Components of physical capacity in patients with chronic obstructive pulmonary disease: relationship with phenotypic expression

Background: More accurate phenotyping of COPD is of great interest since it may have prognostic and therapeutic consequences. We attempted to explore the possible relationship between the extent of emphysema, as assessed by high-resolution computed tomography (HRCT), and COPD severity. We also included some study variables involving exercise tolerance evaluation and peripheral muscle strength (PMS) measurement. Methods: Sixty-four patients with COPD (mean age 64 +/- 7 years) were enrolled in a prospective observational cross-sectional study. All patients underwent clinical and functional evaluations: assessment of dyspnea, body mass index (BMI), health status assessment, spirometry testing, and arterial blood gas analysis. The extent of emphysema was graded using HRCT. Functional capacity was evaluated by a cardiopulmonary maximal exercise testing (CPET), the shuttle walking test, and by estimation of PMS. Results: Half of the study patients had an emphysematous phenotype. There was a significant correlation between the score derived from analysis of HRCT images and BMI and respiratory functional parameters, as well as VO2 max (maximal oxygen uptake) and chest pull 1RM (1 rep max). Compared with subjects with a nonemphysematous phenotype, those with an emphysematous phenotype showed a lower BMI, a reduced PMS, and displayed a lower power at CPET. Significant differences in lung function tests were found for diffusing capacity and hyperinflation. No significant differences in quality of life were observed between the two study groups. Conclusions: Compared with subjects with a nonemphysematous phenotype, subjects with an emphysematous phenotype has a different profile in terms of BMI, lung function, PMS, and exercise capacity.