Impact of Integrative Cardiopulmonary Exercise Testing (21)
Chronic obstructive lung disease (COPD): Because of the physiologic derangement in COPD, spirometry might be anticipated to be highly correlated with exercise performance. However, two factors are important. First, spirometry performed at rest only estimates a patients ventilatory capacity and not the ventilatory requirement for exercise. The latter depends on the degree of ventilation-perfusion mismatching and the level of Pco2 that the patient maintains. Second, many patients with lung disease also have concomitant disease of other organ systems that may affect exercise performance. Cheap Diskus Advair
For example, Jones et al noted that work capacity in patients with COPD needed to be measured directly because it was poorly correlated with the resting FEV,. Although FEVj accounted for 56 percent of the observed variance of Vo2 during exercise, Pineda and colleagues also recommended exercise testing if accurate evaluation of exercise capacity is required. Ries et al found that resting pulmonary function could predict exercise hypoxemia in patients with COPD. In this study, 40 patients with stable COPD performed incremental cycle exercise. In 21 patients, Pa02 decreased by more than 3 mm Hg. Neither FEV/VC or single-breath diffusing capacity for carbon monoxide were satisfactory predictors of fall in Pa02. In particular, the positive predictive value for Deo of less than 20 ml/min/mm Hg was only 65 percent, although a normal Deo was never associated with significant hypoxemia (negative predictive value 100 percent).