Submaximal exercise capacity in adolescent and adult patients with cystic fibrosis.

OBJECTIVE: To determine the submaximal exercise capacity of patients with cystic fibrosis (CF) by means of the 6-minute walk test (6MWT), correlating the results with clinical score, nutritional status, radiographic score, and pulmonary function tests.
METHODS: This was a prospective, cross-sectional study involving patients aged 16 or older enrolled in a program for adults with CF. The patients were submitted to clinical evaluation, determination of maximal respiratory pressures, 6MWT, spirometry, and chest X-ray.
RESULTS: The study comprised 41 patients. The mean age was 23.7 +/- 6.5 years, and the mean forced expiratory volume in one second (FEV1) was 55.1 +/- 27.8%. On the 6MWT, 30 (73.2%) of the patients covered a distance (mean, 556.7 +/- 76.5 m) that was less than the predicted normal value. The distance walked did not correlate significantly with body mass index, clinical score, radiographic score, maximal respiratory pressures, peripheral oxygen saturation at rest, desaturation during the 6MWT, sensation of dyspnea, or fatigue, although it did so with age at diagnosis, FEV1 in liters, and forced vital capacity in liters. Worsening of pulmonary function was associated with greater desaturation during the 6MWT.
CONCLUSION: This study showed that most patients attending an adult CF program had reduced submaximal exercise capacity. The 6MWT can be valuable for identifying patients who might experience oxygen desaturation and physical impairment in daily activities.