Continuous monitoring of single-sweat-gland activity

A conductivity measurement system using a small ion-free-solution perfusion chamber has been developed to monitor single sweat-gland activity (SSGA) continuously at the skin surface. The chamber has a small open space of 0.2 mm2 at the bottom and has a transparent window. Single sweat pores were visualized by the starch/iodine method and the chamber was attached onto a single sweat pore using a magnifying lens affixed at the window. Silver electrodes were installed inside the chamber, and, by perfusing ion-free solution through the chamber at a constant flow rate, the conductivity of the solution was measured at the inlet and the outlet of the chamber. Continuous SSGA was monitored at the palm, finger tip and chest skin surface when the subjects were seated in a resting position and under stresses such as hand grasping with a dynamometer and performing mental arithmetic. Different types of response were observed from different sweat pores. The response time of this system was less than 0.15 s. The present results reveal that continuous sweat activity can be monitored even from a single sweat gland.