Does electrodermal activity track capacitance hygrometry derived sweat rate during steady‐state and transient cholinergic‐induced sweating?

The classification of hyperhidrosis and hypohidrosis requires a precise quantification of sweat secretion. Recent studies have asserted a non‐invasive electrical conductance could be used to quantify precursor sweat formation. Precursor sweat is the isotonic fluid formed in the bulbous coil and the cell type most likely responsible for sweat gland pathology, rather than the modified fluid that reaches the skin surface. This study was designed to compare electrodermal activity (EDA), capacitance hygrometry, and skin blood flow (SkBF) during steady‐state and dose‐response sweating induced by cholinergic agonists to determine measurement congruence. 3 intradermal microdialysis fibers were placed in the dorsal forearm skin of 4 women and 3 men (age 22±2 years, BMI 25±6 k/m 2 ) to perfuse pilocarpine nitrate (1.66 mg/ml for 60 min), 5 doses of acetylcholine (1•10 −5 to 1M via 1•10 −1 increments per dose for 5 min each), or the vehicle (lactated Ringer's). Perfusate flow rates were standardized at 5 μL/min. Forearm SkBF (laser‐Doppler flowmetry), EDA (constant voltage of 0.5 V and gain of 5 μS/V), and sweat rate (capacitance hygrometry) were measured directly over the microdialysis membrane. Cholinergic dose‐response relations increased sweat rate (0.0 to 0.56 mg/ml/min), SkBF (16 to 279 units), and EDA (0.61 to 0.91 μS). ACh dose dependent increases in sweat rate and SkBF were similarly correlated to EDA (r = 0.52 and 0.48), although SkBF increased from the first dose and sweat rate and EDA increased from the 3 rd dose of ACh. EDA was correlated to SkBF (r = 0.52) but not sweat rate (r = −0.17) during the initial climb to steady‐state sweating, while during state‐steady sweating induced by pilocarpine EDA correlated to sweat rate (r = 0.59) but less so to SkBF (r = 0.21). The lactated Ringer's site did not induce changes in sweat rate, SkBF, or EDA; suggesting that the intradermal microdialysis technique does not affect EDA values. Combined, these data indicate EDA does not track capacitance hygrometry derived sweat rate or laser‐Doppler indexed SkBF consistently in either steady state or transient cholinergic‐induced sweating conditions. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .