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The optimal hyperbaric oxygen (HBO2) treatment protocol for acute carbon monoxide (CO) poisoning is unknown. This is indicated by one study that found 18 different protocols to treat CO poisoning by North American multiplace hyperbaric facilities. A pilot study was conducted to evaluate the feasibility of randomizing patients to different protocols and to determine whether any large differences in clinical outcome were present between the two most common protocols.Adult patients with accidental CO poisoning resulting in transient loss of consciousness, presentation to the emergency department within 12 hours, primary language English, high school education, and residence within 100 miles of the hyperbaric facility were recruited. Enrolled patients were randomized to one HBO2 treatment at 2.4 atmospheres absolute (atm abs) pressure with 90 minutes of 100% oxygen breathing vs. treatment by the US Air Force CO protocol (3.0 atm abs maximum pressure). A neurocognitive screening test was performed immediately after hyperbaric treatment and repeated 14-21 days later.From 1995 to 2002, 30 patients age 21 to 88 years were randomized, 18 to treatment at 2.4 atm abs and 12 to 3.0 atm abs. Average carboxyhemoglobin level for the population was 24.8 +/- 8.8% (mean +/- SD). Delay to hyperbaric treatment averaged 313 +/- 129 minutes. Neither variable was different between treatment groups. Six patients had abnormal neurocognitive testing immediately following hyperbaric treatment, 4 in the 2.4 atm abs group (22%) and 2 in the 3.0 atm abs group (17%) (P=0.71). One patient in each group demonstrated abnormality on delayed testing (p=0.75). One in each group did not return for follow-up.It is feasible to randomize CO-poisoned patients to different hyperbaric treatment protocols. Determination of differences in efficacy between treatment protocols will require a large multicenter trial with the use of detailed neurocognitive testing.

Depressive illness and related suicide attempts have been reported to have seasonal variation, possibly related to weather. This study sought to determine the effects of weather and time of year on suicide attempts by carbon monoxide (CO) poisoning. Cases of patients in western Washington State attempting suicide by CO poisoning and referred to a regional hyperbaric oxygen treatment center from 1981-1995 were reviewed retrospectively. Information from the National Climatic Data Center was used to compare date of treatment to local weather data on the day of attempted suicide and on each day of the preceding week. The study population consisted of 264 patients attempting suicide by CO poisoning on 251 days of the 15-yr period. Mean and total precipitation in the preceding 7 days strongly correlated with attempted suicide rate, with incident rate ratios ranging from 1.75 to 2.77 and 1.14 to 1.75, respectively (P values0.05). A decrease in minimum daily temperature also correlated with attempted suicide rate. No other weather variables showed significant correlation with dates of CO suicide attempts. February, March, and October were seen to be separate factors related to a higher incidence of attempted suicide by CO poisoning. Precipitation in Seattle, change in minimum temperature, and month of the year correlated with the regional incidence of suicide attempts with CO poisoning.

To describe the case characteristics of a series of patients poisoned with carbon monoxide (CO) resulting from indoor burning of charcoal briquets.Cases of patients with unintentional CO poisoning referred for treatment with hyperbaric oxygen were reviewed. Cases that occurred as the result of indoor burning of charcoal briquets were analyzed.A private, urban, tertiary care center.Seventy-nine patients ranging from 3 months to 87 years of age referred from 10 counties within the state of Washington between October 1982 and October 1993.Of 509 patients treated for acute unintentional CO poisoning, 79 cases occurred in 32 incidents as a result of indoor burning of charcoal briquets, for the purpose of either home heating or cooking. A majority of cases occurred in the months of October through January, commonly during power outages or when electricity was intentionally disconnected. Patients of minority races were disproportionately represented compared with the general population of the region.Carbon monoxide poisoning is a significant hazard from indoor use of charcoal briquets. All cases are avoidable and public awareness of the risk should be enhanced.