Pulsed light blood oxygen content sensor system and method of using same
First Claim
1. A blood oxygen sensor for use with a pacemaker to sense the level of oxygen in blood, said blood oxygen sensor comprising:
- an LED for emitting light;
means for driving said LED to emit light beginning at a first time;
means for directing the light emitted by said LED onto blood and for allowing light reflected by blood to return to the sensor;
a photodetector for detecting the portion of light from said LED which is reflected by blood and returned to the sensor, said photodetector providing an output proportional to the portion of light from said LED which is reflected by blood;
an integrator for integrating said output from said photodetector and providing as an output an integrated voltage output;
means for determining a predetermined threshold value;
means for comparing said integrated voltage output with said predetermined threshold value and providing an output signal at a second time when said integrated voltage output reaches said predetermined threshold value; and
ameans for monitoring the interval between said fist time and said second time and providing an output signal indicative of the interval between said first time and aid second time, the interval between said first time and said second time being inversely related to the level of oxygen in blood.
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Accused Products
Abstract
A sensor for use with a rate-responsive pacemaker is disclosed which is responsive to blood oxygen content, thereby allowing the cardiac rate of the pacemaker to closely mimic the natural response pattern of the heart to changing physiological need. The sensor integrates the output from a photosensor driven by blood-reflected light from an LED, and when the integrated output reached a predetermined threshold latches the circuit, enabling the use of time to indicate the level of blood oxygen content. The sensor thus advantageously requires neither a voltage doubler in the driving circuitry, or an analog-to-digital converter in the output circuitry, reducing both complexity and power consumption of the blood oxygen sensor.
86 Citations
25 Claims
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1. A blood oxygen sensor for use with a pacemaker to sense the level of oxygen in blood, said blood oxygen sensor comprising:
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an LED for emitting light; means for driving said LED to emit light beginning at a first time; means for directing the light emitted by said LED onto blood and for allowing light reflected by blood to return to the sensor; a photodetector for detecting the portion of light from said LED which is reflected by blood and returned to the sensor, said photodetector providing an output proportional to the portion of light from said LED which is reflected by blood; an integrator for integrating said output from said photodetector and providing as an output an integrated voltage output; means for determining a predetermined threshold value; means for comparing said integrated voltage output with said predetermined threshold value and providing an output signal at a second time when said integrated voltage output reaches said predetermined threshold value; and
ameans for monitoring the interval between said fist time and said second time and providing an output signal indicative of the interval between said first time and aid second time, the interval between said first time and said second time being inversely related to the level of oxygen in blood. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A blood oxygen sensor for use with a pacemaker to sense the level of oxygen in blood, said blood oxygen sensor comprising:
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a first conductor for connection to a pacemaker at one end thereof; a second conductor for connection o a pacemaker at one end thereof; an LED connected between said first and second conductors, said LED for emitting light; means for driving said LED to emit light beginning at a first time, said means for driving being electrically connected between said first and second conductors; means for directing the light emitted by said LED onto blood and for allowing light reflected by blood to return to the sensor; a phototransmistor for detecting the portion of light from said LED which is reflected by flood and returned to the sensor, the emitter of said phototransistor being connected to said first conductor; a transistor, the collector of said transistor being connected to the base of said phototransistor, the base of said transistor being connected to the collector of said phototransistor, the emitter of said transistor being connected to said second conductor; a first resistor connected across the base-emitter junction of said transistor; a second resistor connected across the base-emitter junction of said phototransistor, said transistor and said phototransistor conducting at a second time dependant on the amount of light reflected by blood to said phototransistor; and means for monitoring the interval between said first time and aid second time and providing an output signal indicative of the interval between said first time and said second time, the interval between said first time and said second time being inversely related to the level of oxygen in blood. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
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24. A blood oxygen sensor for use with a pacemaker, said blood oxygen sensor comprising:
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means for emitting light beginning at a first time; means for directing the light emitted by said emitting means onto blood and for flowing light reflected by blood to return to the sensor; means for detecting the portion of light from said emitting means which is reflected by blood and returned to the sensor, said detecting means providing an output proportional to the portion of light from said emitting means which is reflected by blood; means for integrating said output from said detecting means and providing as an output an integrated voltage output; means for determining a predetermined threshold value; means for comparing said integrated voltage output with said predetermined threshold value and providing an output signal at a second time when said integrated voltage output reaches said predetermined threshold value; and means for monitoring the interval between said first time and said second time and providing an output signal indicative of the interval between said first time and said second time, the interval between said first time and said second time being inversely related to the level of oxygen in said blood.
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25. A method of determining the level of blood oxygen suing a sensor, said method comprising:
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driving an LED to emit light beginning at a first time; directing the light emitted by said LED onto blood and allowing light reflected by blood to return to the sensor;
;detecting the portion of light from said LED which is reflected by said blood and returned to the sensor with a photodetector, said photodetector providing an output proportional to the portion of light from said LED which is reflected by said blood; integrating said output from said photodetector with an integrator and providing as an output of said integrator an integrated voltage output; comparing said integrated voltage output with a predetermined threshold value and providing an output signal at a second time when said integrated voltage output reaches said predetermined threshold value; and monitoring the interval between said first time and said second time and providing an output signal indicative of the interval between said first time and said second time, the interval between said first time and said second time being inversely related to the level of oxygen in said blood.
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Specification