Reflex vasoconstrictor responses of the healthy human fingertip skin. Normal range, repeatability, and influencing factors.

Skin vasoconstrictor reflexes (SVCRs) are mediated by sympathetic vasoconstrictor nerve fibers and used to test sympathetic function of the extremities. Since there is a dearth of published systematic data on inspiratory gasp-induced SVCR, we studied its range, repeatability, and influencing factors in 64 healthy subjects (mean age 41.9 years, range 20-78 years, 32 males). Mean vasoconstriction for the second digit was 54% (+/-19)/54% (+/-19) (right/left) and 69% (+/-16)/68% (+/-15) for the fourth digit. Forth digit vasoconstriction was significantly larger than the second digit (P < 0.01), but second and fourth digit correlation was good (Pearson: 0.521-0.741). Repeatability using single measure intraclass correlation was good with 0.62/0.69 for the second digit and 0.64/0.80 for the fourth digit (right/left). A trend for decreasing SVCR was seen with increasing age and weight, no effect was seen for gender, height, or blood pressure. The SVCR repeatability and range of variation seen in this study compare favorably with tests of heart rate variability, thermal threshold detection, and motor nerve conduction.