Abstract： Objective To explore the therapeutic effect of noninvasive positive pressure ventilation coupled with early hyperbaric oxygen (HBO) therapy on severe carbon monoxide poisoning,with aims to increase cure rate and decrease incidence of delayed encephalopathy.Methods One hundred and seventy-eight cases of severe carbon monoxide poisoning were randomly divided into 2 groups:the simple HBO therapy group consisting of 90 patients,and the non-invasive positive pressure ventilation + HBO group consisting of 88 patients.The 2 groups of patients all received routine medical treatment,such as rectification of dehydration,reduction of intracranial pressure,antibiotics,symptom-directed medical support,etc.The patients in the simple HBO therapy group received HBO therapy twice a day within 1 week of admission into the hospital.At other time without HBO therapy,they had normobaric oxygen breathing.The patients in the positive pressure ventilation + HBO group were treated with positive pressure ventilation coupled with HBO therapy twice a day within 1 week of admission,and at other time,they had continuous non - invasive positive pressure ventilation.Then,therapeutic effects,the number of dead cases and the number of delayed encephalopathy were compared between the 2 groups.Results Statistical significance could be noted,when comparisons were made between the simple HBO group and the non-invasive positive pressure ventilation + HBO group(P ＜ 0.05 or P ＜ 0.01 ).For patients with treatment time as an indicator,which was over 6 hours,the therapeutic effects of the noninvasive positive pressure ventilation + HBO group were obviously better than those of the simple HBO group,with statistical significance ( P ＜ 0.05 ).Conclusions For patients with acute severe carbon monoxide poisoning,noninvasive positive pressure ventilation and HBO therapy should be applied as early as possible,so as to increase cure rate,decrease mortality and reduce occurrence of delayed encephalopathy.