Characterization of a three-phase response in gloved cold-stressed fingers.

Seven gloves were studied worn by eight sedentary subjects (six men and two women) exposed to cold-dry, C D, (mean dry bulb temperature Tdb = -17.2 degrees C; mean dew point temperature Tdp = -25.1 degrees C), and cold-wet, C-W, (Tdh = 0 degrees C; Tdp = -8.4 degrees C) conditions. Mean endurance times were 75 min for the C-D and 162 min for the C W conditions. A three-phase response pattern of the temperature in the fingers was characterized. Phase I comprised an initial period during which finger temperature remained close to the pre-exposed level, due to delayed vasoconstriction in the finger. Phase II involved an exponential-like decrease of finger temperature indicative of the onset of vasoconstriction in the finger. Phase III manifested periodic finger temperature changes due to cold induced vasodilatation (CIVD). Mean wave patterns for phase III indicated approximately 3.5 waves x h(-1) in the C D but only about 2 waves x h(-1) in the C-W condition. Extension of endurance time, due to CIVD, was defined as the difference in time between the actual end of the experiment and the time the finger-tip would have reached the set temperature endurance limit as extrapolated by a continued exponential drop. Three overall response patterns of fingers in the cold were characterized: type A exhibiting all 3 phases; type B1 or B2 exhibiting either phases I+ II or phases II+ III; and type C showing only phase II. Considerable inter- and intra-subject variability was found. In both test conditions the final physiological thermal states of the subjects were between comfortable and slightly uncomfortable but acceptable and thus did not correlate with the responses in the fingers.