A fatal case of accidental asphyxia following nitrous oxide inhalation and alcohol consumption.

Nitrous oxide (N2O) abuse is becoming increasingly popular worldwide. Moreover, the use of N2O combined with other substances, such as alcohol, is also common. Accidental deaths associated with N2O abuse are rare in forensic practice, with most fatal cases involving continuous inhalation equipment or exposure in a confined space. In contrast, the inhalation of N2O using balloons is traditionally regarded as a relatively safe method. In this report, we present an unusual fatal case of a 16-year-old girl who died after drinking alcohol and inhaling N2O from balloons. The decedent was found in a prone position with the nose and mouth compressed against the bed. Cyanosis of nails, pulmonary and cerebral edema, and the positive expression of HIF-1α in lung, myocardium and brain, were indicative of asphyxiation. Toxicological analysis revealed a peripheral blood ethanol concentration of 140 mg/dL and cardiac blood N2O concentration of 74.5 μL/mL. N2O was also positively detected in the lungs, stomach contents, gastric air, and the brain. In conclusion, we determined that the decedent died from accidental asphyxia related to N2O inhalation, prone positioning, and alcohol consumption. We also investigated chronic N2O abuse from a forensic perspective. This report aims to help forensic pathologists manage similar cases. It also reminds N2O abusers of potential dangers.