Physiological reactions to wet-cold.

Changes in extremity temperatures during general cold stress were investigated. The changes in local temperatures were found equal to those seen under circulatory arrest. In order to investigate the influence of these changes on motor function, the relation between local temperature and nervous conduction velocity in a peripheral motor nerve (n. ulnaris) was carried out in subjects exposed to a minor cold stress (to aboid the influence of Lewis hunting reaction). The decrease in conduction velocity was found to be 15 m/s per 10 degrees C fall in temperature. At a local temperature of 8-10 degrees C a complete nervous block was established. This leads to an explanation of the clinical findings in wet-cold situations, where the very rapid onset of physical impairment corresponds to the effect of a local cooling in the extremities and not, as commonly accepted, to a developing general hypothermia.