Monitoring of Surgical Wounds with Purely Textile, Measuring Wound Pads – II. Detection of Bacterial Inflammation by Measurement of Wound Tissue Temperature

This study was executed to aquire basic knowledge on relations between design characteristics and the quality of measurements, as well as the optimization of the design of purely textile, measuring wound dressings for the detection of wound tissue warming as an indicator for (bacterial) inflammation.

The normal healing of surgical skin wounds may be disrupted by complications, by far the most common being post-operative bacterial infections.

The temperature of the wound and its surroundings – the main indicative parameter for the onset of bacterial inflammation – can be determined and shown by means of functionalized, purely textile wound dressings with measuring capability when used as part of a measuring and assistance system. The textile sensors comprise insulated electrical wires stitched onto a textile backing designed as double meander, which is appropriate for the detection of temperature, moist, and rectangular transverse elongation (indicating inflammation, bleeding or seroma discharge, and tissue volume increase as a sign of haemorrhage (into the tissue) or seroma formation).

Major design parameters are diameter of the electrical conductor (wire) / distance between an electrical conductor and the nearest (parallel) conductor / spacing of the embroidered seams (upper thread loops) along a conductor / number of meander loops, and length, width, and area of the double meander sensor array.

Skin temperature rises a few degree Celsius resulting in differences in ohmic resistance in the order of a few parts per thousand. The ohmic resistance of the electrical sensor wire as measurement for the temperature under the dressing solely depends on the length of the wire. Neither the spacing between the sections of wire nor the spacing of the upper thread has any detectable direct effect on the determination of the temperature.

To improve measuring accuracy, sensor wires as thin as possible should be used for two reasons: (1) because their ohmic resistance is higher, simplifying measurement, and (2) because they can be stitched closer together in wound dressings, enabling a longer sensor wire to be used in the area of interest.