Measuring hematocrit and estimating hemoglobin values with a non-invasive, optical blood monitoring system
First Claim
1. A method for calibrating and subsequently operating a device during a dialysis session for determining hematocrit values, the method comprising:
- calibrating the device by (a) measuring the hematocrit value of whole blood from a supply of blood containing an anticoagulant using an in vitro method, (b) baselining the measured hematocrit value taken from the supply of blood against an independently determined value of the hematocrit and (c) determining a scaling factor to account for an effect of the anticoagulant on an accuracy of the measured hematocrit values; and
operating the device during the dialysis session by (d) measuring in a non-invasive manner the hematocrit values of a patient'"'"'s blood which does not contain the anticoagulant, (e) scaling the measured hematocrit values in keeping with the scaling factors to account for an absence of the anticoagulant in the patient'"'"'s blood; and
(f) displaying the scaled measured values.
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Abstract
An optical blood monitoring system with a ratiometric model determines hematocrit values for a hemodialysis patient, from which hemoglobin values for the patient are estimated. The ratiometric model is calibrated, normally against a cell counter, using blood from a blood bank. The blood from a blood bank is preserved in a long term preservative which is typically different than that found in clinical settings. The hematocrit value determined by the ratiometric model is scaled by scaling factor so that the estimated hemoglobin level output from the monitor consistently matches that measured in a clinical setting. The hematocrit scaling factor is substantially about 1.033 when the patient'"'"'s blood sample is stored in a short term preservative ethylene diamine tetra acetic, and is substantially about 1.06 when the hematocrit is measured in the blood sample without preservative being added to the blood sample. The hemoglobin value can also be adjusted for altitude.
33 Citations
17 Claims
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1. A method for calibrating and subsequently operating a device during a dialysis session for determining hematocrit values, the method comprising:
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calibrating the device by (a) measuring the hematocrit value of whole blood from a supply of blood containing an anticoagulant using an in vitro method, (b) baselining the measured hematocrit value taken from the supply of blood against an independently determined value of the hematocrit and (c) determining a scaling factor to account for an effect of the anticoagulant on an accuracy of the measured hematocrit values; and operating the device during the dialysis session by (d) measuring in a non-invasive manner the hematocrit values of a patient'"'"'s blood which does not contain the anticoagulant, (e) scaling the measured hematocrit values in keeping with the scaling factors to account for an absence of the anticoagulant in the patient'"'"'s blood; and
(f) displaying the scaled measured values. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A blood monitor for use in a hemodialysis system, the blood monitor comprising:
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a sensor assembly for collecting information from a patient'"'"'s blood in flowing through the hemodialysis system; a controller including a ratiometric model for calculating a hematocrit value from the information collected from the sensor assembly, wherein the ratiometric model is calibrated using a supply of blood containing a first anticoagulant using an in vitro method, and a display for displaying hematocrit values measured from a patient'"'"'s blood during a dialysis session, where the display scales the values to account for an absence of the first or a second anticoagulant in the patient'"'"'s blood in the hemodialysis system. - View Dependent Claims (14, 15, 16, 17)
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Specification