Biomedical Engineering Reference
In-Depth Information
Table 3. Parameters used in the simulations.
Parameter Value
K
0
A
2.61
Μ
mol/min
Q
Α
180 ml/min
Q
Β
180 ml/min
C
ALB
606
Μ
mol/l
C
0,BIL
240
Μ
mol/l
resin mass 240 g
column liquid holdup 120 ml
total dialysate circuit volume 600 ml
K
C
2.1310
−7
cm/s
A
0.043
B
0.54
Superscripts
Α
and
Β
refer to blood (fiber-side of membrane module)
and albumin dialysate, respectively.
This time dependence of
K
C
can be related to the formation of an albumin skin layer on the
resin surface, that results in a further, time-increasing diffusional barrier to bilirubin transfer
to the solid phase.
The data reported in Fig. 5 were fitted using the model presented in this section. The
optimal values found for the parameters of equation (39) are:
K
C
= 2.1310
−7
cm/s,
B = 0.54
,
A = 0.043 min
−0.54
.
5.
Simulation of a Recirculating Albumin Dialysis Liver
Support Device
The models presented in the previous sections can be combined to simulate a complete
LSD, including different units. In this section, an example of this application is presented,
focusing the analysis on bilirubin detoxification.
An albumin dialysis device with recirculation and regeneration of the albumin dialysate
by adsorption on one anionic resin column is considered. This regeneration circuit is equiv-
alent to that of MARS (see Fig. 1.): actually, MARS includes also a conventional dialysis
module and an activated carbon column in the regeneration circuit, but these units have only
a minor effect on bilirubin removal.
The simulations performed were aimed at evaluating the bilirubin clearance obtained by
the device under different operating conditions. Since the analysis is focused on the device
performance, a constant-composition feed was considered for the albumin dialysis module.
Fig. 6 reports time courses of bilirubin clearance obtained with the operating conditions
reported in Tab. 3 and different albumin concentrations in the dialysate, ranging from 50 to
1500
Μ
M. As the albumin concentration in the dialysate is increased, an initial improvement
of the clearance is obtained, while at longer operating times the performance of the device
is worsened.
