UNINTENTIONAL SUFFOCATION BY REBREATHING - A DEATH SCENE AND PHYSIOLOGICAL INVESTIGATION OF A POSSIBLE CAUSE OF SUDDEN INFANT DEATH

As part of a 1-year study of sudden unexpected infant deaths in St. Lo uis, we performed both a specialized death scene investigation and, in selected cases, a physiologic reconstruction of the death scene with a rabbit model. Those cases in which the infant was found face down wi th nose and mouth covered by bedding were chosen for the physiologic t esting; our goal was to assess the potential for lethal rebreathing of expired air. The physiologic studies reconstructed the infants' premo rtem ventilatory environment by using the head from an infant mannequi n positioned on the actual bedding on which an infant had died and a r abbit breathing through the mannequin's nares. The specialized scene i nvestigation was carried out in 31 of 32 deaths from sudden infant dea th syndrome, diagnosed by the usual methods. Of 31 infants, eight died with their faces downward and covered by bedding, and the bedding was obtained for further study in seven of eight cases. The bedding had l ow resistance to airflow (6.25 to 22.6 cm H2O/L per second), and cause d considerable rebreathing that was lethal to the rabbits in five of s even cases. We conclude that items of bedding in common use are capabl e of causing lethal rebreathing by prone-sleeping infants whose nose a nd mouth become covered; suffocation by rebreathing was the probable m echanism of death in a substantial number of these deaths that had bee n attributed to sudden infant death syndrome.