Mass carbon monoxide poisoning among television viewers of a football match.

BACKGROUND: The objective was to study a mass carbon monoxide (CO) poisoning and the characteristics of the asymptomatic cases. METHODS: On the 2nd of February, 2015, a group of more than 30 television viewers of a football match contacted the emergency department due to suspected CO poisoning from a butane stove. A visual inspection of the location of the exposure and a descriptive epidemiological study were conducted. Based on the type of variable, the presence of a statistical association was studied with Fisher's exact test or the Kruskal-Wallis test. RESULTS: Thirty-four of the 39 individuals were affected (87.2%). The exposed individuals had a mean age of 43.8 years (SD, 22.1), and 28.2% (11/39) were women. The time of exposure was 52.4min (SD, 21.0), and the mean distance from the oven was 4.2m (SD, 2.5). The most common symptoms were headache (50%), nausea (20.6%), weakness (20.6%) and dizziness (14.7%). The carboxyhaemoglobin (COHb) levels were very high (13.8% ±5.8%). Some 97.1% of the individuals required oxygen therapy, and 39.4% required hyperbaric chamber treatment. Some 29.5% of the cases had no symptoms but showed COHb levels similar to those that did have symptoms (13.6% vs. 15.3%, nonsignificant difference). The asymptomatic cases had a shorter exposure time (38.3min vs. 53.3min; P<.036). CONCLUSIONS: Almost a third of the exposed individuals were asymptomatic, even with COHb levels similar to those of the symptomatic patients, and the majority of these asymptomatic patients even required oxygen treatment in a hyperbaric chamber.