Functional capacity in severe chronic obstructive pulmonary disease

To investigate the functional capacity in patients with severe chronic obstructive pulmonary disease (COPD) and healthy subjects.

The present study was conducted in the School of Physical Therapy and Rehabilitation, Department of Chest Medicine, Medical School, Hacettepe University, Ankara, Turkey, from June 2002 to July 2003. Forty-five male patients with severe (23 moderately severe, 22 very severe) COPD and 45 healthy controls participated in the study. Pulmonary function tests and 6-minute walk test (6MWT) were performed. The Borg score and heart rate were measured before and after the test. External work of walking was calculated as the product of body weight and walked distance. Functional dyspnea was measured using the modified Medical Research Council (MRC) dyspnea scale.

Both distance and external work of 6MWT were significantly lower in severe COPD patients than healthy subjects (p<0.05). No significant differences in distance, external work, and exertional dyspnea were found between moderately severe and very severe COPD patients (p>0.05). Patients with very severe impairment had a significantly lower percentage of predicted 6MWT distance (p<0.05). In these patients, 6MWT distance was correlated significantly with forced expiratory flow in one second (FEV1), MRC score, and Borg score whereas external work of walking correlated with age, FEV1, forced expiratory flow from 25-75%, MRC, and resting Borg score (p<0.05).

Severe COPD patients had a significantly impaired functional capacity as compared to their healthy counterparts. Patients with FEV1 <35% have a lower percentage of functional capacity. Both distance and external work of 6MWT are influenced by large and small airway function, level of breathlessness reported during daily activity or scored during an exercise test in patients with FEV1 <35%.