Inhaled air trapping effect of Japanese bedding as a risk of sudden unexpected death in infancy.

We assessed some Japanese bedding on the assumption of the effects of air trapping using an infant mannequin. The change of CO2 concentration in the airway of a mannequin head placed on bedding was continuously monitored using a CO2 analyzer during simulated breathing. To compare the level of CO2 dispersal among different items of bedding, CO2 half time (t1/2) values were used. The t1/2 values were calculated by measuring the time required for the expired percent CO2 to reach 1/2 the initial percent end-tidal PCO2. We also measured softness and resistance to airflow (R) of the same items. As for the bedding, 4 types of futon and several types of bottom sheets/towels were combined. The t1/2 value in supine position was 9.8 seconds. When the model was placed prone on futon, the t1/2 values increased to 14.1 seconds (hard mattress type)--17.2 seconds (soft cotton-like futon). With respect to present Japanese baby futon (hard mattress type), there may be a relatively low potential for rebreathing to occur, compared with soft futon. In every case, the t1/2 value was prolonged by the use of a towel spread on the futon. CO2 dispersal may depend not only on the softness of the futon, but also on the combination of bottom sheet/towel and mattress. There was no relationship between R values and t1/2 values. The potential of rebreathing increased in face down position among all bedding, and supine position was the best CO2 dispersal position.