Clinical Research Directory

Inclusion Criteria: 1. Adult patients (≥ 18 years old) scheduled for elective non-cardiothoracic surgery requiring general anesthesia with an endotracheal tube 2. Planned admission to the post-anesthesia care unit (PACU) after surgery 3. BMI ≥ 40 kg/m2 4. At the time of baseline measurements in the PACU, patients meet the following criteria: * Receiving ≤ 6 liters of supplemental nasal cannula oxygen * Alert as defined by a Richmond Agitation Sedation Scale of 0 or -1 * Oriented to person, place, and time Exclusion Criteria: 1. Pregnancy, suspected pregnancy or less than six weeks postpartum Known or current pneumothorax 2. Hemodynamic instability at the time of study assessment in the PACU defined as: * systolic blood pressure \<90 mmHg or \>180 mmHg * mean blood pressure \<60 or \>130 mmHg * Any use of intravenous vasoactive agent * heart rate \< 50 or \> 120 beats per minute 3. Respiratory insufficiency in PACU defined as: * Respiratory rate \> 30 * Oxygen saturation \< 92% * Receiving \> 6 liters of supplemental oxygen 4. Known chronic lung disease requiring supplemental oxygen at home 5. Known systolic heart dysfunction (left ventricular ejection fraction ≤ 30%) 6. Contraindication for esophageal catheter placement: * Known esophageal varices * Known bacterial sinusitis * Recent esophageal, nasopharyngeal, or laryngeal trauma or surgery * Known coagulopathy: including history of thrombocytopenia defined as platelet count \<50,000; presence of hemophilia; known genetic disorder of coagulation (e.g.,deficits of protein C, protein S, von Willebrand factor) or oral and subcutaneous anticoagulation treatment (e.g., heparin, warfarin, and or other oral anticoagulants) 7. Contraindication for electrical impedance tomograph belt placement: * Pacemaker and/or internal cardiac defibrillator * Chest skin injury 8. Concern for study inclusion by the perioperative nurse or anesthesia team