The Bruce Protocol

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Socrates: "And is not bodily habit spoiled by rest and illness, but preserved for a long time by motion and exercise?"

Theaetetus: "True." footnote 1

Called the "Father of Exercise Cardiology," Robert A. Bruce is the developer of the standardized treadmill test for diagnosing and evaluating heart and lung diseases. The Bruce Protocol, as it has come to be known, is used by physicians the world over to test cardiovascular function. In addition to the benefit of its diagnostic applications, Bruce's work over a period of four decades at the UW has enlightened generations of physicians and patients about the physiological processes involved in aerobic exercise and about the value of exercise to good health.

Prior to Bruce's pioneering work, physicians lacked an adequate means for evaluating heart function while patients were engaged in physical activity. Although step tests had been used, they were often too strenuous for patients with heart disease. Accordingly, most physicians relied upon the patient's complaints about exertion, and only examined them at rest. Bruce explains the importance of having an active test by drawing an analogy to evaluating a used car. "You would never buy a used car without taking it out for a drive and seeing how the engine performed while it was running," he quips, "and the same is true for evaluating the function of the heart."

The advent of technologies in the 1940s such as the electrocardiograph and the motorized treadmill provided Bruce and colleagues with the tools they needed to set up a treadmill test. By wiring up patients with the electrodes of the electrocardiograph to monitor heart signals, and by rigging up an oxygen analyzer and thermal-conductivity cell among other gas measurement devices, they were able to continuously monitor cardiac performance, ventilation volumes, and respiratory gas exchanges before, during, and after patients walked for a few minutes on the treadmill, an activity most patients could carry out safely.

Bruce's goals were to develop a method to assess aerobic capacity, to measure cardiorespiratory performance, and to observe mechanisms of cardiac impairment, especially due to decreased blood flow to heart tissues. Initial experiments involved the single-stage test, in which patients walked for 10 minutes on the treadmill at a fixed work load. His first studies, published in 1949, analyzed minute-to-minute changes during the treadmill test in respiratory and circulatory function of normal adults and of those with chest diseases, including beryllium workers with chronic lung ailments.

In 1950, Bruce joined the UW School of Medicine as the first head of cardiology, where studies of the single-stage treadmill focused on the predictive value of the test in cardiac patients, especially to predict the success of surgery for valvular or congenital heart disease. Subsequently Bruce developed the multistage test, consisting of several stages of progressively greater work loads. The multistage test, published in 1963, became known as the Bruce Protocol. In that paper, Bruce reported that the test could detect tell-tale signs of such conditions as angina pectoris (chest pain and a feeling of suffocation), a previous heart attack, or a ventricular aneurysm (bulging in the ventricle of the heart). Also during this period, Bruce and colleagues demonstrated that exercise testing was useful in screening apparently healthy people for early signs of coronary artery disease. They established standards for normal responses and were able to differentiate between changes due to aging and those due to disease states.

With UW cardiologist Harold T. Dodge, Bruce led studies of the Seattle Health Watch, a program initiated in 1971 that would run for the next decade and would involve literally thousands of participants in the Pacific Northwest region, including employees at Boeing. Many physicians used the Bruce protocol to evaluate the clinical feasibility of such exercise testing in hospitals, in private office practices, and in industrial medical departments, such as at Boeing. Signals from the treadmill monitors were sent by dataphone from 15 different test sites to the University Hospital research lab for analysis, and follow-on questionnaires from thousands of patients were accumulated for years. The Seattle Heart Watch demonstrated the feasibility and safety of exercise testing, and confirmed that, when coupled with knowledge about conventional risk factors for heart disease such as cigarette smoking or family history, the Bruce Protocol was a powerful prognostic tool.

Bruce also discovered an interesting beneficial result of treadmill testing: taking the test seemed to motivate people to change bad habits. Sixty-three percent of respondents in one study said that they modified their risky behaviors as a result of simply taking the test. Those who discovered an abnormality as a result of the test were more likely to change their habits, as might be expected.

Bruce estimates that some 70% of the millions of tests done annually in the U.S. to evaluate heart function use this protocol. And while more sophisticated tests may be available, they are also more costly. In the final analysis, Bruce's work not only has provided a highly cost-effective and widely-used diagnostic tool; it has demonstrated the wisdom of the ancients.

  1. Plato, approximately 400 B.C. (Plato: Theaetetus, Great Books, Vol 7, 1952, p. 518.)

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