Blood extraction flow control calibration system and method
First Claim
1. A system for calibrating the control of the flow of fluid in a given direction to or from a subject having a limited flow rate accommodation comprising:
- a pressure cuff coupled to the subject to provide pressurization of the subject'"'"'s blood vessel to increase the dynamic range of operating internal vein pressures;
a fluid pump that is connectable in fluid pumping relationship along a fluid flow path between the subject and a fluid processor or reservoir;
pressure sensing means coupled to sense fluid pressure in the fluid flow path between the fluid pump and the subject and generate indications of the sensed pressure;
a flow rate sensor coupled to provide an indications of fluid flow rates along the first fluid flow path; and
a fluid pump control system coupled to receive the sensed pressure and flow rate indications and provide to the fluid pump flow rate control signals in response thereto, the fluid pump control system including;
(a) means for inflating and deflating the pressure cuff;
(b) means for generating a zero-flow point, including means for sensing the internal fluid pressure within the subject'"'"'s blood pressure at a zero flow rate while the pressure cuff is deflated, said zero flow point being an indication of pressure within the subject at zero flow rate;
(c) means for making periodic flow path pressure measurements while the pressure cuff is inflated and means for generating a calibration flow rate curve comprised of the plurality of periodic flow path pressure measurements;
(d) means for generating a flow rate control curve utilizing the slope of said calibration flow rate curve, said zero-flow point, and a translation from said zero-flow point corresponding to a predetermined intravascular pressure value; and
(e) means for generating control signals limiting the actual flow rate to a magnitude along the flow rate control curve.
1 Assignment
0 Petitions
Accused Products
Abstract
A method and system for calibrating and controlling the withdrawal of a fluid, such as blood, from a fluid source, such as a blood vessel, includes a fluid pump, a pressure sensor, a flow rate sensor, and a microprocessor based flow control subsystem. The flow control subsystem optimizes the flow rate by sensing zero flow rate pressure within the subject, making a plurality of periodic flow path pressure measurements and extrapolating a calibration flow rate curve. A control curve is generated by utilizing the zero-flow rate pressure point, the slope of the calibration curve, and an empirically predetermined pressure. The blood pump is then operated at a maximum speed that is limited by the flow control curve to maximize flow without occlusion or collapse of the blood vessel during blood withdrawal. The method and system of the invention is particularly applicable to automated apheresis systems.
92 Citations
42 Claims
-
1. A system for calibrating the control of the flow of fluid in a given direction to or from a subject having a limited flow rate accommodation comprising:
-
a pressure cuff coupled to the subject to provide pressurization of the subject'"'"'s blood vessel to increase the dynamic range of operating internal vein pressures; a fluid pump that is connectable in fluid pumping relationship along a fluid flow path between the subject and a fluid processor or reservoir; pressure sensing means coupled to sense fluid pressure in the fluid flow path between the fluid pump and the subject and generate indications of the sensed pressure; a flow rate sensor coupled to provide an indications of fluid flow rates along the first fluid flow path; and a fluid pump control system coupled to receive the sensed pressure and flow rate indications and provide to the fluid pump flow rate control signals in response thereto, the fluid pump control system including; (a) means for inflating and deflating the pressure cuff; (b) means for generating a zero-flow point, including means for sensing the internal fluid pressure within the subject'"'"'s blood pressure at a zero flow rate while the pressure cuff is deflated, said zero flow point being an indication of pressure within the subject at zero flow rate; (c) means for making periodic flow path pressure measurements while the pressure cuff is inflated and means for generating a calibration flow rate curve comprised of the plurality of periodic flow path pressure measurements; (d) means for generating a flow rate control curve utilizing the slope of said calibration flow rate curve, said zero-flow point, and a translation from said zero-flow point corresponding to a predetermined intravascular pressure value; and (e) means for generating control signals limiting the actual flow rate to a magnitude along the flow rate control curve. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
-
-
13. A method of controlling a flow rate of a bodily fluid along a flow path between a subject and a processor or reservoir comprising the steps of:
