Finger cold-induced vasodilatation during hypothermia, hyperthermia and at thermoneutrality

BACKGROUND: Exposure of the fingers to severe cold leads to cold-induced vasodilation (CIVD). The influence of ambient temperature on the CIVD-response is well understood and documented, but the response of CIVD to hyperthermia and mild hypothermia has rarely been investigated. METHODS: To investigate the influence of body thermal status on the CIVD response, eight subjects immersed their right hand in 5 degrees C water for 40 min during mild hypothermia (C), thermoneutrality (N) and hyperthermia (W). The mean skin temperature of the body (Tsk), the esophageal temperature (Tes), the temperature of the volar side of the distal phalanx of each immersed finger (Tfi) and the skin perfusion of the immersed middle finger (Qsk) were continuously measured. RESULTS: During the W condition the body temperatures were higher (Tes: 38.0+/-0.1 degrees C; Tsk: 37.9+/-0.7 degrees C) than during N (Tes: 36.8+/-0.2 degrees C; Tsk: 31.8+/-0.7 degrees C) and during C (Tes: 36.1+/-0.8 degrees C; Tsk: 21.2+/-1.9 degrees C). Tfi and Qsk were higher during the W condition (Tfi: 16.5+/-2.3 degrees C; Qsk: 133+/-53 perfusion units (PU)) than during N (Tfi: 8.1+/-1.7 degrees C; Qsk: 57+/-39 PU) and during C (Tfi: 6.8+/-1.2 degrees C; Qsk: 22+/-14 PU). The onset time of CIVD was significantly prolonged in condition C (13.0+/-3.8 min) as compared with N (7.2+/-2.2 min). CONCLUSION: It was concluded that the CIVD response is significantly affected by body core and skin temperatures

Thermal requirements for surviving a mass rescue incident in the arctic - Preliminary results

Maritime and air traffic through the Arctic has increased in recent years. Cruise ship and commercial jet liners carry a large number of passengers. With increased traffic, there is a higher probability that a major disaster could occur. Cruise ship and plane accidents could be catastrophic and may require mass rescue. Due to the remote location, limited search and rescue resources, time for these resources to get to the accident location and large number of survivors, the retrieval time could be several days. Therefore, survivors may be required to survive on their own for days while they await rescue. Recognizing that the International Maritime Organization does not have specific thermal performance criteria for liferafts and lifeboats and personal and group survival kits, the Maritime and Arctic Survival Scientific and Engineering Research Team (MASSERT) initiated a research project to improve safety and provide input for advances to regulations. The objective of the project is to investigate if the current thermal protective equipment and preparedness available to people traveling in the Canadian Arctic are adequate for surviving a major air or cruise ship disaster and to identify the minimum thermal protection criteria for survival. This project builds on the results and tools developed in other research projects conducted by the team on thermal protection of liferafts, lifeboats and immersion suits. The project is divided into three major phases clothing ensemble testing with thermal manikins, a physiology experiment on sustainable shivering duration and ensemble testing in Arctic conditions with human subjects. A numerical model uses these data to simulate survival scenarios. In the first phase of this project, the thermal resistance values of the protective clothing typically available to cruise ship and aircraft passengers were measured using two thermal manikins. The ensembles included Cabin Wear, Deck Wear, Expedition Wear, Abandonment Wear and protective clothing from Canada Forces Major Air Disaster Kit (MAJAID). Tests were conducted on dry and wet ensembles at 5\ub0C and 15\ub0C with and without wind. There is very good agreement between the thermal resistances measured by the two manikins. The differences in thermal resistances observed are likely caused by variations in fit and wrinkles and folds in the ensembles from dressing. With no wind, the thermal resistance is lowest with Cabin Wear and highest with MAJAID clothing inside the down-filled casualty bag. The Expedition Wear, the Abandonment Wear and the MAJAID clothing have about the same thermal resistance. With 7 metre-per-second wind, the thermal resistance of all ensembles decreased significantly by 30% to 70%. These results highlight the importance of having a shelter as a windbreak. For wet clothing ensembles at 5\ub0C, the initial wet thermal resistance was 2 to 2.5 times lower than the dry value, and drying times ranged up to 60 hours. This highlights the importance of staying dry. Preliminary predictions from the numerical model show that the survivors in Expedition Wear, even with sleeping bag and tent, can be mildly hypothermic and need to depend heavily on shivering to maintain thermal balance. In a shelter, the predicted metabolic rate is roughly double the resting rate; it is triple the resting rate without protection from the wind. Further research is required to study shivering fatigue and age effects. Research on mass rescue scenarios for cruise ships and airplanes survivors should ideally involve subjects of both genders and the elderly. Copyright \ua9 2011 by ASME.Peer reviewed: YesNRC publication: Ye