Abstract: A user interface for a medical instrument such as a dialysis machine is described which uses both a touch screen and at least one hard key off of the touch screen to effectuate a change in a parameter associated with the operation of the machine or the treatment session. The user interface is connected to a central computer control system having a host microprocessor and a backup safety microprocessor. The hard key is directly wired to the safety microprocessor. After the user selects a new parametric value on the touch screen, the user presses a hard key. The host and safety microprocessors implement a verification routine to insure that the entered parameter is appropriate for the patient's treatment and the display on the touch screen. If the verification procedure ends in a positive result, the user is prompted to presses a second hard key to confirm the change, causing an additional verification check to be preformed.

Abstract: A user interface for a medical instrument such as a dialysis machine is described which uses both a touch screen and at least one hard key off of the touch screen to effectuate a change in a parameter associated with the operation of the machine or the treatment session. The user interface is connected to a central computer control system having a host microprocessor and a backup safety microprocessor. The hard key is directly wired to the safety microprocessor. After the user selects a new parametric value on the touch screen, the user presses a hard key. The host and safety microprocessors implement a verification routine to insure that the entered parameter is appropriate for the patient's treatment and the display on the touch screen. If the verification procedure ends in a positive result, the user is prompted to presses a second hard key to confirm the change, causing an additional verification check to be performed.

Abstract: Water treatment and pretreatment methods and processes for use in a dialysate preparation machine are described. In one aspect, water is passed through a first filter having chlorine removal properties and then passed into a line. Water is removed from the line at a sample location. The removed water is periodically sampled for the presence of chlorine or chloramines. The presence of chlorine or chloramines indicates that the filtration capacity for chlorine of the first filter is substantially exhausted. The method further includes the step of filtering the water downstream from the sample location in a second filter having chlorine removal properties, and replacing the first filter if chlorine or chlorine is detected during the sampling step. Water pretreatment may be provided by mixing hot and cold water from a source with a temperature-controlled mixing valve and passing the water through the first filter, so as to provide warm, filtered water to the dialysate preparation machine.

Abstract: A method is described for determining the sodium clearance of a dialyzer. Dialysate containing sodium ions is circulated through the dialysate side of the dialyzer. Water is continuously circulated through the blood side of the dialyzer, the water being single passed through the blood side of the dialyzer. Measurements of the conductivity of the dialysate are made prior to the dialysate entering the dialyzer, and measurements of the conductivity of the dialysate are made after the dialysate has passed through the dialyzer. The clearance of the sodium ions by the dialyzer is calculated from the measurements of conductivity. The measurements of conductivity of the dialysate after passing through the dialyzer becomes substantially constant as the dialysate and water are circulated through the dialyzer. The sodium clearance corresponds to urea clearance of the dialyzer, since the two molecules are approximately the same size.

Abstract: A method is described herein for automatically rinsing blood back to a patient. The method comprises the steps of pumping dialysate (or, alternatively, saline solution) through a dialyzer into an extracorporeal circuit, and pumping blood in the extracorporeal circuit out the arterial and venous lines back to the patient. Optical sensors monitor the concentration of blood in the arterial and venous lines as the blood is being pumped from the extracorporeal circuit back to the patient. The return flow of blood is ceased when the concentration of blood in the arterial and venous lines drops to a predetermined threshold level, thereby preventing excess fluids from being returned to the patient.

Abstract: A dialysis machine is described which provides for the detection of leakage anywhere in the machine. The machine includes integral water treatment, dialysate preparation and extracorporeal circuit modules. The floor of the machine is constructed in a non-horizontal manner so as to provide a fluid catchment chamber with a fluid sensor. The extracorporeal circuit is mounted above the dialysate preparation module and the water treatment module. In one embodiment, a drain and drain tube allows fluid that leaks from the extracorporeal circuit module to be conducted to the floor of the machine, where the leak can be detected, along with a fluid leak in the water treatment or dialysate preparation modules. In another embodiment, a separate fluid leakage detector is placed at the base of the extracorporeal circuit module for detection of leakage in situ in the extracorporeal circuit, while the catchment chamber and sensor in the base of the machine detect leaks from the other modules.

Abstract: A method is described for automatically testing the integrity of a dialyzer filter within a dialysis machine. The method consists of substantially removing fluids which may be present from the blood side of the dialyzer filter, pumping air into the blood side of the dialyzer filter with a blood pump to pressurize the dialyzer filter, and measuring the pressurization of the dialyzer filter. If the dialyzer filter pressurizes, the rate of decay of pressurization is measured. The pressurization and rate of decay are indicative of the integrity of the membrane of the dialyzer filter.

Abstract: A vessel storing a batch of chemicals for delivery into a dialysate preparation tank includes a machine readable indicator, permitting automatic identification of the contents of the vessel prior to operating the vessel and introduction of chemicals into a tank where the dialysate solution is mixed. Various types of machine-readable indicators may be used, such as, for example, "touch" memory buttons, bar codes, or magnetic strips. Suitable reading devices for the machine-readable indicators are provided for reading the contents of the bottle.

Abstract: A method for maintaining separation of old and new dialysate in a dialysate preparation tank is disclosed. The new dialysate is stored in the tank at a first temperature and withdrawn from the bottom of the tank. The dialysate is circulated through a dialyzer, and then returned to the tank at the top of the tank at a higher temperature in a substantially non-turbulent manner. The temperature differential between old and new dialysate and the manner of withdrawing and reintroducing the dialysate to the tank cooperate to form discrete zones of old and new dialysate without substantial mixing of the dialysate in the two zones.