Cross-sectional changes in an asymmetric tube with bearing on non-invasive pressure measurements
Technology and Health Care
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A sensor has been designed consisting of a tube holder with a forcetransducer and a tube with a modified cross-section. The holder hasa lid that encloses the tube. By having a stiff holder and acompliant tube, the idea is that the intraluminal pressure in thetube can be obtained from the measured force. The method isintended for non-invasive pressure measurements in blood ordialysate tubes. We have used a tube cross-sectional geometry where the outersurface is elliptic and the inner surface is circular with arelation of 2:1 between the thinnest and thickest tube sides. Thepressure transducer system shows a linear relationship between theapplied pressure and the sensor output (r=0.999). Within thetemperature range, 32°--36°C, which corresponds to theblood and dialysate temperatures, the sensor accuracy is within± 0.8 kPa (± 6 mm Hg). This indicates that the sensorshould be clinically useful during dialysis and similarapplications.