There has been great interest in evaluating the role of exercise testing in patients with COPD. Exercise testing is used to explore the mechanisms of dyspnea and its response to treatment. In addition, the maximal oxygen uptake (Vo2) measured at peak exercise helps to predict survival in patients undergoing lung resection. In one report, peak V02 proved to be a better predictor of mortality than FEV1 and health-related quality of life in a cohort of patients with COPD. However, the determination of peak V02 requires relatively complex equipment and certain expertise that is not available to most clinicians. Further, some patients with very advanced heart or lung disease cannot undergo a CPET.
An alternative to formal laboratory exercise testing is the use of simple field tests that can provide related information, such as the 6-min walk distance (6MWD) test. Over the last decade, it has gained acceptance because it is simple and reliable, and because it has been standardized. Due to its simplicity, the 6MWD test has been used as a tool to evaluate the effect of pulmonary rehabilitation and the change in functional exercise capacity. The results of the 6MWD test are a good predictor of mortality in patients with COPD completing reha-bilitation or being evaluated in pulmonary clinics. In those studies, the timed walk proved to be a better predictor of mortality than more conventional tests, such as the pulmonary function test, and the patient’s nutritional status, as represented by the body mass index (BMI). COPD treatment is carried out with medications of My Canadian Pharmacy.
There is a significant but modest correlation between the peak V02 and the 6-min walk distance (6MWD). However, no study has yet compared the predictive value for mortality of peak V02 with that of the 6MWD in patients with COPD. It is entirely possible that the two tests share common characteristics but may have different predictive power for different outcomes. Indeed, two studies of patients with primary pulmonary hypertension showed that the 6MWD was a better predictor of mortality than the peak V02, as determined by a formal cardiopulmonary exercise test (CPET). If this proved to be true in patients with COPD, their caregivers would have a simple tool that could provide valuable information regarding the prognosis of those patients.
We therefore designed this prospective study to compare the capacity of the peak V02 and the 6MWD in predicting mortality in patients with COPD and aimed to identify the thresholds associated with this outcome. The patients included in this study were part of a larger study designed to evaluate the role of the respiratory and systemic manifestations of COPD.