Closer to the Real Thing

You won’t see it on “ER� or “Chicago Hope,� but many medical students and residents learn some medical procedures by first performing them on dying patients or the cadavers of the newly dead. Some students, for example, learn to do a central venous catheterization--inserting a thin plastic tube into the femoral vein--on people who are being kept alive artificially, even though the procedure offers no benefit to the patient.

Some physicians and ethicists grudgingly endorse this practice because of the importance of training new doctors. But growing numbers object to it, according to a recent study in the New England Journal of Medicine, because it does not place the welfare of the patient foremost, and consent is virtually never obtained.

“This is a practice that should not be performed,� said Dr. Lauris C. Kaldjian of the Yale University School of Medicine, one of the authors of the study.

One way around the problem of practicing on patients is the use of complex manikins called simulators that can mimic not only the normal functioning of the human body but the symptoms of many diseases as well. Fueled by the last decade’s advances in computer technology, the simulators are now able to replace living patients in a wide variety of teaching situations.

“There is no doubt in my mind that [the simulator] facilitates the learning curve of students or residents,� said Dr. Ronald Katz, director of the Simulation Center of Southern California at USC. “I know it saves lives.�

Crude simulators, such as “Resuscidolls� and “Medical Annies,� have been around for decades for such routine uses as teaching cardiopulmonary resuscitation and other simple procedures. But those dolls are as much like the modern simulators as a Model T is like a new Ferrari.

A forerunner of the new generation of simulators was developed at USC in the early 1960s by Dr. Steve Abrahamson, an anesthesiologist, and engineer Sam Denson. The device, called Sim 1, was designed to teach budding anesthesiologists how to deliver medication. But it was grossly limited by the rudimentary computer power available at the time and was never manufactured commercially.

The newest simulators were developed independently by researchers at the University of Florida and a team at Stanford University and the VA Palo Alto Health Care System. The Florida device is manufactured by Medical Education Technologies Inc. of Sarasota, Fla., the other by MedSim Ltd. of Kfar Sava, Israel.

The Medical Education Technologies simulator is “a piece of plastic in the shape of a human, but we literally breathe life into it,� says Lou Oberndorf, president of the company. “It has a working airway, working lungs, a working heart [all simulated], breath sounds, pulses from the foot to the carotid [artery in the neck]. The lungs are very sophisticated in that they take in room air or oxygen from a ventilator and give off carbon dioxide. The chest moves up and down. Every sound and physical movement is as clinically accurate as we can possibly make it.�

Those functions are all controlled by a central computer and implemented with air pressure and mechanical devices. Interchangeable genitalia can convert the simulator into either sex.

Trainees can insert a tube into the lungs to aid breathing or perform an emergency tracheotomy--that area on the simulator is replaceable--if necessary. The simulator, called Stan (for standard man), produces simulated urine, and blood in the urine can be mimicked when appropriate.

Drugs can be injected if needed. The “drugs� themselves are actually water injected into a repository under the skin, but a bar code reader records the drug’s identity, allowing the computer to produce the proper response in Stan.

If Stan’s blood pressure is low, for example, the student can administer epinephrine, and the blood pressure goes up. But if the wrong drug is administered, or if treatment is not appropriate, Stan can “die.�

“A student who makes a mistake can kill a patient,� Katz said. “I’d rather a student killed Stan than a real patient.�

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The main advantage of the simulator “is that it allows people to make decisions in real time, in as realistic an environment as possible,� said Dr. Randy Steadman, head of UCLA’s simulator program. “We have a room that looks like an operating room. We have real equipment that might be used, such as a ventilator, a physiological monitor, etc.�

Stan can be used for simple training, such as teaching how to anesthetize a patient. It is much better for both the patient and the physician if new doctors learn this on a manikin, Steadman said.

The trainer can also be used to simulate rare events, such as malignant hyperthermia, a genetically determined reaction to anesthesia in which the patient’s temperature can surge as high as 115 degrees. Although malignant hyperthermia occurs occasionally in the operating room, a resident might never see it during training, Katz said. But he or she can learn to handle it on the simulator.

Katz said he has heard from former residents who quickly recognized a rare tumor of the thyroid gland called atheochromocytoma because they had practiced with it on Stan.

Medical Education Technologies has recently come out with two other models complementary to Stan. One is a simulator of children called PediaSim. “Pediatric patents are not simply small adults,� Oberndorf said. Their responses to drugs and other treatments can be quite different.

The company also has a military model that is similar to Stan but can simulate traumatic injuries, such as those caused by stepping on a land mine. That model is already being used by the U.S. and Dutch military.

The simulators are not cheap. “They cost about $250,000 and another $50,000 to $75,000 per year for supplies and salaries,� Katz said. “But if you save one life, it’s worth it.