COLD EXPOSURE DURING ALPINE HELICOPTER RESCUE OPERATIONS

Objective: To evaluate the cold exposure of the personnel involved in helicopter rescue operations in an alpine environment to quantify the risk for frostbite or hypothermia. Methods: The weather conditions, the locality and its altitude and the sojourn on scene of the rescue operations of 15 months in the region Oberwallis, Switzerland were analyzed. The equivalent chill temperature was estimated with two independent models. “Mean exposure” and „worst case situation“ were calculated. The results are evaluated according to the „classic“ Siple-Passel-Model, the more recent model of Danielsson, ISO 11079, ISO 9920, the German industrial standard DIN 33403.5, and the German government regulations for work in cold environment (“G21”). Results: There were only marginal differences in chill temperature between both temperature models. Assuming “worst case conditions” the Siple-Passel-model showed 87.1% of the operations at chill temperatures >-30°C, 12.1% in the range of –30 to –45°C, and 0,8% <-45°C. The lowest temperature was –54.6°C. The Danielson model resulted in 77.6% without the risk of frostbite, 20.1% with >5% risk, 6% >50% risk, and 1.8% >95% risk. According to DIN 1.5% of the operations were performed at chill temperatures higher than cold class 1. 2.3% are class 1, 13.3% class 2, 34.7% class 3, 34.6% class 4, and 13.7% class 5. The maximal exposure times of DIN 33404.5 are exceeded in at least 0.5% of the missions. According to ISO 11079 clothing with 2.0 clo is sufficient in 40.2% rsp. 23.9% of the operations (summer, IREQ min. and IREQ neutr.). In winter the corresponding results are 0.3% and 0.0%. Duration of limited exposure is exceeded in 9.1% (IREQ min.) rsp. 19.8% (IREQ neutr.) of the operations in summer and in 10.3% rsp. 19.8% in winter. According to ISO 9920 ICL min. as well as ICL neutr. is exceeded in 100% in summer and winter operations. Conclusions: Alpine rescue operations are a typical place of work in cold – sometimes extreme cold – environment. Because of the limited time of exposure during the majority of the operations the most important danger for rescue personnel is frostbite although hypothermia cannot be excluded in cases of prolonged operations. Special advice to avoid the specific risks must be given to the crews and an examination by occupational medicine, e.g. according to „working in cold environment, G21“ of the German Berufsgenossenschaften, is recommended. Recommendations for adequate clothing are given.