Systems and methods for sensing red blood cell hematocrit

Abstract

Red blood cell sensing systems and methods rely upon straightforward measurement geometries. the systems and methods comprise an incident light source, an optical sensor, and a blood collection tube. The systems and methods hold the blood collection tube a predetermined radial distance from the incident light source where a linear relationship exists between sensed reflected light measured by the optical sensor and red blood cell hematocrit in a range of at least 10 to 90. The systems and methods make possible accurate red blood sensing without use of special optical cuvettes, mirrors, or focusing lenses. The systems and methods also make possible the use of standard transparent plastic tubing, without reliance upon special optical cuvettes.

We claim:  
     
         1 . A blood processing system comprising 
 a separation chamber for processing blood to obtain a blood suspension containing a quantity of red blood cells,    a sensing assembly outside the separation chamber to optically sense presence of red blood cells, and    a fluid circuit including an umbilicus coupled to the separation chamber, a blood inlet tube extending beyond the umbilicus outside the separation chamber for conveying a flow of blood into the umbilicus, a component collection tube extending beyond the umbilicus outside the separation chamber for conveying a flow of the blood suspension from the umbilicus, and a fixture including a holder to hold the blood inlet tube and the component collection tube in an adjacent, spaced-apart relationship for handling as a bundle outside the separation chamber, the fixture being movable into releasable engagement with the sensing assembly outside the separation chamber to hold the component collection tube within the holder in a predetermined relationship with the sensing assembly so that presence of red blood cells in the component collection tube can be sensed.    
     
     
         2 . A blood processing system according to  claim 1   wherein the fixture directs the blood inlet tube and the component collection tube through a bend without substantial kinking.    
     
     
         3 . A blood processing system according to  claim 1   further including a controller communicating with the sensing assembly to control flow of blood suspension through the component collection tube in response to sensing by the sensing assembly.    
     
     
         4 . A blood processing system comprising 
 a separation chamber for processing blood to obtain first and second blood suspensions,    a sensing station outside the separation chamber including a first sensor assembly that operates to optically monitor presence of at least one blood component in the first blood suspension, and a second sensor assembly that operates to optically monitor presence of at least one blood component in the second blood suspension,    a fluid circuit including an umbilicus coupled to the separation chamber, a blood inlet tube extending beyond the umbilicus outside the separation chamber for conveying a flow of blood into the umbilicus, a first component collection tube extending beyond the umbilicus outside the separation chamber for conveying a flow of the first component from the umbilicus, and a second component collection tube extending beyond the umbilicus outside the separation chamber for conveying a flow of the second component from the separation chamber, and    a fixture including a holder to hold the first component collection tube and the second component collection tube in an adjacent, spaced-apart relationship for handling as a bundle outside the separation chamber, the fixture being movable into releasable engagement with the sensing station to hold the first component collection tube and the second component collection tube within the holder in predetermined relationships with the first sensor assembly and the second sensor assembly, respectively, so that so that presence of blood components in the respective first and second component collection tubes can be sensed.    
     
     
         5 . A blood processing system according to  claim 4   wherein the fixture directs the first and second component collection tubes through a bend without substantial kinking.    
     
     
         6 . A blood processing system according to  claim 4   wherein the holder holds the blood inlet tube for handling as a bundle outside the separation chamber with the first and second component collection tubes.    
     
     
         7 . A blood processing system according to  claim 4   further including a controller communicating with the first and second sensing assemblies to affect flow of first and second blood suspensions through the first and second component collection tubes in response to sensing by the first and second sensing assemblies.    
     
     
         8 . A blood processing system according to  claim 1  or  4  
 wherein the fixture comprises an integral part of the fluid circuit.  
 
     
     
         9 . A blood processing system according to  claim 1  or  4  
 wherein the fixture is a separately fabricated part of the fluid circuit.