Temperature Based Dialysate Regneration
TBDR is a temperature-based dialysate regeneration unit. It regenerates used dialysate by physical adsorption and constitutes the essential part of the portable hemodialysis system.
1. Clinical Application
TBDR is the dialysate regeneration device based on cold dialysate adsorption. TBDR can be combined with conventional hemodialysis devices to regenerate dialysate. In particular, TBDR has also been designed to be connected with HBK such that HBK with TBDR can be used for portable hemodialysis at home or while traveling.
2. Core Component and Technologies: TBDR
It is crucial to regulate the temperature of dialysate to perform cold dialysate adsorption. TBDR employs a Joule-Thomson refrigerator for this purpose. Specifically, the refrigerant used for the J-T refrigerator of TBDR is a mixture of HFC, HCFC or HC refrigerants.
The adsorbent (such as activated charcoal) can adsorb molecules of diverse sizes. However, an adsorption efficiency of small-sized molecules including urea nitrogen existing largely in the used dialysate is substantially low. However, it has been reported that the adsorption rate of the urea nitrogen by an activated charcoal can be increased by lowering the dialysate temperatures (termed cold adsorption), and as a result trials have been conducted to regenerate spent dialysate based on the cold adsorption.
However, there is a big hurdle in the effort to achieve the large variation in the dialysate temperature using conventional refrigeration equipment. One effort has also adopted a Peltier device to adjust dialysate temperature. Despite its advantages such as a lower noise level (owing to the absence of mechanical parts), the Peltier device was deemed implausible to accomplish the large variation of dialysate temperature in real time. Otherwise, the Peltier device should be enlarged to achieve such a large temperature variation. The disadvantage of being a large-sized dialysate regeneration device cannot pursue the objectives of a small and light-weighted dialysate regeneration apparatus which is essential for portable hemodialysis devices.
To overcome such a limitation, TBDR adopts a mixed-refrigerant J-T cooling method. The mixed refrigerant is known to efficiently enhance heat transfer due to its wide range of latent heat used in the evaporator and the condenser. As such, the TBDR unit could eventually be formed in a miniaturized lap-top size that is small enough to make a true portable hemodialysis system.
A circuit diagram of TBDR combined with HBK is illustrated below.
The advantage of dialysate regeneration with TBDR is not merely limited to having hemodialysis devices portable or miniaturized. It also contributes to preventing physiologic molecules from being lost from the body. Dialysate possesses a physiologic balance of electrolytes after taking into account preexisting deficits or excesses of patients. In addition, the used dialysate has a composition similar to that of plasma and contains polypeptides and other beneficial substances, such as, hormones and amino acids. As dialysate passes through the adsorbent column, solutes with a wide spectrum of molecular weights are adsorbed, but electrolytes, bicarbonate and/or amino acids freely pass through the column. The regenerated dialysate allows these beneficial nutrients to be reinfused.