Electrode Equivalence for Use in Bioimpedance Spectroscopy Assessment of Lymphedema.

BACKGROUND: Bioimpedance spectroscopy (BIS) is commonly used in the assessment and monitoring of lymphedema. This study investigated electrodes as a source of variability that could impact the accuracy of BIS in the clinic and determined if Ag/AgCl electrocardiograph (ECG) electrodes could be used as an alternative to instrument-specific electrodes. METHODS AND RESULTS: Two types of Ag/AgCl electrodes were studied: instrument-specific bioimpedance electrodes (bioimpedance) and single tab ECG electrodes (cardiac). Six areas of investigation were addressed: intrinsic electrode resistance; electrode age; drive electrode position; electrode width/surface area; concordance between cardiac and bioimpedance electrodes; and mixing electrode types and batches. Participants included women (n = 26) and men (n = 8), both with (n = 4) and without lymphedema (n = 30). Resistance (R0) of the limbs was measured and used to calculate interlimb BIS ratios. Intrinsic electrode resistance varied between batches (p ≤ 0.001), with cardiac electrodes recording higher resistance. Electrode age had no impact on limb resistance (p = 0.85). Drive electrode position biased limb resistance (0.1%-2.3%) and electrode size/surface area had a small (≤1%), but significant effect on limb resistance (p ≤ 0.001). However, calculation of interlimb BIS ratios negated the impact of these as well as any effect of mixing electrode batches and types (p = 0.15-0.96). Electrode type had no impact on arm and leg resistance, or interlimb BIS ratios (p = 0.173-0.289). CONCLUSION: Calculation of interlimb BIS ratios improves accuracy of clinical BIS. Ag/AgCl cardiac electrodes can be used as an alternative to device-specific electrodes to measure limb resistance.

Segmental Bioimpedance Informs Diagnosis of Breast Cancer-Related Lymphedema.

BACKGROUND: Detection of lymphedema, particularly its mild stage, is clinically challenging. The aim of this study was to determine whether segmental bioimpedance spectroscopy (BIS) provided additional information to whole arm BIS in assessing women with or at risk of lymphedema following breast cancer. METHODS AND RESULTS: Participants (n = 66), aged 61.6 ± 10.5 years (mean ± standard deviation [SD]), were grouped according to lymphedema status: (1) at-risk (n = 24) had no indicators of lymphedema and (2) lymphedema (n = 42) were suspected to be developing lymphedema or had previously met lymphedema diagnostic criteria and undergone treatment. For each upper limb, impedance was measured for the whole arm, hand and four 10 cm segments of the arm, commencing at the ulnar styloid. Interlimb impedance ratios for corresponding locations were calculated and compared to previously determined, normatively based thresholds based on 2SD and 3SD above the mean. Segmental BIS classified 19% more women with lymphedema than 3SD whole arm thresholds and the same number as 2SD whole arm thresholds. Segmental BIS identified localized lymphedema and patterns in lymphedema distribution that were undetectable by whole arm BIS. Neither 3SD whole arm nor segmental BIS thresholds found lymphedema where it was not present; however, 2SD whole arm thresholds alone classified one woman in the at-risk group as having lymphedema. CONCLUSION: Segmental BIS classified as many or more cases of lymphedema than whole arm BIS thresholds without finding lymphedema where it was likely not present while also providing additional information regarding the distribution of lymphedema within the limb.