In patients with carbon monoxide poisoning, hyperbaric oxygen therapy was associated with a lower rate of mortality, according to results of a recent retrospective study.

The mortality reduction was particularly evident among patients under 20 years of age and in patients with acute respiratory failure, authors of the study said in a report published in Chest (2017 Nov. doi: 10.1016/j.chest.2017.03.049 ).

“The results provide important references for decision making in the treatment of carbon monoxide poisoning,” Chien-Cheng Huang, MD, department of emergency medicine, Chi-Mei Medical Center, Tainan, Taiwan, and colleagues said in their report.

While hyperbaric oxygen has been suggested for severe carbon monoxide poisoning, 100% normobaric oxygen is considered standard treatment, according to Dr. Huang and colleagues.

“There has been no consensus about whether hyperbaric oxygen therapy is better than 100% normobaric oxygen alone, or the number of sessions of hyperbaric oxygen therapy that are necessary regarding mortality and morbidity,” they wrote.

In a Taiwanese nationwide poisoning database, Dr. Huang and colleagues identified 25,737 patients diagnosed with carbon monoxide poisoning between 1999 and 2012. Of those patients, 7,278 had hyperbaric oxygen therapy.

After researchers adjusted for variables including age, sex, and underlying comorbidities, the mortality rate was lower in patients who underwent hyperbaric oxygen therapy, compared with those who did not (adjusted hazard ratio, 0.74; 95% confidence interval, 0.67-0.81), data show.

The reduction in mortality was especially notable in patients younger than age 20 years (adjusted HR, 0.45; 95% CI, 0.26-0.80), according to the researchers.

A similarly greater magnitude of mortality benefit also was found for patients who had acute respiratory failure, “which supports acute respiratory failure being an indication for hyperbaric oxygen therapy,” investigators wrote. “Further studies are warranted to clarify this issue.”

The number of hyperbaric oxygen therapy sessions appeared to make a difference in mortality. Patients who received two or more sessions had a lower rate of mortality than did those who had only one session, according to the report.

Predictors of mortality, described in more detail in the published report, included older age, diabetes, alcoholism, and suicide attempts, among other factors.

“In addition to considering hyperbaric oxygen therapy for reducing mortality, control of other concomitant mortality predictors is necessary,” the authors concluded based on their results.

Accidental deaths from carbon monoxide poisoning also are a major issue in the United States, where each year, there are an estimated 1,000-2,000 cases, according to the authors. Additionally, accidental carbon monoxide poisoning has “increased greatly in the past 10 years,” they said in the report.

Other studies have shown that, compared with normobaric oxygen, hyperbaric oxygen therapy did not reduce neurologic complications, the authors noted. Even so, that fact “does not suggest that hyperbaric oxygen therapy is not beneficial regarding mortality,” they wrote. “In fact, it is possible that reducing mortality may increase morbidities such as neurologic sequelae.”

Dr. Huang and coauthors reported no conflicts of interest related to the study, which was supported by Chi-Mei Medical Center in Taiwan.