METHOD AND APPARATUS FOR DEMODULATING SIGNALS IN A PULSE OXIMETRY SYSTEM
First Claim
1. A method of determining an indication of a physiological parameter by demodulating a composite output signal from a detector of a noninvasive optical sensor, the method comprising:
- outputting activation signals to activate one or more light sources to cause emissions at least two different wavelengths;
wherein the activation signals include at least one period of inactivation;
receiving a detected composite signal indicative of an attenuation by said body tissue of said at least two different wavelengths;
demodulating said composite signal into a first intensity signal responsive to said attenuation of at least a first of the at least two wavelengths, a second intensity signal responsive to said attenuation of at least a second of the at least two wavelengths and a third signal representative of a non-physiological portion of the composite signal, wherein said demodulation is based at least in part on the inactivation; and
determining an indication of a physiological parameter of said body tissue based on one or more of said first and second intensity signals.
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Accused Products
Abstract
A method and an apparatus measure blood oxygenation in a subject. A light source is activated to cause a first emission at a first wavelength and a second emission at a second wavelength. A detector detects a composite signal indicative of an attenuation of the first and second wavelengths by tissue of a patient. The composite signal is demodulated into a first intensity signal and a second intensity signal. Blood oxygenation in the subject is determined from the first and second intensity signals. In one embodiment, demodulation is based at least in part on a period when at least one of the wavelengths is not activated. In one embodiment, a modulation of the first and second wavelengths is determined in order to avoid frequencies of ambient noise. In one embodiment, the composite signal'"'"'s sampling rate is reduced before and/or after demodulation.
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Citations
4 Claims
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1. A method of determining an indication of a physiological parameter by demodulating a composite output signal from a detector of a noninvasive optical sensor, the method comprising:
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outputting activation signals to activate one or more light sources to cause emissions at least two different wavelengths;
wherein the activation signals include at least one period of inactivation;
receiving a detected composite signal indicative of an attenuation by said body tissue of said at least two different wavelengths;
demodulating said composite signal into a first intensity signal responsive to said attenuation of at least a first of the at least two wavelengths, a second intensity signal responsive to said attenuation of at least a second of the at least two wavelengths and a third signal representative of a non-physiological portion of the composite signal, wherein said demodulation is based at least in part on the inactivation; and
determining an indication of a physiological parameter of said body tissue based on one or more of said first and second intensity signals. - View Dependent Claims (2, 3, 4)
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Specification