Some Factors Influencing the Vasomotor Response to Cold Pressor Stimulation

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Abstract
The purpose of the present experiment was to investigate the effect of initial level of vasomotor tonus, as measured by pulse‐wave amplitude, on the cutaneous blood‐volume response to a 1‐min cold immersioa of an extremity. The design included 3 test sessions, I wk apart, in which room temperature was set at either 32°C, 22°C, or 12°C. Pulse‐wave amplitude and blood volume of the left thumb were recorded plethysmographically. Room temperature manipulated the state of the peripheral vasculature successfully, with subjects at 12°C having smaller pulse‐wave amplitudes than at 32°C, during rest, It has been specifically hypothesized that when subjects were more constricted at rest, as at 12°C, the response to cold immersion would be an increase in blood volume, and when they were more dilated, as at 32°C, that the response would he a drop in blood volume, while subjects at 22°C would fall in between. It was further hypothesized that should CP habituation occur over the 3 sessions, it would be seen as a smaller drop for the 32°C and 22°C sessions and a smaller volume increase for the 12°C sessions. Both hypotheses were supported by the data. The results indicate that the magnitude and direction of change in cutaneous vascular systems depends on prestimulus tonus, and that the response to cold stress is not strictly stimulus bound, but that is dependent equally as much upon initial level of tonus. Habituation is seen as a decrease in response magnitude, regardless of direction.