Thoughts on Teaching Physiology to Medical Students in 2002 

As originally published in The Physiologist
Volume 45, Number 5, October 2002, page 389

John B. West
Department of Medicine, University of California, San Diego

Introduction 
    It was a great pleasure and a distinct honor to be selected as the 2002 Arthur C. Guyton Teacher of the Year. My admiration of Arthur Guyton knows no bounds, and it must be very satisfying to him to have written a textbook of physiology that has had such an enormous influence on thousands of medical students over many years throughout the world (1). I still turn to his book when there is a question on some area of physiology that is unfamiliar to me, and am rarely disappointed.
Apparently it is the tradition for the recipient of this award to write a few remarks about the teaching of physiology. Actually I am glad to have this opportunity because I am very involved in teaching physiology to medical students, and there are few occasions where the issues can be discussed. Like most faculty members, I have never had any formal training in teaching, and I can only offer as my credentials the facts that I have been director of the main physiology course for medical students at the University of California San Diego (UCSD) for 30-odd years, and that I have written several books designed to teach physiology to medical students. Moreover, some interesting issues have arisen in the teaching of physiology to medical students over the past 10 or 15 years and I shall discuss five.

Key Role of Physiology in the Medical Curriculum 
    Never has an understanding of the principles of normal physiology been so important in medical education. As new drugs are introduced, novel diagnostic and interventional techniques are developed, and a better understanding is obtained of how the genome alters function, it is more and more critical for the present-day medical student to understand the principles of both normal and abnormal physiology. This has to be clearly understood in spite of current changes and fashions in medical education. From time to time, legislators emphasize the importance of teaching about aging, cardiopulmonary resuscitation, sex practices, alternative and complementary medicine or whatever, but a clear understanding of how the body works will always be the primary basis of a good medical education. This may sound like bringing coals to Newcastle for the readers of The Physiologist, but it is essential to emphasize this fundamental truth at the very outset.

How Much Physiology Should We Teach in 2002?     
    It may seem odd to raise this issue, but I believe that we have to recognize that the present day medical student cannot be expected to learn as much physiology as was the case 25 years ago. The reason is simply that so much essential new material has entered the pre-clinical medical curriculum, that something has to give. Of course I am not suggesting that all the reduction should be in physiology. Rather it should be shared among all the pre-clinical courses. Naturally, reducing the content of a core course is always difficult. In fact, in our medical school there is continual pressure from some courses to increase the amount of material and expand their courses because this can bolster their case for more resources.
    The question of how much physiology should be currently taught to medical students confronted me when I worked on a new book, Pulmonary Physiology and Pathphysiology: An Integrated, Case-Based Approach (3). The stimulus for this book is that a number of medical schools now teach pathophysiology along with physiology in a combined course. I am not convinced that this is the best way to go because there is a danger of glossing over some of the principles of normal physiology (see the section below on case-based learning). However, a number of medical schools have taken this route so it is a fait accompli for some students. In writing the new book, I carefully reviewed the content of my book Respiratory Physiology-The Essentials (2), and concluded that about 10 percent of the material in that could be omitted without losing the important principles. Some of the material that was deleted was on pulmonary function tests because, in general, it is far more important to understand the principles of how the lung works rather than how this is measured in pulmonary function laboratories.
    I hope I am not leaving the impression that a watered-down course of physiology is acceptable. On the contrary, at UCSD we teach the principles of normal physiology in a rigorous, quantitative way that some schools would probably regard as old fashioned. Also, we should be vigilant to make sure that the time devoted to physiology courses is not unduly reduced as has apparently been the case in some medical schools. However, at the same time, we cannot expect medical students to learn physiology in as much detail as was the case 25 years ago before anybody had envisaged sequencing the human genome.

