Equipment for airway warming in the treatment of accidental hypothermia

Abstract

Airway warming as a method of treating accidental hypothermia produces its main benefit through reducing or preventing the respiratory loss of heat and moisture, though, with some devices, there may be a small additional heat input. Warm water vapour can be added to the inspired gas. The power to heat the water can be provided by electricity or by gas. An alternative method utilizes a chemical reaction to produce heat and moisture, which is transported by the inspired gases passing through the reaction bed. The most widely used reaction is that between carbon dioxide and soda lime, and practical designs use either an open (non-return) or closed breathing system.

Heat and moisture exchangers (HMEs) vary in efficiency, but all are less efficient than the other methods, since they merely reduce the individual's respiratory heat and moisture loss. HMEs probably have a role as first aid equipment to be carried by individuals or groups going into the wild. The more efficient equipment, which provides positive heat and moisture input, is more suitable for rescue services. All the currently available models have practical advantages and disadvantages, and each rescue service will have to decide which design best suits its particular needs.