Relationships between respiratory parameters, exercise capacity and psychosocial factors in people with COPD

Chronic obstructive pulmonary disease (COPD) affects respiratory functioning and psychosocial factors. However, little is known about perceived ability of people with COPD to engage in a regular exercise program. This study assessed respiratory parameters, exercise capacity, psychosocial factors and their relations in people with COPD.

This cross-sectional study involved patients with COPD recruited from a Nigerian university teaching hospital. Respiratory parameters including forced expiratory volume in 1sec (FEV₁) and forced vital capacity (FVC) were assessed by using a spirometer and FEV₁/FVC ratio was calculated. Participants were sitting upright in a comfortable chair and wearing a nose clip for measurements. The procedure was performed in accordance with the American Thoracic Society criteria. Exercise capacity was assessed by the 6-min walk test (6MWT). Gait speed was assessed by the distance covered in 6min. Perceived exercise self-efficacy (PESE) and rating of perceived exertion (RPE) were assessed by exercise self-efficacy and Borg scales, respectively. Data were analysed using descriptive and inferential statistics. Alpha level was set at P<0.05.

The mean age of the 125 participants was 62.0±7.1years (60% male). The mean values for FEV₁, FVC and FEV₁/FVC were 1.8±0.6L, 2.4±0.5L and 58.0±8.8%, respectively, and the mean 6MWT and PESE values were 291.1±41.6m 63.1±11.2%. Exercise capacity was correlated with mean values for the respiratory parameters FEV₁ (r=0.29; P=0.035), FVC (r=0.32; P=0.045) and FEV₁/FVC ratio (r=0.37; P=0.007), and both exercise capacity and PESE were correlated with gait speed (r=0.96, P=0.001 and r=0.57; P=0.042) and RPE (r=0.42, P=0.050 and r=-0.44; P=0.032), but PESE was not correlated with respiratory parameter values (P>0.05). Participants with COPD demonstrated reduced respiratory parameter values and low exercise capacity but moderate PESE. We found significant correlations between exercise capacity and respiratory parameter values, but PESE was correlated with only gait speed and RPE. The study has implications for respiratory health promotion and exercise adherence.