Method and apparatus for noninvasive prediction of hematocrit
First Claim
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1. An apparatus for the noninvasive prediction of hematocrit within mammalian tissue, comprising:
- (a) a light source adapted to noninvasively interrogate the mammalian tissue with light of at least two wavelengths, wherein the at least two wavelengths are selected according to wavelength selection criteria, and wherein the wavelength selection criteria comprise;
(1) a wavelength where absorbance of water is at or near a measurable peak;
(2) at least one wavelength where absorbance of oxyhemoglobin and deoxyhemoglobin are predictable and represent total hemoglobin content;
(3) a wavelength where the absorbance of water greatly exceeds the absorbance of all forms of hemoglobin; and
(4) a wavelength where the absorbance of all forms of hemoglobin greatly exceeds the absorbance of water;
wherein each of the wavelength selection criteria must be satisfied, wherein each selected wavelength can satisfy one or more than one of the wavelength selection criteria, and wherein at least one of the selected wavelengths is in the range 1150-2100 nm;
(b) at least one detector adapted to receive light of the selected wavelengths transmitted through the mammalian tissue, the detector further adapted to convert the transmitted light of each selected wavelength from optical signals into electrical signals; and
(c) processing means, connected to receive the electrical signals from the detector, the processing means for;
determining the intensity of at least one peak, the intensity of at least one valley, and the intensity of at least one direct current value for the transmitted light of each selected wavelength;
determining at least one pseudo-absorption H Value for each selected wavelength, wherein each H Value is based on the intensities of the at least one peak, at least one valley, and the at least one direct current value; and
determining a prediction equation for the noninvasive prediction of hematocrit, wherein the prediction equation is based on true hematocrit values and the pseudo-absorption H Values determined for each selected wavelength.
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Abstract
A method and apparatus for the direct noninvasive prediction of hematocrit in mammalian blood using photoplethysmography techniques and data processing. The method and apparatus also include optional prediction of other analytes of interest: percent oxygen saturation of mammalian blood and methemoglobin of stored blood. The method and apparatus can be used for the immediate, periodic, or continuous noninvasive diagnosis or monitoring of hematocrit levels in mammalian patients without pain to the patient or exposure of the health care practitioner to the blood of the patient.
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Citations
11 Claims
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1. An apparatus for the noninvasive prediction of hematocrit within mammalian tissue, comprising:
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(a) a light source adapted to noninvasively interrogate the mammalian tissue with light of at least two wavelengths, wherein the at least two wavelengths are selected according to wavelength selection criteria, and wherein the wavelength selection criteria comprise; (1) a wavelength where absorbance of water is at or near a measurable peak; (2) at least one wavelength where absorbance of oxyhemoglobin and deoxyhemoglobin are predictable and represent total hemoglobin content; (3) a wavelength where the absorbance of water greatly exceeds the absorbance of all forms of hemoglobin; and (4) a wavelength where the absorbance of all forms of hemoglobin greatly exceeds the absorbance of water; wherein each of the wavelength selection criteria must be satisfied, wherein each selected wavelength can satisfy one or more than one of the wavelength selection criteria, and wherein at least one of the selected wavelengths is in the range 1150-2100 nm; (b) at least one detector adapted to receive light of the selected wavelengths transmitted through the mammalian tissue, the detector further adapted to convert the transmitted light of each selected wavelength from optical signals into electrical signals; and (c) processing means, connected to receive the electrical signals from the detector, the processing means for; determining the intensity of at least one peak, the intensity of at least one valley, and the intensity of at least one direct current value for the transmitted light of each selected wavelength; determining at least one pseudo-absorption H Value for each selected wavelength, wherein each H Value is based on the intensities of the at least one peak, at least one valley, and the at least one direct current value; and determining a prediction equation for the noninvasive prediction of hematocrit, wherein the prediction equation is based on true hematocrit values and the pseudo-absorption H Values determined for each selected wavelength. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Current AssigneeTerumo Cardiovascular Systems Corporation (Terumo Corporation)
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Original AssigneeMinnesota Mining and Manufacturing Co (3M Company)
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InventorsErickson, David P., Rude, Michael J., Kelliher, William J. Jr., Ekholm, Bruce P., Carim, Hatim M., Knudson, Orlin B.
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Primary Examiner(s)Bahr, Jennifer
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Assistant Examiner(s)WINAKUR, ERIC FRANK
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Application NumberUS08/711,612Time in Patent Office623 DaysField of Search128/633, 128/664, 128/665, 128/666, 356/39, 356/40, 356/41US Class Current600/323CPC Class CodesA61B 2562/0233 Special features of optical...A61B 2562/046 in a matrix arrayA61B 5/14535 for measuring haematocritA61B 5/14551 for measuring blood gasesA61B 5/14552 Details of sensors speciall...A61B 5/6843 Monitoring or controlling s...A61B 5/7228 Signal modulation applied t...A61B 5/7239 using differentiation inclu...G01N 21/314 with comparison of measurem...G01N 21/359 using near infrared lightY10S 977/905 Specially adapted for trave...
