A study on electrode gels for skin conductance measurements

Low-frequency skin conductance is used within several clinical applications and is mainly sensitive to sweating and the moisture content of the stratum corneum, but also how electrodes introduce changes in the electrical properties. Four electrode gels were investigated with regard to sorption characteristics and electrical properties. Skin conductance time series were collected from 18 test subjects during relaxation, exercise and recovery, wearing different pairs of electrodes contralaterally on the hypothenar and the T9 dermatome. Pressure test was applied on the T9 electrodes. Impedance frequency sweeps were taken on the T9 electrodes the same day and the next, parameterized to the Cole model. ANOVA on the initial skin conductance level change, exercise response amplitude, recovery offset and pressure-induced changes revealed significant differences among gel types. The wetter gels caused a higher positive level change, a greater response amplitude, larger recovery offset and greater pressure-induced artifacts compared to the solid gels. Sweating on the T9 site led to negative skin conductance responses for the wetter gels. Correlations were found between the desorption measurements and the initial skin conductance level change (hypothenar: R = 0.988 T9: R = 0.901) RM-ANOVA on the Cole parameters revealed a significant decrease in R(s) of the most resistive gel. Clinical implications are discussed.

[1]  H. Shwachman,et al.  Measurement of the electrical conductivity of sweat; its application to the study of cystic fibrosis of the pancreas. , 1957, Clinical chemistry.

[2]  A. Ohkawara.  [Structure and function of the skin]. , 1983, Iyo denshi to seitai kogaku. Japanese journal of medical electronics and biological engineering.

[3]  B R Eggins.  Skin contact electrodes for medical applications. , 1993, The Analyst.

[4]  J G Webster,et al.  A comparison of electrodes for potential use in paediatric/infant apnoea monitoring. , 1994, Physiological measurement.

[5]  Low Frequency Dielectric Dispersion of Microporous Membranes in Electrolyte Solution , 1998 .

[6]  W. Iacono,et al.  Electrodermal activation in first-episode psychotic patients and their first-degree relatives , 1999, Psychiatry Research.

[7]  Hazel Tonge,et al.  The structure and function of the skin , 1999 .

[8]  Sverre Grimnes,et al.  Measuring depth depends on frequency in electrical skin impedance measurements , 1999 .

[9]  H. Tagami,et al.  Number of cell layers of the stratum corneum in normal skin – relationship to the anatomical location on the body, age, sex and physical parameters , 1999, Archives of Dermatological Research.

[10]  Sverre Grimnes,et al.  Bioimpedance and Bioelectricity Basics , 2000 .

[11]  Sverre Grimnes,et al.  Facts and Myths about Electrical Measurement of Stratum corneum Hydration State , 2001, Dermatology.

[12]  G. Hobbs,et al.  Redistribution of sudomotor responses is an early sign of sympathetic dysfunction in type 1 diabetes. , 2001, Diabetes.

[13]  Jennifer Healey,et al.  Detecting stress during real-world driving tasks using physiological sensors , 2005, IEEE Transactions on Intelligent Transportation Systems.

[14]  Sverre Grimnes,et al.  Cole electrical impedance Model-a critique and an alternative , 2005, IEEE Transactions on Biomedical Engineering.

[15]  S. Grimnes,et al.  Skin impedance and electro-osmosis in the human epidermis , 1983, Medical and Biological Engineering and Computing.

[16]  E. McAdams,et al.  Factors affecting electrode-gel-skin interface impedance in electrical impedance tomography , 1996, Medical and Biological Engineering and Computing.

[17]  S. Grimnes.  Impedance measurement of individual skin surface electrodes , 1983, Medical and Biological Engineering and Computing.

[18]  F. Wiesel,et al.  Niacin skin-flush response and electrodermal activity in patients with schizophrenia and healthy controls. , 2006, Prostaglandins, leukotrienes, and essential fatty acids.

[19]  H. Storm,et al.  The assessment of postoperative pain by monitoring skin conductance: results of a prospective study * , 2007, Anaesthesia.

[20]  P. Quinton.  Cystic fibrosis: lessons from the sweat gland. , 2007, Physiology.

[21]  Sverre Grimnes,et al.  Electrical measurement of sweat activity. , 2008, Physiological measurement.

[22]  T. Ledowski,et al.  Monitoring Electrical Skin Conductance: A Tool for the Assessment of Postoperative Pain in Children? , 2009, Anesthesiology.

[23]  Andreas Demosthenous,et al.  A comparison study of electrodes for neonate electrical impedance tomography , 2009, Physiological measurement.

[24]  Sverre Grimnes,et al.  Noise properties of the 3-electrode skin admittance measuring circuit , 2009 .

[25]  Gerhard Tröster,et al.  Discriminating Stress From Cognitive Load Using a Wearable EDA Device , 2010, IEEE Transactions on Information Technology in Biomedicine.