What is the efficacy of hyperbaric oxygen therapy for treating carbon monoxide (CO) toxicity?

Updated: Dec 31, 2020
  • Author: Guy N Shochat, MD; Chief Editor: Gil Z Shlamovitz, MD, FACEP  more...
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Hyperbaric oxygen (HBO) therapy currently rests at the center of controversy surrounding management of CO poisoning. Increased elimination of HbCO clearly occurs. Certain studies proclaim major reductions in delayed neurologic sequelae, cerebral edema, pathologic central nervous system (CNS) changes, and reduced cytochrome oxidase impairment.

Despite these individual claims, systematic reviews have not revealed a clear reduction in neurologic sequelae with HBO. [39, 40] A 2017 clinical policy statement from the American College of Emergency Physicians (ACEP) concluded that it remains unclear whether HBO therapy is superior to normobaric oxygen therapy for improving long-term neurocognitive outcomes. [25]  

A study by Han et al, in which 224 patients with acute CO poisoning were followed for up to 6 months, found no difference in the incidence of delayed neuropsychiatric sequelae between patients receiving HBO (n=198) and those receiving normobaric oxygen (n=26). [41]  In contrast, a nationwide observational study from Japan reported that patients who received HBO therapy had significantly lower rates of depressed mental status and reduced activities of daily living at discharge compared with a control group. Similar benefits were seen in patients with non-severe CO poisoning. The study used one-to-one propensity score matching to pair 2034 patients who received HBO therapy within 1 day of admission with an equal number of patients who did not receive HBO. [42]

However, evidence of a mortality benefit with HBO therapy has emerged. A retrospective study by Rose et al that reviewed 1099 cases of CO poisoning in adults concluded that HBO therapy was associated with an absolute risk reduction of 2.1% in both inpatient and 1-year mortality. [43]  

Lower mortality with HBO therapy was also reported in a retrospective nationwide population-based cohort study from Taiwan that included 7,278 patients who received HBO and 18,459 patients who did not. Overall, the adjusted hazard ratio [AHR] for death in HBO-treated patients was 0.74 (95% CI, 0.67-0.81). In patients younger than 20 years, the AHR was 0.45 (95% CI, 0.26-0.80) and for those with acute respiratory failure, the AHR was 0.43 (95% CI, 0.35-0.53). The lower mortality rate was noted for a period of 4 years. [44]  

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