Methods

The complexity of multi-compartmental models for human thermoregulation is realised as Information Technology (IT) in Borland C++ Builder 2010 [2]. IT is a suitable tool that allows user to input individual data, water and air parameters, immersion level and physical exercise. Output data represent the dynamics of all local temperatures, muscles and skin blood flows, shivering, water convection, heat internal flows, heat losses, etc. Three levels of the human immersion in cold water were simulated:# 1: whole body immersion;# 2: head out of water;# 3: head, arms and hands out of water. Water and air temperatures were 10 C.

Results

Modelling (Figure 1) showed that brain temperature dropped to 35 C during all cases of human immersion. But time characteristics were significantly different. During whole body immersion brain temperature decreased to 35 C in 25 min, during head out immersion in 49 min, for head, arms and hands out of water in 74 min. Heat losses by water convection to this moment were 759 W (# 1), 638 W (# 2) and 465 W (# 3). Modelling showed that internal organs temperature achieves critical value (35 C) later. For full immersion it was 53 min, for head out of water 65 min and for head, arms and hands out 120 min. These data correlate with actual measurements of esophageal temperature in humans [3].