HEAT LOSS FROM THE RESPIRATORY TRACT IN COLD
Abstract
Methods especially suited for measuring the temperature and water vapor content of expired air have been developed. A new instrument for measuring water vapor, the dielectric hygrometer, is described. Temperature and water vapor content of expired air were measured in standing resting subjects at ambient temperatures ranging from 0 to -40C. From these and from previous measurements it is found that expired air leaves the nose at temperatures corresponding to the following rule: starting at an ambient temperature of 25C, where the expired air is 34C, for every 5C reduction of ambient temperature there is a 1C drop in the temperature of expired air. In cold conditions expired air is always saturated or supersaturated with water vapor, at the temperature corresponding to the above rule. Heat loss calculations made on the basis of these findings, and assuming a median figure of 600 liters per hour for standing resting ventilation, show that a man in 0C air loses 14 kg-cal/hour through the respiratory tract. A man in -20C air loses 15 kg-cal/hour, and in -40C he loses 17 kg-cal/hour. These values are lower by 50 to 60% than calculated values based on the assumption that expired air is at body temperature (37C) and saturated. This represents a considerable and useful conservation of heat. Heat conservation in the respiratory tract is most noticeable in very cold environments. The mechanism involved simulates that of a simple heat exchanger. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1955
- Accession Number
- AD0293194
Entities
People
- Paul Webb