Sequential Variability in Localized Thigh Skin Dermal Tissue Water

Objectives. To learn to use tissue dielectric constant (TDC) measurement devices and apply them as part of research training to study variability of biophysical values. Background. Skin TDC-values have been used as indices of local skin tissue water and its change in a variety of clinically-related applications but the temporal variability in lower extremity TDC-values in young adults has not been previously reported. Because TDC-values vary by anatomical site such information is valuable directly as a reference and also to help set criteria for sequential studies in which measurements are made in patients over days or weeks. Methods. Six male student research-trainees performed self-TDC measurements on their anterior thigh while in a seated position at five sessions; day0, day1, day7, day21 and day 28. At each session TDC was measured in triplicate to a skin depth of about 1.5 mm which is a depth that includes the epidermis and dermis but not the underlying hypodermis or subcutaneous fat. For reference, the TDC value of 100% pure water measured at 300 MHz is about 78. Data was analyzed by a person not involved with the measurements. Results. TDC-values for the five sequential sessions (mean±SD) were respectively 33.3±2.1, 33.9±3.6, 34.1±2.8, 34.5±2.0 and 34.9±4.0. Although an ANOVA for repeated measures showed no overall time effect (p = 0.629) an increasing trend appears present. As compared to day0, subsequent TDC-values increased sequentially by 1.7%, 2.6%, 3.6% and 4.5%. Conclusions. Interpretation of sequential changes in thigh dermal tissue water must take into account the normal timedependent variations.