Chest wall muscle atrophy as a contributory factor for forced vital capacity decline in systemic sclerosis-associated interstitial lung disease.
OBJECTIVE
To investigate the potential contribution of accessory respiratory muscle atrophy to the decline of forced vital capacity (FVC) in patients with SSc-associated interstitial lung disease (ILD).


METHODS
This single-centre, retrospective study enrolled 36 patients with SSc-ILD who underwent serial pulmonary function tests and chest high-resolution CT (HRCT) simultaneously at an interval of 1-3 years. The total extent of ILD and chest wall muscle area at the level of the ninth thoracic vertebra on CT images were evaluated by two independent evaluators blinded to the patient information. Changes in the FVC, ILD extent, and chest wall muscle area between the two measurements were assessed in terms of their correlations. Multiple regression analysis was conducted to identify the independent contributors to FVC decline.


RESULTS
Interval changes in FVC and total ILD extent were variable among patients, whereas chest wall muscle area decreased significantly with time (P=0.0008). The FVC change was negatively correlated with the change in ILD extent (r=-0.48, P=0.003) and was positively correlated with the change in the chest wall muscle area (r = 0.53, P=0.001). Multivariate analysis revealed that changes in total ILD extent and chest wall muscle area were independent contributors to FVC decline.


CONCLUSION
In patients with SSc-ILD, FVC decline is attributable not only to the progression of ILD but also to the atrophy of accessory respiratory muscles. Our findings call attention to the interpretation of FVC changes in patients with SSc-ILD.
['Nawata|Takashi|T|', 'Shirai|Yuichiro|Y|', 'Suzuki|Mikito|M|', 'Kuwana|Masataka|M|']
D018450:Disease Progression D005260:Female D006801:Humans D064169:Intermediate Back Muscles D017563:Lung Diseases, Interstitial D008297:Male D008875:Middle Aged D009133:Muscular Atrophy D012044:Regression Analysis D012129:Respiratory Function Tests D012132:Respiratory Muscles D012189:Retrospective Studies D012595:Scleroderma, Systemic D064171:Superficial Back Muscles D013904:Thoracic Vertebrae D013997:Time Factors D014057:Tomography, X-Ray Computed D014797:Vital Capacity
forced vital capacity interstitial lung disease respiratory muscles systemic sclerosis