Sudden death in infants sleeping on polystyrene-filled cushions

Infants are at risk for both the sudden infant death syndrome (SIDS) and accidental suffocation. On postmortem examination, however, it is difficult to distinguish one from the other without information from the scene of death. Healthy infants are assumed to be able to turn their heads and, if not otherwise restrained, to obtain fresh air. We assessed this assumption in an investigation of infant deaths that occurred during sleep on cushions filled with polystyrene beads.

We obtained data on 25 deaths from the U.S. Consumer Product Safety Commission. We also used mechanical and animal models to study physiologic aspects of ventilation relevant to these results, by simulating the effects on an infant of breathing into a cushion. We measured the effects of softness, malleability (molding of the cushion about an infant's head), airflow resistance, and rebreathing of expired gases.

All 25 study infants were prone when found dead, and at least 88 percent were face down with nose and mouth obstructed by the cushion. SIDS was the diagnosis in 19 of the 23 infants who underwent autopsy. Our findings show, however, that the cushion would have limited movement of the infant's head to obtain fresh air, and the amount of rebreathing we estimated to have occurred in the infants was lethal in a rabbit model.

Accidental suffocation by rebreathing was the most likely cause of death in most of the 25 infants studied. Consequently, there is a need to reassess the cause of death in the 28 to 52 percent of the victims of SIDS who are found with their faces straight down. Safety regulations setting standards for softness, malleability, and the potential for rebreathing are needed for infant bedding.