Hyperbaric Oxygen Therapy for Ulcerative Colitis (HBOT-UC)

Inclusion Criteria:

• Participants with known or newly diagnosed UC who require hospitalization for anacute moderate to severe flare

• Age 18-85

• Able to fully participate in all aspects of the trial

• Consented and able to receive first HBOT session within first 48 hours of initiationof intravenous steroids

• Agreement to not participate in another trial for the duration of the activeintervention period

Exclusion Criteria:

• Received hyperbaric oxygen therapy either as part of standard of care or through aclinical trial prior to enrollment

• Complication requiring urgent surgical intervention

• Requirement for new start of a biologic or small molecule during the hospitalizationprior to randomization and/or anticipated requirement for rescue medical or surgicaltherapy within 48 hours of randomization

• Toxic megacolon

• Inability to receive intravenous steroids

• Historically failed or been exposed to 4 or more classes of advanced therapeuticoptions

• Known or suspected diagnosis of Crohn's colitis, indeterminate colitis, ischemiccolitis, radiation colitis, diverticular disease associated with colitis,microscopic colitis or infectious colitis

• Received any investigational drug within 30 days

• Clinically significant cardiac, renal, neurological, endocrine, respiratory orhepatic impairment that increases the risk for HBOT toxicity

• Women who are pregnant or nursing

• Unwillingness to complete course of HBOT