Calorimetrical comparison of insulative properties of metalized plastic, clear polyethylene, and polyester blanket.

The thermal insulation properties of metalized plastic sheeting (MPS), clear polyethylene sheeting (CPS) and 100 per cent polyester thermal bed blanket (TBB) were tested and compared quantitatively using direct calorimetry. The experiments were carried out on individual subjects sitting in a whole body calorimeter and covered first with a TBB bag up to the neck. Then the three materials were tested, one at a time, over the original TBB up to the neck. The temperature of the calorimeter was set at normal operating room temperature of 18 degrees C. MPS provided the greatest reduction in sensible heat loss (SHL) of all three materials tested. The total SHL saving provided by an MPS over TBB was 29.7 per cent and was statistically highly significantly different from that provided by a CPS or TBB over TBB (the difference is 9.6 and 9.9 per cent, respectively, p less than 0.001 for both). While the SHL saving provided by a CPS over TBB was 20.1 per cent, and a TBB over TBB was 19.8 percent, the difference of 0.3 per cent is statistically not significant (p greater than 0.5). An additional finding was that MPS is electrically conductive on one side. Precautions must be taken when it is used on patients connected to electrical devices. Also, insensible perspiration trapped inside the bag can be as much as 10 g X hour-1 and may become a problem when the patient is wrapped in MPS for an extended period of time.