1 - Wescor Inc.

S E C T I O N 3INTERPRETING THE SWEAT TEST3.2 Automatic AveragingRate of Sweating (g/m 2 /min)Fig. 1890768070605504A403B302C20100 5 10 15 20 25 3010035Time (minutes)Conductivity v TimeRate of Sweating v TimeConductivity (mmol/L)Automatic AveragingExamination of the data showing the relationshipbetween sweat conductivity and time after attachingthe sensor, obtained on all the subjects in theoriginal test of the system, and typically shown inFig.1, allowed the selection of optimal settings forthe averaging circuitry. After a variable lapse oftime (Period A, Fig.1) during which the sweat isgradually filling the channel in the sensor, it reachesthe second electrode, thereby completing theconductivity cell circuit and producing a displayedconductivity reading. During the next 3 minutes(Period B, Fig.1), this reading usually falls sharply,and then assumes a steady rate of decrease thatis maintained thereafter.This initial rapid change has been termed the “firstsample phenomenon” and the reason for it is notyet clear. In the steady phase of decrease of conductivity,the average rate of decrease is about15% per 10 minutes (during the period 10 to 20minutes after the first reading). The best time periodfor averaging commences after the initial rapidfall stabilizes, that is at 3 minutes from the firstreading, thus avoiding the “first sample phenomenon”.It then continues for the next five minutes(Period C, Fig 1) during which the sweating rate isstill near-maximal.The induction/analysis module is therefore programmedto make an average conductivityassessment by noting the time at which the firstconductivity result is displayed, allowing a timelapse of 3 minutes and then commencing a 5minute averaging period, after which the meanvalue is displayed.27