SKIN TEMPERATURE AND CUTANEOUS PAIN DURING WARM WATER IMMERSION,

Measurements of skin temperature were made during the sudden immersion of the skin of human subjects in water baths at 36-41C and related to the reports of pain elicited during the first few seconds of immersion. Within 0.5 seconds, the skin temperature rose to bath temperature and remained at this level during the 10-15 seconds of immersion, pain was reported at 37-41C occurring 1-5 seconds after the start of the immersion and adapting in 2-6 seconds. Calculation of the subcutaneous temperature and thermal gradients indicate maximal thermal gradients in superficial skin layers during the first 0.1 - 0.2 seconds of immersion 60Cmm decreasing rapidly during the first 5 seconds to 6Cmm. Analysis of the transient pain indicated that it could be considered as the more sensitive phasic response of the pain ending of which the static unadapting response occurs at skin temperatures of 43-46C. Several alternative explanations including subcutaneous thermal gradients, vasomotor reactions, and thermo-chemical changes in the nerve membrane were considered as possible explanations. The last most likely possibility requires a second order kinetic system with highly temperature sensitive reaction velocities to account for both the phasic and static components of the pain. Author