The risk index for frostbite

The lowest skin temperatures during operations in the cold are generally observed in the human<br />extremities. The hands are particularly vulnerable since they are difficult to cover when manual dexterity is required. Fortunately, cold induced vasodilation (CIVD) occurs at very low finger temperatures and this mechanism transports warm blood to the extremities. The magnitude of the CIVD-reaction differs considerably between subjects and there were some indications that those subjects with a fast CIVD reaction with high amplitude had a reduced risk for cold injuries. The purpose of this investigation was to monitor and describe the CIVD reaction in marines. Later, we evaluated whether marines in whom cold injuries occurred during operations in cold areas did have a poor CIVD response in previous tests.<br />In order to evaluate the magnitude of the CIVD response, 226 marines immersed their left middle finger in<br />ice water for 30 minutes. The Risk Index for Frostbite (RIF) according to Yoshimura was determined on<br />the basis of the finger skin temperature response. This index ranges from 3 (high risk) to 9 (low risk)<br />dependent on the response time and response magnitude.<br />The calculated RIF was relatively good as compared to a Japanese male soldiers (7.0 ¦ 1.7 versus 5.7 ¦<br />1.7). Unexpectedly, smokers had a better RIF-score than non-smokers had. The RIF-score was inversely<br />related to pain.<br />One year later 54 marines obtained cold injuries during training in Norway. Twelve or them were in the<br />measured pool of 226 marines. These twelve marines had a RIF of 5.3 ¦ 1.6, as compared to 7.1 ¦ 1.6 for<br />the remaining marines. This was significantly different (t-test, t=-3.6, df = 209, p<0.001).<br />In conclusion, the RIF shows considerable differences between subjects and the RIF, determined in a<br />simple lab test, may be related to the risk for cold injuries during operations in the field.