Transthoracic ultrasound artifact in lung diseases

What is it about?

Artifacts are commonly generated at interfaces between soft tissue and gas or between fluid and gas, characterized by substantial differences in acoustic impedance. This difference results in almost complete reflection of the incident beam. Interfaces of this type are likely to be more numerous in several pleuropulmonary diseases, including those considered in our study. These conditions are associated with an increased fluid component or tissue (fibrotic). This mechanism would explain the increased number of B-lines observed in diseased lungs. On the other hand, our data highlighted the importance of the correct machine setting and the non-specificity of B-lines.

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Why is it important?

The aim of this multicenter study was to determine whether B-lines number differs in normal and diseased lungs and whether these numbers can be used to discriminate between different types of pulmonary disorders in acutely ill patients. Therefore, we investigated the B-lines observed on transthoracic US scans performed with both low–medium and high frequency US probes in a large series of patients with acute dyspnea and in control groups composed of healthy subjects and of patients who had undergone pneumonectomy. In this multicentric study, we evaluated the number of B-lines in ultrasound pulmonary examination in a large sample of patients with acute dyspnea and compared the results with those obtained in healthy lungs and in the post-pneumonectomy chest cavities. The B-lines were almost two times more numerous in the lungs of patients with dyspnea than in those of healthy subjects and in the chest cavities of patients who had undergone pneumonectomy. However, this difference is common to several diffuse pleuropulmonary diseases. Consequently, in real-life clinical settings, the evaluation of B-lines offers no concrete benefits in terms of the differential diagnosis of dyspnea in diffuse pleuropulmonary diseases. Transthoracic ultrasound represents a potentially useful complementary tool in the study of pleuropulmonary diseases. Nevertheless, the quantification of B-lines alone does not make any significant contribution to the differential diagnosis or prognostic assessment of these diseases, especially in acute settings.

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