Assessing Upper and Lower Extremities Via Tissue Dielectric Constant: Suitability of Single Versus Multiple Measurements Averaged

Harvey N. Mayrovitz, Lymphatic Research and Biology, 2018

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Assessing Upper and Lower Extremities Via Tissue Dielectric Constant: Suitability of Single Versus Multiple Measurements Averaged

Harvey N. Mayrovitz, Lymphatic Research and Biology, 2018

Background: Tissue dielectric constant (TDC) measurements as an index of local tissue water are useful in a range of applications most notably to characterize and assess lymphedema. Once a measuring device is applied to skin and a result is obtained in less than 10 seconds, but multiple sites may be required and use of the standard triplicate measurements may be time prohibitive. Thus, this study’s goal was to provide data from which informed judgments could be made as to the impact of making a single measurement to reduce expended clinic time.

Methods and Results: Sixty subjects (30 female) were recruited with an average age (mean–standard deviation) of 30.6–13.4 years. TDC was measured in triplicate bilaterally at forearm, hand palm, lateral calf, medial calf, and foot dorsum. The agreement in absolute TDC values and interside ratios was evaluated for assessments made using only the first TDC measurement, the average of duplicates and the standard triplicate. Results showed that differences between single and multiple measurement averages were anatomical site dependent with the smallest coefficient of variation (2.19%) at the forearm and the largest at the lateral calf (4.59%).

Conclusions: Results suggest that when clinical time is of major concern, useful TDC data may be obtained in upper limbs using single TDC measurements per anatomical site whereas lower extremity skin assessments should be done using at least duplicate and preferably triplicate measurements. However, as with all such time reliability considerations, clinical judgment should be exercised and aided by the various findings of this study.

Main findings

  • A total of 60 subjects, equally divided between female and male, were recruited for participation in this research study. Subjects were recruited from first and second year medical students and from others, including university faculty and College of Medical Sciences.
  • TDC was measured at five anatomical sites that are representative and have relevance to potential lymphedema development areas in upper or lower limbs.
  • The two upper limb sites were (1) the anterior forearm located 5cm distal to the antecubital fossa and (2) the hand palmer surface at the approximate midpoint of the thenar eminence. The three lower limb sites were (1) the lateral lower leg (10cm proximal to the lateral malleolus), (2) the medial lower leg (10cm proximal to the medial malleolus), and (3) the foot dorsum between the first and second toes. All measurements were done bilaterally and in triplicate at each site with each subject supine.
  • The greatest TDC value was recorded at the hand (42.7–8.3 and the least TDC value recorded at the forearm (31.1–4.5).
  • Based on current knowledge, a reasonable minimum protocol would be to routinely assess five bilateral sites preoperatively and repeat at a patient’s subsequent visits. One set of five standardized sites that might be used for breast cancer related tracking would include hand (dorsum or palmer), medial forearm, medial upper arm, lateral thorax, and upper back. At a minimum, the measurements alone would take 10 minutes for such an assessment.
  • The forearm is revealed as the site most amenable to utilizing a single measurement in that 96.7% of measurements are within –5% of those determined using triplicate measurements.
  • The overall composite findings suggest that when clinical time is a major concern, useful TDC data may be obtained in upper limbs using single TDC measurements per anatomical site, whereas assessments of lower extremity skin should be based on at least duplicate and preferably triplicate measurements.