Heated socks maintain toe temperature but not always skin blood flow as mean skin temperature falls

Introduction: This study was conducted to examine whether toe skin blood flow (Qtoe) could be maintained in subjects exposed to cold air by warming the foot using a heated sock. Methods: Four male subjects were exposed to air at 4°C. They wore aramid shirt and trousers, a coverall made from metalized spun bonded polyethylene (“space blanket” fabric), arctic mittens, a 4-ply aramid balaclava, and loose fitting padded boot liners. The subjects rested recumbent on a couch with a pair of heated socks turned on for 120 min and with socks turned off for a further 60 min. Qtoe was measured using laser Doppler flowmetry. Results: Although the heated socks maintained the skin temperature of the feet above 37°C, Qtoe was not maintained in two of the four male subjects for the 120 min that the socks were turned on. Discussion: Heated socks cannot be relied on to maintain Qtoe or to prevent non-freezing cold injuries during prolonged exposure to cold conditions.