sensing diffusion zone comprising a gel containing a dye that is optically sensitive to H⁺ ions; and

(b) components coupled to said gel including an optical element having an end portion in optical communication with the gel; and

a semi-permeable membrane at least partially enclosing said pCO₂ sensor and said gel and components and comprising a material permeable to CO₂ molecules but substantially impermeable to H⁺ ions;

wherein at least one of said components is covered by a coating comprising a substance that is substantially impermeable to H⁺ ions.

2. The optical probe of claim 1 wherein said coating covers said end portion of said optical element.

3. The optical probe of claim 1 further comprising an optical reflector optically coupled to said optical element and a coating covering said optical reflector that is substantially impermeable to H⁺ ions.

4. The optical probe of claim 3 wherein said optical reflector comprises a metal.

5. The optical probe of claim 1, wherein said coating comprising a substance that is substantially impermeable to H⁺ ions is an adhesive for fastening said semi-permeable membrane to said gel and components.

6. The optical probe of claim 1 wherein said substance that is substantially impermeable to H⁺ ions is silicone or a copolymer of silicone and polycarbonate.

7. The optical probe of claim 1 wherein the substance that is substantially impermeable to H⁺ ions is hexamethyldisilazane or other silylating agent.

8. The optical probe of claim 1 wherein said adhesive is the coating that covers said at least one of said components.

15. The optical probe of claim 8 wherein said optical element comprises a plastic fiber optic.

9. An optical probe for the invasive measurement of at least the pCO₂ of a biologic circulatory system comprising:

a pCO₂ sensor, said sensor having a diffusion zone with a dye-containing gel that is optically sensitive to H⁺ ions;

a semi-permeable membrane that is permeable to CO₂ molecules but substantially impermeable to H⁺ ions at least partially enclosing said diffusion zone;

an optical fiber comprising a plastic material extending into the pCO₂ sensor and through said semi-permeable membrane including an end portion of said plastic optical fiber juxtaposed with said dye-containing gel; and

a coating covering at least said end portion of the plastic optical fiber extending into the pCO₂ sensor that comprises a substance that is substantially impermeable to H⁺ ions.

10. The optical probe of claim 9 further comprising an adhesive for fastening the semi-permeable membrane to said sensor, said adhesive comprising a substance that is substantially impermeable to H⁺ ions.

11. The optical probe of claim 9 wherein the substance that is substantially impermeable to H⁺ ions is silicone or a copolymer of silicone and polycarbonate.

12. The optical probe of claim 9 wherein the substance that is substantially impermeable to H⁺ ions is hexamethyldisilazane or other silylating agent.

13. A method for manufacturing an optical probe for the invasive measurement of at least the pCO₂ of a biologic circulatory system including an optical component and a diffusion zone with dye-containing gel that is optically sensitive to H⁺ ions enclosed within a semi-permeable membrane that is permeable to CO₂ molecules but substantially impermeable to H⁺ ions, said method comprising the steps of:

coating said optical component with a substance substantially impermeable to H⁺ ions before the optical probe is assembled; and

assembling the optical component such that the optical component is in juxtaposition to the gel within said semi-permeable membrane.

14. The method of claim 13 wherein said probe includes a semi-permeable membrane that is permeable to CO₂ molecules and substantially impermeable to H⁺ ions, said method further comprising the step of adhesively fastening said membrane to said optical components and diffusion zone using a substance substantially impermeable to said H⁺ ions.