Alternate Quantification Approaches for Cold Induced Vasodilation in Human Glabrous Skin

Abstract

Cold‐induced vasodilation (CIVD) is a phenomenon involving a counterintuitive increase in skin blood flow during cold exposure. Although CIVD was first described in 1930, CIVD mechanisms remain unknown. The majority of CIVD research has assessed vasodilation via skin‐surface temperature rather than direct assessment of skin blood flow. The study objective was to determine if laser‐Doppler flux, cutaneous vascular conductance (CVC), or skin erythrocyte concentration provides better assessment of CIVD. Twelve (8 men and 4 women) healthy (via health history and vital signs) subjects' laser‐Doppler flux, erythrocyte concentration, and skin‐surface temperature were measured in the left second and third fingers and right third finger, while arterial blood pressure (ABP) was measured in the right fourth finger on a beat‐by‐beat basis. The left hand was exposed to: baseline (10 min 22–23°C air), warming (10 min 35°C water), cooling (30 min 8°C water), and recovery (15 min 22–23°C air) and the right hand to 22–23°C air throughout. In addition to occurrence and mean data, beat‐by‐beat oscillations in skin blood flow were also analyzed via a fast‐Fourier transform binned within 0.009–0.02 Hz, 0.02–0.06 Hz, and 0.06–0.2 Hz. Temperature CIVD was observed in all participants, with an average of 2.33±0.98 occurrences. Flux and concentration CIVDs were observed in 11 and 9 subjects, respectively, with an average occurrence rate of 1.67±1.37 and 0.92±1.16, respectively. CVC increased during warming by 38.1±11.8% (P=0.006), then decreased during the first 5 min of cooling by 54.1±8.4% (P<0.001) but was not different by the end of cooling (P=0.143). Left hand second and third finger values and responses were congruent. In addition, left hand skin blood flow spectral power decreased during cooling compared to both baseline and warming within all bins (P<0.05), but no changes were noted during cooling (P>0.05). Right hand CVC was not initially altered but decreased by the end of opposite hand cooling (P=0.008). Right hand skin blood flow spectral power did not change across conditions (P>0.05). Cooling increased ABP by an average of 17.3±0.08% (P<0.001). These data indicate skin blood flow sympatholysis in the immersed hand during CIVD that is not observed in the non‐immersed hand. Direct measures of skin blood flow and erythrocyte concentration appear to add different aspects to the traditional indirect assessment of CIVD via skin surface temperature and may allow new investigations into CIVD mechanisms.