Thoracic Ultrasound Strain Elastosonography as a Noninvasive Biomarker of Chronic Obstructive Pulmonary Disease-Associated Lung Injury: A Feasibility Study

Background: Transthoracic strain elastosonography (TSE) is being increasingly studied for estimating lung-pleura interface stiffness in pulmonary fibrosis. To date, no data exist on its application in chronic obstructive pulmonary disease (COPD). Objectives: The aim of this article was to describe the TSE pattern in patients with COPD and healthy subjects, either smokers or nonsmokers, and evaluate the feasibility of this technique for early detection of COPD in smokers. Methods: Nineteen patients with COPD, twenty-one healthy smokers, and twenty healthy nonsmokers underwent spirometry and TSE. Elastosonography was performed by one ultrasound-certified operator on 12 different scans for each participant, on right and left sides, anteriorly and posteriorly, on upper and lower lobes. For each scan, lung-pleura interface stiffness index (SI) was calculated, and the average SI on all 12 scans (SI-12) and on posterior basal scans (SI-PB) was calculated and used for comparisons among groups of participants and correlations with spirometric parameters. Results: Patients with lung injury (i.e., with COPD or healthy smokers) exhibited significantly increased lung-pleura interface stiffness on TSE, measured by SI-12 and SI-PB, than healthy nonsmokers (p < 0.05). Unlike SI-12, SI-PB was able to discriminate between subjects with lung injury and healthy nonsmokers on receiver operating characteristics analysis (area under the curve 0.846, 95% confidence interval 0.730-0.926, p < 0.001) and correlated with forced expiratory volume in the first second (r = -0.31, p = 0.018). Conclusion: The measurement of lung-pleura interface stiffness by TSE in posterior basal scans was able to discriminate patients with lung injury from healthy nonsmokers. The role of TSE for detecting early lung damage in COPD should be further investigated.