Effect of timing of hyperbaric oxygen therapy on prognosis of patients with acute moderate to severe carbon monoxide poisoning

Objective To investigate the the timing of the first time of hyperbaric oxygen therapy and its effect on the recovery of neurological function and quality of life in patients with acute moderate to severe carbon monoxide poisoning. Methods A retrospective analysis was carried out in the patients with acute carbon monoxide poisoning admitted to our hyperbaric oxygen treatment center from January 2015 to June 2018. The patients who met the criteria of poisoning within 24 h, did not receive hyperbaric oxygen treatment in other hospitals, and had moderate or severe poisoning were divided into 3 groups according to the first treatment time, that is, ultra-early group (shorter than 6 h after poisoning), early group (within 6~12 h), and ordinary group (in 12~24 h after poisoning). The degree of recovery (complete recovery, partial recovery, no recovery), Glasgow coma index (GCS), simple mental state scale (MMSE), Barthel index (BI) and incidence of delayed encephalopathy after treatment was compared among the 3 groups. Results A total of 136 patients were eligible for admission, including 39 in the ultra-early group, 51 in the early group and 46 in the ordinary group. There were no significant differences in age, sex distribution and total treatment times among the groups. At the end of treatment, the proportions of patients with complete recovery were 43.5%, 31.4%, and 17.4%, respectively in the ultra-early group, early group and ordinary group. The improvement of GCS score was 4.85, 3.87 and 3.01, respectively, that of MMSE score was 19.01, 14.05, and 12.34, respectively, and that of BI was 75.48, 68.24 and 54.58, respectively, in the 3 groups. In 1 year after the treatment, delayed encephalopathy was observed in 2 cases (5.1%) in the ultra-early group, 7 cases (13.7%) in the early group, and 14 cases (30.4%) in the ordinary group. The ultra-early group obtained all better indicators than the ordinary group, and better percentage of complete recovery of symptoms, MMSE score and lower incidence of delayed encephalopathy when compared with the early group (all P < 0.05). Conclusion Implementation of hyperbaric oxygen therapy within 6 h after poisoning can result in a better prognosis for patients with moderate to severe acute carbon monoxide poisoning.