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|Title:||Development of three-dimensional spacer fabrics as absorbent and cushioning layer for advanced composite wound dressing||Authors:||Tong, Shuk Fan||Degree:||Ph.D.||Issue Date:||2018||Abstract:||Wound management has become more sophisticated and modern wound dressings now focus more on providing an optimal microclimate for wound healing. There are various types of wound dressings on the current market designed for different types of wounds. Pressure sores are one of the most prevalent types of chronic wounds that can be difficult to heal once they have developed and thus become the burden of caretakers, hospitals and the government. An ideal wound dressing for pressure ulcers should allow the transmission of liquid and gas, absorb exudates, provide cushioning and help to relieve pressure all at the same time. However, there are few wound dressings available in the market that are designed to manage pressure ulcers and their absorbency and cushioning performance are questionable. The heels are one of the most common sites for pressure ulcer development. However, there are a lack of suitable wound dressings for pressure ulcers, especially for those that would accommodate the 3-dimensional (3D) shape of the heel region. The answer could be to use spacer fabrics, which are 3D knitted fabrics that have been recently used as cushioning material in protective work clothing, such as for medical personnel, due to their excellent compression, moisture-wicking, and temperature-controlling properties. Furthermore, the properties of 3D knitted spacer fabrics are versatile by changing the knitting parameters. Therefore, the aim of the study is to develop 3D knitted spacer fabrics as a substitute material for the absorbent layers of wound dressings which will provide both absorbency and cushioning effects. This study consists of different parts including (a) a clinical study which involves heel interface pressure measurements of elderly individuals and an assessment of their skin conditions, (b) an evaluation of spacer fabrics as a cushioning and absorbent layer in wound dressings for pressure ulcers, (c) the formulation of a pressure simulation model for a wound dressing for pressure ulcers, and (d) the development of wound dressing composite with spacer fabrics as the absorbent layer and evaluation of the wound dressing composite. Thirty percent of pressure ulcers occur in the heel region. Therefore, the bedridden and elderly are at high risk for pressure ulcer development. In response, a thorough 6-month clinical study at an elderly home is first carried out. The development of the heel pressure ulcer and the wound management process are monitored and recorded. Due to the low metabolism and different kinds of chronic illnesses of the elderly, their heel ulcer requires more than 6 months to heal. It is found that apart from pressure relief, the key contributing factors are also proper wound care, nutrition and daily care for the healing of ulcer wounds. Interviews and surveys with caretakers and wound nurses are conducted to solicit their opinions on existing wound dressings and their priorities for choosing wound dressings. Based on their feedback and raised concerns, it is found that the critical physical requirements are breathability, cushioning effect and absorbency for wound dressings to treat pressure ulcers. They also point out that existing wound dressings cannot adequately absorb exudates, provide a cushioning effect or allow breathability. The conformity of the wound dressings is yet another one of their concerns. Pressure is one of the most important factors in the development of pressure ulcers and interface pressure is one of the most commonly used non-invasive methods to predict the risk of their development. To determine the heel interface pressure of the elderly and the effects of heel position and mattress type on the heel interface pressure, an evaluation of the heel interface pressure is conducted on both the bedridden and healthy elderly. The results show that the neutral position of their feet is when they place their heel in the neutral external rotation and upright positions in a relaxed supine position. However, the upright position may place the bedridden elderly at a higher risk of developing a heel ulcer as opposed to the neutral external rotation position. It is also found that some of the elderly are still at high risk for developing pressure ulcers even with the use of a pressure relieving mattress. Assessments of their skin conditions are also carried out, and the results show that the skin of their heels is considered to be very dehydrated and lack sebum content which may increase skin abrasion and friction as well as the chances of developing a heel ulcer.
