8. Ultrafiltration
8. ULTRAFILTRATION
8.1 OVERVIEW
The Arena Instrument accurately controls fluid removal. A
volumetric flow equalizer controls and balances dialysate to and
from the dialyzer. The volume of fresh dialysate measured and
delivered to the dialyzer by the predialyzer side of the flow
equalizer is equal to the volume of used dialysate removed from
the dialyzer by the postdialyzer side of the flow equalizer. In the
following discussion and graphics, the terms "predialyzer" and
"postdialyzer", when referring to one side or the other of the Flow
Equalizer, will be shortened to "pre" and "post".
Figure 8-1. Volumetric Control
Between the balanced "pre" and "post" flow equalizer
compartments are two openings. One is the dialyzer membrane
surface; the other is the UF flow meter. The UF flow meter is
controlled by the UF-Proportioning Controller board to remove a
known or calibrated amount of spent dialysate from the dialysate
compartment. The fluid removed by the UF flow meter causes an
identical amount of fluid to be removed from the blood side of the
dialyzer. Since the flow equalizer balances the dialysate flowing
to and from the dialyzer, the fluid going through the UF flow meter
is equivalent to the ultrafiltrate removed from the patient
157-1278-915 Rev A 8-3
January 2004
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