COULD YOU EVER LIVE FOREVER? - 3. New Parts for Old
Figure 1. Heart transplant surgery.
Figure 2. A young patient waits to have an X-ray picture taken by an X-ray machine.
Figure 3. Using an endoscope, a surgeon observes a cancerous growth in the body and removes a sample for testing.
Figure 4. Older people with arthritis often have painful and swollen hip joints. In this case, an artificial hip joint can replace the damaged natural one. A stainless steel "head" is fitted to the end of the thigh bone. The head moves smoothly in a plastic cup joined to the hip bone.
Figure 5. Dr. Barney Clark and the artificial heart he received.
When part of the human body breaks down or wears out completely, an operation may be a patient's only hope of recovery. Today, life-saving operations can replace such organs as the heart, lungs, and kidneys. Healthy organs can be taken from someone who has just died and given to a living person. In addition, artificial devices have been developed to take the place of missing limbs, diseased arteries, burned skin, and other damaged body parts.
Many people now have the chance to live longer, healthier lives because of organ transplants. In 1967, Dr. Christiaan Barnard performed the first such operation in South Africa. He transplanted the healthy heart of a 25-year-old woman (the donor), who had just died, into the body of a 55-year-old man (the recipient). The first heart transplant patient survived for 18 days. Since then, thousands of transplant operations have been carried out all over the world with increasing success. A number of patients are alive today, 15 years or more after receiving their new hearts (see Figure 1).
Following a transplant, the recipient faces a serious danger. His or her immune system may treat the new organ as if it were an invader. This is known as rejection. In an effort to avoid rejection, doctors carefully match the blood and tissue type of the recipient to those of the donor. The best chance of an exact match occurs when the donor and recipient are closely related. For this reason, it is common for a kidney donor to be the brother, sister, or parent of someone whose own kidneys have failed. The donor can continue to lead a healthy life because his or her remaining kidney can take over most of the work of the missing one.
Various machines enable patients to survive both before and after a transplant operation. These machines take the place of one or more organs that are not working properly.
During heart transplants and other major operations on the heart, the patient is connected to a heart-lung machine. Blood from the patient's main arteries and veins is sent through the machine. While surgeons replace or repair the heart, the machine takes the place of the heart and lungs. It removes waste carbon dioxide gas from the blood, and adds fresh oxygen, which is vital to all living cells. Then it pumps blood back into the body.
Another piece of equipment, known as a kidney dialysis machine, does the work of of a human kidney. This organ cleans the blood of various wastes. A patient whose own kidneys have failed must be connected to a dialysis machine for about two hours every few days. Then, if a suitable donor is found, the patient may receive one or a pair of new, healthy kidneys.
In addition to life-support machines, doctors can use a range of advanced equipment for finding out what is wrong with a patient. Such equipment can help doctors discover a disease in its early stages, when the chances of treating it successfully are higher. In this way, new medical technology helps extend the life of many people.
X-ray machines have been available for many years as a tool for looking inside the body (see Figure 2). X-rays pass easily through soft body parts, such as skin and flesh. But they do not pass through bone. On a photographic film placed on the other side of the patient from the X-ray beam, bones and dense tissue appear as shadows. By injecting a patient with special dyes that absorb X-rays, doctors can also use this method to study diseased organs and disorders of the blood system.
In recent years, other ways of probing the human body have been developed. Some of these use a combination of a moving X-ray beam with a computer. In this way, doctors are able to create a three-dimensional picture of a particular area of the body. Other advanced scanners employ a powerful magnetic field or beams of high-energy particles to study soft body parts in close detail. With such equipment, doctors can identify and treat many diseases at a very early stage.
|Operations without Cuts
Doctors will soon be able to perform operations on the heart and other organs of the body. Already a device called an endoscope can be inserted through a small opening in a vein (often in a leg) and pushed through until it reaches the area of concern (see Figure 3).
