The study of the correlations between the mass and fat infiltration of intercostal muscles and the severity of airflow obstruction in patients with chronic obstructive pulmonary disease by quantitative CT

Objective To investigate the correlations between the mass and fat infiltration of intercostal muscles and their severity of airflow obstruction in patients with chronic obstructive pulmonary disease(COPD). Methods One hundred and sixty-three COPD patients and 102 normal subjects between August 2015 to March 2017 underwent chest MSCT scans and all data were analyzed retrospectively. All subjects underwent pulmonary function tests (PFT). According to the global initiative for chronic obstructive lung disease(GOLD, updated 2015), the COPD patients were classified into GOLD 1(n=37), GOLD 2(n=46), GOLD 3 (n=48), GOLD 4 (n=32) by pulmonary function results, respectively. The mass and fat infiltrations of intercostal muscles were quantified as the cross-sectional area (CSA) and attenuation of these muscles using CT histogram analysis. Intercostal indexes and attenuation indexes were defined as intercostal CSA and attenuation divided by body mass index(BMI). Comparison of intercostal indexes and attenuation indexes between the COPD and control groups was perfomed using t test. The comparisons between the 4 COPD subgroups were carried out using ANOVA test, and comparison between the two groups by LSD. The correlation between intercostal indexes and attenuation indexes and PFT were evaluated by the Spearman rank correlation test. Results The CSA and attenuation indexes of COPD patients groups were (4.3±2.1) mm2·m2·kg-1, (-1.6±6.9) HU·m2·kg-1, respectively,both were significantly lower than that of the control group [ (6.9±1.7) mm2·m2·kg-1, (11.6±5.7) HU·m2·kg-1]. The difference was statistically significant (t=12.82, 10.87, P<0.01) . The CSA and attenuation indexes of COPD patients in any subgroups and the control group were of significant difference(F=92.79, 8.80, P<0.01) .The CSA and attenuation indexes were negatively correlated with the GOLD grades, the difference was statistically significant (r=-0.615,-0.551, P<0.05) . Conclusions Mass and fat infiltration of intercostal muscles of COPD patients measured by CT histogram analysis were correlated with their severity of airflow obstruction. In other words, a decrease in intercostal mass and an increase in intercostal fat are associated with worsening of COPD severity. Key words: Pulmonary disease, chronic obstructive; Intercostal muscles; Respiratory function tests; Tomography, X-ray computed