Biomedical Engineering Reference
In-Depth Information
goal of complete attenuation of infl ammation and ischemia-reperfusion
injury following CPB remains elusive.
2
This chapter discusses the employment and development of novel extra-
corporeal technologies as well as clinical applications in cardiovascular
surgery to aid in understanding the current state-of-the-art and future direc-
tions of CPB.
6.2
Historical development of
cardiopulmonary bypass
In 1931, John Gibbon began to think of means to bypass the heart and
lungs to permit safe entry and exit from the pulmonary artery. He and
his wife Mary began work in Dr Edward Churchill's laboratory in Boston
in July 1934 and, by the end of the year, they had built the fi rst heart-
lung machine from rubber, glass, homemade valves, a rotating cylinder,
fi nger cots and assorted laboratory air pumps and paraphernalia. There
were separate venous and arterial pumps composed of fi nger cots within
pressure chambers driven by mechanical pumps. They solved the problem
of obstructed venous return by an elaborate electromagnetic clamp, kept
the blood fl uid with newly available heparin, warmed the circuit by mul-
tiple water jackets, and ventilated the blood by a rotating cylinder oxy-
genator that they invented. In 1950, Bigelow and colleagues introduced
hypothermia for correction of heart defects. Sealy, Brown and Young
added a heat exchanger, developed with the help of the radiator unit of
General Motors, to the extracorporeal circuit and inaugurated perfusion
at reduced fl ow rates at 28-30 °C in 1958. Nazih Zuhdi and colleagues
introduced hemodilution in 1961. DeWall made a huge advance in 1955
by developing a bubble oxygenator with a unique method for removing
bubbles from the freshly oxygenated blood. Soon, engineers developed
polycarbonate microporous membranes with 25 mm pores that dramati-
cally improved gas exchange across the membrane. These membranes
were made into hollow fi bers and the resulting oxygenator was combined
with a heat exchanger into one disposable, sterile unit. In the 1970s,
membrane oxygenators replaced bubble oxygenators in the United
States.
3
A wide range of these biomaterials have been employed in CPB over
the years including polypropylene, polycarbonate, polyurethane, polyes-
ter, polyamide, polyvinyl chloride, silicone, stainless steel and aluminum.
These basic materials have altered little over the years, and are present
in the perfusion circuit over very large surface areas. The expanse of
materials employed varies depending on the complexity of the circuit, but
estimates of total surface area vary between 3.5 and 21 m
2
for adult
systems.
4
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