Epidural oxygen sensor

• US 5,127,407 A
• Filed: 11/13/1990
• Issued: 07/07/1992
• Est. Priority Date: 08/17/1989
• Status: Expired due to Fees

• Current Assignee: Critikon Co. LLC (GE Aerospace)
• Original Assignee: Critikon, Inc. (Johnson & Johnson)
• Inventors: Tan, Josef K. S.
• Primary Examiner(s): Smith, Ruth S.
• Assistant Examiner(s): NASSER, ROBERT L
• Application Number:
  US07/612,744
• Time in Patent Office: 602 Days
• Field of Search: 128/633-635, 128/664-666, 128/748, 356/41
• US Class Current: 600/339
• CPC Class Codes: A61B 5/031 Intracranial pressure
• CPC Class Codes: A61B 5/14553 specially adapted for cerebral tissue

Abstract

A sensor for measuring the oxygen saturation of blood flow within the skull is described. In a first embodiment the sensor comprises a photodetector and a pair of light emitting diodes surface mounted near the end of a length of flexible printed wiring. The sensor is hermetically sealed by a coating of rubber or polymeric material which has an optical window over the photodetector and light emitting diodes. The sensor is inserted through a burr hole drilled in the skull and slides between the skull and the dura of the brain. The light emitting diodes are pulsed to illuminate blood within the dura and brain with light, and light reflected by the blood is received by the photodetector and converted to electrical signals. The signals are processed by a pulse oximeter to provide an indication of blood saturation. In a second embodiment the photodetector and light emitting diodes are mounted at the end of a core of compressible foam extending from the end of a hollow bone screw. As the bone screw is screwed into a burr hole in the skull the photodetector and light emitting diodes will contact the dura and the foam will compress to maintain optical contact between the electrical components and the dura. Light from the diodes is reflected by blood in the dura and brain, received by the photodetector, and the resultant electrical signals are processed by the pulse oximeter.

Claims

1. A sensor for measuring cerebral oxygen saturation through a burr hole in the skull by optical reflectance comprising:

a hollow bone screw;

a core of compressive material located in said hollow bone screw and having an upper surface oriented toward the top of said bone screw and a lower surface oriented toward the bottom of said bone screw; and

a photodetector and a pair of light emitting diodes located at said lower surface of said core of compressive material, wherein electrical connection is made to said photodetector and said light emitting diodes through said hollow bone screw.

2. The sensor of claim 1, further comprising a core of relatively less compressive material located within said bone screw above said upper surface of said compressive core.

3. The sensor of claim 1, wherein a portion of said core of compressive material extends out from the lower end of said hollow bone screw.