Patients undergoing general anesthesia require mechanical ventilation (artificial delivery of air and oxygen to their lungs). It is well known that during mechanical ventilation so called atelectasis formation occurs. This is a condition characterized by partial or complete collapse of lung tissue that can result in a reduction in oxygen uptake through the lung. A known risk factor for atelectasis formation during mechanical ventilation is the utilization of high oxygen concentration as the oxygen molecules are absorbed in the lung, which then can lead to collapse of the tissue. Despite the proven association standard operating procedure at the end of anesthesia still requires utilization of 100% oxygen. Its justification is the goal to ensure sufficient oxygenation throughout the extubation phase. However, clinical observation doesn't show a lack of oxygenation in this phase but the patient is still exposed to the risk of atelectasis formation.
This study aims to investigate the hypothesis of whether the utilization of reduced oxygen concentration before extubation (70% compared to 100%) reduces atelectasis formation. Patients who participate in this study are randomly (i.e. by chance) assigned to either the control group receiving standard care (100% oxygen at the end of anesthesia), or the intervention group receiving 70% oxygen. Of note, this is still 3 times as much as when breathing "standard" room air, which has 21% oxygen. During the intervention, parameters such as the oxygen content in the blood (oxygen saturation, SpO2), heart rate and blood pressure are recorded and atelectasis formation is measured using a technique called electrical impedance tomography (EIT). EIT measurements are performed at designated timepoints during the procedure. Anesthesia care providers are asked to document procedural, patient and ventilator data in a questionnaire. Secondary outcomes are the homogeneity and distribution of air measured with EIT, as well as some clinical outcomes including post-extubation desaturation (<90% SpO2), incidence of re-intubation or non-invasive ventilation and the Post-anesthesia Care Unit (PACU) length of stay.