Blood extraction and reinfusion flow control system and method
First Claim
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1. A system for controlled withdrawal of blood from a blood vessel, said system comprising:
- a fluid reservoir fluidly connected to said blood vessel by a first fluid flow path;
a pump for pumping blood from said blood vessel through said first fluid flow path to said fluid reservoir;
a pressure sensor for sensing the pressure within said first fluid flow path;
a flow rate sensor for sensing the flow rate within said first fluid flow path;
an adaptive flow rate control system operatively connected to (1) said pressure sensor, (2) said flow rate sensor and (3) said pump, to receive pressure and flow rate signals from said pressure and flow rate sensors and to send control signals to said pump;
said adaptive flow rate control system comprising;
(a) means for receiving and storing a maximum flow rate limit setting entered by an operator;
(b) means for receiving said pressure and flow rate signals from said pressure sensor and said flow rate sensor and for generating therefrom and storing a standard flow rate/pressure curve defining the flow rate/pressure relationship of blood passing freely through said blood vessel and said first flow path without substantially reduced pressure within said blood vessel as determined;
(c) means for calculating a control curve in relation to, and below, said standard flow rate/pressure curve;
(d) means for setting an initial adaptive flow rate limit no greater than said maximum flow rate setting;
(e) means for signaling said pump to pump blood at a rate substantially equal to said initial adaptive flow rate, for a first timed pumping period;
(f) means for sensing whether the pressure within the first flow path has remained above the control curve throughout the immediately preceding timed pumping period and, if so, for increasing the adaptive flow rate limit by a predetermined increment amount and, thereafter, for signaling the pump to pump blood at the increased adaptive flow rate limit, for a subsequent timed pumping period;
(g) means for sensing whether the pressure within the first flow path has fallen below the control curve and, if so, for signaling the pump to decrease the flow rate to a rate at which steady-state pressure on said control curve is established for a timed stabilization period;
(h) means for determining, after completion of the timed stabilization period, whether the point on said control curve whereat steady-state pressure has been established for said stabilization time period is more than a predetermined amount below said adaptive flow rate limit, and if so, for;
decreasing the adaptive flow rate limit by a predetermined decrement amount to establish a decreased adaptive flow rate limit and, thereafter;
signaling the pump to pump at said decreased adaptive flow rate limit for a subsequent timed pumped period.
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Abstract
A method and system for adaptively controlled withdrawal/infusion of a fluid, such as blood, to or from a fluid source, such as a blood vessel. An adaptive flow rate limit is established and periodically adjusted during the course of withdrawal/infusion so as to maximize and optimize the withdrawal/infusion rate while, at the same time, providing for rapid corrective adjustments in flow rate responsive to early indications of flow disruption, such as occlusion or collapse of the blood vessel during blood withdrawal. The method and system of the invention is particularly applicable to automated apheresis systems.
251 Citations
51 Claims
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1. A system for controlled withdrawal of blood from a blood vessel, said system comprising:
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a fluid reservoir fluidly connected to said blood vessel by a first fluid flow path; a pump for pumping blood from said blood vessel through said first fluid flow path to said fluid reservoir; a pressure sensor for sensing the pressure within said first fluid flow path; a flow rate sensor for sensing the flow rate within said first fluid flow path; an adaptive flow rate control system operatively connected to (1) said pressure sensor, (2) said flow rate sensor and (3) said pump, to receive pressure and flow rate signals from said pressure and flow rate sensors and to send control signals to said pump; said adaptive flow rate control system comprising; (a) means for receiving and storing a maximum flow rate limit setting entered by an operator; (b) means for receiving said pressure and flow rate signals from said pressure sensor and said flow rate sensor and for generating therefrom and storing a standard flow rate/pressure curve defining the flow rate/pressure relationship of blood passing freely through said blood vessel and said first flow path without substantially reduced pressure within said blood vessel as determined; (c) means for calculating a control curve in relation to, and below, said standard flow rate/pressure curve; (d) means for setting an initial adaptive flow rate limit no greater than said maximum flow rate setting; (e) means for signaling said pump to pump blood at a rate substantially equal to said initial adaptive flow rate, for a first timed pumping period; (f) means for sensing whether the pressure within the first flow path has remained above the control curve throughout the immediately preceding timed pumping period and, if so, for increasing the adaptive flow rate limit by a predetermined increment amount and, thereafter, for signaling the pump to pump blood at the increased adaptive flow rate limit, for a subsequent timed pumping period; (g) means for sensing whether the pressure within the first flow path has fallen below the control curve and, if so, for signaling the pump to decrease the flow rate to a rate at which steady-state pressure on said control curve is established for a timed stabilization period; (h) means for determining, after completion of the timed stabilization period, whether the point on said control curve whereat steady-state pressure has been established for said stabilization time period is more than a predetermined amount below said adaptive flow rate limit, and if so, for; decreasing the adaptive flow rate limit by a predetermined decrement amount to establish a decreased adaptive flow rate limit and, thereafter; signaling the pump to pump at said decreased adaptive flow rate limit for a subsequent timed pumped period. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. An extracorporeal blood processing system wherein blood is withdrawn from a blood vessel through a first flow path, processed in an extracorporeal processing apparatus and at least a portion of the blood is then infused from said blood processing apparatus through a second flow path into a blood vessel, said system comprising:
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a blood processing apparatus for effecting a desired processing of blood; a first flow path fluidly connectable between a blood vessel and said blood processing apparatus to permit withdrawal of blood from said blood vessel into said blood processing apparatus; a second flow path fluidly connectable between said blood processing apparatus and a blood vessel for infusing at least a portion of said blood from said blood processing apparatus into a blood vessel; a withdrawal pump operatively mounted to said first flow path to pump blood from said blood vessel to said blood processing means; an infusion pump operatively mounted to said second flow path to pump blood from said blood processing means to said blood vessel; a first pressure sensor for sensing pressure within said first flow path; a first flow rate sensor for sensing flow rate within said first flow path; a second pressure sensor for sensing pressure within said second flow path; a second flow rate sensor for sensing flow rate within said second flow path; a flow rate control system operatively connected to (1) said first and second pressure sensors;
(2) said first and second flow rate sensors; and
(3) said withdrawal and infusion pumps to receive pressure and flow rate signals from said first and second pressure sensors and said first and second flow rate sensors and to send control signals to said pump(s);said flow rate control system comprising; (a) means for receiving and storing a maximum withdrawal flow rate limit setting entered by the operator; (b) means for receiving and storing a maximum infusion flow rate limit set by the operator; (c) means for utilizing pressure and flow rate signals from said first flow path to generate a standard withdrawal flow rate/pressure curve defining the flow rate/pressure relationship of blood being withdrawn through said first flow path; (d) means for calculating a withdrawal control curve in relation to, and below, said standard withdrawal flow rate/pressure curve; (e) means for changing the sign of said withdrawal control curve to establish a base infusion control curve; (f) means for raising said base reinfusion control curve by a predetermined adjustment factor to establish an upwardly adjusted infusion control curve prior to beginning infusion through said second flow path; (g) means for altering the slope of said adjusted infusion control curve by a predetermined slope adjustment factor prior to beginning infusion through said second flow path. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51)
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Specification