Method and apparatus for controlling the flow rate of washing solution during the washing step in a blood centrifugation bowl

Abstract

A method of washing blood mixed with undesirable elements not normally found in healthy whole blood to remove the undesirable elements, the method comprising: separating the blood into components according to relative densities of the components with a rotating centrifuge bowl; providing a port through which fluid exits the bowl, the exiting fluid having a concentration of undesirable elements; flowing washing solution into the centrifuge bowl at an initial flow rate; monitoring the fluid exiting the bowl with an optical sensor having an output signal indicative of the composition of the exiting fluid; and increasing and decreasing the flow rate of the wash solution as a function of the output signal.

We claim: 
     
         1 . An apparatus for removing undesirable elements not normally found in healthy whole blood from blood mixed with the undesirable elements, the apparatus comprising:
 a rotatable centrifuge bowl for separating the blood into components according to relative densities of the components;   a controllable pump for flowing washing solution into the centrifuge bowl; a port through which fluid exits the bowl;   an optical sensor for monitoring the fluid exiting the bowl and generating an output signal indicative of the composition of the exiting fluid; and   a controller operatively coupled to the pump for comparing the output signal with one or more predetermined values and causing the pump to increase, decrease, or hold constant the flow of washing solution into the centrifuge bowl.   
     
     
         2 . The apparatus of  claim 1 , further comprising a container for reinfusing at least one of the components into a patient. 
     
     
         3 . The apparatus of  claim 1 , further comprising a port for admitting blood into the bowl. 
     
     
         4 . The apparatus of  claim 1 , wherein the optical sensor comprises a light source and a light detector, the light source emitting light which passes through the fluid exiting the bowl and the detector receiving the light after it passes through the fluid. 
     
     
         5 . The apparatus of  claim 1 , wherein the optical sensor comprises a light source and a light detector, the light source emitting light which contacts the fluid exiting the bowl and the detector receiving the light after it is reflected by the fluid. 
     
     
         6 . The apparatus of  claim 1 , wherein the optical sensor measures light having a wavelength in the range from 530 to 580 nm. 
     
     
         7 . The apparatus of  claim 6 , wherein the optical sensor measures light having a wavelength of 565 nm. 
     
     
         8 . The apparatus of  claim 1 , wherein the optical sensor comprises a light emitting diode. 
     
     
         9 . The apparatus of  claim 1 , wherein the optical sensor measures only one wavelength of light. 
     
     
         10 . The apparatus of  claim 1 , wherein the controller causes the pump to decrease the flow rate of the washing solution if the optical sensor has an output signal indicative of slight red blood spilling into the exiting fluid. 
     
     
         11 . The apparatus of  claim 1 , wherein the controller causes the pump to increase the flow rate of the washing solution if the optical sensor has an output signal indicative of no red blood spilling into the exiting fluid. 
     
     
         12 . The apparatus of  claim 1 , wherein the controller causes the pump to decrease to zero the flow rate of the washing solution if the optical sensor has an output signal indicative of massive red blood spilling into the exiting fluid. 
     
     
         13 . The apparatus of  claim 12 , wherein the controller causes the pump to increase from zero the flow rate of the washing solution after a certain amount of time. 
     
     
         14 . The apparatus of  claim 1 , wherein after a predetermined total volume of washing solution has been used the controller compares the output signal of the optical sensor with a predetermined threshold value indicative of the amount of free Hgb in the exiting fluid. 
     
     
         15 . The apparatus of  claim 14 , wherein the controller causes the pump to flow an additional amount of washing solution into the centrifuge bowl if the output signal does not meet the threshold value indicative of the amount of free Hgb in the exiting fluid. 
     
     
         16 . A method of washing blood mixed with undesirable elements not normally found in healthy whole blood to remove the undesirable elements, the method comprising:
 separating the blood into components according to relative densities of the components with a rotating centrifuge bowl;   providing a port through which fluid exits the bowl, the exiting fluid having a concentration of undesirable elements;   flowing washing solution into the centrifuge bowl at an initial flow rate;   monitoring the fluid exiting the bowl with an optical sensor having an output signal indicative of the composition of the exiting fluid; and   increasing and decreasing the flow rate of the wash solution as a function of the output signal,   wherein the flow rate of the washing solution is increased if the optical sensor has an output signal indicative of no red blood spilling into the exiting fluid.   
     
     
         17 . The method of  claim 16 , wherein the total time for the washing method is minimized while the hematocrit of the washed blood is held constant in comparison with the same method in which the flow rate is maintained at the initial rate. 
     
     
         18 . The method of  claim 16 , wherein the hematocrit of the washed blood is increased in comparison with the same method in which the flow rate is maintained at the initial rate. 
     
     
         19 . The method of  claim 16 , wherein the flow rate of the washing solution is decreased if the optical sensor has an output signal indicative of slight red blood spilling into the exiting fluid. 
     
     
         20 . The method of  claim 16 , wherein the flow rate of the washing solution is decreased to zero if the optical sensor has an output signal indicative of massive red blood spilling into the exiting fluid and wherein the flow rate of the washing solution is increased from zero after a certain amount of time. 
     
     
         21 . The method of  claim 16 , wherein after a predetermined total volume of washing solution has been used, the output signal of the optical sensor is compared with a predetermined threshold value indicative of the amount of free Hgb in the exiting fluid. 
     
     
         22 . The method of  claim 21 , wherein an additional amount of washing solution is flowed into the centrifuge bowl if the output signal does not meet the threshold value indicative of the amount of free Hgb in the exiting fluid. 
     
     
         23 . The method of  claim 16 , wherein the optical sensor measures the transmission of light. 
     
     
         24 . The method of  claim 16 , wherein the optical sensor measures the reflection of light. 
     
     
         25 . The method of  claim 16 , wherein the optical sensor measures light having a wavelength in the range from 530 to 580 nm. 
     
     
         26 . The method of  claim 25 , wherein the optical sensor measures light having a wavelength of 565 nm. 
     
     
         27 . The method of  claim 16 , wherein the optical sensor comprises a light emitting diode. 
     
     
         28 . The method of  claim 16 , wherein the optical sensor measures only one wavelength of light. 
     
     
         29 . The method of  claim 16 , wherein the undesirable elements comprise at least one of free Hgb, cellular debris, clotting proteins, activated platelets, coagulation byproducts, and anticoagulant. 
     
     
         30 . The method of  claim 29 , wherein the undesirable elements comprise free Hgb. 
     
     
         31 . The method of  claim 16 , further comprising reinfusing at least one of the components into the patient. 
     
     
         32 . The method of  claim 16 , wherein the washing solution is a saline solution.