Appeal No. 95-3830
Application No. 07/942,460
deduced from the fresh and used liquid pressure measured by
sensors 94 and 96, the above-quoted text of Shouldice et al.
merely suggests calculating the actual transmembrane pressure and
then comparing it with a predetermined transmembrane pressure to
see if it is too high.
Based on the foregoing, we find that the examiner has
equated determining the general transmembrane pressure to
calculating an actual clearance of the artificial kidney for a
type of impurity. That is erroneous.
Consistent with the appellant's specification (see pages 14-
15), regarding artificial kidneys the "clearance" for a type of
impurity is based on the concentration of substances in the
blood, on the flow rates of blood and the dialysis liquid in the
exchanger, and on the membrane characteristics of the exchanger.
It concerns the efficiency for removing the type of impurity.
For instance, in the appellant’s preferred embodiment (pages 14-
15), conductivity of the dialysis liquid is measured, based on
which the concentration of ionized substances, predominantly
sodium, is calculated, and then through extrapolation and known
rules of correspondence the "clearance" of urea is determined
based in part on the characteristics of the exchanger and the
flow rates of the blood and dialysis liquid. Alternatively, the
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