Effects of Pneumoperitoneum on Dynamic Alveolar Stress-strain in Anesthetized Pediatric Patients

Esophageal pressure will be measured by an esophageal ballon to assess transpulmonary pressure during laparoscopy surgery. Lung collapse will detected when transpulmonary pressure became negative and using lung ultrasound images. Lung ultrasound examinations will be performed at different times-points: after anesthesia induction, 10 minutes after pneumoperitoneum insufflation, and at the end of surgery. A lung recruitment maneuver will be applied if these patients present atelectasis during surgery.