Aksys Gmbh

Derek Wiebenson

Dilip H Shah

Tom L Brose

Shincy Maliekkal

Rodney S Kenley

A method of calibrating a dialysis machine to determine the volume of a dialysate flow path of the machine including a dialysate preparation tank includes the steps of introducing a known quantity of electrically conductive chemicals into the dialysate preparation tank, filling the dialysate solution flow path with water, mixing the chemicals with water to form a solution, measuring the conductivity of the solution, calculating the system volume (V,) according to the relation: V,&equals;M/(a,r&plus;b,) where M is the mass in grams of the chemicals, a,and b,are a coefficient of linearity and a constant of linearity, respectively, for the chemicals and r is the measured conductivity of the solution.

Method of determining system volume of a dialysis machine

A method of disinfection of a dead-ended fluid line in a medical instrument such as a dialysis machine is described. The method comprises introducing a heated fluid into the fluid line, allowing the fluid to remain in the line for an experimentally determined optimal dwell period, removing the fluid from the fluid line, and then repeating the cycle for a time period sufficient to achieve a disinfection of the fluid line. The optimum dwell period and frequency for exchanging the heated fluid is determined so that the heated fluid is left resident in the line to exert a cidal effect but not so long that the it cools to the point of being ineffective, nor changed so frequently that that the time spent with no hot water resident in the line begins to detract (e.g., unduly prolong) the disinfection process. A representative cycle is introducing water at a temperature of about 85 degrees C, allowing it to reside in the fluid line for about 10 seconds, withdrawing the water, and then reintroducing water at 85 degrees C. The process continues for 1-2 hours. Variation from the representative cycle will be expected based on parameters such as the degree to which disinfection is to be achieved, the length and diameter of the fluid line, the temperature of the fluid, the ambient temperature, the presence of elements in the fluid line that contribute to heat loss, the material used for fluid line tubing, and whether the fluid comprises water or a disinfection solution such as a dilute citric acid solution. The optimum dwell period and frequency of the cycles can be determined experimentally from the teachings described herein.

Disinfection of dead-ended lines in medical instruments

A batch of dialysate solution is made from a mixture of bicarbonate formulation and a liquid acid formulation. The liquid acid formulation is introduced into a dialysate tank and then removed from the tank and stored elsewhere, such as in an ultrafiltration tank, where it is diluted with a few litres of water. The dialysate tank is then filled with water and the bicarbonate formulation is added to the dialysate tank. The bicarbonate formulation is mixed and dissolved by circulation in a closed loop, with the liquid acid formulation kept separate. When the bicarbonate solution has been prepared, the liquid acid solution and the bicarbonate solution are mixed together and stored in the dialysate preparation tank. An additional quantity of dilution water is introduced into the dialysate system to bring the final conductivity down to the desired range. The excess dialysate solution can be used for several purposes, such as an endotoxin flush of the blood tubing set or a dialyzer clearance test.

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Palatine, IL, United States of America

Derek Wiebenson