Patent ID: 7162290

Claim:
Apparatus for periodically and automatically testing a patient's blood glucose level, comprising: a disposable testing unit, a first infusion line having first and second ends connected at said first end to a catheter in a blood vessel of said patient and at said second end to said disposable testing unit, a second infusion line having first and second ends wherein said first end is connected to a source of infusion fluid and said second end is connected to said disposable testing unit, and a reversible peristaltic pump connected to said second infusion line, said pump adapted to either pump infusion fluid forwardly through said first and second infusion lines and said disposable testing unit into said patient blood vessel, to stop pumping, or to pump infusion fluid and blood backwardly from said patient blood vessel into and through said disposable testing unit, said disposable testing unit having a testing chamber in fluid communication with said infusion lines, a blood glucose testing means, and fluid opacity sensing means for sensing the opacity of said infusion fluid and blood pumped backwardly through said testing chamber wherein fluid opacity sensing means comprises a first light source and a first photodetector positioned adjacent a first end of said testing chamber and a second light source and a second photodetector positioned adjacent a second end of said testing chamber and for determining when said testing chamber is filled with undiluted blood from said patient blood vessel by comparing outputs from said first and second photodetectors, and when said outputs are equal and sufficiently great to indicate the presence of blood, an undiluted sample is present in said test chamber.