MEASUREMENT OF BLOOD OXYGEN SATURATION
First Claim
1. A sensor device comprising a light source for emitting a light beam, a photodetector for receiving the light beam after passing through or being reflected within living tissue and arranged to provide signals corresponding to the intensities of the respective wavelength of light received by the photodetector wherein the sensor device is configured to measure blood oxygen saturation.
1 Assignment
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Accused Products
Abstract
Oxygenation of a subject'"'"'s blood is determined by sensing an absorption spectrum of light directed either invasively or non-invasively into the blood, and then calculating an oxygenation value by evaluating a cost function of the remitted spectrum relative to at least two pre-determined reference absorption spectra representing different, known levels of blood oxygenation. The source of light preferably uses stable, long-life, white LEDs, in which case white-balancing of the remitted spectrum can be accomplished by predetermining and storing the spectrum of the LEDs, one time for all, and then adjusting the remitted spectrum accordingly to compensate for deviations of the LED spectrum from the constant ideal.
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Citations
26 Claims
- 1. A sensor device comprising a light source for emitting a light beam, a photodetector for receiving the light beam after passing through or being reflected within living tissue and arranged to provide signals corresponding to the intensities of the respective wavelength of light received by the photodetector wherein the sensor device is configured to measure blood oxygen saturation.
- 2. A sensor device according to Claim I, wherein the sensor is configured to measure a plurality of wavelengths.
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17. A blood oxygenation monitoring system comprising:
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a sensor configured to transmit light containing a plurality of wavelengths into blood and to measure a remitted spectrum over the plurality of wavelengths; and a monitoring device connected in communication with the sensor, said processor configured to; calculate a measured blood absorption spectrum from the remitted spectrum; estimate local rates of change in the measured blood absorption spectrum at a plurality of the wavelengths, including at least one isobestic wavelength; and
,calculate an estimate of SO2 as a function of absolute values of the local rates of change of the measured blood absorption spectrum. - View Dependent Claims (18, 19, 20)
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21. All SO2 monitoring system, comprising:
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a sensor configured to transmit light containing a plurality of wavelengths into the blood and measure a remitted spectrum over the plurality of wavelengths; and a monitoring device connected in communication with the sensor and configured to; calculate an estimate of SO2 in blood to be monitored; correct said estimate of SO2 in blood by a scaling factor; calculate a measured blood absorption spectrum from the remitted spectrum; estimate local rates of change in the measured blood absorption spectrum at a plurality of the wavelengths, including at least one isobestic wavelength; and
,calculate the estimate of SO2 as a function of absolute values of the local rates of change of the measured blood absorption spectrum. - View Dependent Claims (22, 23, 24)
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25. A blood oxygenation monitoring system comprising:
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a sensor configured to transmit light containing the plurality of wavelengths into blood and measure a remitted spectrum over the plurality of wavelengths; and a monitoring device configured to; determine a first reference spectrum over a plurality of wavelengths; determine a second reference spectrum over the plurality of wavelengths; calculate a measured blood absorption spectrum as a function of the remitted spectrum, the first reference spectrum and the second reference spectrum; and
,remove effects of light scattering from the measured blood absorption spectrum by calculating a correction function that is a function of a plurality of isobestic points of the measured blood absorption spectrum by correcting the measured blood absorption spectrum by the correction function, normalizing the measured blood absorption spectrum following the correcting step, calculating an optimal spectrum as a function of a substantially oxygenated reference absorption spectrum and a substantially deoxygenated reference absorption spectrum, so that the optimal spectrum best matches the measured blood absorption spectrum in a determined sense and, calculating an estimate of SO2 as a function of the optimal spectrum. - View Dependent Claims (26)
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Specification