Lung Recruitment in Laparoscpic Surgery

"The patients will be divided into three groups:~Control group:(31 patients); Patients will have controlled mechanical ventilation with these parameters (fixed Tidal Volume 6-8ml/Kg IBW - fixed fio2 0.5% - fixed PEEP 6 cmH2O - fixed respiratory rate10-14 RR/min) II) Group (II) Sustained inflation group (SI): (31 patients); Patients will have controlled mechanical ventilation then after abdominal deflation, sustained inflation for 30 second by applying pressure 40 cmH2O, with 5 these parameters (fixed Tidal Volume 6-8ml/Kg IBW - fixed fio2 0.5% - fixed PEEP 6 cmH2O - fixed respiratory rate 10-14 RR/min) III) Group (III) Stepwise PEEP increasing: (31 patients); Patients will have controlled mechanical ventilation, then after abdominal deflation gradual increasing in PEEP 2 cmH2O every 5 respiratory cycle with maximum 10-12 cmH2O guided by hemodynamics \& airway pressure not exceeding 40 cmH2O."