Method for non-invasive spectrophotometric blood oxygenation monitoring
First Claim
1. A method for non-invasively determining a blood oxygen saturation level within a subject'"'"'s tissue using a near infrared spectrophotometric sensor, said method comprising the steps of:
- transmitting a light signal into the subject'"'"'s tissue at a predetermined first intensity using the sensor, wherein the transmitted light signal includes a first wavelength, a second wavelength, and a third wavelength;
sensing a second intensity of the light signal, using the sensor, along the first, second, and third wavelengths after the light signal travels through the subject;
wherein the sensor is calibrated using empirical data that relates to the subject'"'"'s tissue that is sensed by the sensor to account for light signal attenuation resulting from light signal scattering within the subject'"'"'s tissue;
determining an attenuation of the light signal for each of the first, second, and third wavelengths using the predetermined first intensity and the sensed second intensity of the first, second, and third wavelengths;
determining a difference in attenuation of the light signal between the first wavelength and the second wavelength, and between the first wavelength and the third wavelength;
determining the blood oxygen saturation level within the subject'"'"'s tissue using the difference in attenuation between the first wavelength and the second wavelength, and the difference in attenuation between the first wavelength and the third wavelength.
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Accused Products
Abstract
A method and apparatus for non-invasively determining the blood oxygen saturation level within a subject'"'"'s tissue is provided that utilizes a near infrared spectrophotometric (NIRS) sensor capable of transmitting a light signal into the tissue of a subject and sensing the light signal once it has passed through the tissue via transmittance or reflectance. The method includes the step of determining attenuation of the light signal as the sum of: (i) attenuation attributable to deoxyhemoglobin; (ii) attenuation attributable to oxyhemoglobin; and (iii) attenuation attributable to light scattering within the subject'"'"'s tissue. The present method also makes it possible to account for attenuation attributable to fixed or constant light absorbing biological tissue components, and attenuation attributable to variable characteristics of the sensor. By determining differential attenuation as a function of wavelength, the attenuation attributable to tissue light scattering characteristics, fixed light absorbing components, and measuring apparatus characteristics are mathematically cancelled out or minimized relative to the attenuation attributable to deoxyhemoglobin, and attenuation attributable to oxyhemoglobin.
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Citations
44 Claims
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1. A method for non-invasively determining a blood oxygen saturation level within a subject'"'"'s tissue using a near infrared spectrophotometric sensor, said method comprising the steps of:
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transmitting a light signal into the subject'"'"'s tissue at a predetermined first intensity using the sensor, wherein the transmitted light signal includes a first wavelength, a second wavelength, and a third wavelength;
sensing a second intensity of the light signal, using the sensor, along the first, second, and third wavelengths after the light signal travels through the subject;
wherein the sensor is calibrated using empirical data that relates to the subject'"'"'s tissue that is sensed by the sensor to account for light signal attenuation resulting from light signal scattering within the subject'"'"'s tissue;
determining an attenuation of the light signal for each of the first, second, and third wavelengths using the predetermined first intensity and the sensed second intensity of the first, second, and third wavelengths;
determining a difference in attenuation of the light signal between the first wavelength and the second wavelength, and between the first wavelength and the third wavelength;
determining the blood oxygen saturation level within the subject'"'"'s tissue using the difference in attenuation between the first wavelength and the second wavelength, and the difference in attenuation between the first wavelength and the third wavelength. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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3. The method of claim 2, wherein the sensor is calibrated by using empirical data to determine a first calibration constant and a second calibration constant.
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4. The method of claim 3, wherein the step of determining the blood oxygen saturation level within the subject'"'"'s tissue utilizes the equation:
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where Ψ
HbO2 represents the first calibration constant, Ψ
Hb represents the second calibration constant, AHbO2 represents a difference in attenuation of light signal attributable to oxyhemoglobin, and AHb represents a difference in attenuation of light signal attributable to deoxyhemoglobin.
