This invention relates to artificial kidney systems; and more particularly, to a proportioningtype dialysis machine for use in such systems.
In an artificial kidney system, a dialysis machine delivers dialysis solution under carefully controlled conditions to a dialyzer or artificial kidney. There are two basic types of dialysis machines. One is known as a batch-type machine and the other is a proportioning or continuous feed machine.
In both types of machines dialysis concentrate is mixed with water to provide the dialysis solution which is delivered to the dialyzer. Both machines also include means for sterilizing the machine, a heater system for maintaining the dialysis solution at body or physiological temperature (about 37.degree. C.), a device for removing gas and minimizing gas in the dialysis solution, and means for controlling the pressure and flow rate of the dialysis solution in the dialyzer. Furthermore in proportioning machines, provisions are also made for continuously preparing the dialysis solution by mixing or proportioning the water and dialysis concentrate and for controlling the composition of the dialysis solution.
Proportioning machines are generally more compact and smaller in size than the batch-type machine. For this reason, among others, the proportioning machines have experienced increased popularity.
Existing proportioning machines generally include the required gas removers, heaters, pressure controls, etc., but have been found to be deficient in certain respects. For example, one type of gas removal system, as shown in U.S. Pat. No. 3,738,382, includes a heater for heating the water to a high temperature and a debubbling chamber for removing gas from the heated water at atmospheric pressure. This system does not effectively degass the water and the heating of the water caused dissolved minerals to precipitate and clog passageways within the dialysis machine.
A second type of gas removal system is shown in U.S. Pat. No. 3,528,550. In this system water is fed to a degassing chamber which is maintained at a pressure below atmospheric pressure by a venturi through which dialysis solution flows. Thus the pressure in the degassing chamber is directly related to the dialysis solution flow rate through the venturi. The venturi only applies a moderate negative pressure to the degassing tank and thus does not effectively degass the water.
It is therefore an object of this invention to provide an effective degassing system, and particularly for use in a proportioning dialysis machine.
In the degassing system shown in U.S. Pat. No. 3,528,550, the degassing chamber pressure may vary with dialysis solution flow rate, which, in turn, may vary with dialysis conditions, such as patient size, etc. Variations in degassing chamber pressure may affect gas removal.
It is therefore an object of this invention to provide a degassing system which functions independently of the dialysis solution flow rates.
During dialysis it is desirable to control the dialysis solution pressure in the dialyzer. However, changes in the dialysis solution flow rate through the dialyzer cause the dialysis solution pressure to vary.
It is also an object of this invention to provide means for controlling the dialysis solution pressure in the dialyzer as the dialysis solution flow rate changes.
These and other objects of this invention will become apparent from the following description and appended claims.