This application relates to novel apparatus, which may be used in a dialysis delivery system for blood dialysis or the like and which provides a means for removing bubbles or other low density materials from a liquid, while at the same time providing pressurized, bubble-free liquid to its desired point of use.
In blood dialysis, blood is passed through a dialysis unit on one side of a membrane of cellulose or the like, and dialysis solution is passed across the other side of the membrane, containing a sufficient concentration of salt to render the dialysis solution generally isotonic with respect to the blood. During dialysis, unwanted materials such as urea, creatinine, and some water pass through the membrane from the blood into the dialysis solution, so that the dialyzer serves the function of the natural kidney in many important ways.
There are many different designs of apparatus for supplying the dialysis solution to the dialysis unit. One well-known design is the RSP Dialyzer sold by Travenol Laboratories, Inc. of Deerfield, Ill. This apparatus provides large quantities of dialysis solution to a coil-type artificial kidney, and recirculates a portion of the dialysis solution through the artificial kidney repeatedly, while constantly withdrawing a fraction of the spent dialysis solution and supplying a corresponding portion of fresh dialysis solution. This method of providing dialysis solution is commonly known as the recirculating single pass technique.
Other dialysis delivery systems which are available provide a lower quantity of dialysis solution to a Kiil-type, flat plate dialyzer or the like, in which the dialysis solution typically passes through a dialyzer in a single pass, and then is discarded.
In all instances of dialysis solution delivery to various dialyzers, it is desirable to remove air bubbles from the dialysis solution, since the air bubbles can block the capillary passages of the dialyzer and otherwise reduce its dialysis efficiency. The air bubbles are formed in particular when the dialysis solution is heated before use to a temperature which approximates body temperature, to avoid undue chilling of the patient during dialysis. As is well known, aqueous liquids which are warmed release some of the dissolved gases which are in them, to form bubbles.
It is desirable to have the capability of venting these gas bubbles to the atmosphere. However, at the same time, the dialysis solution is administered under pressure (either positive pressure, or reduced pressure caused by suction) to the artificial kidney. In both of these cases where the pressure is other than atmospheric, it becomes difficult to continuously vent the gas bubbles.
In accordance with this invention, a device is provided for separating low density materials such as gas bubbles from a liquid, and permitting the gas bubbles or the like to be vented or otherwise removed, while at the same time providing a pressurized, bubble-free liquid to the site of use, which is typically an artificial kidney.