Electro interstitial scan system: assessment of 10 years of research and development

Abstract

BackgroundTen years of research and development have allowed an understanding of how the electro interstitial scan (EIS) works and what its clinical applications may be.Materials and methodsThe EIS is a galvanic skin response device. The measurements are performed by electrical stimulation of the post sympathetic cholinergic fiber with weak DC current and voltage 1.28V applied during 2 minutes and in bipolar mode.Current scientific knowledgeEIS electrical measurements are related to: (1) the concentration of free chloride ions in the interstitial fluid, which affects the transfer of electrical current and the ratio intensity/voltage; (2) the morphology of the interstitial fluid, which is related to the electrical dispersion calculated from the Cole equation (α parameter); (3) electrical stimulation, which causes a change in sweat rate at the passive electrodes – post sympathetic cholinergic fiber electrical stimulation appears to be responsible for activating M2 receptors, which regulate nitric oxide (NO) production in the endothelial cell and cause vasodilation and a released sweat response; and (4) the electrochemical redox reactions (electrolysis) of the released sweat on electrodes, which are different on the bulk of the metal electrodes (O2 + [4H+] + [4e−]) and on the Ag/AgCl disposable electrodes (AgCl precipitation).ResultsFor each of the EIS clinical results, various explanations were posited, such as: (1) electrical stimulation of the postsympathetic cholinergic fiber-activating NO production in the endothelial cell, which causes vasodilation and a released sweat response (diabetes detection); (2) estimation of interstitial fluid’s acid–base balance, which is reflected in an electrochemical reaction on the bulk of the electrodes through the released sweat (prostate cancer detection); (3) estimation of cerebral interstitial fluid chloride ions (detection of ADHD in children); and (4) estimation of the morphology of the interstitial fluid (selective serotonin reuptake inhibitor treatment response).ConclusionAfter 10 years of development, the analysis of current scientific knowledge and results of clinical investigations have allowed a better understanding of EIS electrical measurements.