Forearm and biceps circumferential variations in skin tissue dielectric constant and firmness.

Tissue dielectric constant (TDC) and skin firmness assessed via indentation force (FORCE) help quantify lymphedema and track changes. We sought to determine potential differences in these parameters dependent on arm circumferential locations. Thus, TDC and FORCE were measured in 40 healthy women at medial, anterior and lateral locations on forearm and biceps. In five other women with unilateral lymphedema (68.6±7.6 years), TDC was measured at corresponding circumferential forearm positions. Measurements were done in triplicate using compact noninvasive devices. Results for healthy women (23.8±2.7 years) showed forearm medial TDC values (26.7±2.2) were less than anterior (28.0±2.4) or lateral (28.0±2.5) positions (p<0.001). Lymphedema patients had elevated values but similar medialanterior- lateral patterns (33.7±8.0, 39.8±10.2 and 42.9±10.0). Biceps medial TDC values (24.1±2.2) were also less than either anterior (27.0±2.1) or lateral (28.2±3.3). Contrastingly, medial FORCE values at forearm and biceps were less than at anterior and lateral locations (p<0.001) and increased in the order of medialanterior- lateral on forearm (p<0.001). The present findings provide reference values for both TDC and FORCE of commonly measured arm sites with specificity as to circumferential variations. This observed variation indicates the need for care in locating measurement positions for tracking patients with lymphedema.