Use of hyperbaric oxygen therapy for preventing delayed neurological sequelae in patients with carbon monoxide poisoning: A multicenter, prospective, observational study in Japan

The purpose of this study was to clarify the practical clinical treatment for acute carbon monoxide (CO) poisoning in Japan and to investigate the efficacy of hyperbaric oxygen (HBO.sub.2) therapy in preventing delayed neurological sequelae (DNS) in the acute phase of CO poisoning. We conducted a multicenter, prospective, observational study of acute CO poisoning in Japan. Patients with acute CO poisoning were enrolled and their treatment details were recorded. The primary endpoint was the onset of DNS within 2 months of CO exposure. Factors associated with DNS were assessed with logistic regression analysis. A total of 311 patients from 57 institutions were registered and 255 were analyzed: 171 received HBO.sub.2 therapy (HBO.sub.2 group) and 84 did not (normobaric oxygen [NBO.sub.2 ] group). HBO.sub.2 therapy was performed zero, once, twice, or three times within the first 24 h in 1.8%, 55.9%, 30.9%, and 11.3% of the HBO.sub.2 group, respectively. The treatment pressure in the first HBO.sub.2 session was 2.8 ATA (47.9% of the HBO.sub.2 group), 2.0 ATA (41.8%), 2.5 ATA (7.9%), or another pressure (2.4%). The incidence of DNS was 13/171 (7.6%) in the HBO.sub.2 group and 3/84 (3.6%) in the NBO.sub.2 group (P = 0.212). The number of HBO.sub.2 sessions in the first 24 h was one of the factors associated with the incidence of DNS (odds ratio, 2.082; 95% confidence interval, 1.101-3.937; P = 0.024). The practical clinical treatment for acute CO poisoning, including HBO.sub.2 therapy, varied among the institutions participating in Japan. HBO.sub.2 therapy with inconsistent protocols showed no advantage over NBO.sub.2 therapy in preventing DNS. Multiple HBO.sub.2 sessions was associated with the incidence of DNS.