Figure 4.

Microvascular blood flow patterns recorded in three subjects in response to several sequences of painful heat pulses (pain, T2–T5) demonstrate significant subject-to-subject variability in neural-mediated vasoconstriction responses. (1) Subject 1 vasoconstricts and recovers blood flow between individual pain pulses; (2) Subject 2 has prolonged vasoconstriction with every sequence of pain stimuli, but recovers blood flow between the sequences; and (3) Subject 3 remains vasoconstricted after the initial stimulus with poor blood flow recovery.