Biomedical Engineering Reference
In-Depth Information
simulations, linear
simulations, non-linear
experiments, mean
experiments, 25th and 75th percentiles
experiments, 10th and 90th percentiles
30
25
20
15
10
5
0
0
0.25
0.5
0.75
1
1.25
1.5
Shear stress (Pa)
Fig. 10.24.
Average rolling velocity of infected RBCs depending on the WSS in comparison with
the experiments of cell rolling on purified ICAM-1 [81]. Experimental data include mean values
and curves that correspond to the 10th, 25th, 75th, and 90th percentiles (from [51])
high shear rates. The DPD simulations suggest that the adhesive dynamics of Pf-
RBCs is not very sensitive to a moderate change (below 30 %-40 %) in
k
on
and
k
off
;
however, cell dynamics may be strongly affected if these parameters are changed
considerably. Moreover, experimental data show a much larger scatter in the aver-
age RBC velocity for different cells observed than that in simulations (not shown).
This is likely to be related to non-uniform distributions of receptors on the RBC
membrane and ligands on the wall. In the simulations, distributions of both recep-
tors and ligands are fixed and are nearly homogeneous with approximately the same
area occupied by each receptor or each ligand. A scatter in behaviour among distinct
RBCs in the simulations is solely related to the stochastic nature of the adhesive
model. However, in experiments irregular distributions of receptors and ligands are
likely to significantly contribute to a scatter in RBC adhesive dynamics.
10.5.2 Whole infected blood
Finally, we simulate blood flow in malaria as a suspension of healthy and Pf-RBCs at
the trophozoite stage and hematocrit
H
t
=
45. Several parasitemia levels (percent-
age of Pf-RBCs with respect to the total number of cells in a unit volume) from 5 % to
100 % are considered in vessels with diameters 10 and 20
0
.
m. The inset of Fig. 10.25
shows a snapshot of RBCs flowing in a tube of diameter 20
μ
m at a parasitemia level
of 25 %. The main result in Fig. 10.25(a) is given by the plot of the relative appar-
ent viscosity in malaria - a measure of flow resistance as in Sect. 10.4.2 - obtained
at different parasitemia levels. The effect of parasitemia level appears to be more
prominent for small diameters and high
H
t
values. Thus, at
H
t
=
μ
45 blood flow re-
sistance in malaria may increase up to 50 % in vessels of diameters around 10
0
.
μ
mand
up to 43 % for vessel diameters around 20
μ
m. These increases do not include any
