Biomedical Engineering Reference
In-Depth Information
4.28
A person is performing a physical work at a rate of 250 N.m/s. Assume all
the physiological work is derived from protein metabolism in the muscle. The
breathing rate is 15 breaths/minute and each breath has a volume of 0.5L. As-
sume air contains a 21% volume fraction of oxygen.
(a) If the efficiency of conversion of physiological work to physical work is
25%, what is the amount of oxygen required?
(b) Is there sufficient oxygen?
(c) If the breathing rate is increased to 20, what volume of air is required to
achieve the desired work?
4.29
Consider the model of the heart as a pump. The right side takes blood return-
ing from the veins at almost 0 mmHg and discharges blood toward the lungs
at 15 mmHg. The left side takes blood in from the lungs at 6 mmHg and
discharges it to the systemic circulation at about 90 mmHg. Assuming the
steady-state operation, apply the macroscopic energy balance over the heart
to estimate the rate of work done by the heart. Assume viscous losses
l
V
are
small.
4.30
Verkerke et al. [11] performed numerical simulation of a pulsatile catheter
(PUCA) pump which is a type of LVAD that could be mounted outside quickly.
It consists of a single port membrane pump and a valved catheter, which is
introduced into an easily accessible artery and positioned with its distal tip
in the left ventricle. The pump aspirates blood from the left ventricle during
systole (thus unloading it) and ejects into the ascending aorta during diastole,
which ensures an adequate blood supply to the coronary arteries. To provide
all organs with an adequate pulsatile blood flow, a pump output of 5 L/min
is required. What is the pressure in the pump required for the aspiration and
ejection when the pump is synchronized with a 70 beats per minute heart and
bears a 100% load? 60% load?
The following data are known. The mean aortic pressure is 65 mmHg, and
mean left ventricular pressure is 38 mmHg. Flow resistances caused by diam-
eter changes from the membrane pump to the catheter during aspiration
Kc
=
0.5. Mean flow resistance in the valve during
aspiration appeared to be 3.0, and during ejection, 3.2. Furthermore,
fV
2
/2g
can be approximated by 0.096
1.0 and during ejection
Kc
=
−
0.0157*log
10
(Re). The catheter is 0.5m long.
4.31
The Jarvik 2000 heart is a compact axial flow impeller pump positioned in-
side the ventricle with an outflow graft for anastomosis to the descending
aorta. The pump rotor contains the permanent magnet of a brushless direct
