Ultrasound Guided Recruitment Manauvere Versus Individualized Positive End Expiratory Pressure in Pediatric Patients Undergoing Laparoscopic Abdominal Surgery

Patients will receive a fixed positive end-expiratory pressure (PEEP) of 5 cmH2O throughout the surgical procedure.

Patients will receive ultrasound-guided lung before pneumoperitoneum, after pneumoperitoneum then once an hour, until the end of surgery. Alveolar recruitment will be conducted the same as that for the conventional manoeuvre with a simultaneous continuous ultrasound assessment if atalectasis is detected until no collapsed areas are visualized. When the collapsed lung areas are absent on the sonogram, positive end-expiratory pressure (PEEP) can no longer increase at this point. Subsequently, the pressure will be maintained for approximately 10 breaths.

Patients will receive individualized positive end-expiratory pressure (PEEP). After the first recruitment Maneuvere (RM), titration of PEEP will be performed by setting the initial PEEP to 5 cm H2O, then increasing PEEP according to the gradient of 2 cmH2O every 3 min, calculating static compliance (Cstat) according to the formula: \[Cstat = VT/Pplat - PEEP\] (Pplat = plateau pressure), then gradually increasing PEEP, until the calculated Cstat shows a downward trend, the we set its previous PEEP (corresponding to PEEP for high Cstat) as the optimal PEEP for this patient. The highest PEEP is limited to 15 cmH2O.