Death scene gas analysis in suspected methane asphyxia.

Two cases of methane asphyxia occurring in two boys (age 11 and 12 years) who were found at the bottom of a 37-ft (11.1-m)-deep sewer shaft are described. Attempted resuscitation of the first patient was unsuccessful and achieved only temporary stabilization of the second, who died 48 h after his discovery. Autopsies revealed relatively minor multifocal traumatic injuries, with evidence of hypoxic-ischemic encephalopathy in the patient who survived for 2 days. Subsequent analysis of gas in the shaft revealed 21% oxygen at the surface, 14.3% at a depth of 5 ft (1.5 m), and only 4.8% at depths of 10 ft (3 m) and below. Other gases detected at the lower levels were methane, nitrogen, and carbon dioxide (4.3%). These cases demonstrate the value of atmospheric gas analysis in cases of possible methane asphyxia in confirming the presence of methane and in demonstrating levels of oxygen below that necessary to support life.