“The most useful way to estimate the body’s physiological reserve is to assess the patient’s tolerance for exercise. Exercise is a good model of the surgical stress response. The greater the patient’s tolerance for exercise, the better the perioperative outcome is likely to be, though marathon-running is not required. For most patients, the ability to sustain a little light exercise, such as playing a round of golf, or carrying a heavy shopping bag up a flight of stairs, is all that is required.
When I am in doubt about my patient’s exercise tolerance, I ask them to accompany me on a short walk up the hospital stairs, which usually clarifies the matter one way or the other. It is possible to put patients on a treadmill and measure their exercise tolerance formally (so-called CPX, cardiopulmonary exercise testing), but this is time-consuming, and is therefore reserved for especially difficult cases.”