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5. The method of claim 4, further comprising the steps of:
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determining a photon pathlength d*B; and
determining a concentration of oxyhemoglobin and a concentration of deoxyhemoglobin within the subject'"'"'s tissue using the first and second calibration constants.
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6. The method of claim 5, wherein the concentration of oxyhemoglobin and the concentration of deoxyhemoglobin within the subject'"'"'s tissue are determined using the equation:
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7. The method of claim 6, wherein the step of determining a difference in attenuation of the light signal between the first wavelength and the second wavelength utilizes the equation:
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8. The method of claim 6, wherein the step of determining a difference in attenuation of the light signal between the first wavelength and the second wavelength utilizes the equation:
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9. The method of claim 6, wherein the step of determining a difference in attenuation of the light signal between the first wavelength and the second wavelength utilizes the equation:
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10. The method of claim 1, wherein the step of determining a difference in attenuation of the light signal between the first wavelength and the second wavelength utilizes the equation:
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11. The method of claim 1, wherein the step of determining a difference in attenuation of the light signal between the first wavelength and the second wavelength utilizes the equation:
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12. The method of claim 1, wherein the step of determining a difference in attenuation of the light signal between the first wavelength and the second wavelength utilizes the equation:
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13. The method of claim 2, further comprising the steps of:
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determining a blood oxygen saturation level attributable to arterial blood within the subject'"'"'s tissue using a pulse oximetry technique; and
determining a blood oxygen saturation level attributable to venous blood within the subject'"'"'s tissue using the equation;
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14. A method for determining a blood oxygen saturation level within a subject'"'"'s tissue using a near infrared spectrophotometric sensor attached to the skin of the subject, said method comprising the steps of:
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transmitting a light signal into the subject'"'"'s tissue at a predetermined first intensity, wherein the transmitted light signal includes a first wavelength, a second wavelength, and a third wavelength;
sensing a second intensity of the light signal along the first, second, and third wavelengths after the light signal travels through the subject;
determining an attenuation of the light signal for each of the first, second, and third wavelengths using the predetermined first intensity and the sensed second intensity of the first, second, and third wavelengths;
determining a difference in attenuation of the light signal between the first wavelength and the second wavelength, and between the first wavelength and the third wavelength;
determining a first calibration constant and a second calibration constant using empirical data developed from the subject at or about the same time as when the sensing occurs;
determining the blood oxygen saturation level within the subject'"'"'s tissue using the difference in attenuation between the first wavelength and the second wavelength, and the difference in attenuation between the first wavelength and the third wavelength, and the first calibration constant and the second calibration constant. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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18. The method of claim 17, wherein the step of determining the blood oxygen saturation level within the subject'"'"'s tissue utilizes the equation:
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where Ψ
HbO2 represents the first calibration constant, Ψ
Hb represents the second calibration constant, AHbO2 represents a difference in attenuation of light signal attributable to oxyhemoglobin, and AHb represents a difference in attenuation of light signal attributable to deoxyhemoglobin.
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19. The method of claim 18, further comprising the steps of:
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determining a photon pathlength d*B; and
determining the concentration of oxyhemoglobin and deoxyhemoglobin within the subject'"'"'s tissue using the first and second calibration constants.
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20. The method of claim 19, wherein the concentration of oxyhemoglobin and deoxyhemoglobin within the subject'"'"'s tissue are determined using the equation
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( dB ) - 1 - [ Ψ Hb Ψ HbO 2 ] ( dB ) - 1 = [ Hb HbO 2 ] .
