Airflow resistance and CO2 rebreathing properties of anti-asphyxia pillows designed for epilepsy

PURPOSE Seizure related unconscious face-down positioning could contribute to sudden unexpected death in epilepsy via asphyxia. Low airflow resistance lattice foam pillows have been advocated for this group. However, data to support this approach remain lacking, and low airflow resistance per se may not negate asphyxia risk from expired gas rebreathing. This study was designed to compare the airflow resistance and CO2 rebreathing properties of lattice vs conventional pillows. METHODS Airflow resistance and inspired CO2 levels during replicate 10 min periods of simulated adult ventilation and CO2 rebreathing were compared between cotton, latex and two lattice pillows designed for use in epilepsy (one commercially available, one prototype). Kaplan-Meier and Cox regression analyses were used to examine the hazard of exceeding 10% inspired CO2 within 10-min of rebreathing. RESULTS Inspiratory resistance was significantly lower in the commercially available and prototype lattice compared to cotton and latex pillows (mean±SD; 3.2±0.8, 2.6±0.4, 26.1±3.5, 4.6±0.4 cm H2O l(-1)s respectively at 0.2l s(-1)). During simulated rebreathing, inspired CO2 exceeded 10% within 2 min with cotton and latex pillows, compared to an upper asymptote around 8-9% at 10 min with lattice pillows. The hazard of exceeding 10% inspired CO2 was therefore markedly reduced with lattice compared to cotton and latex pillows (hazard ratio vs cotton pillow; commercial 0.04 [0.01-0.18], prototype 0.08 [0.02-0.26], latex 0.79 [0.33-1.87]). CONCLUSION Conventional pillows can rapidly accumulate potentially life-threatening CO2 levels during simulated rebreathing. Lattice pillows appear to reduce asphyxia risk but accumulated CO2 may still reach levels threatening to health and survival.