Biomedical Engineering Reference
In-Depth Information
Reservoir
Pump
Oxygenator
Heat
exchanger
From patient's
heart
To patient's
heart
Figure 1.4
Mobile heart-lung machine.
through the coronary vessels. The surgeon is thus enabled to open the heart and
make the necessary repairs while the heart is not obstructed by blood. During the
surgical procedure, the heart-lung machine is operated by a perfusionist whose role
is to maintain the circuit, adjust the flow as necessary, prevent air from entering the
circulation, and maintain the various components of the blood within physiologic
parameters.
Ideally the heart-lung machine has to meet many requirements including:
1. The transfer of adequate oxygen;
2. Blood flow rates that approach normal without danger of air;
3. The maintenance of a stable blood volume and body metabolism without
significant change in pH, blood pressure, and body temperature;
4. A lack of serious damage to blood elements.
The efforts to bring this concept into reality began many decades ago. At the
end of the nineteenth century, many experiments by physiologists such as von
Schroder, the German scientist who developed the oxygenator, Max von Frey, Max
Gruber, who described the artificial blood oxygenation flow system, and C. Jacobj,
who developed the apparatus that relied on donor lungs for gas exchange, laid the
foundation for different artificial oxygenation devices.
The pump component of the heart-lung machine circuitry serves a major func-
tion of providing blood flow through the circuit and maintaining an artificial cir-
culation throughout the body. The pump found in the heart-lung machine uses a
roller that progresses along a blood-containing resilient tube propelling the blood
column in front of the roller and propelling out of the pump. A roller pump (also
