Sweat activity measurement

Tronstad C, Gjein GE, Grimnes S, Martinsen 0G, Krogstad A-L, Fosse E. 2008. Electrical measurement of sweat activity. Physiol Meas 29(6), S407-S415. 

The kidney is an important organ for the excretion of toxic materials and their metaboHtes, and measurement of these substances in urine may provide a convenient basis for monitoring the exposure of an individual to the parent compound in his or her immediate environment. The Hver has as one of its functions the metaboHsm of foreign compounds some pathways result in detoxification and others in metaboHc activation. Also, the Hver may serve as a route of elimination of toxic materials by excretion in bile. In addition to the Hver (bile) and kidney (urine) as routes of excretion, the lung may act as a route of elimination for volatile compounds. The excretion of materials in sweat, hair, and nails is usually insignificant. 

Many of the manifestations of thyroid hyperactivity resemble sympathetic nervous system overactivity (especially in the cardiovascular system), although catecholamine levels are not increased. Changes in catecholamine-stimulated adenylyl cyclase activity as measured by cAMP are found with changes in thyroid activity. Possible explanations include increased numbers of 13 receptors or enhanced amplification of the 13 receptor signal. Other clinical symptoms reminiscent of excessive epinephrine activity (and partially alleviated by adrenoceptor antagonists) include lid lag and retraction, tremor, excessive sweating, anxiety, and nervousness. The opposite constellation of effects is seen in hypothyroidism (Table 38-4). 

It is possible that a skin, which is moist and cool gives exactly the same electrical response to measurements made at a single frequency as a skin, which is dry and warm. To separate and specify potentially confounding influences such as water content, temperature change, and sweat gland activity, it is necessary to use some form of electrical spectroscopic technique, that is, stimulation at three or more different frequencies, or a time-domain approach followed by Fourier transformation.44-46... 

Thermal sweat gland activity is unlikely if the ambient air temperature is below 20°C, humidity is between 30 and 60%, and the skin temperature is below 30°C, provided that the skin is not exposed to forced convection and no excessive body heat is produced (as a result of physical exercise).47-49 Subjects in fact, should be relaxed and adapted to the measuring environment for at least 20 min before testing takes place. Therefore, skin should be exposed to the ambient air of the test environment for at least 10 min before taking measurements.21... 

The TEWL measurement has been a valuable tool in barrier repair experiments where repair kinetics were followed by TEWL. However, there are some problems with this method when the efficacy of moisturizers is to be evaluated. Some ingredients of moisturizers like petrolatum are shown to be occlusive.8 Therefore TEWL readings might reflect the occlusive effect of the cream, rather than an improved, less permeable SC. Measurements performed shortly after application of the moisturizer may represent surface water loss of residual emulsion water instead of TEWL. The TEWL measurements must be performed in an environmental chamber with constant temperature and humidity after an appropriate rest period in order to minimize the contribution of sweat gland activity.9... 

Hershey et al, since 1954 (H17, H18, H19, H20) have reported on several glycolytic, pentose shunt, and Krebs cycle enzymes in human epidermis measured by Lowry s microtechniques. They have also compared enzyme activities in various structures of the skin (e.g., hair follicle, sweat gland, sebaceous gland, dermis, and epidermis), and have reported on their susceptibility to heat inactivation. 

Q.22.2 When most people lie or make an untrue statement their sympathetic nervous system becomes active (fight or flight response). This leads to increased sweat secretion and thus decreased skin resistance. In a lie detector, a current is passed between two silver chloride electrodes held at 5 v. A current of 4.2 mA is measured when the subject gives his name. Later in the interview he lies and a current of 8.9 mA is measured. What is the skin resistance in the (a) honest and (b) dishonest state ... 

Zinc metabolic studies in which the difference between the total dietary intake and the total excretion in faeces and in urine, is measured over a period of several days. The difficulties of this procedure include problems of ensuring complete collections of excreta and measurement of losses in sweat, shed skin and hair. These losses although minor, may cause cumulative errors. Analytical problems caused by accidental zinc contamination are also a worry, although here the use of stable zinc isotopes and mass spectrometry or neutron activation is an advantage. 

Sweat data pH Measuring the pH of sweat during activity... 

Skin conductivity Measuring skin conductivity to characterise sweat-gland activity... 

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