An artificial kidney is a device that removes water and waste products from the blood. One kind of artificial kidney is a hollow fiber hemodialyzer. Arterial blood flows through a bundle of cellulose acetate tubes and dialyzing fluid (water with dissolved salts) flows around the outsides of the tubes. Water, urea, creatinine, uric acid, and phosphate ions pass through the cellulose acetate into the dialyzing fluid and clean blood is returned to the patient's body. Operational data is given below.
|
Arterial (entering) blood
|
Venous (exiting) blood
|
|
Flow rate
|
200.0 ml/min
|
195.0 ml/min
|
|
Urea concentration
|
1.90 mg/ml
|
1.75 mg/ml
|
a) Calculate the rates at which urea and water are being removed from the blood.
b) If the dialyzing fluid enters at a rate of 1500 ml/min, calculate the concentration of urea in the dialysate.
c) Suppose we want to reduce a patient's urea level from 2.70 mg/ml to a final value of 1.1 mg/ml. If the total blood volume is 5 L how long will it take? You may assume negligible change in blood volume.