Cold-Induced Vasodilation Reaction of Skin Vessels at 2 ATA

The temperature reaction of middle fingers to cold (hunting reaction) was examined in 8 male volunteers at 2 atmospheres absolute (ATA), 28℃ and at normal atmosphere, 26 and 28℃.The skin temperature of the finger immersed in ice water fluctuated during the immersion. The magnitude of the reactions was analyzed by comparing 4 compartments of the temperature curve, i. e., mean skin temperature of the finger during the period of immersion (from 5 to 30 min after immersion), the time and the temperature of the finger at which the temperature curve begins to rise, and the difference between the skin temperature of the finger at the first rise and that at the maximum of this rise. Personal reactivity of the skin vessels to cold tended to be enhanced at 2 ATA, while no significant differences were observed between 1 and 2 ATA. Skin temperatures were reduced by raising the ambient pressure. When only the ambient temperature was lowered, which also reduced the skin temperatures, personal reactivity seemed to become less. The skin temperature of the opposite non-immersed finger also fluctuated during the immersion. Amplitude of the fluctuation was significantly smaller at 2 ATA than at 1 ATA. These evidences suggest that a high ambient pressure might have some direct effects on neural mechanism controlling vasomotor function.