Thermal responses to whole-body cooling in air with special reference to arteriovenous anastomoses in fingers.

The arteriovenous anastomoses (AVAs) in the distal parts of the extremities play a significant role in the heat exchange with the environment. The aim of the study was to examine the thermal responses to whole-body cooling in air, and especially the behaviour of finger skin temperature (T(f) , rich in AVAs). Eight young men sat in minimal clothing at 32°C air temperature (T(a) ), which was then lowered gradually to 13°C in 100 min. In the beginning of cooling, T(f) was high and fluctuating, and then suddenly exhibited a rapid fall, while temperatures in other skin sites fell fairly linearly along decreasing T(a) to the end of cooling. During the period from start to the rapid fall in T(f) , rectal temperature decreased from 37·4°C (SD 0.2) to 37·2°C (0·2), mean skin temperature (T(sk) ) from 34·6°C (0·5) to 31·2°C (2·0) and whole-body thermal sensation from 'slightly warm/warm' to 'slightly cool/cold'. The start of the steep fall in T(f) varied considerably between individuals in terms of time (2-75 min), T(a) (16·7 - 32·0°C) and T(sk) (28·8 - 34·7°C). On the other hand, the range of T(f) at that point was narrower (32·1 - 35·8°C). The findings stress the importance of taking into account the distal skin temperatures in thermoregulatory studies in addition to the ordinarily used more proximal and central skin sites. Also, it might be advisable to start such experiments with relatively high and fluctuating T(f) to guarantee that the thermal state of the subject is well defined.