Liquid Nitrogen-Induced Asphyxia

INTRODUCTION

Nitrogen gas (N2), as a major inert gas of the atmosphere, is liquefied to liquid nitrogen (LN2) on cooling to -196℃ and easily vaporizes at room temperature. Known to be harmless with the exception of potential frostbite injury, LN2 is widely used in laboratories and in industry for freezing, filling, or cleaning purposes (1, 2). The few reported cases of accidental harm from LN2 (3-5) were caused by careless management, which may have involved sudden LN2 evaporation leading to oxygen depletion in limited spaces. However, those reports (3-5) did not reveal indisputable evidence of the cause of asphyxia even though they included complete autopsies, toxicological analysis, and blood gas analysis. In this case report, a postgraduate student was found dead in an underground dry area where a cylinder of LN2 had been disposed. By a complete autopsy, we analyzed the atmosphere gas of the dry area through a reconstruction of the accidental scene in order to help define the cause of death.