Continuous core temperature monitoring of search and rescue divers during extreme conditions.
OBJECTIVES: To study the feasibility of continuously monitoring core temperatures of search and rescue divers, to compare core temperature gradients occurring during warm and cold diving events, and to identify conditions under which divers are subjected to extreme temperatures. METHODS: Between June 1994 and March 1995, emergency medical technicians (EMTs) from two midwestern dive teams volunteered to ingest an encapsulated temperature sensor developed for the National Aeronautics and Space Administration. The capsule monitored continuous core temperatures and transmitted the data to a recorder worn under the divers' dry suits. RESULTS: Twenty male EMTs, mean age 34 years and mean body weight 184 pounds, were monitored during training. Nine dives were ice dives, with ice thickness averaging 9 inches, and mean ambient temperatures of 33 degrees F. Eleven dives were warm-water dives; average water temperature was 70 degrees F and mean ambient temperature was 74 degrees F. The average time spent in the dry suit was 95 minutes, and the mean total bottom time was 15 minutes. The ice divers showed a mean increase in core temperature of 1.0 degrees C, while the warm-water divers showed a mean increase of 1.2 degrees C. Divers experiencing the most extreme fluctuations were those in the role of safety diver, regardless of the season. Divers reported more subjective discomfort during ice dives than during warm-water dives. CONCLUSIONS: Continuous monitoring of body temperature during the duration of dive operations is possible, but labor-intensive. Safety measures to protect divers from extreme core temperature fluctuations should focus on the safety diver as well as the active diver.