Fig. 1

Algorithm to assess recruitment maneuver by ultrasound. Ultrasound diagnoses lung collapse (step 1) and assesses hemodynamics (step 2) before the lung recruitment maneuver is done (step 3). During the step-wise increment in airways pressure (Paw) of the recruitment maneuver, ultrasound can detect the plateau pressure at which dependent lungs collapse disappear (opening pressure—upper circle). Then, ultrasound defines the start of lung re-collapse in the most dependent pulmonary areas during the PEEP trial (closing pressure—lower circle). The images were obtained in an anesthetized child using a linear 7–13 MHz probe placed in the oblique position of the most dependent lung zones