This study aims to investigate the effects of the personalized application of respiratory pressures applied to patients undergoing laparoscopic bariatric surgery when they are connected to a ventilator under general anesthesia, on the postoperative period. The effects of the ventilation practices that are fixed in routine practice and revised according to various variables during the surgery during artificial respiration after intubation under general anesthesia will be examined with ultrasonography. No change will be made to the routine anesthesia practice for this purpose, the pressure values in the ventilator under general anesthesia will be adjusted during the surgery within the framework of the values used in anesthesia practice. After the surgery, the lung area will be examined with ultrasound in the recovery unit and the findings will be recorded. This study does not have any undesirable effects or risks. This study does not include any interventional procedures.

Our study is a double-blind study and the specialist physician performing the postoperative lung ultrasound will not know which group the patient is in. Before the patients are taken into surgery, they will be determined by a permanent anesthesiologist in the preoperative evaluation room using the closed envelope method. The teams that perform all measurements and randomize the patients will remain constant throughout the study. Patients who agree to participate in the study will undergo standard monitoring (heart rate - HR, peripheral oxygen saturation - SpO2, noninvasive blood pressure - NIBP, end-tidal carbon dioxide pressure - etCO2) followed by anesthesia induction. After endotracheal intubation, patients will begin to breathe with volume-controlled ventilation-VCV mode.

In the first group (group PEEP8), a tidal volume of 6-8 ml/kg will be adjusted according to their ideal weight and a fixed PEEP of 8cmH20 will be applied throughout the intraoperative period, and a manual recruitment maneuver (with a pressure of 30 cmH2O for 40 seconds) will be applied after the pneumoperitoneum is terminated. The second group (Group DC) will be ventilated in VCV mode again and a tidal volume of 6-8 ml/kg will be given according to their ideal weight. The PEEP value at which the highest compliance value determined in the anesthesia device is obtained will be adjusted. In this group, PEEP titration will be repeated during pneumoperitoneum and skin closure. While applying PEEP titration to patients, a recruitment maneuver will also be applied. In this maneuver, PEEP will be increased at 2-minute intervals so that the maximum peak pressure is 45 cmH2O and the driving pressure is 15 cmH2O, and when the target is reached, it will be decreased and the PEEP value will be adjusted at the value at which the highest compliance is obtained. The spO2 values of the patients in both groups will be targeted as 92-94%, the EtCO2 values as 35-45 cmH2O, and the FiO2 and respiratory rate will be adjusted accordingly. After extubation, the patient will be taken to the recovery room and monitored. After 15 minutes, lung ultrasound (USG) will be performed on patients in both groups by an experienced anesthesiologist who is blinded to the study using the MyLab ™ Seven convex probe (2-5 MHz). Both hemithoraxes will be divided into 6 regions by 3 vertical lines from the anterior axillary, parasternal and posterior axillary lines; 2 horizontal imaginary lines 1 cm above the nipple and at the level of the diaphragm. Each region will be evaluated for lung sliding movement, A lines, B lines, consolidation, air bronchograms, pleural effusion and pneumothorax, and the total score calculated using the modified lung ultrasound score will be recorded and compared.

Inclusion Criteria:

- Patients over the age of 18, with a body mass index of 35 and above, and who are scheduled for laparoscopic bariatric surgery will be included in our study.

Exclusion Criteria:

• Patients with advanced COPD,
• Patients with a history of pneumothorax,
• Patients with lung bullae,
• Patients who have undergone thoracic surgery,
• Patients with a diagnosis of major cardiac disease (valve diseases, heart failure, systolic dysfunction),
• Patients with severe respiratory failure,
• Patients with previous pulmonary surgery will not be included in the study.

It will be shared once enough data has been accumulated.

this study is a double-blind study. the patient and the specialist physician performing the postoperative lung ultrasound will not know which group the patient is in.