Therapeutic Oxygen for Gastrointestinal Atony (TOGA)

Inclusion Criteria: * patient or health proxy has been adequately informed of risks and benefits and agrees to his/her participation in the study. * patient is a hospitalized inpatient diagnosed with ileus, bowel obstruction or colonic pseudo-obstruction \[clinician interpretation or small bowel diameter ≥3.5 cm, cecal diameter ≥ 9 cm, sigmoid colon diameter ≥ 6 cm\]. * patient is clinically and hemodynamically stable * patient does not require supplemental oxygen greater than 2 liters per minute via nasal cannula * patient does not have any respiratory contraindications to 100% oxygen * failure to respond to non-surgical/non-endoscopic therapy for at least 24 hours, therapy at discretion of treating physician \[to eliminate patients with trivial ileus not requiring advanced intervention\] Exclusion Criteria: * patient is not expected to survive in the short term. * patient is a pregnant or lactating woman. * patient presents with severe or unstable psychiatric disorders. * patient is participating in concomitant research studies that would interfere with this study. * patient is an alcohol or drug abuser. * respirator support required. * unable to tolerate 100% oxygen for respiratory reasons or any other reasons. * perforation of the viscus. * inability to obtain informed consent. * hypoxemia, as in room air oxygen saturation less than 90%.