Self-reports of pain and associated cardiovascular response dimensions during two types of the cold pressor test

Patterns of cardiovascular adjustments associated with self-reports of pain during the forehead and foot cold pressor (CP) tests were examined in 40 college men. Each subject participated in two CP sessions of the same type, one of which included ratings of pain. Blood pressure responses during the two tests were comparable in size. Cardiovascular response to foot stimulation consisted of a transient rise in cardiac output, followed by the increase in peripheral resistance, whereas during forehead stimulation, the increase in peripheral resistance was the primary mediator of the blood pressure increase throughout the test. Subjects in the foot CP group gave higher ratings of pain during stimulation than subjects in the forehead CP group. Ratings of pain made after an 8-min delay were identical for both groups. During both tests, increases in blood pressure were proportional to ratings of pain. During the forehead, but not the foot CP test, reporting pain was uniformly associated with increased systolic blood pressure responses through increased peripheral resistance. In contrast, the effect of the pain reporting procedure on diastolic blood pressure was inversely related to the level of reported pain.In the forehead, but not in the foot condition, subjects who responded to stimulation with increased cardiac output (30% of the sample), also gave higher pain ratings, without, however, demonstrating more than an average level of blood pressure increase. Among the remaining 70% of the subjects, in both CP groups, those who reported higher pain ratings also had higher blood pressure responses. This suggested that a positive relationship between blood pressure and pain was present among subjects who increased their blood pressure primarily by increasing their peripheral resistance, whereas the perception of pain was unrelated to blood pressure responses among subjects whose blood pressure increases were mediated in part by increases in cardiac output