Body positional effects on bioimpedance spectroscopy measurements for lymphedema assessment of the arm

Background: Bioimpedance spectroscopy (BIS) measurements have conventionally been performed using a device that uses gel-backed electrodes with the patient in a supine position. More recently, impedance devices that use stainless steel electrodes with the patient in a standing position have become available. The aim of this study was to assess and compare BIS measurements made in three different body positions using two different impedance devices (lead device and stand-on device) in women with and without arm lymphedema. Methods: A cross-sectional study design was used to recruit two cohorts of women, healthy controls (n = 47) and those who had been diagnosed with breast cancer (n = 53) and were either at risk of (n = 14) or with unilateral arm lymphedema (n = 39). BIS measurements were taken three times in each position for each device. Results: Impedance measurements were reliably made using either a lead or stand-on device with a coefficient of variation being 0.6% or lower. Absolute impedance measurements for the stand-on device were larger than the comparable lead device values due to the difference in electrode position, but were highly correlated (r = 0.92, p < 0.0001). Interarm impedance ratios and L-Dex scores were slightly (3.1% equivalence), but significantly different. Conclusion: The findings support impedance measurements being made reliably using either the lead or stand-on device, representing supine and upright measurement positions, respectively. Data between devices were, however, not directly interchangeable.