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21. The method of claim 20, wherein the step of determining a difference in attenuation of the light signal between the first wavelength and the second wavelength utilizes the equation:
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22. The method of claim 20, wherein the step of determining a difference in attenuation of the light signal between the first wavelength and the second wavelength utilizes the equation:
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23. The method of claim 20, wherein the step of determining a difference in attenuation of the light signal between the first wavelength and the second wavelength utilizes the equation:
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24. The method of claim 14, wherein the step of determining the blood oxygen saturation level within the subject'"'"'s tissue utilizes the equation:
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where Ψ
HbO2 represents the first calibration constant, Ψ
Hb represents the second calibration constant, AHbO2 represents a difference in attenuation of light signal attributable to oxyhemoglobin, and AHb represents a difference in attenuation of light signal attributable to deoxyhemoglobin.
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25. The method of claim 24, further comprising the steps of:
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determining a photon pathlength d*B; and
determining the concentration of oxyhemoglobin and deoxyhemoglobin within the subject'"'"'s tissue using the first and second calibration constants.
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26. The method of claim 25, wherein the concentration of oxyhemoglobin and deoxyhemoglobin within the subject'"'"'s tissue are determined using the equation
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( dB ) - 1 - [ Ψ Hb Ψ HbO 2 ] ( dB ) - 1 = [ Hb HbO 2 ] .
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27. The method of claim 26, wherein the step of determining a difference in attenuation of the light signal between the first wavelength and the second wavelength utilizes the equation:
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28. The method of claim 26, wherein the step of determining a difference in attenuation of the light signal between the first wavelength and the second wavelength utilizes the equation:
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29. The method of claim 26, wherein the step of determining a difference in attenuation of the light signal between the first wavelength and the second wavelength utilizes the equation:
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30. A method for calibrating a near infrared spectrophotometric sensor for use in determining the blood oxygen saturation level within a subject'"'"'s tissue, said method comprising the steps of:
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transmitting a light signal into the subject'"'"'s tissue at a predetermined first intensity, wherein the transmitted light signal includes a first wavelength, a second wavelength, and a third wavelength;
sensing a second intensity of the light signal along the first, second, and third wavelengths after the light signal travels through the subject;
determining an attenuation of the light signal for each of the first, second, and third wavelengths using the predetermined first intensity and the sensed second intensity of the first, second, and third wavelengths;
determining a difference in attenuation of the light signal between the first wavelength and the second wavelength, and between the first wavelength and the third wavelength;
determining a first calibration constant and a second calibration constant using empirical data developed from the subject at or about the same time as when the sensing occurs; and
calibrating the sensor using the first calibration constant and the second calibration constant. - View Dependent Claims (31, 32, 33, 34, 35, 36)
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34. The method of claim 33, wherein the step of determining a difference in attenuation of the light signal between the first wavelength and the second wavelength utilizes the equation:
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35. The method of claim 33, wherein the step of determining a difference in attenuation of the light signal between the first wavelength and the second wavelength utilizes the equation:
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36. The method of claim 33, wherein the step of determining a difference in attenuation of the light signal between the first wavelength and the second wavelength utilizes the equation:
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37. A method for calibrating a NIRS sensor, said method comprising the steps of:
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transmitting a light signal from a calibrated NIRS sensor into a reference sample at a predetermined first intensity, wherein the transmitted light signal includes a first wavelength, a second wavelength, and a third wavelength;
sensing a second intensity of the light signal with the calibrated NIRS sensor along the first, second, and third wavelengths after the light signal travels through the reference sample;
determining a first attenuation of the light signal for each of the first, second, and third wavelengths using the predetermined first intensity and the second intensity of the light signal sensed with the calibrated NIRS sensor;
transmitting a light signal from an uncalibrated second NIRS sensor into the reference sample at the predetermined first intensity, wherein the transmitted light signal includes a first wavelength, a second wavelength, and a third wavelength;
sensing a second intensity of the light signal with the uncalibrated second NIRS sensor along the first, second, and third wavelengths after the light signal travels through the subject;
determining a second attenuation of the light signal for each of the first, second, and third wavelengths using the predetermined first intensity and the second intensity of the first, second, and third wavelengths sensed with the uncalibrated second NIRS sensor;
adjusting the uncalibrated second NIRS sensor so that the second attenuation substantially agrees with the first attenuation.
