Multiple region pulse oximetry probe and oximeter

• US 5,218,962 A
• Filed: 04/15/1991
• Issued: 06/15/1993
• Est. Priority Date: 04/15/1991
• Status: Expired due to Term

• Current Assignee: Nellcor Puritan Bennett Incorporated (Medtronic Plc)
• Original Assignee: Nellcor Incorporated (Medtronic Plc)
• Inventors: Chung, D. Christopher, Mannheimer, Paul D., Ritson, Carl
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): NASSER, ROBERT L
• Application Number:
  US07/685,414
• Time in Patent Office: 792 Days
• Field of Search: 128/633-634, 128/664-666, 356/41
• US Class Current: 600/331
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/1464 specially adapted for foetal tissue
• CPC Class Codes: A61B 5/6853 with a balloon
• CPC Class Codes: A61B 5/6885 Monitoring or controlling sensor contact pressure

Abstract

A first light emitting element directs light through a first region of tissue, a second light emitting element directs light through a second region of tissue that is spatially distinct from the first region of tissue, and a photodetector detects light traveling through the first and second regions. First and second oxygen saturation values are calculated from the amount of light detected from the first and second regions of tissue, respectively. A difference calculating unit calculates a difference value which represents how much the first oxygen saturation value differs from the second oxygen saturation value, and a comparator compares the difference value to a threshold value. A threshold indicating signal is provided when the difference value has a selected mathematical relationship (e.g., less than or equal) to the threshold value.

Claims

1. A pulse oximeter comprising:

light emitting means for directing light through first and second unique regions of tissue;

detecting means for detecting the light directed through the first and second regions of tissue;

wherein the light emitting means and the detecting means are disposed in close proximity to each other;

saturation calculating means, coupled to the detecting means, for calculating a first oxygen saturation value from the amount of light detected from the first region of tissue and a second oxygen saturation value from the amount of light detected from the second region of tissue;

difference calculating means, coupled to the saturation calculating means for calculating a difference value which represents how much the first oxygen saturation value differs from the second oxygen saturation value;

threshold comprising means, coupled to the difference calculating means, for comparing the difference value to a threshold value; and

threshold indicating means, coupled to the threshold comparing means, for providing a threshold indicating signal when the difference value is not greater than the threshold value.

2. The probe according to claim 1 wherein the light emitting means comprises:

a first light emitting element for directing light through the first region of tissue;

a second light emitting element for directing light through the second region of tissue.

3. The probe according to claim 2 wherein the detecting means comprises:

a first photodetector disposed in close proximity to the first light emitting element and spaced apart therefrom for detecting the light directed through the first region of tissue; and

a second photodetector disposed in close proximity to the second light emitting element and spaced apart therefrom for detecting the light directed through the second region of tissue.

4. The probe according to claim 3 wherein the first light emitting element, the second light emitting element, the first photodetector, and the second photodetector are disposed in a common housing.

5. The probe according to claim 3 wherein the first light emitting element and the first photodetector are disposed in a first housing, and wherein the second light emitting element and the second photodetector are disposed in a second housing.

6. The probe according to claim 4 further comprising placement means, coupled to the housing, for placing the first light emitting element, the second light emitting element, the first photodetector, and the second photodetector in close proximity to the first and second regions of tissue.

7. The probe according to claim 6 wherein the placement means comprises an elongated handle having a first end attached to the housing.

8. The probe according to claim 7 wherein the handle is formed for allowing bending in a first direction and for resisting bending in a second direction.

9. The probe according to claim 8 wherein the handle comprises a substantially flat first rod coupled to the housing.

10. The pulse oximeter according to claim 1 further comprising displayed saturation calculating means, coupled to the detecting means and to the threshold indicating means, for calculating a displayed saturation value when the difference value is not greater than the threshold value and for inhibiting the display of the displayed saturation value when the difference value is greater than the threshold value.

11. A method of determining a characteristic of blood comprising the steps of:

directing electromagnetic radiation through a first region of tissue;

detecting the electromagnetic radiation from the first region of tissue;

calculating a first blood oxygen saturation value from the amount of electromagnetic radiation detected from the first region of tissue;

directing electromagnetic radiation through a second region of tissue, the second region of tissue being unique from the first region of tissue and in close proximity to the first region of tissue;

detecting the electromagnetic radiation from the second region of tissue;

calculating a second blood oxygen saturation value from the amount of electromagnetic radiation detected from the second region of tissue;

calculating a difference value which represents how much the first blood oxygen saturation value differs from the second blood oxygen saturation value;

comparing the difference value to a threshold value; and

providing a threshold indicating signal when the difference value is not greater than the threshold value.

12. The method according to claim 11 further comprising the steps of:

calculating a displayed saturation value when the difference value is not greater than the threshold value; and

inhibiting the display of the displayed saturation value when the difference value is greater than the threshold value.