Method and apparatus for reducing ambient noise effects in electronic monitoring instruments
First Claim
1. A pulse oximeter comprising:
- (a) a sensor including two light sources and a photodetector, the two light sources alternately generating light pulses which pass through a patient'"'"'s skin to produce attenuated optical signals monitored by the photodetector;
(b) a demultiplexer coupled to the sensor for separating the attenuated optical signals from the two light sources, the demultiplexer and the light sources operating at an adjustable selected demultiplexing frequency;
(c) a ROM having a plurality of available frequencies recorded;
(d) a first processor coupled to the demultiplexer and the ROM for periodically determining the noise associated with the available frequencies, the first processor selecting, and adjusting if necessary, the adjustable selected demultiplexing frequency; and
(e) a second processor coupled to the sensor for periodically determining the patient'"'"'s blood oxygen saturation from the optical signals monitored by the photodetector.
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Abstract
The present invention provides a method and apparatus for adapting to noise sources affecting a pulse oximeter. Various available frequencies are evaluated to determine their respective noise levels and one is selected to act as the operating demultiplexer frequency. During normal operation of the pulse oximeter, the various available demultiplexer frequencies are periodically scanned to determine which has the lowest associated noise. The noise level associated with the operating frequency is used to determine the signal-to-noise ratio of the pulse oximeter signals and thereby qualify certain signals from the pulse oximeter. Those pulses associated with a signal-to-noise ratio below a predetermined threshold are rejected and excluded from use in calculating blood oxygen saturation.
205 Citations
7 Claims
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1. A pulse oximeter comprising:
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(a) a sensor including two light sources and a photodetector, the two light sources alternately generating light pulses which pass through a patient'"'"'s skin to produce attenuated optical signals monitored by the photodetector; (b) a demultiplexer coupled to the sensor for separating the attenuated optical signals from the two light sources, the demultiplexer and the light sources operating at an adjustable selected demultiplexing frequency; (c) a ROM having a plurality of available frequencies recorded; (d) a first processor coupled to the demultiplexer and the ROM for periodically determining the noise associated with the available frequencies, the first processor selecting, and adjusting if necessary, the adjustable selected demultiplexing frequency; and (e) a second processor coupled to the sensor for periodically determining the patient'"'"'s blood oxygen saturation from the optical signals monitored by the photodetector. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification