In laparoscopic cholecystectomy method, Insufflation of CO2 in abdominal cavity causes positioning of the diaphragm upwards, a decrease in lung's volume and its compliance, an increase in the airway resistance, mismatch between the atelectasis and the ventilation perfusion. Although there are numerous studies in laparoscopic surgery, only a few of them investigate the effects of laparoscopic surgery on the cardiopulmonary and the respiratory mechanics. The investigator aimed To examine the effects of pressure-controlled and volume-controlled ventilation modes on cerebral oximetry and blood gases in laparoscopic cholecystectomy operations.

Since the laparoscopic methods have been introduced to the surgical operations, laparoscopic cholecystectomy has become the golden standard in gall bladder surgical treatments. In this method, carbon dioxide (CO2) pneumoperitoneum method is used to achieve the desired surgical and visual conditions. Alongside the advantages of the Laparoscopic cholecystectomy method (e.g. shortening the patient's length of stay at the hospital, minimal postoperative pain and rapid recovery), it has various intraabdominal pressure related systemic disadvantages . Insufflation of CO2 in abdominal cavity causes positioning of the diaphragm upwards, a decrease in lung's volume and its compliance, an increase in the airway resistance, mismatch between the atelectasis and the ventilation perfusion. Various ventilation strategies have been introduced to increase arterial oxygenation, functional residual capacity (FRC), and the lung compliance. Recent studies; demonstrates that pressure-controlled mechanical ventilation is superior to volume-controlled mechanical ventilation in providing arterial and tissue oxygenation.

Although there are numerous studies in laparoscopic surgery, only a few of them investigate the effects of laparoscopic surgery on the cardiopulmonary and the respiratory mechanics. Several experimental and clinical studies describe that the cardiovascular effects of the high intraabdominal pressure and the CO2 insufflation is complex. In fact, the results are linked to the studied patients' population, the lung's position and its volume. As it is known in laparoscopic surgeries, the oxygenation in cerebral tissue decreases as the intraabdominal pressure increases. At present, bispectral index (BIS), electroencephalography (EEG), auditory evoke potential (AEP) (and several others) and functional NIRS (fNIRS) are used to measure cerebral oxygenation and anaesthetic depth. NIRS monitorisation makes use of the combined effects of the transmission, the reflection, the dispersion, and the absorption of light. It can also measure the oxygen saturation in tissues that does not have pulsatile circulation. The investigator aimed To examine the effects of pressure-controlled and volume-controlled ventilation modes on cerebral oximetry and blood gases in laparoscopic cholecystectomy operations.

Inclusion Criteria:

• ASA (American Society of Anesthesiology) score of 1 and 2
• body mass index < 30 kg/m2
• planned elective laparoscopic cholecystectomy operation
• 18-65 years old

Exclusion Criteria:

• who are applied with emergency laparoscopic cholecystectomy operation
• ASA (American Society of Anesthesiology) score of 3 and above
• hematocrit value 30 and below
• body mass index> 30 kg/m2
• major pulmonary disease (this condition was defined as having capacity and currency flow speed values that are below %70 in respiratory functional tests)
• patients with a history of thoracic surgery