Association between thoracic muscle mass assessed by high-resolution computed tomography and static lung volume in patients with COPD - a pilot study

Abstract

Introduction: Patients with COPD are at risk of progressive muscle mass reduction, but it is unclear whether there is a relationship between thoracic muscle mass and static lung volume.

Aim: To investigate whether there is an association between thoracic muscle mass and static lung volume in patients with COPD.

Methods: An observational study based on outpatients with stable COPD, who received a body plethysmography and high-resolution thoracic computed tomography (HRCT).

Skeletal muscle tissue with Hounsfiled units between -29 to +150 was segmented on an axial HRCT image at the first slice above the aortic arch using in-house software.

Measures of muscle area was reported as cumulated height adjusted skeletal muscle index (SMI, cm²/m²), thus excluding the intercostal muscle. Baseline values were reported as median (interquartile range). Linear regression analysis was applied for SMI with the total lung capacity (TLC), residual volume (RV), inspiratory capacity/TLC ratio (IC/TLC) corrected for gender.

Results: In total 42 patients were included (21 male/21 female), age of 65 (61-69) y.o., SMI 56.8 (49.4-66.3) cm²/m², TLC 115.5% (105-122%), RV 160.5% (133-195%), IC/TLC. 815 (.695-. 991). SMI had a negative linear relationship with TLC (adj R2=.441) and RV (adj R2=.416) and a positive linear relationship with IC/TLC ratio (adj R2=.436) (all p-values=<.0001).

Conclusion: This pilot study indicates that there is a significant linear association between the muscle measure SMI and the static lung volumes in patients with COPD. Static lunge volumes may help to identify patients with reduced muscle mass. However, further studies are needed.