Blood extraction and reinfusion flow control system and method

An adaptive blood flow control system for extracting blood from a subject donor at an optimum rate during a plasmapheresis operation comprising:

• tubing defining a blood flow path between a donor attachment and a reservoir for receiving blood, the tubing being suitable for replacement after each plasmapheresis operation;
• a blood pump disposed to pump blood along the blood flow path at a commanded rate and provide a signal that is indicative of the instantaneous actual flow rate;
• a pressure sensor disposed to detect and indicate blood pressure in the blood flow path at a point upstream from the blood pump;
• and
• a control system including a data processor coupled to receive the indications of pressure and actual flow rate and in response thereto provide flow rate commands to the blood pump, the control system data processor receiving sensed pressure data at a first flow rate test point, receiving sensed pressure data at a second flow rate test point different from the first test point, generating a flow rate limit curve in response to the received sensed pressure data at the first and second flow rate test points and commanding a maximum pumping rate limited by a nominal maximum rate or a dropping of sensed pressure below the flow rate limit curve, whichever occurs at a lower pumping rate.

An adaptive bodily fluid flow rate control system for extracting bodily fluid from a living subject at an optimum rate comprising:

• a fluid pump disposed along a fluid flow path to pump intravenous bodily fluids along the flow path between a living subject and a reservoir at a commanded rate and generate an actual flow rate signal that is indicative of the instantaneous actual flow rate;
• a pressure sensor disposed to detect actual fluid pressure in the fluid flow path on a side of the fluid pump adjacent the living subject and generate an actual pressure signal indicative of the sensed pressure;
• and
• a control system coupled to receive the actual flow rate signal and actual pressure signal and provide flow rate commands to the fluid pump in response thereto, the control system including means for deriving first test point pressure data from the actual pressure signal at a first test point flow rate, deriving second test point pressure data from the actual pressure signal at a second test point flow rate different from the first test point flow rate, extrapolating and translating the first and second test point data to generate a flow rate limit curve defining pressure limits for optimizing the flow rate for the living subject, and commanding a maximum pumping rate for an optimum bodily fluid flow rate, the pumping rate being limited to prevent actual sensed pressure from exceeding the flow rate limit curve.

An adaptive fluid flow control system optimizing a reinfusion fluid flow rate in a plasmapheresis system, the fluid flow control system comprising:

• apparatus defining a sterile, noninvasive fluid flow path between an intravenous coupling to a living subject and a reservoir of a plasmapheresis system;
• a noninvasive fluid pump disposed along the fluid flow path to pump fluid therethrough at a rate responsive to a pump flow rate command;
• a pressure sensor coupled to sense pressure in the fluid flow path between the fluid pump and the intravenous coupling and generate a pressure indication signal representative of the sensed pressure;
• and
• a flow rate controller coupled to receive the pressure indication signal and generate the pump flow rate command in response thereto, the flow rate controller including means for generating two different test point flow rate command signals to cause two different fluid flow rates through the fluid flow path, means for determining sensed pressure from the pressure indication signal at the resulting two different test point flow rates, and means for extrapolating the sensed pressure into a flow rate curve, translating the flow rate curve by an amount equal to an acceptable change in intravenous pressure to generate a second curve, deriving a flow rate limit curve from the second curve, and generating the flow rate command to produce a maximum fluid flow rate limited to a flow rate at which the sensed fluid pressure is not outside the flow rate limit curve.

A method of controlling a flow rate of bodily fluids along a flow path between a subject and a reservoir comprising the steps of:

• sensing pressure data along the flow path at two different test point flow rates known to produce minimal change in intravenous pressure in the subject;
• generating a flow rate limit curve in response to an extrapolation of the sensed pressure data, the flow rate limit curve representing sensed extravenous pressures corresponding to acceptable intravenous pressure limits within the subject as a function of fluid flow rate;
• and
• pumping bodily fluid along the flow path while sensing the fluid pressure, the pumping being controlled to limit the bodily fluid flow rate to a rate at which the magnitude of the sensed fluid pressure is less than the magnitude of the pressure intercepted by the flow rate limit curve at any given flow rate.

A method of controlling a flow rate of bodily fluids along a flow path between a subject and a reservoir comprising the steps of:

• sensing pressure data along the flow path at two different test point flow rates known to produce minimal change in intravenous pressure in the subject;
• generating a flow rate limit curve in response to an extrapolation of the senses pressure date, the flow rate limit curve representing sensed extravenous pressures corresponding to acceptable intravenous pressure limits within the subject as a function of fluid flow rate, the generating step including the steps of linearly extrapolating the sensed pressure data to generate a flow rate curve representing sensed flow path pressure as a function of fluid flow rate at a constant intravenous pressure and translating the flow rate curve by a magnitude equal to a maximum acceptable change in intravenous pressure to generate the flow rate limit curve;
• and
• pumping bodily fluid along the flow path while sensing the fluid pressure, the pumping being controlled to limit the bodily fluid flow rate to a rate at which the magnitude of the sensed fluid pressure is less than the magnitude of the pressure intercepted by the flow rate limit curve at any given flow rate.

A method of controlling a flow rate of bodily fluids along a flow path between a subject and a reservoir comprising the steps of:

• sensing pressure data along the flow path at at least two different test points having different flow rates that are known to produce minimal change in internal pressure in the subject;
• generating a flow rate limit curve in a coordinate representation having a pressure axis and a flow rate axis in response to the sensed data by generating the flow rate limit curve as a curve that has a selected relationship to and is different from a full pressure-flow rate curve passing through the test points;
• and
• pumping bodily fluid along the flow path while sensing the fluid pressure, the pumping being controlled to produce a bodily fluid flow rate tending to minimize any difference between a sensed fluid pressure at a current flow rate and a pressure intercept of the flow rate limit curve at the current flow rate.

An adaptive bodily fluid flow control system comprising:

• a bodily fluid flow path defined between a subject and a reservoir;
• a pump disposed to pump bodily fluid along the bodily fluid flow path at a rate commanded by a flow rate command signal;
• a pressure sensor disposed to detect and indicate fluid pressure in the fluid flow path at a location between the pump and the subject;
• a control system including a data processor that is coupled to receive current indications of current pressure from the pressure sensor and to control the pump in response thereto, the data processor commanding at least two different test point flow rates which are known to produce little fluid pressure drop internally of the subject and receiving from the pressure sensor and storing test point pressure indications at each of the test point flow rates to establish at least two test points in a coordinate system having a pressure axis and a flow rate axis, the data processor further establishing a full pressure flow rate curve passing through the test points, a flow rate limit curve that is selectively translated and selectively rotated relative to the full pressure flow rate curve, and generating a flow rate command signal tending to reduce any difference between a currently sensed pressure and a pressure intercept of the flow rate limit curve at a current fluid flow rate.