Diaphragm ultrasound in patients with interstitial lung disease (ILD): a prospective study

Abstract

<b>Background:</b> diaphragm ultrasound (DUS) has been extensively used in critical ill patients receiving mechanical ventilation while data on its role in patients with interstitial lung disease are scarce. In this study, we measured diaphragmatic function by ultrasound in outpatients with connective tissue disease-associated interstitial lung disease (CTD-ILD) and Idiopathic Pulmonary Fibrosis (IPF). <b>Methods:</b> 31 CTD-ILD (59±10.7years) and 41 IPF patients (73±6.1years) were prospectively enrolled. 15 healthy subjects (54±5.8years) served as controls. A portable ultrasound was used to measure, during quiet breathing, right diaphragm displacement (DD) and right thickening fraction (TF) during follow-up visits. <b>Results:</b> DD was significantly lower in patients with CTD-ILD compared with those affected by IPF and compared with healthy subjects [1.3(0.6–2.5), 1.8(0.9–2.6), 1.5(1.1–2.4) respectively; p=0.009]. In addition, in CTD-ILD but not in IPF patients, a positive correlation was observed between TF and FVC%pred. (r=0.48, p=0.007), TLC%pred. (r=0.39, p=0.028), and DLCO% (r=0.62, p=0.0002). In the entire patient population, a TF &lt;30% was associated with dyspnea score (mMRC ≥2) in univariate (OR 3.88, 95%CI1.27–11.86; p=0.018) and multivariate analysis (OR 3.56, 95%CI1.27–11.27; p=0.031). <b>Conclusion:</b> diaphragm displacement is significantly decreased in patients with CTD-ILD compared with IPF patients and healthy subjects. Thickening fraction is an independent predictor of dyspnea and positively correlates with several functional parameters. Diaphragm impairment is common in patients with CTD-ILD while not in patients with Idiopathic Pulmonary Fibrosis.