Table 4.

Basic definitions of lung ultrasound (LUS) findings.

LUS Finding	Definition
A-lines (A-line artefacts)	Repetition of the pleural line at a standardized distance equal to the skin–pleural line distance.
B-lines (B-line artefacts)	Comet-tail artefacts that arise from the pleural line and move simultaneously with the breathing cycle. The other optional 4 criteria are: screen-long, well-defined, erasing A-lines, and hyperechoic.
Consolidation	Hypoechoic, subpleural tissue-like area, caused by fluid displacing alveolar air. In case of a large consolidation, the appearance is characteristically liver-like. Usually, a consolidation has blurred margins and the following associated features: –The loss of pleural line echogenicity over the area of consolidation and the absence of A-lines within the area. –Comet-tail artefacts arising from the deep edge of the consolidation. –B-lines surrounding the area of consolidation. – An air bronchogram—observed as multiple hyperechoic specks or branching tree-like structure within the area of consolidation: a) Dynamic—moving simultaneously with the breathing cycle; or b) Static. –A fluid bronchogram—an anechoic or hypoechoic branched tubular structure along the airways, within the area of consolidation. –Vascular pattern in color Doppler option—observed as branching tree-like structures with blood flow.
I-lines, Z-lines (I- and Z-line artefacts)	Short vertical hyperechoic artefacts arising from the pleural line, not reaching the distal edge of the screen.
Interstitial syndrome	≥3 B-lines visible in the longitudinal plane between two ribs.