Han S, Nah S, Choi S, et al. - In patients with acute carbon monoxide (CO) poisoning, the development of delayed neuropsychiatric sequelae (DNS) can be averted by using hyperbaric oxygen (HBO) therapy, however, there is no clear consensus concerning the optimal number of HBO therapy sessions. Researchers conducted this prospective observational study recruiting 299 patients with CO poisoning with the aim to compare the development of DNS after 3 and > 3 sessions of HBO therapy in these patients. The analysis was performed of 183 (59.0%) patients, excluding patients on the basis of following reasons: age < 18 years, not underwent HBO therapy, discharged against medical advice, and loss to follow-up. DNS development was observed in 17.5% of the patients. No difference was reported in DNS development after 3 and > 3 sessions of HBO therapy.