Multi-wavelength physiological monitor
First Claim
1. A physiological monitor for determining blood oxygen saturation of a patient, the physiological monitor comprising:
- a pulse oximetry sensor, wherein the pulse oximetry sensor comprises;
three or more light emitting diodes, wherein each light emitting diode is operative to emit light of a different wavelength; and
a detector adapted to receive light from the three or more light emitting diodes after being attenuated by tissue of a medical patient, wherein the detector provides an output signal based at least in part upon the received light; and
a processor configured to;
compute a ratio based at least in part on three or more plethysmographic signals obtained from the output signal, the ratio configured to have reduced tolerance at lower blood oxygen saturation levels compared to a two wavelength blood oxygen saturation system, wherein the ratio comprises a quotient of a first weighted sum of the output signals corresponding to each of the light emitting diodes multiplied by a first set of vector coefficients and a second weighted sum of the output signals corresponding to each of the light emitting diodes multiplied by a second set of vector coefficients, the first and second sets of vector coefficients determined based upon calibration data or fitting of experimental data; and
determine blood oxygen saturation based at least in part upon a blood oxygen saturation curve using said ratio, wherein said blood oxygen saturation curve is substantiall linear over a range of blood oxygen saturation values from about 70% to about 100%.
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Abstract
A physiological monitor for determining blood oxygen saturation of a medical patient includes a sensor, a signal processor and a display. The sensor includes at least three light emitting diodes. Each light emitting diode is adapted to emit light of a different wavelength. The sensor also includes a detector, where the detector is adapted to receive light from the three light emitting diodes after being attenuated by tissue. The detector generates an output signal based at least in part upon the received light. The signal processor determines blood oxygen saturation based at least upon the output signal, and the display provides an indication of the blood oxygen saturation.
794 Citations
16 Claims
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1. A physiological monitor for determining blood oxygen saturation of a patient, the physiological monitor comprising:
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a pulse oximetry sensor, wherein the pulse oximetry sensor comprises; three or more light emitting diodes, wherein each light emitting diode is operative to emit light of a different wavelength; and a detector adapted to receive light from the three or more light emitting diodes after being attenuated by tissue of a medical patient, wherein the detector provides an output signal based at least in part upon the received light; and a processor configured to; compute a ratio based at least in part on three or more plethysmographic signals obtained from the output signal, the ratio configured to have reduced tolerance at lower blood oxygen saturation levels compared to a two wavelength blood oxygen saturation system, wherein the ratio comprises a quotient of a first weighted sum of the output signals corresponding to each of the light emitting diodes multiplied by a first set of vector coefficients and a second weighted sum of the output signals corresponding to each of the light emitting diodes multiplied by a second set of vector coefficients, the first and second sets of vector coefficients determined based upon calibration data or fitting of experimental data; and determine blood oxygen saturation based at least in part upon a blood oxygen saturation curve using said ratio, wherein said blood oxygen saturation curve is substantiall linear over a range of blood oxygen saturation values from about 70% to about 100%. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A physiological monitor sensor comprising:
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three or more emitters configured to transmit light through a tissue site of a medical patient; and at least one detector configured to; measure the light transmitted through the tissue site of the medical patient by the three or more emitters; and generate output signals configured to be used by a processor to compute a ratio based at least in part on the output signals, the ratio configured to have reduced tolerance at lower blood oxygen saturation levels compared to a two wavelength blood oxygen saturation system, and determine blood oxygen saturation based at least in part upon a blood oxygen saturation curve using said ratio, wherein said blood oxygen saturation curve is substantiall linear over a range of blood oxygen saturation values from about 70% to about 100%; wherein the ratio comprises a quotient of a first weighted sum of the output finals corresponding to each of the three or more emitters multiplied by a first set of vector coefficients and a second weighted sum of the output signals corresponding to each of the three or more emitters multiplied by a second set of vector coefficients, the first and second sets of vector coefficients determined based upon calibration data or fitting of experimental data. - View Dependent Claims (9, 10, 11)
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12. An apparatus for determining a blood oxygen saturation of a medical patient, the apparatus comprising:
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a signal input adapted to receive a composite electrical signal from a detector capable of removable attachment to tissue, wherein the composite electrical signal is indicative of attenuation of at least three wavelengths of light by the tissue; and one or more processors configured to perform a ratio calculation based at least in part on at least three waveforms derived from the composite electrical signal, wherein the ratio calculation computes a quotient of a first weighted sum of the at least three waveforms multiplied by a first set of vector coefficients and a second weighted sum of the at least three waveforms multiplied by a second set of vector coefficients, the first and second sets of vector coefficients determined based upon calibration data; wherein the apparatus is adapted to determine a blood oxygen saturation based at least in part upon a blood oxygen saturation curve using upon the ratio, wherein said blood oxygen saturation curve is substantially linear over a range of blood oxygen saturation values such that the blood oxygen saturation exhibits higher accuracy at lower blood oxygen saturation levels compared to a two wavelength blood oxygen saturation system.
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13. A method of determining the blood oxygen saturation of a patient, the method comprising:
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receiving at least three photoplethysmographic signals indicative of at least three wavelengths of light that have been attenuated by tissue; determining at least three output signals based upon the at least three photoplethysmographic signals, wherein determining the at least three output signals comprises determining a root mean square (RMS) value of each of the at least three photoplethysmographic signals; calculating a ratio with one or more processors based at least in part on the at least three output signals, wherein the ratio comprises a quotient of a first weighted sum of the at least three output signals multiplied by a first set of vector coefficients and a second weighted sum of the at least three output signals multiplied by a second set of vector coefficients; and determining a blood oxygen saturation based at least in part on a blood oxygen saturation curve using the ratio, wherein said blood oxygen saturation curve is substantially linear over a range of blood oxygen saturation values. - View Dependent Claims (14, 15, 16)
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Specification