The endoscope is a long, flexible tube. Bundles of special glass fibers, called optic fibers, pass through the tube. One bundle carries a beam of light that brightens the area around the tip of endoscope. Another bundle carries back pictures taken by a tiny television camera. These pictures are shown on a screen in the operating room so that the surgeon has a clear view from inside the patient's body. Other tubes and wires, passing along the length of the endoscope, control instruments at the tip. These allow small samples of tissues to be collected for testing. Jets of air and water can also be sent through to the tip.
In the future, it will be possible to perform operations using tiny surgical instruments fixed to the tip of an endoscope. In addition, small replacement parts, such as artificial heart valves, will be sent along the endoscope and fitted into place. These parts will be folded up to pass easily through the narrow tube. Then they will be opened in the correct position. In this way, major operations that once put a patient's life at risk will be carried out quickly while the patient is still awake. As a result, many people will live longer and healthier lives.
Spare Part Surgery
Hearts, lungs, kidneys, and livers have all been successfully transplanted from one person to another. But what happens if a suitable donor is not available?
Until a donor is found, the patient may use one of the life-saving machines just described. But these machines are expensive, and there are not enough for everyone who needs them. In the future, the best solution may be to give patients artificial organs.
Human-made body parts are already common. Many old people, for example, are fitted with artificial hip joints (see Figure 4). These replace natural joints that have been damaged by disease. The operation involves removing the socket of the hip joint and replacing it with a sturdy plastic cup. Meanwhile, the head of the thigh bone is removed and replaced with a smooth metal ball. This ball is attached to a long stem. The stem is then fixed into a hole drilled into the rest of the thigh bone.
Artificial legs, arms, hands, and feet have also been developed. These are designed to make many of the movements of real limbs. Normally, tiny electrical signals in the upper parts of the limb trigger muscle movements in the lower part. When a person has lost all or part of a limb, though, these signals can be picked up and used to control an artificial replacement. The signals travel down tiny wires to small motors that make each of the artificial joints work. An artificial hand can be fitted that will allow a person to write normally, pick up a delicate object without breaking it, or seize something with a strong grip. Currently, researchers are working on an improved hand. It will have pressure sensitive electronic devices in the fingertips to give the wearer a sense of touch.
A human-made hand that is less than perfect is better than no hand at all. But a human-made organ, such as an artificial heart or kidney, has to work almost as well as the real one, or it is useless. Natural organs are complex structures. Yet, they are also tough and long-lasting. In an average lifetime, for instance, the heart beats faultlessly about 40 million times without rest.
Replacing an organ such as the heart with a human-made copy, then, is extremely hard. The first person to receive an artificial heart was a 61-year-old dentist, Dr. Barney Clark. The operation took place at the Utah Medical Center, Salt Lake City, in 1982. Clark's new heart, known as a Jarvik-7, kept him alive for 112 days after the operation (see Figure 5). Surgeons placed the new heart in Clark's chest. But in order for it to work, it had to be constantly supplied with compressed air from a large pump at the patient's bedside. In 1990, officials decided that operations of this type would stop until an improved artificial heart could be developed.
Future artificial hearts and other organs will be much smaller and more reliable than early devices such as the Jarvik-7. They may be controlled by tiny computers that can gather information from various parts of the body. This information would allow the computers to measure how well the artificial organ was performing. They could make immediate adjustments if needed. For example, a computer attached to an artificial heart could change the rate at which the heart beats to match the amount of blood needed by the body. It might check to see that there is no buildup of fatty substances in the main arteries leading from the heart. Finally, if it did find anything wrong, it could send radio warning signals to a device outside the body.
In the future, it may be possible to replace large sections of the human body so that people become part human, part machine. Today, that may sound frightening and unpleasant. But if the new artificial parts help us to live happily for much longer, will anyone object? Already, millions of people have artificial limbs, joints, and devices called pacemakers to help their hearts beat regularly. Many more wear false teeth, braces, hearing aids, and glasses. Some even have their faces altered by plastic surgery. So, is it far-fetched to imagine that someday there will be people whose bodies are more than half machine?
Still, replacing natural body parts may not be the easiest way to help people live longer. In the end, more success is likely to come from understanding why we age and how we can stop or slow the aging process.