Recently HBO has also been used in cases of liver failure and liver transplantation [5]. HBO with 100% oxygen at twice sea level atmospheric pressure can create an arterial oxygen tension in excess of 2000 mmHg, and almost 400 mmHg in tissues [6]. Here we examined the utility of HBO for various gastroenteric diseases. Methods Thirty-nine patients with gastro enteric conditions that had proved refractory to conservative therapies such as antibiotics or drainage were treated with HBO between 2007 and 2012 in our department (Table 1). Patients were treated once a day in a hyperbaric chamber (BARA MED, Koike Medical, Tokyo, Japan) at a pressure of 2.0 atmospheres absolute and received 100% oxygen (Figure 1). Session duration was 60 min, and decompression was initiated at 15 min. Each patient provided written informed consent to undergo HBO. Acute appendicitis HBO was applied to 7 cases of acute appendicitis. Appendectomy was not performed for 2 of these cases because of severe extension of retroperitoneal abscess or phlegmon. The other cases involved postappendectomy abscesses. The mean number of HBO sessions was 9.9 (range 7 to 14). Pyrexia decreased to below 38 degrees 1.8 days (range 1 to 3 days) after initiation of HBO. The mean white blood cell count decreased from 13183 to 7185 micro little, and the CRP level from 13.7 to 0.7 mg/dl. All seven patients were discharged without further drainage surgery (Figures 3a and 3b).