-
placing a deflated pressure cuff on the subject; sensing the internal fluid pressure within the subject'"'"'s blood vessel at zero flow rate while the pressure cuff is deflated and generating a zero-flow pressure point; inflating the pressure cuff, waiting until the vein pressure stabilizes, initiating a blood draw, and making a plurality of periodic flow path pressure measurements; using the flow path pressure measurements to generate a calibration flow rate curve; generating a flow rate control curve utilizing the slope of said calibration flow rate curve, said zero-flow pressure point, and a translation from said zero-flow pressure point corresponding to a predetermined intravascular pressure value; and generating during conditions of normal operation flow rate control signals limiting the actual flow rate to a magnitude along the flow rate control curve. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
-
-
33. A system for calibrating the control of the flow of fluid in a given direction to or from a subject having a limited flow rate accommodation comprising:
-
a pressure cuff coupled to the subject to provide pressurization of the subject'"'"'s blood vessel to increase the dynamic range of operating internal vein pressures; a fluid pump that is connectable in fluid pumping relationship along a fluid flow path between the subject and a fluid processor or reservoir; pressure sensing means coupled to sense fluid pressure in the fluid flow path between the fluid pump and the subject and generate indications of the sensed pressure; a flow rate sensor coupled to provide an indications of fluid flow rates along the first fluid flow path; and a fluid pump control system coupled to receive the sensed pressure and flow rate indications and provide to the fluid pump flow rate control signals in response thereto, the fluid pump control system including; (a) means for inflating and deflating the pressure cuff; (b) means for generating a zero-flow point, including means for sensing the internal fluid pressure within the subject'"'"'s blood pressure at a zero flow rate while the pressure cuff is deflated, said zero flow point being an indication of pressure within the subject at zero flow rate; (c) means for generating a calibration flow rate curve including means for rapidly and uniformly accelerating said fluid pump while the pressure cuff is inflated so that a plurality of flow path pressure measurements can be taken periodically; (d) means for generating a flow rate control curve utilizing the slope of said calibration flow rate curve, said zero-flow point, and a translation from said zero-flow point corresponding to a predetermined intravascular pressure value; and (e) means for generating during conditions of normal operation flow rate control signals limiting the actual flow rate to a magnitude along the flow rate control curve. - View Dependent Claims (34, 35, 36, 37)
-
-
38. A system for calibrating the control of the flow of fluid in a given direction to or from a subject having a limited flow rate accommodation comprising:
-
a pressure cuff coupled to the subject to provide pressurization of the subject'"'"'s blood vessel to increase the dynamic range of operating internal vein pressures; a fluid pump that is connectable in fluid pumping relationship along a fluid flow path between the subject and a fluid processor or reservoir; pressure sensing means coupled to sense fluid pressure in the fluid flow path between the fluid pump and the subject and generate indications of the sensed pressure; a flow rate sensor coupled to provide an indications of fluid flow rates along the first fluid flow path; and a fluid pump control system coupled to receive the sensed pressure and flow rate indications and provide to the fluid pump flow rate control signals in response thereto, the fluid pump control system including; (a) means for inflating and deflating the pressure cuff; (b) means for generating a zero-flow point, including means for sensing the internal fluid pressure within the subject'"'"'s blood pressure at a zero flow rate while the pressure cuff is deflated, said zero flow point being an indication of pressure within the subject at zero flow rate; (c) means for generating a calibration flow rate curve including means for rapidly and uniformly accelerating and decelerating said fluid pump while the pressure cuff is inflated so that a plurality of flow path pressure measurements can be taken periodically; (d) means for generating a flow rate control curve utilizing the slope of said calibration flow rate curve, said zero-flow point, and a translation from said zero-flow point corresponding to a predetermined intravascular pressure value; and (e) means for generating during conditions of normal operation flow rate control signals limiting the actual flow rate to a magnitude along the flow rate control curve. - View Dependent Claims (39, 40, 41, 42)
-
Specification