Transthoracic ultrasonography in patients with interstitial lung disease

Transthoracic ultrasonography (TUS) is suggested as a noninvasive, radiation-free method for the assessment of interstitial lung disease (ILD). This study was designed to study TUS features of ILD. Furthermore, possible correlations of these features with parameters of spirometry, arterial blood gas (ABG) analysis and 6-min walk test (6MWT) were assessed.

Fifty patients with ILD were diagnosed based on history, examination, chest X-ray/high-resolution computed tomography, and spirometry. Each patient underwent 6MWT, ABG analysis, and TUS. TUS was also performed on 20 healthy volunteering controls.

The TUS features among patients were B pattern in 40 patients (80.0%, P < 0.001), decreased lung sliding in 22 patients (44.0%, P < 0.001), pleural line thickening in 28 patients (56.0%, P < 0.001), pleural line irregularity in 39 patients (78.0%, P < 0.001) and subpleural changes in 22 patients (44.0%, P < 0.01). Increasing pleural line thickness was inversely correlated with forced vital capacity (FVC) percent predicted (r = -0.345, P < 0.05), pO₂ (r = -0.335, P < 0.01), SpO₂ at rest (r = -0.444, P < 0.01), 6-min walk distance (6MWD) (r = -0.554, P < 0.001) and distance-saturation product (DSP) (r = -0.572, P < 0.001). Increasing distance between B lines also correlated inversely with FVC percent predicted (r = -0.278), pO₂ (r = -0.207), SpO₂ at rest (r = -0.170), 6MWD (r = -0.209), and DSP (r = -0.214); however these correlations were not statistically significant (P > 0.05).

TUS seems to be a useful imaging method for the diagnosis of ILD. It can be used to estimate the severity of ILD. It is simple, bedside, cost-effective, and radiation-free. It may be especially useful in the follow up of patients in low resource settings, pregnant females, and bed-ridden or unstable patients who cannot be shifted to radiology suite.