Hyperbaric Oxygen Therapy for Ulcerative Colitis Flares

Inclusion Criteria: * Hospitalized patients with known or newly diagnosed moderate to severe ulcerative colitis (as defined by the Mayo score ≥6) * Consented within the first 48 hours of initiating IV steroids * Risk score of \>3 points (pts) * Mean stool frequency/24 hrs (\<4 = 0 pts, 4-6 = 1 pt, 7-9 = 2 pts, \>9 = 4 pts) * Colonic Dilation = 4pts * Hypoalbuminemia (\< 3mg/dL) = 1 pts * Mayo endoscopic sub-score \>2 (moderate to severe) * Age \>18 and able to make their own medical decisions Exclusion Criteria: * Complication requiring urgent surgical intervention (in the opinion of the investigators) * Clinically significant cardiac, renal, neurological, endocrine, respiratory or hepatic impairment in the opinion of the investigator, including but not limited to: * Pulmonary (COPD with CO2 retention; Previous/current imaging showing hyperinflation/air trapping/bullous disease/blebs (opinion of investigators), Current pneumothorax or previous spontaneous pneumothorax, Bronchogenic cyst(s)) * Cardiac (Uncontrolled HTN (systolic \>160 or diastolic \>100), Unstable angina or myocardial infarction within the previous 3 months, Ejection fraction \< 35%, Current or previous amiodarone use, ICD in place, Pacemaker in place not approved for chamber use) * Hematological/Oncological (Current chemotherapeutic drug use, and past history of bleomycin use,Hereditary Spherocytosis, Sickle cell anemia) * Gastrointestinal and Infectious Disease (Known or suspected Crohn's disease, Previous infection with mycobacterium, fungus, HIV, Hepatitis B or C, Severe gastrointestinal or systemic infection (opinion of investigator), Current capsule endoscopy or previously non-retrieved capsule * Endocrinology (Uncontrolled hyperthyroidism) * Neurological and Psychological (Vagal or other nerve stimulators, Uncontrolled seizure disorder, Medications or medical conditions that lower seizure threshold (opinion of the investigator), Drug or alcohol abuse/dependence,Current treatment for alcohol cessation with disulfiram, Current or recent (within past week) use of baclofen) * Head and Neck (Previous middle ear damage, surgery or infection(s) which may increase the risk for needing ear tubes (opinion of the investigator),Current or previous retinal detachment or optic neuritis, Retinal or vitreous surgery within the past 3 months) * Implanted devices not on the approved list for use with HBOT * Women who are pregnant or nursing. Women with childbearing potential were required to use effective birth control if not surgically sterile or postmenopausal for \>2 years.