System and method for noninvasive hemodynamic measurements in hemodialysis shunts
First Claim
1. A method for determining access blood flow (Qa) in a dialysis system having arterial and venous tubing lines reversed, said method comprising the steps of:
- selecting an initial ultrafiltration rate (UFR);
measuring the post dialyzer hematocrit, Ha, at the initial UFR;
changing the value of the UFR to a second UFR;
measuring a post dialyzer hematocrit, Ho, at the second UFR with the dialyzer blood flow being fixed and known; and
solving the equation ##EQU6##
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Accused Products
Abstract
Access recirculation in a shunt is determined quantitatively by a method in which a standard solution, such as a saline, is injected into a patient'"'"'s bloodstream upstream of the shunt. At a point in the access line, a photometric measurement is conducted of the change in hematocrit (ΔH) with respect to time. Electronic circuitry receives signals from the detector and compares the integrated area of ΔH with respect to time of the standard solution initially flowing through the access and of the recirculated solution and provides display of access recirculation. In another aspect, access recirculation and access blood flow are quantitatively determined without injecting a solution into the bloodstream. In this aspect the extent of access recirculation and/or access blood flow is determined quantitatively by a method in which the dialyzer blood flow rate or the ultrafiltration rate (UFR) is changed and the corresponding change in concentration of a blood constituent is measured. In this technique, the concentration of a blood constituent is measured as a function of dialyzer blood flow rate or UFR and electronic circuitry converts these measurements into quantitative determinations of access recirculation and/or access blood flow that can be displayed.
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Citations
23 Claims
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1. A method for determining access blood flow (Qa) in a dialysis system having arterial and venous tubing lines reversed, said method comprising the steps of:
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selecting an initial ultrafiltration rate (UFR); measuring the post dialyzer hematocrit, Ha, at the initial UFR; changing the value of the UFR to a second UFR; measuring a post dialyzer hematocrit, Ho, at the second UFR with the dialyzer blood flow being fixed and known; and solving the equation ##EQU6## - View Dependent Claims (2)
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3. A method for determining access blood flow (Qa) in a dialysis system having arterial and venous tubing lines reversed, said method comprising the steps of:
- selecting an initial ultrafiltration rate (UFR);
measuring a pre-dialyzer hematocrit, Ha, at the initial UFR; changing the value of the UFR to a second UFR; measuring a pre-dialyzer hematocrit, Hi, at the second UFR; and solving the equation Qa =Hi (UFR)/(Hi -Ha).
- selecting an initial ultrafiltration rate (UFR);
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4. A method for measuring access recirculation in a dialysis system having arterial and venous tubing lines, said method comprising the steps of:
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ensuring that ultrafiltration is off; introducing a predetermined amount of saline into an injection site in the arterial line over a predetermined period of time; measuring a percentage change in hematocrit over a first period of time; measuring a percentage change in hematocrit over a second period of time taking place after the first period of time; and comparing the measured change in hematocrit over the second period of time to the measured change in hematocrit over the first period of time to yield a signal that is directly proportional to access recirculation. - View Dependent Claims (5, 6, 7, 8, 9, 10)
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11. A method for measuring dialyzer blood flow in a dialysis system having arterial and venous tubing lines, said method comprising the steps of:
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introducing a predetermined amount of saline into the arterial line over a predetermined period of time; measuring the percentage change in hematocrit over a first period of time; comparing the volume of saline introduced to the product of the measured change in hematocrit over the first period of time and a predetermined conversion factor to yield a signal that is indicative of dialyzer blood flow rate.
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12. A method for measuring priming dialyzer circuit volume in a dialysis system having arterial and venous tubing lines, said method comprising the steps of:
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introducing a predetermined amount of saline into the arterial line over a first period of time; measuring the percentage change in hematocrit over a second period of time; measuring the percentage change in hematocrit over a third period of time; comparing the volume of saline introduced into the arterial line to the product of the measured change in hematocrit over the first period of time and a predetermined conversion factor to yield a signal that is indicative of dialyzer blood flow rate; multiplying the dialyzer blood flow rate by the sum of the first, second and third periods of time and dividing the result by 60 to yield a signal that is indicative of the priming dialysis circuit volume.
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13. A method for eliminating injection-induced transients when injecting a solution into an arterial or venous line, the method comprising the steps of:
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ensuring that ultrafiltration is off; introducing a predetermined amount of a solution into at least one of the arterial and venous lines over a predetermined period of time; measuring the area (Aream) under a curve that is indicative of the percentage change in hematocrit over a period of time; determining the uncorrected blood flow rate (Qi (raw)); determining the area of push rate of the solution injection (Areap) as a function of Qi (raw) and span where span equals the time interval from the start of the solution injection to the end of the injection, in seconds; measuring the volume of the injected solution; dividing the volume of the injected solution by (Aream -Areap) times a measurement unit conversion factor to yield a result that is indicative of the corrected blood flow rate. - View Dependent Claims (14, 15)
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16. A method for determining percentage access recirculation (AR) in a dialysis system having arterial and venous tubing lines, said method comprising the steps of:
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selecting an initial ultrafiltration rate (UFR); measuring an initial dialyzer blood flow rate (Qi); determining the access hematocrit (Ha) at either the initial UFR or the initial dialyzer blood flow rate; changing one of the UFR or the dialyzer blood flow rate to a second value; measuring the arterial hematocrit (Hi) at the second value; computing percentage access recirculation (AR) as a function of a change in either the UFR or the dialyzer blood flow rate. - View Dependent Claims (17, 18)
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19. A method for measuring access blood flow in a dialysis system having arterial and venous tubing lines, said method comprising the steps of:
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introducing a predetermined amount of saline into the venous line over a first period of time; determining dialyzer blood flow rate; measuring the percentage change in hematocrit over a second period of time; measuring the percentage change in hematocrit over a third period of time; comparing the measured change in hematocrit over the third period of time to the measured change in hematocrit over the second period of time to yield a signal that is directly proportional to reversed access recirculation (RAR); subtracting the 1 from the inverse of the RAR and multiplying that result by the dialyzer blood flow rate to yield a signal indicative of access blood flow rate.
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20. A method for determining access blood flow in a dialysis system having arterial and venous tubing lines, said method comprising the steps of:
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selecting an initial ultrafiltration rate (UFR); determining the access hematocrit at the initial UFR; changing the value of the UFR to a second UFR; measuring the arterial hematocrit at the second UFR; multiplying the arterial hematocrit by the second UFR and dividing the result by the arterial hematocrit minus the access hematocrit to compute the access blood flow.
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21. A method for determining percentage access recirculation (AR) in a dialysis system having arterial and venous tubing lines, said method comprising the steps of:
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selecting an initial ultrafiltration rate (UFR); measuring an initial dialyzer blood flow rate (Qi); determining the access hematocrit (Ha) at either the initial UFR or the initial dialyzer blood flow rate; changing one of the UFR or the dialyzer blood flow rate to a second value; measuring the arterial hematocrit (Hi) at the second value; computing percentage access recirculation (AR) as a function of a change in either the UFR or the dialyzer blood flow rate. - View Dependent Claims (22, 23)
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Specification