Do Today’s Medical Students have Fewer Quantitative Skills Than 15 Years Ago? 
    There is a strong impression among the faculty who teach our physiology course that medical students find some concepts in physics and mathematics more difficult than they did 15 years ago. Unfortunately, I cannot document this in any formal way. In fact, when I asked the Dean of Admissions of our medical school about this he was quick to point out that the average Medical College Admission Test (MCAT) score for Physical Sciences of our incoming students this year was 11.3 or the 85th percentile of all applicants admitted to medical schools nationally, and that there has been no decline over the last few years. But the fact remains that students seem to have more difficulty with concepts such as pressure, flow, resistance and elasticity than used to be the case.
    Part of the reason for this is probably that the teaching of physics at the college level has been de-emphasized. Friends tell me that this is the case all over the world. Again, to some extent this may be the inevitable result of competing interests. Modern biology emphasizes the spectacular advances in molecular and cell biology of the last 15 years and perhaps it is inevitable that physics and mathematics receive less attention.
    The same trend can be seen in the hobbies that students have. While I was growing up, I built radios from scratch, and notions of voltage, current and resistance were taken for granted. Today, very few young people can use a soldering iron, and when a change is made to a piece of electrical equipment such as a computer, this is done by unplugging one unit and replacing it with another. I remember poking around under the hood of our car with my son (now a molecular biologist/pathologist), and noting that he was reluctant to touch the battery terminals. I think he was unsure about the difference between 12 and 110 volts.
    The lack of intuition about pressures, flows and resistances leads to curious errors. One of our common questions in respiratory physiology is what happens to pulmonary vascular resistance if the blood flow to one lung is blocked by an embolus or whatever. Some students will argue that of course the resistance of the lung with the occluded artery is increased, but the vascular resistance of the unoccluded side is reduced because the increased blood flow there raises the vascular pressure and, thus, causes recruitment and distension of some capillaries. So far, so good. However, when the student is asked what happens to overall pulmonary vascular resistance (that is, of both lungs together), a significant number will reply that it has decreased! To most of us, it is so intuitive that if you block part of the circulation of the lung the pulmonary vascular resistance has to increase, but some students apparently just cannot see this. This is a relatively trivial example, but many other conceptual difficulties arise when the present day student is introduced to notions of compliance, transmural pressure and surface tension.
    It would be interesting to see data on the quantitative skills of incoming medical students as tested by simple mathematical concepts. For example, how many students know that y = mx + c is the equation of a straight line where m is the slope and c is the y-axis intercept? Some apparently do not, judging from the blank looks that greet a mention of this in a lecture. Again, if a student is told that a tank of water develops a hole near the bottom, how likely is he/she to see intuitively that the rate of fall of the water level is proportional to its height, and, therefore, the rate is exponential? It would be nice to have some numbers on this. Of course these concepts are important over a whole range of topics in respiratory, cardiovascular and renal physiology, and are also fundamental in pharmacology for understanding the clearance of drugs from the circulation.

