An asymmetric dialysis tube as an integrated part of a pressure-monitoring sensor

Abstract

A sensor has been designed consisting of a tube holder with a force transducer and a tube with a modified cross-section. The holder has a lid that encloses the tube. By having a stiff holder and a compliant tube, the idea is that the intraluminal pressure in the tube can be obtained from the measured force. The method is intended for non-invasive pressure measurements in blood or dialysate tubes. We have used a tube cross-sectional geometry where the outer surface is elliptic and the inner surface is circular with a relation of 2:1 between the thinnest and thickest tube sides. The pressure transducer system shows a linear relationship between the applied pressure and the sensor output (r=0.999). Within the temperature range, 32 degrees --36 degrees C, which corresponds to the blood and dialysate temperatures, the sensor accuracy is within +/- 0.8 kPa (+/- 6 mm Hg). This indicates that the sensor should be clinically useful during dialysis and similar applications.