In their letter, Bronshteyn et al. pinpoint a critical issue concerning lung ultrasound training: the identification and interpretation of vertical artifacts, the so-called B lines.

Vertical artifacts have been indifferently termed comet tail artifacts, ultrasound lung comets, ring-down artifacts, and B lines. Multiple internal reverberations issued from subpleural airspaces surrounded by edematous tissue is the main biophysic mechanism producing B lines. In experimental models,4,5  the generation of B lines requires two conditions: (1) The existence of acoustic traps combining transonic access channels and air bubbles. The multiple reflections between bubbles reradiate the incident wave to the probe, with a wavelength that depends on transonic access channels’ shape and size. (2) The acoustic trap should have a minimal size under which it cannot emit a B line. The ratio between...

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