Introduction: Patients with COPD are prone to progressive muscle mass reduction; however, how exacerbations (EXAs) affect the thoracic muscle mass is not fully understood.

Aim: To investigate EXAs? effect on thoracic muscle mass

Methods: A prospective 1-year follow up of patients with stable COPD. Patients underwent body plethysmography and HRCT.

One axial HRCT image at the first slice above the aortic arch was segmented using in-house semiautomated software. Hounsfield units (HU) between -29 to 150 was regarded as muscle.

Muscle mass was reported as cumulated height adjusted skeletal muscle index (SMI, cm2/m2) and skeletal muscle density (SMD, mean HU of the muscle area). Baseline values reported as mean (95% confidence interval). A linear regression was applied between the changes in SMI and number of exacerbations. An independent t-test was applied changes in both SMI and SMD vs EXA groups: rare (0-1) and frequent (2?).

Results: Thirty-three patients (16 men, 17 women) were included with mean age of 65.1 y.o. (61.9;68.3); FEV1 63.8% (57.4;70.2); BMI 26.8(24.5;29.0); EXAs 1.5/year (0.86;2.0) at baseline.

There were no significant changes in demographics at follow-up. SMI was significantly reduced by -2.1 cm²/m² (-2.9;-1.3, p<0.0001), the same applied for SMD -1.69 HU (-2.9;-0.46, p=0.009). There was no association between changes in SMI and the number of EXAs nor any significant differences between exa groups.

Conclusion: This pilot study indicated that there is a significant reduction in SMI and SMD within 1 year. The changes in SMI and SMD may not be related to the number of exacerbation/year. However, further studies are needed