Method and apparatus to measure blood flow rate in hemodialysis shunts
First Claim
1. A method for determining shunt flow in a shunt connected between first and second points in a circulating system, comprising the steps of:
- a) establishing a first flow rate in said circulating system;
b) measuring, during said first flow rate, a first line velocity in the shunt between a first point in the shunt and a second point in the shunt;
c) establishing a second flow rate in said circulating system;
d) measuring, during said second flow rate, a second line velocity in the shunt between the first point in the shunt and the second point in the shunt; and
e) calculating said shunt flow from said first line velocity and second line velocity and said first and second flow rates.
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Accused Products
Abstract
A device for determining shunt flow in a hemodialysis shunt connected between two points in a cardiovascular-hemodialysis system includes a flow sensor connected to either the hemodialysis inflow (arterial) line or the outflow (venous) line. An indicator is preferably introduced into the system that is sensed by first and second sensors that are spaced apart and disposed effective for sensing the indicator at two locations in the cardiovascular-hemodialysis system. Natural indicators produced by the body, such as density variations in the blood caused by rhythmic breathing, are optionally used instead of an introduced indicator. A detector connected to the flow sensor and the first and second sensors determines, at a first flow rate, a first time a first indicator takes to move between the two locations, and at a second flow rate, a second time a second indicator takes to move between the two locations. The shunt flow is then calculated from the first and second times and the first and second flow rates.
55 Citations
29 Claims
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1. A method for determining shunt flow in a shunt connected between first and second points in a circulating system, comprising the steps of:
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a) establishing a first flow rate in said circulating system; b) measuring, during said first flow rate, a first line velocity in the shunt between a first point in the shunt and a second point in the shunt; c) establishing a second flow rate in said circulating system; d) measuring, during said second flow rate, a second line velocity in the shunt between the first point in the shunt and the second point in the shunt; and e) calculating said shunt flow from said first line velocity and second line velocity and said first and second flow rates. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A device for determining shunt flow in a shunt connected between first and second points in a circulating system, comprising:
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means for establishing a flow rate in said circulating system; means for measuring a line velocity in the shunt; such that when the means for establishing a flow rate is operated at a first flow rate, the means for measuring a line velocity measures a first line velocity in the shunt; and
when the means for establishing a flow rate is operated at a second flow rate, the means for measuring a line velocity measures a second line velocity in the shunt;means for calculating said shunt flow from said first line velocity and second line velocity and said first and second flow rates. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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Specification