Sensor for transcutaneous measurement of vascular access blood flow
First Claim
1. A sensor for the transcutaneous measurement of vascular access blood flow comprising two pairs of complementary emitter and detector elements, wherein the pairs of emitter and detector elements define two lines at right angles to each other.
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Abstract
An optical sensor includes a sensing pair of complementary emitter and detector elements for measuring the bulk absorptivity (α) of an area parallel to and including a hemodialysis access site, and a normalizing pair of complementary emitter and detector elements for measuring the absorptivity (αo) of the tissue itself perpendicular to the access site. The pairs of emitter and detector elements define two lines at right angles to each other, and one of the pairs lies to one side of the line defined by the other of the pairs, such that the two pairs of emitter and detector elements form a “T” shape. Indicator dilution techniques are used to measure vascular access flow rates during routine hemodialysis, using the sensor.
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Citations
24 Claims
- 1. A sensor for the transcutaneous measurement of vascular access blood flow comprising two pairs of complementary emitter and detector elements, wherein the pairs of emitter and detector elements define two lines at right angles to each other.
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7. A sensor for the transcutaneous measurement of vascular access blood flow comprising:
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a body having upper and lower surfaces;
a sensing emitter/detector element pair on the lower surface of the body for positioning over and parallel to an access site; and
a normalizing emitter/detector element pair on the lower surface of the body for positioning to one side of and perpendicular to the access site. - View Dependent Claims (8, 9, 10, 11, 12, 13, 16, 17, 18, 19)
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14. Apparatus for non-invasively measuring one or more blood parameters associated with a vascular access site, comprising:
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means for optically measuring a blood parameter over and parallel to the access site; and
means for optically measuring the blood parameter to one side of and perpendicular to the access site.
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15. A method of measuring a blood parameter transcutaneously in the vascular system of a patient having a vascular access site, using a sensor comprising two pairs of complementary emitter and detector elements, wherein the pairs of emitter and detector elements define two lines at right angles to each other, the method comprising the steps of:
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placing the sensor at a measurement site on the skin of a patient with one of the pairs of emitter and detector elements parallel to the vascular access site and the other of the pairs of emitter and detector elements perpendicular to the vascular access site;
perturbing a region of the vascular system upstream of the measurement site;
using the sensor to transcutaneously measure the perturbation over a predetermined period of time at the measurement site; and
calculating the blood parameter based on the measured perturbation.
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20. A method of transcutaneously measuring access blood flow in a hemodialysis circuit including a vascular access site having an arterial needle site and a venous needle site downstream of the arterial needle site, a dialyzer having an inlet and an outlet, a dialysis arterial line connecting the dialyzer inlet to the arterial needle site, and a dialysis venous line connecting the dialyzer outlet to the venous needle site, using a sensor capable of determining the relative changes in hematocrit in the access blood flowing under the skin, the sensor comprising two pairs of complementary emitter and detector elements, wherein the pairs of emitter and detector elements define two lines at right angles to each other, the method comprising the steps of:
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placing the sensor on the skin with one of the pairs of emitter and detector elements parallel to and over the vascular access site downstream of the venous needle site, and with the other of the pairs of emitter and detector elements perpendicular to the vascular access site;
using the sensor to output a signal proportional to the hematocrit in the vascular access site (Ha);
recording the signal with a monitoring system associated with the sensor;
obtaining a stable baseline Ha value;
after a stable is Ha obtained, injecting a known volume (V) of a reference diluent into the dialysis venous line upstream of the sensor; and
using the signals produced from the time the diluent is injected to the time the signal returns to the baseline value to calculate access blood flow based on the ratio of percent change in hematocrit Δ
H to a time-dependent hematocrit H using the monitoring system. - View Dependent Claims (21, 22, 24)
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23. A method of transcutaneously measuring access blood flow at an access site in a patient cardiovascular circuit using a sensor comprising two pairs of complementary emitter and detector elements, wherein the pairs of emitter and detector elements define two lines at right angles to each other, comprising the steps of:
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placing the sensor on the skin of a patient with one of the pairs of emitter and detector elements parallel to and over the vascular access site and with the other of the pairs of emitter and detector elements perpendicular to the vascular access site;
infusing a specific volume (Vi) of an indicator diluent into the patient cardiovascular circuit at the access site in the presence of a hemodialysis circuit to effect a change in a blood parameter; and
using the sensor to measure the percent change in the parameter.
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Specification