Ultrasound assessment of quadriceps muscle in COPD patients: Functional and clinical implications

Abstract

Background: Current evidence indicates that decreased muscular mass of the lower limbs significantly increases both mortality and healthcare costs in COPD patients. One tool that provides a non-invasive, quick, and reliable assessment of muscle quality is Ultrasound imaging. Objective: The purpose of the study was to determine the association between functionality assessed with the 6-minute walk (6MWT), with muscle thickness and echo intensity (EI) of quadriceps as measured through ultrasound in COPD patients. Methods: Thickness and EI of the rectus femoris (RF) and vastus intermedius (VI), were evaluated in 20 COPD patients with B-mode US imaging. Functionality was assessed with the 6MWT. Differences between muscles were determined with the Student9s t-test. Pearson and Spearman rank correlation coefficients were used to analyze relationships between variables of interest, according to data characteristics. Finally multivariate regression models were applied. Results: There was a good correlation between the thickness of the RF and VI (r=0.427, p=0.030 and r=0.469, p=0.018, respectively), Multivariate regression analysis showed that the EI of the RF, EI of the VI, and thickness of the VI explained 70% of the variance in the distance walked during the 6MWT. Conclusions: In COPD patients exercise capacity is associated with quantitative (thickness) and qualitative (echo intensity) characteristics of the quadriceps assessed with ultrasound. Reference: Diaz O, Morales A.,et al. CT and physiological determinants of dyspnea and exercise capacity during the six minute walk test in mild COPD. Respiratory Medicine 2013;107:570-579.