CO2 (Carbon Dioxide) - Cerebral Oxygenation

On the day of surgery patients will be randomized. After induction of anesthesia and endotracheal intubation patients will be managed by the study team to perform the intervention and the measurements.

According to randomization, investigational medical product (IMP) or comparator will be administrated by ventilator 1/ventilator 2.

At time point 1 apnea will be performed by disconnecting the ventilator from the endotracheal tube until the NIRS value has dropped by 20% from baseline. After that, re-ventilation will be resumed immediately, until parameters have returned to baseline.

During apnea time NIRS and vital signs will be recorded permanently, blood samples will be drawn at definite time points.

Application of IMP (or comparator) will be performed in this cross-over study design in the same manner after the baseline level is reached again.

At the end of the study procedure, after the baseline level of end-expiratory CO2 is reached again, patient will be taken over by the clinical anesthesia team and surgeons.

Inclusion criteria

• Patients who are designated for bariatric surgery at the University Hospital Zurich (USZ)
• Informed Consent as documented by signature
• BMI >35 kg/m2

Exclusion criteria

• Severe end-organ damage: chronic obstuctive pulmonary disease (COPD) GOLD (cassification) III and IV, known hepatic insufficiency or elevated liver enzymes, renal creatinine clearance <30ml/min
• Severe cardiovascular disease (NYHA classification III and IV)
• Known pulmonary Hypertension
• Cerebrovascular disease
• Pregnancy and lactation
• Cardiac dysrhythmias
• acidosis, chronic pulmonary disease
• Known or suspected non-compliance, drug or alcohol abuse