Calibration of pumps, such as blood pumps of dialysis machine
First Claim
1. A method of operating a pump subject to repeated use, said pump placed in a fluid conduit, comprising the steps of:
- (a) recording inlet pressures in said fluid conduit during a previous use of said pump;
(b) deriving, from said recordings of inlet pressure, a mean inlet pressure during said previous use of said pump;
(c) calibrating the flow rate of said pump, said step of calibrating performed while said inlet pressure to said fluid conduit is maintained at said mean inlet pressure; and
(d) subsequently using said pump.
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Accused Products
Abstract
A method of calibrating a pump that is subject to variations in flow rate based on inlet pressure variations, such as a peristaltic pump found in medical instruments. The pressure at the inlet of the pump is measured and recorded during prior uses of the pump. A mean or average inlet pressure is derived from the measurements, either directly or indirectly from the measurements of using regression techniques, as a way of forecasting the inlet pressure during the next use of the pump. The pump is then calibrated at an inlet pressure that is set or adjusted to match the mean or average inlet pressure. The calibration is thus accurately performed for the pump, and is independent of the absolute accuracy of the inlet pressure sensor.
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Citations
20 Claims
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1. A method of operating a pump subject to repeated use, said pump placed in a fluid conduit, comprising the steps of:
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(a) recording inlet pressures in said fluid conduit during a previous use of said pump;
(b) deriving, from said recordings of inlet pressure, a mean inlet pressure during said previous use of said pump;
(c) calibrating the flow rate of said pump, said step of calibrating performed while said inlet pressure to said fluid conduit is maintained at said mean inlet pressure; and
(d) subsequently using said pump. - View Dependent Claims (2, 3, 4, 5, 6, 7)
moving a known volume of fluid with said pump at a predetermined pump revolutions per minute;
measuring the time taken to move said known volume of fluid; and
determining the volume of fluid moved by said pump per revolution;
wherein said step of moving is performed while said inlet pressure to said fluid conduit is maintained at said mean inlet pressure.
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5. The method of claim 4, further comprising the steps of placing a restriction between a source of said known volume of fluid and the inlet to said fluid conduit, and adjusting said restriction so as to create an inlet pressure in said fluid conduit substantially matching said mean inlet pressure.
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6. The method of claim 1, wherein:
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said blood pump is incorporated into a medical instrument having a central processing unit, said step of recording comprises the step of reading measurements of inlet pressure to a computer-readable storage medium associated with said central processing unit, and said step of deriving is performed by said central processing unit retrieving said measurements from said storage medium and executing a software program to derive said mean inlet pressure from said measurements.
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7. The method of claim 1, wherein during said step of calibrating the flow rate of said pump, said inlet pressure is varied periodically about said mean inlet pressure.
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8. A method of calibrating a peristaltic blood pump of a hemodialysis machine, said hemodialysis machine having an extracorporeal circuit comprising an arterial line, a venous line, and a dialyzer, wherein said blood pump pumps blood from a patient through said arterial line and dialyzer and delivers said blood back to said patient via said venous line, comprising the step of:
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recording inlet pressures in said arterial line during dialysis sessions for said patient;
deriving from said recorded inlet pressures a calibration inlet pressure Pc to be used for calibration of said blood pump;
adjusting the inlet pressure of said arterial line and moving a known volume of fluid with said blood pump while maintaining said inlet pressure of said arterial line at said pressure Pc to thereby calibrate said pump at said pressure Pc. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. A method of operating a dialysis machine having an extracorporeal circuit comprising a blood pump, an arterial line, a venous line and a dialyzer, comprising the steps of:
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calibrating said blood pump at an inlet calibration pressure Pc derived from recorded inlet pressures in said arterial line from an at least one previous dialysis session of said dialysis machine to thereby derive a relationship for said blood pump between said inlet calibration pressure Pc and a known volume of fluid moved by said blood pump per revolution at said inlet calibration pressure Pc, and during a subsequent dialysis session of said dialysis machine, adjusting the speed of said blood pump to achieve a substantially constant flow of blood through said extracorporeal circuit regardless of changes in the inlet pressure of said arterial line during said use of said dialysis machine. - View Dependent Claims (17, 18, 19)
recording inlet pressures in said arterial line during previous dialysis sessions;
deriving from said recorded inlet pressures said calibration inlet pressure Pc;
adjusting the inlet pressure of said arterial line and moving a known volume of fluid with said blood pump while maintaining said inlet pressure of said arterial line at said pressure Pc to thereby calibrate said pump at said pressure Pc.
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18. The method of claim 16, wherein said step of adjusting is performed for at least one minute during the treatment of a patient during said subsequent dialysis session.
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19. The method of claim 16, wherein said step of adjusting is performed for at least 10 minutes.
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20. A method of operating a blood pump subject to repeated use, said blood pump placed in a fluid conduit comprising an extracorporeal circuit, comprising the steps of:
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(a) recording inlet pressures in said fluid conduit during at least one previous use of said pump;
(b) deriving, from said recordings of inlet pressure, a mean inlet pressure during said at least one previous use of said pump;
(c) using a computed volume of fluid moved by said blood pump per revolution at said mean inlet pressure to calibrate said pump.
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Specification