Pulse oximeter probe-off detection system

• US 20030139656A1
• Filed: 02/24/2003
• Published: 07/24/2003
• Est. Priority Date: 06/18/1999
• Status: Active Grant

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Diab, Mohamed K., Kiani, Massi E.
• Granted Patent: US 6,771,994 B2
• Time in Patent Office: Days
• US Class Current: 600/322
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure

Abstract

The present invention provides a number of improvements that can be incorporated into a pulse oximeter probe to detect when a probe has become dislodged from a patient and/or to prevent a probe-off condition. A probe-off condition occurs when the optical probe becomes partially or completely dislodged from the patient, but continues to detect an AC signal within the operating region of the pulse oximeter. In one aspect, the present invention provides electrical contacts that contact the skin of a patient when the probe is properly attached. In another aspect, the present invention provides a number of louvers placed in front of the sensor'"'"'s photodetector to filter out oblique light rays that do not originate from a point in front of the detector. Accordingly, if the emitter and photodetector are not properly aligned, the photodetector will not produce a signal within the valid operating range of the pulse oximeter. In accordance with a method of the present invention the pulse oximeter can sound an alarm or display a warning if it determines that the probe is not properly attached to the patient.

Claims

1. A pulse oximetry probe comprising:

a flexible probe body configured to contact the skin of a patient on opposing surfaces of a body member of the patient when the probe body is properly affixed to the patient;

light emitting diodes incorporated into the probe body;

a light sensitive detector which detects light from a first direction originally emitted by the light emitting diodes, wherein the light comprises at least first and second wavelengths and has been transmitted through body tissue carrying pulsing blood; and

at least one structure positioned approximately parallel to the first direction and is configured to filter out light from reaching the light sensitive detector from a direction substantially different from the first direction.

2. The pulse oximetry probe of claim 1, wherein the structure comprises one or more louvers.

3. The pulse oximetry probe of claim 1, wherein the structure comprises a plurality of louvers.

4. The pulse oximetry probe of claim 1, further comprising a coding resistor.

5. The pulse oximetry probe of claim 1, further comprising an circuit configured to contact at least a portion of the body tissue.

6. The pulse oximetry probe of claim 1, wherein the flexible probe body comprises a reusable optical probe.

7. The pulse oximetry probe of claim 1, wherein the flexible probe body comprises a disposable optical probe.

8. The pulse oximetry probe of claim 1, wherein the flexible probe body comprises reusable and disposable portions of an optical probe.

9. A pulse oximeter for processing signals received from an optical probe, the pulse oximeter comprising:

an input for receiving at least first and second intensity signals from a light-sensitive detector which detects light of at least first and second wavelengths transmitted through body tissue carrying pulsing blood; and

a signal processor which determines a probe-off condition when at least one of the first and second intensity signals is substantially attenuated.

10. The pulse oximeter of claim 9, wherein the attenuation is caused by improper application an optical probe to the body tissue.

11. The pulse oximeter of claim 9, further comprising an audio alarm indicating when the probe-off condition is determined.

12. The pulse oximeter of claim 9, further comprising an visual alarm indicating when the probe-off condition is determined.

13. The pulse oximeter of claim 9, further comprising a coding resistor.

14. The pulse oximeter of claim 9, further comprising an circuit configured to contact at least a portion of the body tissue.

15. A sensor which generates at least first and second intensity signals from a light-sensitive detector which detects light of at least first and second wavelengths transmitted through body tissue carrying pulsing blood;

the sensor comprising;

at least one light emission device;

a light sensitive detector; and

a plurality of louvers positioned over the light sensitive detector to accept light from the at least one light emission device originating from a general direction of the at least one light emission device and then transmitting through body tissue carrying pulsing blood, wherein the louvers accept the light when the sensor is properly applied to tissue of a patient.

16. A method of processing one or more signals to detect a condition of improper positioning of an optical probe, the method comprising:

expecting to receive at least first and second intensity signals from a light-sensitive detector which detects light of at least first and second wavelengths transmitted through body tissue carrying pulsing blood;

blocking light originating from an angle oblique to a proximate relationship between the detector and a light source; and

receiving one of an un-interpretable signal or signal other than the expected first and second intensity signals because the light is blocked; and

indicating a probe off condition.

17. The method of claim 16, wherein the indicating comprises at least one of an audible or visual alarm.

18. The method of claim 16, wherein blocking light comprises positioning a plurality of louvers between the light source and the light-sensitive detector.