Ultrasonographic Assessment of Lung Recruitment Maneuvers in Children Undergoing Lengthy Microsurgery Operations

Patients will receive recruitment maneuver (RM) followed by decremental PEEP titration 1min. after establishment of mechanical ventilation and after documented lung re-collapse.

The patient will be ventilated with volume control mode with tidal volume 6 ml/kg, PEEP 3 cmH2O, an inspiratory expiratory ratio of 1:1.5, respiratory rate 20-25 breaths per minute depending on the patient's age and FiO2 of 0.3.