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About this Article
Written by: Julie Woodburn
Written on: July 17th, 2009
Tags: health & medicine, biomedical engineering
Thumbnail by: European Hospital/European Hospital
About the Author
In summer 2009, Julie Woodburn was a senior at the University of Southern California majoring in Biomedical Engineering. She became fascinated with the heart-lung machine after watching an open-heart surgical procedure as a junior in high school.
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Volume XI Issue I > Engineering the Heart-Lung Machine
Coronary bypass surgery, widely used to treat cardiovascular disease, involves redirecting a patient’s bloodflow around the heart in order to allow surgeons to operate. Heart-lung machines synthetically oxygenate and pump blood during such surgeries in order to keep the patient alive. The first heart-lung machine dates back to the 1930s and consisted of many of the same components as the machines of today. The design of each of these components is inspired by different principles of physics and engineering, including fluid dynamics and pressure gradients. Engineers are now applying these same concepts to create new heart-lung machine models such as miniaturized or portable versions. With its foundations in biology, physics, and engineering, the heart-lung machine has proven to revolutionize the treatment of heart disease.

Introduction

Heart disease is a major health problem facing Americans today. According to the American Heart Association, 80 million men and women suffered from cardiovascular disease in 2006. In 2005, over 860,000 cardiovascular disease patients died [1]. Despite these statistics, the situation is not hopeless. Different solutions exist, such as lifestyle changes, medicines, or in the most severe cases, coronary bypass surgery. Patients can undergo different types of cardiac bypass surgery to repair their faulty hearts or blood vessels. The surgery is commonly referred to as open heart surgery because the doctors actually open up the patient’s chest cavity, expose the heart, and operate on it. In order to allow such a surgery to be performed, the heart must be temporarily stopped from beating.
Obviously the heart is an essential organ. If it stops beating, oxygen-carrying blood cannot be circulated through the body, and a person will die shortly afterward. This presents quite a predicament for cardiovascular surgeons: how can they stop the heart to operate on it, yet keep the patient alive? The answer lies with a special apparatus, called the heart-lung machine, or cardiopulmonary bypass machine. The heart-lung machine is a device that is connected to the blood vessels and serves as the person’s heart and lungs for a period of time. In other words, the patient’s blood bypasses the heart to enter the machine instead, where it is oxygenated just as it would be in the lungs. From there, the machine pumps the blood out into the rest of the body (Fig. 1).
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Figure 1: A schematic demonstrating the sequence of blood flow between the heart-lung machine and the body.
In doing so, the heart-lung machine essentially replaces the most vital organs, thereby sustaining the patient’s life. From its original development to the components of current models to its future applications, the heart-lung machine is truly an impressive feat of technology that integrates the engineering principles of fluid flow, pressure gradients, and heat transfer into one life-saving device.