Biomedical Engineering Reference
In-Depth Information
Figure 18.1 (See color insert following page 302)
ELAD artificial liver system. (Courtesy of Vital Therapies Inc,
San Diego, CA.)
clinical application of such systems is currently limited, although some of the bio-artificial liver
support systems have shown favorable clinical outcomes (Demetriou et al., 2004; van de Kerkhove
et al., 2004).
18.5
HEART AND LUNG MACHINE
A 20-year quest by John Gibbon realized the dream of building an artificial heart-lung machine,
which in turn allowed the field of open heart surgery to bloom (Gibbon, 1954). The day was May 6,
1953, when this device was first used to repair a hole in the upper chambers of the heart. Since then, the
machine has undergone several changes (Boettcher et al., 2003) from the initial disc and screen
oxygenators to De Wall bubble oxygenators and finally to the membrane oxygenators (Cook, 2004).
The modern heart-lung machine consists essentially of a venous reservoir which drains venous blood
from the vena cava system. The blood is then pumped through a membrane oxygenator and subse-
quently pumped back into the aorta to support the circulation. There is a heat exchanger incorporated
in the circuit. Over the years various sensors and safety features have been added to this system,
although the basic design has remained the same for the last few decades (Boettcher et al., 2003).
The conventional bypass machine requires considerable priming fluid which can lead to
significant hemodilution. This in turn can have adverse effects on the functioning of the cellular
components of the blood. The large surface area initiates an immune systemic response. The latest
efforts have been to miniaturize the heart-lung machine (Boettcher et al., 2003; Remadi et al.,
2004; von Segesser et al., 2003).
The widespread use of the heart-lung machine has provided an opportunity for its use in heart
failure. The earlier attempts were to use the heart-lung machine for extended time to allow the heart
to recover (FC Spencer, 1959). But they had inherent problems associated with damage to the blood
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