Pulse oximeter probe-off detection system

DETAILED DESCRIPTION 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 may continue to detect an AC signal within the operating region of the pulse oximeter.
In one aspect, the present invention provides a number of electrical contacts that contact the skin of a patient when the probe is properly attached.
The pulse oximeter can check the continuity through the contacts to determine whether the probe is properly attached.
If the probe is not properly attached, the pulse oximeter can identify a probe-off condition even though the oximeter measures an AC signal that appears like the probe is still attached.
In another aspect, the present invention provides a number of louvers placed in front of the probe's photodetector to filter out oblique light rays that do not originate from a point in front of the detector.
If the probe becomes dislodged, the emitter will not likely remain in front of the photodetector.
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.
The louvers prevent light from an oblique angle from reaching the photodetector and creating a false signal that might be interpreted by the pulse oximeter as a physiological signal.
Accordingly, the pulse oximeter can determine that a probe has become dislodged when the photodetector does not produce a valid signal.
Furthermore, probe-off conditions can avoided since oblique light rays are not able to reach the photodetector to produce an apparently valid signal.