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38. A method for determining a blood oxygen saturation level within a subject'"'"'s tissue attributable to venous blood, said method comprising the steps of:
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providing a NIRS sensor for sensing the subject'"'"'s tissue;
determining a blood oxygen saturation level with the subject'"'"'s tissue using the NIRS sensor;
determining a blood oxygen saturation level attributable to arterial blood within the subject'"'"'s tissue using a pulse oximetry technique; and
determining a blood oxygen saturation level attributable to venous blood within the subject'"'"'s tissue using the equation;
- View Dependent Claims (39)
transmitting a light signal into the subject'"'"'s tissue at a predetermined first intensity, wherein the transmitted light signal includes a first wavelength, a second wavelength, and a third wavelength;
sensing a second intensity of the light signal along the first, second, and third wavelengths after the light signal travels through the subject;
determining an attenuation of the light signal for each of the first, second, and third wavelengths using the predetermined first intensity and the sensed second intensity of the first, second, and third wavelengths;
determining a difference in attenuation of the light signal between the first wavelength and the second wavelength, and between the first wavelength and the third wavelength;
determining a first calibration constant and a second calibration constant using empirical data developed from the subject at or about the same time as when the sensing occurs;
determining the blood oxygen saturation level within the subject'"'"'s tissue using the difference in attenuation between the first wavelength and the second wavelength, and the difference in attenuation between the first wavelength and the third wavelength.
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40. A method for non-invasively determining a concentration of oxyhemoglobin and a concentration of deoxyhemoglobin within a subject'"'"'s tissue using a near infrared spectrophotometric sensor, said method comprising the steps of:
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(a) determining a blood oxygen saturation level with the subject'"'"'s tissue by transmitting a light signal into the subject'"'"'s tissue from a NIRS sensor at a predetermined first intensity, wherein the transmitted light signal includes a first wavelength, a second wavelength, and a third wavelength;
sensing a second intensity of the light signal along the first, second, and third wavelengths after the light signal travels through the subject using the sensor;
wherein the sensor is calibrated using empirical data that relates to the subject'"'"'s tissue that is sensed by the sensor to account for light signal attenuation resulting from light signal scattering within the subject'"'"'s tissue;
determining an attenuation of the light signal for each of the first, second, and third wavelengths using the predetermined first intensity and the sensed second intensity of the first, second, and third wavelengths;
determining a difference in attenuation of the light signal between the first wavelength and the second wavelength, and between the first wavelength and the third wavelength;
determining a first calibration constant and a second calibration constant using empirical data developed from the subject at or about the same time as when the sensing occurs;
determining the blood oxygen saturation level within the subject'"'"'s tissue using the difference in attenuation between the first wavelength and the second wavelength, and the difference in attenuation between the first wavelength and the third wavelength, and the first calibration constant and the second calibration constant;
(b) determining a photon pathlength d*B; and
(c) determining the concentration of oxyhemoglobin and the concentration of deoxyhemoglobin within the subject'"'"'s tissue using the first and second calibration constants. - View Dependent Claims (41)
where Ψ
HbO2 represents the first calibration constant, Ψ
Hb represents the second calibration constant, AHbO2 represents a difference in attenuation of light signal attributable to oxyhemoglobin, and AHb represents a difference in attenuation of light signal attributable to deoxyhemoglobin.
