| Author: | Xiong, Ying |
| Title: | Pressure management for medical compression stockings : prediction, computer integrated manufacturing and pressure monitoring by fabric sensors |
| Advisors: | Tao, Xiaoming (ITC) |
| Degree: | Ph.D. |
| Year: | 2022 |
| Subject: | Antiembolism stockings Leg -- Blood-vessels -- Diseases -- Treatment Hong Kong Polytechnic University -- Dissertations |
| Department: | Institute of Textiles and Clothing |
| Pages: | 176 pages : color illustrations |
| Language: | English |
| Abstract: | Chronic venous disease (CVD) is the most common venous disease in the lower limbs venous system, affecting 5%-30% of adults worldwide. Compression therapy is considered to be an effective method of prevention and treatment for CVD. Medical compression stockings (MCSs) with different pressure levels and gradient pressures are widely applied to conduct compression therapy for CVD. Pressure exerted by MCSs is one of the most significant factors affecting the therapy efficacy, health, security and comfort. Pressure management is significant in MCSs design and wearing process. It is necessary to design customized MCSs to achieve effective pressure distribution, while the current MCSs design and fabrication are based on the experience, and no available computer integrated manufacturing (CIM) for fabricating MCSs with required pressure profile. It is also critical to conduct the pressure monitoring in wearing to ensure the proper compression. General commercial pressure measurement devices need place the probe between MCSs and the human leg, which is easy to shift, and the pressure is only measured by professionals at the first wear. To improve the pressure management for MCSs, this thesis presents systematic research on the pressure prediction, CIM for design and production, and pressure sensor integrated with MCSs for pressure monitoring. To set up the computer aided design (CAD) and CIM for producing MCSs with target pressure distribution, this thesis presents investigations on pressure prediction and control based on materials, fabric construction and machine setting in production. The pressure calculation was based on Laplace's formula and the common fabric construction of compression stocking. The pressure was related to the tensile properties of inlay yarn, tensile strain of inlay yarn, walewise density of fabric and circumference of tube in the model. Experiments were conducted to explore the relationship between the parameters with the pressure. To verify the pressure prediction model, the calculated pressure values were compared with the measured ones by two samples t-test. The test result with P (Sig.(2-tailed)) = 0.264 > 0.05, indicated the hypothesis that there was no statistically significant difference between the means of the two groups was accepted. The Pearson correlation coefficient was 0.96, revealing a high correlation between the predicted and measured pressure values. The predication model together with the developed database of the yarns and fabrics parameters were used to develop the CAD/CIM tool for circular knitted MCSs. A representative compression stocking was customized fabricated for a lab-made silicone lower limb mannequin. The mean values of the measured and predicted pressure were compared. An acceptable small difference of ±3 mmHg was obtained. It indicates that the developed prediction model can be used as a CAD/CIM tool for MCSs. Low-pressure (<10 kPa) sensor with a thin and stable structure is essential for the MCSs pressure measurement. A fabric-based capacitive pressure sensor was developed, with suitable conductive woven fabrics selected as electrodes, and polydimethylsiloxane (PDMS) film used as dielectric. Efforts were made to achieve satisfactory performance of the pressure sensor. 3D microstructure dielectric layer was generated by abrasive paper to improve the deformation and recovery of the sensor, so that improve its sensitivity and reduce the response time. Carbon black (CB) particles was mixed in PDMS to improve the relative permittivity of composites, thus enhancing the initial capacitance. The sensitivity, hysteresis, repeatability, effect of temperature and humidity on pressure sensor were characterized. The sensitivity of fabric sensor over the pressure range of 2-9 kPa was 0.19 kPa-1, and the sensor was stable in this range, which covered the operational range of MCSs of Class 1 to Class 3 according to RAL-GZ 387/1. The hysteresis was about 8 % at a pressure of 4 kPa. Response and relaxation time was 90 ms and 121 ms, respectively with a pressure load of 2 kPa. Moreover, the sensor could recover after pressure loading of 9.5 hours. The capacitance change was stable under 10000 cycles of 4 kPa compression with frequency of 0.1 Hz. For the temperature range from 35℃ to 40℃, the capacitance change was 1.3 %. For relative humidity in the range of 20-100 %, the capacitance change of the composite was 2.15 %. Thus, the fabric sensor is acceptable for the measurement on the human body. The fabricated pressure sensor was mounted and adhered with MCSs by thin TPU film through hot pressing. The possible influencing factors of the sensor during wearing including time, stretch, bending and washing were explored. The sensor had a time effect because of the creep properties of the dielectric layer, so the relationship between capacitance changes and time was needed to establish to achieve long time continuous pressure measurement. Tensile test indicated that the smart MCS was robust and reliable under stretching. Tensile strength of the fabric was not affected by the fabric sensor integrated. The capacitance value of the pressure sensor during the fabric stretching to 50 % was fluctuated in a small range of ± 2 %, with corresponding pressure error of ± 0.52 mmHg. However, the bending of pressure sensor was noticeable, as the capacitance change of the sensor increased as the bending radius decreased. With bending radius of 42 mm, relative change of capacitance was about 8.48 %, and the corresponding pressure error was 2.10 mmHg. The pressure sensor was better to be used for places where the curvature radius was greater than 75 mm. MCSs integrated with pressure sensor was washable, the capacitance change of the pressure sensor fluctuated within 2 % in 10 times washing, with corresponding pressure error of 0.52 mmHg. The smart MCSs integrated with pressure sensor was demonstrated to achieve direct pressure measurement on the lower limbs. In summary, this thesis comprehensively studied the design, fabrication and pressure monitoring of MCSs, and provided valuable technical information to MCSs designers and manufacturers for developing customized MCSs and improving the pressure management. |
| Rights: | All rights reserved |
| Access: | open access |
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