Taking the feedback and comments of the nurses into consideration, it is found that the breathability, absorption and cushioning of pressure wound dressings are critical factors. To understand the physical properties of existing wound dressings designed for pressure ulcer wounds and the possibility of using 3D knitted spacer fabrics as the material for the absorbent and cushioning layer, several physical experiments have been carried out, such as testing the compression, absorbency, wettability, water vapor and air permeabilities, thermal conductivity and extensibility. The results indicate that the compression resistance of weft knitted spacer fabrics is higher than pressure ulcer wound dressings which proves that spacer fabrics can provide a good cushioning effect to protect the wound and relieve pressure to prevent further ulceration. The absorbency of spacer fabric which has polyester falls short of wound dressings made of highly absorbent materials, however, it is comparable to those with an adhesive layer. The weft knitted spacer fabrics also have better wettability than most of the wound dressings. The water vapor permeability of both the warp and weft knitted spacer fabrics is better than that of the wound dressings. In terms of the breathability, both the warp and weft knitted spacer fabrics have a better performance than that of the wound dressings. The thermal conductivity and extensibility of the spacer fabrics are comparable to or even excel some of the existing wound dressings. Therefore, based on the results, the overall physical properties of the 3D knitted spacer fabrics are comparable to or even better than most of the existing wound dressings. This indicates that spacer fabrics meet the criteria of existing wound dressings and it is possible to use them as the substrate for the absorbent and cushioning layer of wound dressings. By changing the knitting parameters of the 3D knitted spacer fabrics, such as type of yarn, and yarn angle and density, their physical properties are changed. In this study, the finite element model (FEM) is adopted to simulate the pressure onto the skin in relation to the contours of the heels and properties of the spacer fabrics, in other words, to simulate the heel-spacer fabric interface pressure. Furthermore, by simply changing the material properties of the spacer fabrics, the FEM can be used to predict their compressional behaviour. The simulation modelling can show the trend of pressure distribution with good accuracy. In addition, the FEM shows the compression behaviour of spacer yarns under pressure. It is found that there is shearing movement in the outer layers of the spacer fabrics under loading. After an evaluation of the physical properties of the 3D knitted spacer fabrics and their cushioning performance, wound dressing composites are fabricated with three layers, including (a) a layer that is in direct contact with the wound to protect the wound bed during changing of the wound dressing, (b) 3D knitted spacer fabric as the absorbent layer that provides cushioning, and (c) an adhesive coversheet for the outermost layer of the dressing for fixation purposes. Laboratory tests are carried out to evaluate the performance of the newly developed wound dressing composites, especially its absorbency and cushioning properties. The bacterial barrier properties are also evaluated. It is found that the compression resistance of the newly developed wound dressing composites higher than most of the existing wound dressings. The 3 layers of the wound dressing composite have comparable or even excel the performance of current wound dressings. The 3 layers are also more water vapor and air permeable than most of the existing wound dressings. Furthermore, their thermal conductivity is comparable to the existing wound dressings. The extensibility of the newly developed wound dressing composites is comparable to or even better than existing wound dressings. The wound dressings composites demonstrate comparable results to wound dressings that do not have an adhesive layer. The bacterial barrier properties are excellent and the results indicate that the new wound composites are able to protect the wound against bacteria. The study results prove that the newly developed wound dressing composites have a good physical performance and meet the requirements of wound dressings. The research results and the input from the nurses on the wound dressings available in the market provide useful information on the effects of intrinsic and extrinsic factors on pressure ulcer wound healing. In addition, the neutral heel positions and the effectiveness of pressure relieving mattresses to alleviate the pressure induced onto the heel of elderly individuals have been identified which may advance current knowledge towards new developments in preventive treatments and devices for heel ulcers. The relationship between the knitting parameters and different physical properties of the 3D knitted spacer fabrics is useful for further development of spacer fabrics. The simulation model can also be used to predict the pressure distribution of spacer fabrics. Finally, the outputs of this project can extend to the development of spacer fabrics for different cushioning purposes and help to reduce the production costs of textile medical devices.
|Subjects:||Hong Kong Polytechnic University -- Dissertations
Textile fabrics -- Technological innovations
Surgical dressings -- Materials
Wounds and injuries -- Treatment -- Equipment and supplies
Bandages and bandaging
|Pages:||xxiv, 266 pages : color illustrations|
|Appears in Collections:||Thesis|
View full-text via https://theses.lib.polyu.edu.hk/handle/200/9485
Citations as of May 15, 2022
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