Inclusion Criteria:  Patients scheduled for either:  open thoracic or video-assisted thoracoscopic surgery under general anesthesia requiring one-lung ventilation abdominal surgery with a known history of chronic obstructive pulmonary disease (as documented in the electronic medical record)  Exclusion Criteria:  Emergency surgery surgery requiring the use of transesophageal echocardiography refusal of informed consent pregnancy esophageal surgery lung transplantation contraindications for placement of esophageal stethoscope including esophageal varices strictures, motility disorders, diverticula or a history of prior esophageal injury or surgery age less than 18 years old prisoner