If you’ve spent any time around soon-to-retire, senior physiologists, you’ve probably heard nostalgic talk of the old dog labs. I am a member of what may be the last generation that participated in these in a medical/graduate school environment. The old-timers will tell you that there was no better way to teach physiology than by demonstration and experimentation with an anesthetized dog. The experience was dramatic, and the various concepts were obviously relevant. Nevertheless, time marches on, and with changes in economics and societal values, we are unlikely to ever see the return of the dog labs in medical or graduate school.
For the purposes of teaching physiology in a medical environment, much of the impact and value of the dog labs can be obtained through simulation. Centers that use high-fidelity manikins and other simulation technology are becoming more and more common, and if your institution doesn’t have one yet, there is probably one in the pipeline. However, you may be skeptical of the high-price tag that the equipment carries and its relevance to bench scientists. After all, most of us teaching physiology aren’t clinicians, and we have neither the expertise nor the experience to teach medicine. I was firmly of that opinion when the Texas Tech University Health Sciences Center first opened its simulation center, but I’ve tried to keep an open mind, and I’m happy to say that I’ve learned to incorporate these resources into my teaching. More importantly, simulation works for the same reason the old dog labs worked: it provides a clear and dramatic demonstration of fundamental physiological concepts.
Although the equipment available in most simulation centers is capable of reproducing some pretty sophisticated disorders, there is little need for such advanced capability during the pre-clinical years of medical training. The basics are more than adequate, and they can be covered adequately without obtaining a medical degree. Cardiovascular physiology was my entry point using this new approach to teaching. There are few things in life more fundamental than a heartbeat, and nearly every simulation center will have cardiopulmonary manikins that allow the student to practice auscultation. This is not to say that heart sounds can’t be taught with alternatives, such as good digital recordings, but the use of manikins adds an important degree of realism. I first ask the students to practice positioning the stethoscope for optimal detection of the various heart sounds in a healthy individual. Demonstrating where to best hear the sound associated with pulmonary valve closure, for example, draws the connection between cardiac anatomy and physiology more closely together. I then ask the students to explore various valve pathologies and illustrate what they would expect to see on Wiggers diagrams and pressure-volume loops. The four murmurs that are most relevant to first-year medical students, aortic valve stenosis and regurgitation and mitral valve stenosis and regurgitation, are great starting points for illustrating the relevant changes in pressure that are associated with these defects. For example, the combined use of auscultation and Wiggers diagrams make it easier to appreciate the excessive pressures developed in the left ventricle as a consequence of aortic valve stenosis. It also makes it easier to understand how the high velocities of flow and resulting turbulence can cause the distinctive murmur. In my class, I follow up the auscultation activity with standardized patients and ultrasonography, allowing the students to correlate the sounds that they hear with the coordinated movements in the heart, as visualized with the ultrasound probe.
The cardiopulmonary manikins provide a great resource for showing the practical relevance of hemodynamics to the clinical setting, but we must turn to high-fidelity manikins if we are truly to recapture the drama of the old dog labs. I remember vividly the effects on an anesthetized dog when, as a student, I infused a sympathetic agonist or antagonist. Now, as an instructor, I achieve a similar memorable effect with a full-blown simulation of hemorrhagic shock. This is the capstone event in the cardiovascular physiology section of our course, when the students must recognize the problem and come up with a solution. Our simulation center has rooms like you would find in the emergency department in which we place the manikins. The potential “treatments” available for use by the students include a muscarinic antagonist, a sympathetic agonist, and the infusion of normal saline. As I did with the dogs back in the day, today’s students apply various drugs or treatments to the manikin, and, from the attached control room, I can simulate the appropriate physiological response. There are few things that bring home the importance of preload and stressed volume like the “recovery” evoked by rapid infusion of saline, especially if this follows unsuccessful attempts at treatment with various drugs. Later in our class, we have additional simulations that illustrate fundamental principles associated with respiratory physiology and endocrinology. I admit that it took some persuasion to convince my bench-investigator colleagues that they had sufficient experience to facilitate these activities. However, after trying it a time or two, they usually find that the activities require more physiological knowledge and deductive reasoning than clinical skill, and, as an added bonus, they have fun.
So why not take advantage of that high-priced center that your medical school just built or is in the process of developing? You’ll find that simulations provide hard-to-ignore demonstrations of physiology’s relevance to the clinics. If my experience is any indication, your dean will be happy that you’re trying new things, and you’ll be rewarded by students who respond enthusiastically.
The nitty-gritty to get you started:
My colleagues and I have boiled down the use of simulation to a few key points that can provide a good start to your own efforts.
1) Keep it simple. You’re teaching physiology, not a subspecialty. As described above, we require the students to recognize a loss of blood volume as the fundamental problem in hemorrhagic shock.
2) Require a decision or intervention. The students must follow a problem logically, putting into practice the physiology that they are learning. In the hemorrhage scenario, they treat the “patient” with a rapid intravenous administration of saline.
3) Provide some background material. You’re providing a value-added experience that goes beyond simple lecture, but the students need some guidance to prepare. For the shock simulation, they study a 20-minute online presentation focusing on low cardiac output the night before the activity.
4) Do a debrief. If things work well, there will be a lot of excitement and keyed-up emotion. You’ll want to give the students a chance to talk things out and assess their performance as a team.
Thomas A Pressley is a Professor in the Department of Medical Education at Texas Tech University Health Sciences Center. After earning his undergraduate degree at Johns Hopkins University, he entered the graduate program in biochemistry at the Medical University of South Carolina. His postdoctoral training was in the College of Physicians and Surgeons at Columbia University. He was recruited by the University of Texas Medical School in Houston in 1987, and he transferred to Texas Tech in 1995. Tom has served as an interim dean, a visiting professor at multiple institutions, a member of grant review committees, and the chair of the Education Committee of the American Physiological Society. He is the current chair of the APS Career Opportunities in Physiology Committee. He has also developed numerous courses, and he has reviewed degree programs at several institutions.