The LUS was always carried out by the same expert operator with a 5–10 MHz linear probe (L38e—Sonosite
MicroMaax Systems). The probe was placed perpendicular, oblique and parallel to the ribs
in the anterior, lateral and posterior thorax as described by Copetti&Cattarossi (2008) with
the patient in the supine position and sitting position to scan the posterior thorax.