Group A patients received the standard ventilation protocol as follows: volume-controlled ventilation mode, with VT 6 ml/kg of ideal body weight, inspiratory : expiratory ratio 1 : 2, a PEEP of 4 cmH2O, and respiratory rate 10-12 breaths/min that will be adjusted to keep end-tidal carbon dioxide tension (EtCO2) between 35 and 40 mmHg and inspired oxygen fraction of 0.5.

Patients in group B received the standard ventilation protocol with stepwise peep until end of surgery and extubation.

• a PEEP of 4 cmH2O will be used after intubation till 5 minutes after pneumoperitonium, and adjusted in a step wise approach after lung ultrasound by adding 2 cmH2O, repeating ultrasound 5 minutes after every change in peep till no lung collapse is detected by lung ultrasound with a maximal peep of 10 cmH2O, or if hemodynamic instability occurs.
• Lung ultrasound examination will be performed at a minimum three times in each patient; the first will be performed 1 min after starting mechanical ventilation of the lungs, 5 minutes after pneumoperitonium, 5 min after every peep increase in stepwise peep group and the last time at the end of the surgery.

We define anaesthesia-induced atelectasis to be significant if any region has a consolidation score of ≥ 2.

to evaluate the effect of lung ultrasound in optimizing peep in obese patients undergoing laparoscopic surgeries on the Incidence of intraoperative hypoxia and atlectasis

Evaluating the effect of stepwise PEEP approach on the incidence of early postoperative in the first 24 hours atelectasis and oxygenation.