John Gibbon MD, from Boston, Massachusetts, invented the cardiopulmonary bypass procedure and performed the first intracardiac repair using extracorporeal perfusion in 1953. His bubble oxygenator, which looked surprisingly like a computer, was manufactured and financed by IBM; this achievement stimulated rapid development of the knowledge base and equipment necessary for accurate diagnoses of cardiac disease and successful intracardiac operations.
It was recognized that the main problems with film oxygenators were (1) poor efficiency, (2) excessive hemolysis, (3) large priming volumes, and (4) the development of bubbles and foam in the blood. All designs required blood flows of 2.2 L/m2/min, usually three to four units of blood for priming, and another two units of blood for the rest of the circuit. Furthermore, after each use, the machine had to be broken down, washed, rinsed in hemolytic solutions, reassembled, resterilized, and reconfigured.
During this era, Richard DeWall came to work at the University of Minnesota, initially, as an animal attendant in Lillehei's research lab. DeWall would manage the pump while the anesthesiologists would take breaks, and soon he began to take an interest in the problems associated with oxygenating blood. Eventually, Lillehei challenged DeWall to find a way to eliminate bubbles in the procedure. Subsequently, DeWall produced
a huge technological breakthrough in 1955 by developing a bubble oxygenator with a unique method for removing bubbles from the freshly oxygenated blood (Fig. 7). In DeWall's design, blood entered the bottom of a tall cylinder along with oxygen passed through sintered glass to create bubbles. As the bubbles and blood rose, gas exchange occurred at the surface of each bubble. At the top of the cylinder, arterialized bubble-rich blood passed over stainless steel wool coated with silicone antifoam; it then traveled through a long helical settling coil to allow bubbles to rise slowly and exit the blood.
Two important components in the Lillehei-DeWall bubble oxygenator were the tubing and the silicon antifoam solution. The tubing was Mayon polyethylene tubing (typically used in the dairy industry and in the production of mayonnaise), available from Mayon Plastics (Hopkins, MN), with a company chief executive officer who was a classmate of Lillehei's and a graduate of the university's chemical engineering program. The silicone antifoam solution, Antifoam A, was used to coat the tubing to prevent foaming of the liquids transported.
The oxygenator was wonderfully efficient; animals (and later patients) did not show detectable effects of residual gas emboli. More important, this design eventually led to the development of a plastic, prepackaged, disposable, sterile oxygenator that replaced the expensive stainless steel, labor-intensive screen, and film devices. An economic and reliable oxygenator had arrived, and the medical industry began to use disposable components for the heart-lung machine.
Two years after its introduction, the DeWall-Lillehei bubble oxygenator had been used in 350 open heart operations at the University of Minnesota. DeWall steadily improved the device through three generations of models, but it remained a very simple, disposable, and heat-sterilizable device that could be built to accommodate only the amount of blood required for each patient and then discarded.
In 1956, another one of Lillehei's residents, Vincent Gott, invented a bubble oxygenator in which DeWall's helix design was flattened and enclosed between two heat-sealed plastic sheets (Fig. 8). This sheet bubble oxygenator proved to be the key to subsequent widespread acceptance of the device for open heart surgery because it could be easily manufactured and distributed in a sterile package; it was inexpensive enough to be disposable. The University of Minnesota licensed rights to manufacture and sold the device to Travenol Inc. (Minneapolis, MN). With the bubble oxygenator and techniques developed by Lillehei and his colleagues, the University of Minnesota had become prominent for the making open heart surgery possible and relatively safe (4).
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.