In Response to Performance of a Chemical Heat Blanket by Greene et al

To the Editor:

We read with interest the article “Performance of a Chemical Heat Blanket in Dry, Damp, and Wet Conditions Inside a Mountain Rescue Hypothermia Wrap.” ¹ We would like to provide additional information regarding our report, “Successful Field Rewarming of a Patient with Apparent Moderate Hypothermia Using a Hypothermia Wrap and a Chemical Heat Blanket,” ² cited in this article. In the case we described, we believe that the failure of the first chemical heat blanket (CHB) occurred immediately because of a leak in the packaging, allowing premature oxygen exposure, and not from the CHB becoming wet.

Our experience in the SAR environment is that the Ready-Heat CHBs require additional protective packaging to avoid perforation of the original factory packaging. We would also like to clarify our comment about the CHB not working when wet. This was based on knowledge of the chemical reaction in the CHB and direct observation that the CHB performs poorly when thoroughly wet. We are glad that the authors found that the CHB performed well with damp clothing. It would be useful to know the performance of the CHB when placed immediately outside an inner vapor barrier, which avoids water exposure from wet clothes. It has been our practice to put the CHB outside the inner vapor barrier and under the insulation layer and outer waterproof layers.

We suggest that the manufacturer consider placing a colorimetric O₂ detector inside the packaging to make it apparent when there has been premature exposure to oxygen.