Effects of respiratory disease and age in quadriceps muscle mass: a pilot study with ultrasonography

Abstract

Introduction Patients with chronic obstructive pulmonary disease (COPD) have been shown to present more muscle wasting than their healthy peers, which affects their quality of life [1,2]. The mechanisms behind muscle wasting in COPD are still little understood and even less is known in other chronic respiratory diseases (e.g. interstitial lung diseases – ILD) [3]. Ultrasound (US) is a safe and inexpensive imaging modality which can provide reliable measurements of muscle size and quality [2]. Thus, US may be a useful technique to enhance our understanding of muscle waste in chronic respiratory diseases. This study aimed to explore differences in quadriceps muscle mass in patients with COPD, hypersensitivity pneumonitis (ILD-HP) and healthy people (elderly and young). Materials and methods A cross-sectional pilot study was conducted with 10 patients with ILD-HP (68.4 ± 9.8yrs), 10 patients with COPD (69.4 ± 6.7yrs) and 10 healthy elderly volunteers (67.8 ± 8.7yrs). Groups were gender (5f/5m) and age matched. A group of 10 young university students (21.9 ± 3yrs) was also included. An US equipment (GE LOGIQ P6) with multifrequency linear probe (10–13 MHz) was used to obtain B-mode US images. The following measures were taken: Rectus Femoris Thickness (RFT), Quadriceps Thickness (QT) and Rectus Femoris cross sectional area (RFCSA). Data were analysed using SPSS version 24. Data normality and homogeneity were assessed. Between-group differences and correlations were performed with non-parametric tests (Kruskal–Wallis, Mann–Whitney U-test and Spearman´s correlation coefficient). Statistical significance was set at .05. Results RFCSA (median and IQR) was 5.44 [3.56–6.57] cm2; 4.29 [3.58–4.50] cm2; 6.06 [4.61–9.41] cm2 and 7.99 [5.92–9.41] cm2 for ILD-HP, COPD, elderly and young people, respectively. RFT results were 1.51 [1.08–1.78] cm; 1.16 [1.07–1.53] cm; 1.64 [1.36–1.76] cm and 2.06 [1.68–2.27] cm, respectively. There were significant differences in RFCSA (p = .027), RFT (p = .041) and QT (p = .011) between COPD and elderly people. No differences were found between ILD-HP group and elderly. Significant differences between the elderly and young groups were found for the same measurements (RFCSA p = .034; RFT p = .016; QT p = .034). Moderate and negative correlations were found between age and RFCSA (r s=–0.416), RFT (r s=–0.540) and QT (r s=–0.450). A strong and positive correlation was found between RFT and RFCSA (r s=0.891). Discussion and conclusions Our results seem to corroborate previous findings supporting the existence of quadriceps muscular wasting in patients with COPD when compared with age-matched healthy controls [2,4]. In the group of patients with ILD-HP, muscle mass seems to be somewhat preserved. To confirm our results, future studies should include a larger sample with quantitative measures of muscular quality (e.g. echointensity) and relationship between muscle size/quality and muscle strength.