Treating and monitoring water for dialysis in Europe.

The quality of water used for dialysis is not subject to any mandatory regulations in most European countries. A survey of haemodialysis facilities in 14 countries carried out by the European Dialysis and Transplant Nurses Association/European Renal Care Association (EDTNA/ERCA) showed that the majority of centres aimed to meet the requirements of the European Pharmacopoeia, but only 50% carried out tests to check compliance. The wide variation in policies for maintaining and monitoring the equipment and the distribution system indicates that guidelines for water treatment are urgently needed in Europe.

Simulating the effect of exercise on urea clearance in hemodialysis.

A two-compartment model of urea kinetics during hemodialysis is used to predict the effect of exercise on hemodialysis dose. It is assumed that the two compartments represent tissues that are perfused by low and high blood flows (initially 1.1 L/min and 3.8 L/min). The effect of changing the distribution of flows between the compartments, emulating the effect of exercise, is simulated using the model equations for a range of dialyzer clearances. Compartmental volumes are assumed constant (33.4 L and 8.6 L for low- and high-flow compartments, respectively). The analysis identifies muscle perfusion as a rate-limiting factor during the later stages of hemodialysis and illustrates the benefit of exercise during this phase in increasing dialysis efficiency. The model suggests that the postdialysis rebound in the blood urea concentration is eliminated by increasing flow to the low-flow compartment from 1.1 L/min to 7.1 L/min and sustaining this for at least 30 min of a 150-min dialysis session, independent of the dialyzer clearance. Additional exercise will not increase the dialysis dose. Experimental studies are required to confirm the analysis.

Monitoring body fluid distribution in microgravity using impedance tomography (APT (applied potential tomography)).

For an astronaut, the excitement of going into orbit is accompanied by a shift of 1 to 1.5 l of fluid from the legs into the upper body. Information on the way the redistributed fluid is handled by the body is very useful to space physiologists studying the process of adaptation to zero-gravity. Applied potential tomography (APT) can be used to image changes in fluid distribution. To ensure that the technique was capable of measuring fluid shifts induced by changing gravitational forces on the body, a standard Sheffield APT system was used to study several subjects during the eight ESA parabolic flight campaign. The results clearly demonstrated the feasibility of using APT for monitoring fluid redistribution during space flight. A battery-powered, body-worn APT system has now been developed for use in space. The equipment was tested on the eleventh parabolic flight campaign. The data collected with the miniaturised system was comparable to that obtained in the earlier experiment. Ergonomic tests indicated that the equipment is no more difficult to operate and maintain under weightless conditions than on earth. The system is undergoing space qualification tests in Munich. If no problems arise it will be used by German astronauts on missions to MIR and Skylab.