after being informed about the study and potential risks. All patients giving written consent will be randomized by double blind manner into 2 groups each one containing 24 patients Group SPV: will be ventilated using volume controlled ventilation (7ml/kg tidal volume) with addition of 5 cm H₂O fixed PEEP till the end of the surgery .~Group OLA: The patients will undergo ARM followed by personalized PEEP.
the purpose of this study is to compare open lung approach versus conventional protective ventilation in obese patients undergoing open abdominal surgery