Abstract

Method and apparatus are disclosed for controlling dialysis and ultrafiltration. Precision control over the operation of an artificial kidney (dialyzer), particularly the removal of waste water by ultrafiltration, is achieved by the use of two pumps in the respective paths to and from the artificial kidney. One of the pumps may be operated at constant speed and the other at a variable speed under control from a level sensor at the storage tank, whereby a prescribed rate of ultrafiltration is maintained by a third pump. If desired, the pumps may be operated at complementary speeds so that as the speed of one is increased, the speed of the other is decreased, maintaining a prescribed rate of ultrafiltration by a third pump, under the control of the level sensors at the tank. A further feature provides automatic switching back and forth between two storage tanks of blood cleansing fluid (dialysate) in conjunction with the two pumps in the respective paths to and from the artificial kidney.The fluid systems are open to the atmosphere rather than being physically enclosed. The maintenance of an essentially constant volume of blood cleansing fluid (dialysate) within the apparatus is dependent upon the use of feedback control of the relative pump speeds derived from a fluid level sensor within the open dialysis liquid tank.