Finger Cooling During Cold Air Exposure

Abstract

This paper presents a method for predicting the onset of finger freezing. It is an extension of a tissue-cooling model originally developed to predict the onset of cheek freezing. The extension to the finger is presented as a more conservative warning of wind chill. Indeed, guidance on the risk of finger freezing is important not only to safeguard the finger, but also because it pertains more closely to susceptible facial features, such as the nose, than if only the risk of cheek freezing was provided. The importance of blood flow to the finger and the modeling of vasoconstriction are demonstrated through cooling predictions that agree reasonably well with several reported observations. Differences in the prediction between the present physiologic-based model and the engineering model used to develop the wind chill index are also discussed. New wind chill charts are presented that tabulate the mean cooling rates and corresponding onset times to freezing of the finger for various combinations of air temperature and wind speed. Results indicate that the surface of the finger cools to its freezing point in approximately one-eighth of the time predicted for the cheek. For combinations that result in the same wind chill temperature (WCT), the rate of finger cooling is faster at the higher wind speed. This asymmetry was previously disclosed through the application of the model to cheek cooling, and it reiterates the ambiguity associated with the reporting of WCT. It is further emphasized that the reporting of onset times to freezing, or safe exposure limits, is a more logical and meaningful alternative to the WCT.

Advances, shortcomings, and recommendations for wind chill estimation

“…Wind speed values are shown for 10 m above the ground nose. The dynamic cooling model was applied for the prediction of finger cooling, which concurred with several independent observations (Tikuisis 2004). Specifically, the rate of cooling, and thus the onset of finger freezing (see Table 3), was found to be considerably faster (about eight times) than the cheek under the same exposure.…”

“…Osczevski (2000) then presented a steady-state analysis of wind chill, and Tikuisis and Osczevski (2002) developed a dynamic tissue cooling model that was solved numerically to yield imminent freezing times. Tikuisis and Osczevski (2003), and Tikuisis (2004) used the dynamic cooling model to predict, respectively, the onsets of facial and finger freezing that included the effects of blood flow. Shitzer (2006) discussed the cooling effects due to different correlations expressing the convective heat transfer coefficients on wind chill, employing a one-dimensional, steadystate cylindrical model of the head/face.…”

Freezing and Frostbite on Mount Everest: New Insights into Wind Chill and Freezing Times at Extreme Altitude

“…Extremities freeze at a rate up to eight times that of facial skin (Tikuisis, 2004), and climbers are therefore acutely at risk of suffering frostbite on their hands and feet, as has been reported (Harirchi et al, 2005;Subedi et al, 2010). The common occurrence of high winds at high altitudes (Moore and Semple, 2006) therefore suggests that individuals at high altitude are at a greater risk of cold injury than previously thought (Huey and Eguskitza, 2001).…”

Cold Stress Effects on Exposure Tolerance and Exercise Performance

“…However, fingers will cool more rapidly than the face and frostbite certainly is more prevalent in the fingers compared to the cheek. To this end, Tikuisis, modeled heat loss in the finger and presented modified wind chill charts for uncovered fingers (227). He found that the time to finger freezing was more rapid compared to the cheek, by a factor of ∼8.…”