Microprocessor-based air plethysmograph for the examination of compressed tissue of limbs

Abstract

Purpose This paper aims to propose a simple microprocessor-based air plethysmograph that uses a measurement of changes in air pressure in a closed cuff to determine the changes in the volume of the compressed limb. Methods The microprocessor-controlled measurement system applies pressure to the object (ultimately the limb) by pumping air into the cuff surrounding the object. Changes in pressure and air temperature in the cuff over time are recorded. The results supplemented with the calibration procedure allow to determine the changes in the volume of the object. Results Measurement-independent calibration and temperature correction of pressure changes in the system proved to be necessary components of the measurement procedure for volume changes. When comparing the device test results with the actual changes observed with the limb model, there was a discrepancy between 0.2 and 0.7 percent of the total volume under the cuff. Conclusions Studies have shown that the proposed air plethysmograph is useful for assessing the changes in the volume of the limb model within the range that are expected in the diagnosis of lymphedema. The solution is a cheaper and less complicated alternative to most of the available methods of measuring changes in the volume of edema tissue under controlled pressure.