Problem-based Learning and Case-Based Learning 
    I embark on this topic with some trepidation because I know that feelings run high, and also that others have had far more experience in the field. However, we have had case-based learning sessions in the cardiovascular section of our physiology course for many years, and since the rest of the course is taught in the more traditional way with lectures, discussion groups and laboratories, it is possible to make some comparisons. Possibly these remarks will be of interest to people who are considering moving from one form of teaching to the other.
    There is no doubt that many medical students find case-based learning very stimulating and enjoyable. The opportunity of discussing the case history of a typical patient together with aspects of the physical examination and some of the laboratory and other investigations is so much more interesting to many students than listening to a lecture, or reading a book chapter on the pulmonary circulation. Good MD facilitators can greatly stimulate the discussion by referring briefly to their own experience in clinical situations. The bright students often do exceptionally well because they can see some of the implications of the discussion well ahead of the other students. Finally, a good case is a great aid to memory, and it is much easier to “remember the postman” rather than “remember our discussion of dynamic compression of the airways.”
    However, we have had some problems with case-based learning. First, it is enormously expensive of faculty time and this is a major reason why we have only instituted case-based learning in the area of cardiovascular physiology. This is the only area where we have enough faculty members who are sufficiently well-informed about physiology and pathophysiology and are willing to give up the time. Another serious objection, at least in our experience, is that the basic physiological principles tend to get short shrift, and their coverage tends to be spotty. We sometimes hear complaints from students after an exam that a particular topic on which there was a question was not adequately covered in their case-based learning group. In some cases this may be because of uneven expertise of the facilitators. The reduced emphasis on basic physiological principles is understandable because some students find a discussion of clinical aspects much more interesting than equations, graphs, or other ways of looking at the basic principles. A further potential difficulty with case-based learning is that some of the weaker students may be left behind. I have frequently heard this comment when I interview students who have failed one of the exams. They complain that the very bright students tend to dominate the discussion and the material is covered too fast for some of the weaker students to digest it.
    One of the buzz words that is tossed around about problem-based and case-based learning is that this is “active” learning, as opposed to “passive” learning of formal lectures. There may be something in this, but a good lecture certainly requires a great deal of active participation by the student if he is to follow the arguments presented by the lecturer. Of course, you can fall asleep during a lecture but this is really a reflection on the lecturer rather than the mode of presenting the material.
    I think a good compromise is the use of formal lectures followed by extensive discussion groups, and this is a format that we use extensively. After all, a formal lecture is an extremely efficient way of presenting information to the 125 students or so that we have in a class. The class then breaks up into discussion groups of, say, 12 students each. A series of questions for discussion has previously been prepared and may be structured around a clinical problem. However, the questions themselves deal with basic physiological processes. Each question is assigned to one of the students in the group ahead of time and the assignment is indicated in the syllabus that is given out at the beginning of the course. The appropriate student then presents his/her answer to the question in five to 10 minutes while standing at the blackboard and the other students in the group raise questions. The facilitator sits at the back, at the other end of the room from the blackboard, and only interrupts if it is clear that the student is going off the rails. At the end of the discussion of a question, he may bring out some additional points that have not been covered. Note that this format is also expensive in terms of facilitators’ time, but we can use postdoctoral fellows and graduate students as long as they have had some experience with the procedure. In fact, we have them sit in on the sessions for one year’s course before they become facilitators in the next. This procedure has some of the aspects of the classical problem-based or case-based learning format because the student has to seek out the answer to the question, but it is more structured in the sense that the questions are prearranged, and the student who discusses the question is identified ahead of time.
    Incidentally, sometimes the students ask us to hand out written answers to the questions at the end of the sessions, or put them on the web. Initially we did this but we found that some students obtained the answers from second year students and simply parroted these. Clearly, this defeats the purpose and so we now do not give out the answers to the questions.

Animal Laboratories 
    We have animal laboratories using anesthetized dogs in the cardiovascular physiology section of the course. Our belief is that direct exposure to the cardiovascular system in this way provides a deeper understanding than can come from textbooks, lectures, films or computer simulations alone. The students are not only able to directly observe the processes of normal integrative physiology but also examine how these are changed by myocardial ischemia, cardiac arrhythmias, and a variety of pharmacological agents that students will administer to patients later in their career. The animals are anesthetized by professional veterinarians in the Animal Care Program and are treated in the most humane way possible.
    For those students who have difficulty with a live animal physiology laboratory because of religious, moral, or other reasons, a simultaneous video is provided in an area adjacent to the laboratory. This provides an overview of concepts reviewed in the laboratory, although we do not feel that the video can replace the actual laboratory experience. All the students are brought together several times during the laboratory session to discuss the concepts presented in the live animal laboratory or viewed in the video session. This is done in discussion groups that are the same as those used for the case-based learning sessions. The videos are also made available to the entire class in the Learning Resource Center where they can be played at any time.
    In justifying the use of animal laboratories, we emphasize the general importance of the use of animals in medical research, training and education. Almost everyone agrees that animals are essential for medical research. It should also be axiomatic that doctors should train in interventional procedures using animals prior to carrying out these procedures on patients. It is a small step from this to arguing the value of the use of anesthetized animals in teaching physiology.
    In conclusion, there is probably no best way of teaching physiology to medical students in the year 2002. Very likely the most effective way depends on a number of factors including the number of faculty available, and the excellence or otherwise of the students. The above remarks simply describe some of our experiences at UCSD, and it may well be that other medical schools will find other formats equally or even more successful. 

References 
1. Guyton AC and Hall JE. Textbook of Medical Physiology, 10th edition. Philadelphia: W.B. Saunders, 2000.
2. West JB. Respiratory Physiology - The Essentials, 6th edition. Philadelphia: Lippincott Williams & Wilkins, 2000.
3. West JB. Pulmonary Physiology and Pathophysiology: An Integrated, Case-Based Approach. Philadelphia: Lippincott Williams & Wilkins, 2001.

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