Probability of survival during accidental immersion in cold water.
BACKGROUND
Estimating the probability of survival during accidental immersion in cold water presents formidable challenges for both theoreticians and empirics. A number of theoretical models have been developed assuming that death occurs when the central body temperature, computed using a mathematical model, falls to a certain level. This paper describes a different theoretical approach to estimating the probability of survival.


METHODS
The human thermal model developed by Wissler is used to compute the central temperature during immersion in cold water. Simultaneously, a survival probability function is computed by solving a differential equation that defines how the probability of survival decreases with increasing time. The survival equation assumes that the probability of occurrence of a fatal event increases as the victim's central temperature decreases. Generally accepted views of the medical consequences of hypothermia and published reports of various accidents provide information useful for defining a "fatality function" that increases exponentially with decreasing central temperature.


RESULTS
The particular function suggested in this paper yields a relationship between immersion time for 10% probability of survival and water temperature that agrees very well with Molnar's empirical observations based on World War II data.


CONCLUSIONS
The method presented in this paper circumvents a serious difficulty with most previous models--that one's ability to survive immersion in cold water is determined almost exclusively by the ability to maintain a high level of shivering metabolism.
Wissler
Eugene H
EH
Department of Chemical Engineering, the University of Texas at Austin, 78731, USA. ehwissler@mail.utexas.edu
D001833:Body Temperature Regulation / Q000502:physiology; D003080:Cold Temperature / Q000009:adverse effects*; D006801:Humans; D007035:Hypothermia / Q000401:mortality*; D007101:Immersion / Q000503:physiopathology*; D008432:Mathematical Computing; D008954:Models, Biological; D009326:Naval Medicine / Q000379:methods; D011336:Probability; D013534:Survival / Q000502:physiology*; D013997:Time Factors