Biomedical Engineering Reference
In-Depth Information
heart beats, changes in the electrical potential due to this beating, and the concentrations of
various gases and nutrients in the blood. If these parameters are out of specification, then
various forms of intervention can be applied. For example, internal or external electrical
stimulation can be used to restart the heart or to maintain a regular heartbeat. In extreme
cases, if the heart has been damaged mechanical pumps can augment its capability or even
replace it completely. This chapter documents some of these applications.
8.3
HEART-LUNG MACHINES
The purpose of a heart-lung machine is to remove oxygen-poor blood from the right side
of the heart and return oxygen-rich blood to the left side. This bypasses the heart and lungs
and allows the heart to be stopped for short periods, allowing surgery to take place.
8.3.1 History
The first heart-lung machine was built by physician John Gibbon in 1935 and is shown in
Figure 8-6. He is therefore considered the inventor of the heart-lung or pump oxygenator.
This experimental machine used two roller (peristaltic) pumps and had the capacity to
replace the heart and lung action of a cat and keep it alive for 26 minutes. Further work
on the device was postponed by WWII.
Gibbon joined forces with Thomas Watson in 1946 when Watson, an engineer and the
chair of IBM, provided the financial and technical support for Gibbon to further develop his
heart-lung machine. Gibbon, Watson, and a number IBM engineers designed an improved
machine that minimized hemolysis and prevented air bubbles from entering the circulation.
The new device used a refined method of cascading the blood down a thin sheet of film for
oxygenation rather than the original whirling technique, which could potentially damage
blood cells. Using the new method, 12 dogs were each kept alive for more than 1 hour
FIGURE 8-6
The
first heart-lung
machine. (Courtesy
of the Mayo Clinic.)
