Arm positioning alters lung volumes in subjects with COPD and healthy subjects

Subjects with chronic obstructive pulmonary disease (COPD) have difficulty performing arm exercise, particularly if the arms are unsupported and elevated. The purpose of this study was to evaluate the effect of arm position on static lung volumes in COPD and healthy subjects. Lung volumes were measured by plethysmography in nine COPD subjects (mean age +/- SD = 67.3 +/- 10.3 years; % pred FEV1 +/- SD = 39.7 +/- 10.9%) and nine healthy subjects (mean age +/- SD = 55.8 +/- 8.8 years; % pred FEV1 +/- SD = 102.9 +/- 12.2%) with the arms below 90 degrees shoulder flexion, at 90 degrees shoulder flexion and above 90 degrees shoulder flexion. In all subjects a significant increase in functional residual capacity (FRC) and reduction in inspiratory capacity (IC) was shown with arms above 90 degrees shoulder flexion when compared with both arms below 90 degrees shoulder flexion (mean increase in FRC (95% CI) was 0.17 L (0.06 to 0.27) for COPD and 0.29 L (0.11 to 0.47) for healthy subjects; mean reduction in IC (95% CI) was 0.24 L (0.1 to 0.38) for COPD and 0.45 L (0.22 to 0.68) for healthy subjects) and arms at 90 degrees shoulder flexion (mean increase in FRC (95% CI) was 0.15 L (0.01 to 0.29) for COPD and 0.22 L (0.11 to 0.34) for healthy subjects; mean reduction in IC (95% CI) was 0.14 L (0.01 to 0.26) for COPD and was 0.29 L (0.17 to 0.42) for healthy subjects). These changes may alter lung mechanics and, in COPD subjects, may affect their ability to perform arm exercise above shoulder height