Upper-extremity volume measurements in women with lymphedema: A comparison of measurements obtained via water displacement with geometrically determined volume

Background and Purpose. Upper-extremity (UE) swelling following breast cancer treatment is a frequent manifestation of lymphedema. In order to document outcomes from lymphedema treatments, reliable, valid, and practical measurements of UE swelling are necessary. The purpose of this study was to compare geometric methods of determining UE volumes with water displacement methods. Subjects. The edematous hand, forearm, and upper arm of 50 women with UE swelling secondary to lymphedema were measured. Methods. Upper-extremity volumes were determined by water displacement using arm and hand volumeters. Displaced water was weighed to determine volume. Circumferential girth measurements were taken. Width and depth measurements of the hand were taken with a tension-controlled caliper. Geometric volume formulas for a cylinder, frustum, rectangular solid, and trapezoidal solid were used to calculate volumes of the arm and hand at different measurement intervals. Results. Intraclass correlation coefficients [2,1] for interrater and intrarater reliability of all water and geometric measurements of the arm and hand were .91 to .99 and .92 to .99, respectively. Water displacement correlated with geometric measurements in the arm (r = .97-.98) and in the hand (r = .81-.91). The limits of agreement (LOA) indicated that water and geometric measurements of arm volume differed by 479 to 655 mL. Scatterplots of the LOA data indicated in that geometric volumes were either larger or smaller than water volumes. The smallest standard error of measurement for the arm measurements was for the 6-cm frustum method at 115 mL; for the hand measurements, the smallest standard error of measurement was for the frustum method at 16 mL. Discussion and Conclusion. Volume of an edematous UE calculated by geometric formulas correlated strongly with volume determined by water displacement. Although strongly correlated,the measurements obtained by the 2 methods did not agree.