VALIDATION OF AN OPTOELECTRONIC LIMB VOLUMETER (PEROMETER®)

Abstract

The Perometer, a device designed for the measurement of limb volume, has been rigorouslyassessed by comparison with other methods. Differences in the volume of geometric shapes andlimbs determined by the Perometer and a tape measure/meter rule (i.e., Perometer minus directmeasurement) were -0.8 to -2.4% (cylinders), -4.6% (truncated cone), -3.3% (mannequin limbs),6.1% (normal human arms) and 6.8% (lymphedema arms). The larger differences were likely tobe due to deviation from circular or elliptical cross-section (Perometer or tape method) andcompression of the arm (tape method). Errors arising from incorrect positioning within themeasuring frame were generally small, but larger errors occurred when a cylinder was partiallyrotated within the frame (i.e., no longer perpendicular to the light beams). The Perometer washighly reproducible, each measurement taking only a few seconds.When recording the change in volume with time of a segment of arm during venousocclusion (blood flow measurement by venous occlusion plethysmography) using the Perometerplus a mercury strain gauge, between-method differences for individual blood flow recordingswere apparent. The source of these differences is discussed. However, using the average of anumber of blood flow recordings the Perometer and the strain gauge agreed fairly closely forboth the normal and lymphedema arms.The Perometer is thus a reliable and convenient tool for the measurement of limb volume,and may also be used to measure the rate of swelling during venous occlusion plethysmography.