Assessment of functional capacity in patients with chronic obstructive pulmonary disease: correlation between cardiopulmonary exercise, 6 minute walk and 15 step exercise oximetry test.

BACKGROUND

Different exercise tests are used to evaluate the functional capacity in chronic obstructive pulmonary disease. The cardiopulmonary exercise test is considered the gold standard, but the 6 minute walk and the 15 step exercise oximetry test are considerably less expensive.

OBJECTIVES

To determine whether reliable data could be obtained at lower cost.

METHODS

The study sample consisted of 50 patients with mild to severe stable COPD. All underwent pulmonary function test and the cardiopulmonary exercise test, 6 minute walk and 15 step exercise oximetry test as part of their regular follow-up visit. Functional capacity was graded according to each test separately and the functional capacities obtained were correlated.

RESULTS

The results showed that most of the patients had severe COPD according to pulmonary function tests (mean forced expiratory volume in the first second 46.3 +/- 19.9% of predicted value). There was a good correlation between the cardiopulmonary exercise test and the 6 minute walk functional capacity classes (r = 0.44, P = 0.0013). We did not find such correlation between the 15 step exercise oximetry test and the cardiopulmonary exercise test (r = 0.07, P = 0.64).

CONCLUSIONS

The study shows that the 6 minute walk is a reliable and accurate test in the evaluation of functional capacity in COPD patients.