Biomedical Engineering Reference
In-Depth Information
(c) What is the half-life of the drug?
(d) What is the plasma concentration of the drug after 5 hours?
10.8
An artificial liver is a device that utilizes cultured liver cells to replace the
metabolic function of the normal liver. One way to evaluate the performance
of the device is to measure its metabolic activity under steady state operating
conditions. Consider an artificial liver in a flow system where blood is intro-
duced to the device from an artery and returned to the body through a vein.
Blood enters and leaves the device at a flow rate of 250 mL/min. No other
fluid flows enter or leave the artificial liver; however, reactions take place. In
particular, blood glucose concentrations are measured at some particular time
and are found to be 2.00 mg/mL at the arterial inlet and 1.80 mg/mL at the
venous outlet. What is the glucose metabolic activity, measured in units of mg/
min, of the device?
10.9
In the laboratory, a group of students investigated the modeling of an artificial
kidney using a scheme shown in the following table. The thick arrow repre-
sents transport across the dialysis membrane that separates the blood fluid
from the dialysate fluid. The urea concentration (
C
U
) is also known the litera-
ture as blood urea nitrogen (BUN). The concentrations are typically expressed
as mg%, which is equivalent to mg/100 mL. Let the body fluid volume be 50L.
The relationship between the outlet
(
C
)
and inlet
(
C
)
urea concentrations
0
1
are given by
(
)
CC
=
exp
−
VF
U
U
Cl
0
1
where
V
Cl
is the clearance parameter and
F
is the inlet blood flow rate. Assume
the clearance and flow rates are constant during dialysis, but the inlet concen-
tration changes with dialysis time.
Flow Rate
(mL/min)
BUN
(mg)
Arterial (entering) blood
200
190
Venous (exiting) blood
195
175
(a) What is the clearance for the device as shown?
(b) How long does it take for the patient's BUN to reach 50 mg%? How much
water is removed in this time?
10.10 Twenty mg of a PET tracer was administered intravenously to a 70-kg patient.
The plasma concentrations of the tracer are given in the following table. The
minimum plasma concentration required to cause significant enhancement of
gastric emptying is 100 ng/mL.
t(h)
12 468 0
C
P
(ng/mL)
180 136
80
43
24
14
(a) Plot the tracer concentration versus time and draw a compartmental
scheme showing the number of compartments involved.
