A Textile Sensor Using Piezoelectric Fibres for Measuring Dynamic Compression of a Bowel Stent

Jorge Alberto Arroyo Vazquez, MD1, Maria Bergstrom1, Anna Vahlberg2, Anja Lund, DTech2, Per-Ola Park1. 1Dept of Surgery, South Alvsborg Hospital & Gothenburg University, 2Swedish School of textiles, University of Boras, Boras, Sweden

Introduction

Covered Stents are increasingly used for treatment of postoperative or ulcer-caused gastro-intestinal leaks. Covered stents used for these treatments carry a risk of migration that potentially can create grave clinical situations. It may be assumed that the shape and mechanical properties of the stent together with the geometrical response of the stent to bowel movements will affect the probability of migration. These factors have not yet been studied due to lack of adequate models. Here we introduce novel piezoelectric textile fibres integrated in a stent. The piezoelectric fibres have the ability to generate an electric voltage in response to elongation and their function as sensors for bowel and stent movements was investigated.

Methods

Piezoelectric fibres were melt spun as previously reported. They were coated with a conductive silicone, Elastosil® LR 3162 A/B (Wacker Chemie AG) which constitutes the outer electrode, and then manually inserted/sewn into an uncovered Dodenal Hanarostent (M.I. Tech).

The experiment was conducted in two phases. 1) Bench-top: The stent was subjected to dynamic compression using in-house constructed rings, and the fibres’ piezoelectric outputs with respect to the position and amplitude of compression was measured using an oscilloscope (PicoScope 5442 A). 2) In vivo in a non-survival pig model: The stent was placed in the pig-pylorus through laparotomy and gastrotomy. The stomach was closed with suture and the leads from the piezoelectric fibers were brought out to the oscilloscope. Piezo-electric out-put was measured during 30 minutes both at base line and then after Neostigmine stimulation.

Results

Ex-vivo compressions of the stent caused the piezoelectric fibres to generate a voltage. Different compression forces generated different voltages. In vivo testing in pig pylorus: base line voltage out-put measurements showed correlation to visible pyloric contractions. When stimulated with Neostigmine increased out-put voltages were recorded during increased pyloric activity.

Conclusion

The present study indicates that piezoelectric fibres integrated in a stent will be able to sense bowel movements. With refinements of this model including calibration and signal interpretation, a sensor-stent is expected to be useful as a tool to study the effect of stents on intestinal motility in general, and to evaluate this effect as a function of the geometry and mechanical properties of the stent.

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