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42. A method for non-invasively determining a concentration of oxyhemoglobin and a concentration of deoxyhemoglobin within a subject'"'"'s tissue at an initial time t1 and a subsequent time t2 using a near infrared spectrophotometric sensor, said method comprising the steps of:
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(a) determining a blood oxygen saturation level with the subject'"'"'s tissue by transmitting a light signal into the subject'"'"'s tissue from a NIRS sensor at a predetermined first intensity, wherein the transmitted light signal includes a first wavelength, a second wavelength, and a third wavelength;
sensing a second intensity of the light signal along the first, second, and third wavelengths after the light signal travels through the subject using the sensor;
wherein the sensor is calibrated using empirical data that relates to the subject'"'"'s tissue that is sensed by the sensor to account for light signal attenuation resulting from light signal scattering within the subject'"'"'s tissue;
determining an attenuation of the light signal for each of the first, second, and third wavelengths using the predetermined first intensity and the sensed second intensity of the first, second, and third wavelengths;
determining a difference in attenuation of the light signal between the first wavelength and the second wavelength, and between the first wavelength and the third wavelength;
determining a first calibration constant and a second calibration constant using empirical data developed from the subject at or about the same time as when the sensing occurs;
determining the blood oxygen saturation level within the subject'"'"'s tissue using the difference in attenuation between the first wavelength and the second wavelength, and the difference in attenuation between the first wavelength and the third wavelength, and the first calibration constant and the second calibration constant;
(b) determining a photon pathlength d*B;
(c) determining the concentration of oxyhemoglobin and the concentration of deoxyhemoglobin within the subject'"'"'s tissue at the initial time t1 using the equation;
where Ψ
HbO2 represents the first calibration constant, Ψ
Hb represents the second calibration constant, AHbO2 represents a difference in attenuation of light signal attributable to oxyhemoglobin, and AHb represents a difference in attenuation of light signal attributable to deoxyhemoglobin; and(d) determining a change in the concentration of oxyhemoglobin and a change in the concentration of deoxyhemoglobin from the initial time t1 to a subsequent second time t2 are determined using the equation;
and (e) determining the concentration of oxyhemoglobin and the concentration of deoxyhemoglobin within the subject'"'"'s tissue at the subsequent time t2 using the equations;
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43. A method for non-invasively determining a blood oxygen saturation level within a subject'"'"'s tissue using a near infrared spectrophotometric sensor, said method comprising the steps of:
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transmitting a light signal into the subject'"'"'s tissue at a predetermined first intensity using the sensor;
sensing a second intensity of the light signal along three or more selectively chosen wavelengths after the light signal travels through the subject using the sensor;
wherein the sensor is calibrated using empirical data that relates to the subject'"'"'s tissue that is sensed by the sensor to account for light signal attenuation resulting from light signal scattering within the subject'"'"'s tissue;
determining an attenuation of the light signal for at least “
n”
number of the selectively chosen wavelengths using the predetermined first intensity and the sensed second intensity of the selectively chosen wavelengths, where “
n”
is an integer equal to or greater than three;
determining a difference in attenuation of the light signal between a first wavelength and each of “
n”
number of the selectively chosen wavelengths;
determining the blood oxygen saturation level within the subject'"'"'s tissue using the difference in attenuation between the first wavelength and each of the “
n”
number of other selectively chosen wavelengths.
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44. A method for determining a blood oxygen saturation level within a subject'"'"'s tissue using a near infrared spectrophotometric sensor attached to the skin of the subject, said method comprising the steps of:
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transmitting a light signal into the subject'"'"'s tissue at a predetermined first intensity;
sensing a second intensity of the light signal along three or more selectively chosen wavelengths after the light signal travels through the subject;
determining an attenuation of the light signal for at least “
n”
number of the selectively chosen wavelengths using the predetermined first intensity and the sensed second intensity of the selectively chosen wavelengths, where “
n”
is an integer equal to or greater than three;
determining a difference in attenuation of the light signal between a first wavelength and each of “
n”
number of the selectively chosen wavelengths;
determining a first calibration constant and a second calibration constant using empirical data developed from the subject at or about the same time as when the sensing occurs;
determining the blood oxygen saturation level within the subject'"'"'s tissue using the difference in attenuation between the first wavelength and each of “
n”
number of the selectively chosen wavelengths, and the first calibration constant and the second calibration constant.
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Specification