ABSTRACT
This chapter describes aspects of exercise testing obese patients. First, it is important to recognize the high energy requirements for an obese person to simply walk at a normal pace. This is especially important for a CPET study utilizing treadmill exercise. To achieve an 8–12 minute test, the exercise protocol must start at a low treadmill speed with very small inclination increases. While using a cycle ergometer compared with a treadmill offloads some of the burden of moving a large body mass, simple unloaded pedaling may require two or even three times the normal-weight oxygen consumption for that exercise stage. For subsequent watt increases in an ergometer CPET, however, height-normal intervals are appropriate. It is important to recall that normalizing the maximum oxygen uptake in mL/minute by body weight will give a reasonable estimate of functional impairment but will not give a good marker of maximal cardiac output. If an estimate of the maximal cardiac output is the reason for performing the test, then the absolute maximal oxygen consumption should be compared to the predicted value for a nonobese person of the same height, age, and sex. Because of the high energy requirements to initiate movement, many obese patients will demonstrate a moderate drop on oxygen saturation after the first minute of exercise, and that desaturation will resolve as the exercise intensity increases. This initial exercise desaturation is a normal response for any subject who suddenly begins high-intensity exercise from rest without the prior hyperventilation that is a characteristic of sprint athletes.
