Does the COPD assessment test associate to skeletal muscle dysfunction in individuals with chronic obstructive pulmonary disease?

Background: Skeletal muscles provide the mechanical basis for breathing and movement, and skeletal muscle dysfunction which is frequently observed in individuals with chronic obstructive pulmonary disease (COPD) has important clinical implications. Aims: The objective of the present study was to investigate whether the COPD assessment test (CAT) score may be associated with quadriceps muscle thickness, handgrip strength, peripheral muscle endurance and respiratory muscle strength in individuals with COPD enrolled in a pulmonary rehabilitation program. Methods: This is a cross-sectional study with evaluation of the following outcomes: quadriceps muscle thickness (ultrasonography), handgrip strength (muscle strength dynamometer), peripheral muscle endurance (30-second sit-to-stand test) and respiratory muscle strength (manovacuometry). Results: Twenty-three individuals (65 ± 10.1 years; GOLD I (n=2), II (n=8), III (n=7) and IV (n=6)) participated in the study. The CAT score correlated negatively and moderately with handgrip strength (r=-0.655; p<0.001), negatively and moderately with quadriceps muscle thickness (r=-0.562; p=0.005) and peripheral muscle endurance (r=-0.573; p=0.004). There was no correlation between CAT score and respiratory muscle strength. The multiple linear regression model including the variables quadriceps muscle thickness, handgrip strength and peripheral muscle endurance was the best to predict the CAT score, explaining 65% of the variance. Conclusions: Our results suggest that the CAT score was associated with skeletal muscle dysfunction through quadriceps muscle thickness, handgrip strength and peripheral muscle endurance in a sample composed predominantly of women with COPD, ex-smokers or without previous smoking history enrolled in a pulmonary rehabilitation program.