Biomedical Engineering Reference
In-Depth Information
(a) Calculate the resistances of the three lobes in CGS units.
(b) If they are considered to be in parallel, what is the net resistance to flow?
4.11
Calculate the flow resistance in a 6-mm capillary. In the capillary, the Fah-
raeus-Lindqvist effect dominates, hence you need to use the actual viscosity.
Assume the central-blood viscosity to be 8 cP and the cell-free plasma layer
thickness to be 1 mm. If you were to ignore the Fahraeus-Lindqvist effect and
calculate the flow resistance using viscosity of blood to be 3 cP, what is the
change in resistance?
4.12
A cardiac patient undergoes bypass surgery in which an artery is replaced by
one that is 10% larger in diameter. What is the percentage change in blood
flow in the artery, assuming all other factors remain the same?
4.13
In Example 4.2, if there the air is flowing in the upward direction at 1 m/s,
then how would it affect the settling velocity? If a person has 15 breaths per
minute, will the particle settle or come out? How would you alter the settling
properties?
4.14
In Example 4.5, if the flow is pulsatile (1-Hz frequency), how would the wall
shear stress change? What is the St number? What information is required to
calculate the pressure drop during a cycle of systole and diastole?
4.15
One of the areas of toxicology is understanding how a workplace affects the
health of a person, particularly those working in locations where the process
emits particle into the air. In one of the study sites, the process emits 20-mm
rectangular particles (density
2.0 gm/cm
3
) into the air. A person working in
that area breaths at 16 breath/min and has a 25-cm-long trachea of a 25-mm
diameter. The tidal volume is 6 L/min. Will the particle settle in the bottom of
the trachea:
=
(a) When the air flow rate is neglected?
(b) When the air flow rate is included?
4.16
If blood is flowing at 3 L/min in a 20-mm artery at an average pressure of 110
mmHg, what is the drag force experienced by a white blood cell of a 15-
m
diameter? The density of the white blood cell is 1.10 gm/cm
3
. If the thickness
of the cell is 5
μ
μ
m, then what is the change in the drag coefficient?
4.17
A person is 6 feet tall and his heart is located 2 feet from the top of the head. If
the flow resistance to the top of the head and bottom of the foot are 5 mmHg,
and arterial pressure near the heart is 110 mmHg, calculate the pressure in a
location if the person is standing (orthostatic position) or if the person is lay-
ing flat (supine position). If the pressure in the venous pressure near the hear
is 75 mmHg, which way would blood flow?
4.18
Blood is flowing through a blood vessel of 6-mm in diameter at an average ve-
locity of 50 cm/s. Let the mean pressure be 100 mmHg. Assume blood density
to be 1.056 gm/cm
3
and viscosity to be 3 cP.
(a) If the blood were to enter a region of stenosis where the diameter of the
blood vessel is only 3 mm, what would be the approximate pressure at the
site of narrowing?
