[Studies on the ultrafiltration in coil-type dialysers for recirculation].

Ultrafiltration in recirculating coil dialysers is discussed. The difficulty of determining the exact transmembrane pressure is stressed. The data normally available are insufficient and take no account of the direction of recirculation, which may be a determining factor. Input and output dialysing fluid pressure were measured in vitro and the respective ultrafiltration values were compared with those observed clinically. Calculation of the mean blood pressure in the dialyser circuit is examined. If determined from the simple arithmetical mean between the input and output pressure, this does not reflect the real situation inside the filter. It is thus unreliable when used to calculate the real transmembrane pressure, and hence the ultrafiltration.