After cleaning the selected area of skin on the patient, the electrodes with Pilogel discs installed are attached to the patient's arm with the provided straps. Pressing RUN on the Webster Sweat Inducer activates Iontophoresis. If everything is normal the current flow reaches its peak at about 20 seconds as pilocarpine iontophoresis begins.
Sweat stimulation occurs under the positive electrode while the disc under the negative electrode completes the electrical circuit. Reliable, uniform, gel-to-skin contact ensures delivery of pilocarpine over the whole skin area, thus providing total gland stimulation and maximal sweat yield.
Once iontophoresis is complete, the electrodes are removed, the skin area under the positive electrode is cleaned and a Macroduct Sweat collector is firmly attached to the stimulated skin site. The base of the sweat gland is 2 to 3 mm beneath the surface of the skin. Fluid secreted by the gland creates hydraulic pressure that moves the fluid upward through the sweat duct to emerge from the skin as sweat. When sweat surfaces beneath a Macroduct collector, the same hydraulic pressure forces it into the air-free interface between the skin and the concave surface of the collector and the secreted sweat is directed to the orifice and into the plastic "macroduct" tubing.
After attachment, sweat becomes visible in the spiral tube of Macroduct within one to four minutes, depending on the relative elasticity of the skin and the subjects sweating rate. The emergent sweat is turned blue by contact with a small amount of blue water soluble dye applied to the Macroduct collection surface This allows easy assessment of the sweat volume at any time during collection.
When collection is completed, the spiral tubing containing the sweat sample is extended and severed from the Macroduct base and the sweat specimen is introduced into the Sweat-Chek analyzer or expressed into a storage cup for analysis at a later time. A typical Macroduct sweat collection produces many times the sweat volume needed for analysis. In cases where sweat yield is below average, measurement is possible using 6 to 10 microliters of sweat, with careful technique.
Readings can be characterized in the following categories: 0 to 60 mmol/L are in the normal range; 60 to 80 mmol/l are borderline; and reading above 80 mmol/L should be considered abnormal.
The Sweat-Chek Sweat Conductivity Analyzer with its temperature controlled measurement cell, flow through operation and wide range digital readout, is a modern adaptation of a proven analytical method. Dr. Lewis Gibson, one of the worlds leading authorities on sweat testing, commented on Sweat Chek: "If this machine is kept clean, it gives results that are every bit as reliable as an analysis for sodium or chloride."