We enjoyed the exhaustive narrative review by Covic et al.1 We particularly appreciated the caution expressed regarding clinical interpretation of B-lines, which are lung ultrasound artifacts, because many recent articles have endorsed the validity of counting artifacts for the diagnosis of pulmonary edema or any extravascular lung water. This is troubling because such findings lack disease specificity.2 Whatever the cause, B-lines are mostly generated when the ultrasound beam crosses areas of difference in acoustic impedance (chest wall vs air) that reduce the propagation speed of the ultrasound beam.