Examensarbete för kandidatexamen med huvudområde textilteknologi – inriktning Textil Produktutveckling och Entreprenörskap vid Textilhögskolan i Borås
2017-05-24 Rapport nr 2017.12.06
Monitoring pH in wounds
The possibilities of textiles in healthcare
Figure 13
Abstract
Wound care is a difficult process in the healthcare sector, especially the problem with chronic and infected wounds. There are a lot of patients suffering from these wounds and it is both painful and time consuming for nurses and patients. A wound on the verge of slowing down in the healing process has a shift in its pH value from acidic to neutral and alkaline. If healthcare staff could easily identify this change the chances of treating the wound in time increases, which could stop the developing of a chronic wound.
This report aims to research the possibilities of textile materials that can respond to pH changes and be used in the healthcare sector as a wound dressing. If this becomes a reality, it can both reduce the number of patients suffering from infected and chronic wounds and facilitate the efficiency of healthcare workers' work.
Through interviews and a selective reading into the subjects of: pH, chronic wounds and wound dressings, textile materials and healthcare requirements sketches and ideas were created on how to incorporate a pH indicator into a textile material and through this: into a wound dressing.
What was found was that the technique of electrospun polyamide together with bromocresol purple (pH indicator) in the solution creates a highly suitable fiber for use in pH monitoring wound care. The fiber provides the possibility to construct a fabric, that have the application of detecting and changing color between the pH values in the range between 5.2-6.8, which is the critical pH range for healing wounds.
Wound dressing that's interacting with healthcare staff and provides clues on how the wound is evolving could be the future of wound dressings. Not just to create the perfect environment for the wound but actively analyzing on how it is healing.
Sammanfattning
Sårvård är en svår process inom hälsovårdssektorn och då särskilt problemet med kroniska och inflammerade sår. Det finns många patienter som lider av dessa sår och det är smärtsamt och tidskrävande för likaså patient som vårdpersonal. Ett sår som är på gränsen att stanna i läkningsprocessen har ett skifte i sitt pH-värde från surt till neutralt och alkalisk. Om
sjukvårdspersonal kan identifiera denna förändring ökar chansen för att såret blir behandlat i tid, vilket skulle kunna hindra utvecklingen av ett kroniskt sår.
Denna rapport syftar till att undersöka möjligheterna för ett textilt material som kan reagera på pH-förändringar och användas inom sjukvården i formen av ett sårförband. Om detta blir verklighet kan det både minska antalet patienter som lider av infekterade och kroniska sår samt underlätta vårdpersonalens arbete.
Genom intervjuer och selektiv forskning inom ämnena: pH, kroniska sår och sårförband, textila material och hälsovårdskrav togs skisser och idéer fram på hur man införlivar en pH-indikator i ett textilmaterial och genom detta applicerar funktionen i ett sårförband.
Acknowledgment
First and foremost, we would like to thank Peter Apell, who got us interested in this subject and who has been supportive since day one, helping and providing us with endless of ideas and thoughts. Also, a warm thanks to our mentor, Felicia Syrén for guidance and feedback.
Special thanks to Patricia Joxelius who managed to get us many of the important interviews, and thanks to family and friends who has been supportive during the whole process.
The last thank you is for all the interviewees, you made this project possible!
Ebba Wahlström & Ester Svensson
Ebba Wahlström & Ester Svensson
Index
Abstract 2 Sammanfattning 3 Acknowledgment 4 Index 5List of figures 8
List of tables 8
Glossary 9
1. Background and problem formulation 13
1.1 Purpose 15 1.2 Research questions 15 1.3 Limitations 15 2. Method 16 2.1 Literature Studies 17 2.2 Interviews 17 2.2.1 Interview selection 18
2.3 Product development Process 19
2.4 Reliability and validity 20
2.5 Alternative methods 21
2.6 Assessment of the methodology 21
3. Theory 22
3.1 The skin anatomy and its basic functions 22
3.2 Healing process 24
3.2.1 Wound healing phases 24
3.3 pH in the body and skin 26
3.3.1 Wound healing phases as regard to pH 26 3.3.2 The body's own mechanisms of action 27
3.4 pH indicators 28
3.5 Healthcare and care hygiene 29
3.5.1 Sample procurement 29
3.5.2 Principles of care hygiene 29
3.5.3 Treatment of chronic wounds 30
3.6.1 Material 31 3.6.1.1 Natural fibers and healthcare uses 31
3.6.1.1.1 Cotton 31
3.6.1.2 Manufactured regenerated fibers and healthcare uses 32
3.6.1.2.2 Viscose 33
3.6.1.3 Synthetic fibers and healthcare uses 33
3.6.1.3.1 Polyamide 34
3.6.1.3.2. Nylon 34
3.6.1.3.3 Polyurethane 35
3.6.1.3.4 Polyvinyl alcohol (PVA) fiber 35
3.6.1.3.5 Polypropylene 35
3.6.2 Manufacturing processes 36
3.6.2.1 Electrospinning 36
3.6.2.2 Weaving, knitting, non-woven and film technologies 37
3.6.2.3 3D-textile 39
3.7 Laws & requirements for textile in healthcare 39
3.7.1 European Union 40
3.7.2 Sweden 40
3.7.2.1 Medical Product Agency 40
3.7.2.2 The National Agency for Public Procurement 41 3.7.2.3 SIS - Swedish Institute of standards 41
3.8 Summary 42
4. Result 43
4.1 Interviews 43
4.1.1 Interview group, Healthcare 43
4.1.2 Interview group, Textile & finishing 44 4.1.3 Interview group, Product development and market 44
4.2 Product development 45
4.2.1 Start-up phase 45
4.2.1.1 Design criteria’s 46
4.2.1.1.1 First layer - Wound surface contact layer 46
4.2.1.1.2 Second layer - Transfer layer. One way fluid resistance layer 47
4.2.1.1.3 Third layer - Absorption and moist management 47
4.2.3 Outlining/brainstorming 49
4.2.3 Processing 50
5. Analysis 52
5.1 Motivation for the material selections 52
5.1.1 Layer 1 52
5.1.2 Layer 2 52
5.1.3 Layer 3 53
5.1.5 Layer 4 53
5.2 Sustainability / Environmental aspects 53
5.3 Profitability 54
5.4 Revision of method 54
5.6 Analysis and answer of research questions 55
6. Conclusion 57
6.1 Future development/research 58
7. References 59
8. Attachments 64
List of attachments 64
List of figures
Figure 1: Elderly with wound Figure 2: Deductive workflow
Figure 3: Design development process Figure 4: Skin layers
Figure 5: Re-epithelialization Figure 6: Wound healing phases Figure 7: pH spectrum in wounds
Figure 8: pH indicators suitable for wounds Figure 9: Cross sections of man-made fibers Figure 10: Electrospinning process
Figure 11: Plain weave Figure 12A: Warp knitting Figure 12B: Weft knitting
Figure 13: Illustration of the prototype Figure 14: Cross section of the prototype
List of tables
Table 1: Interview group, healthcare
Table 2: Interview group, textile & finishing Table 3: Interview group, development & process Table 4: Reference guide
Table 5: Layer 1 Table 6: layer 2 Table 7: Layer 3 Table 8: Layer 4
Table 9: Overall criteria’s
Glossary
Acidosis - The body fluids are acidic, with a pH value lower than 7.35
Adipic acid - A white, crystalline, slightly water-soluble solid, used especially in the
synthesis of nylon.
Amorphous polymer - Where the polymers do not have a defined orientation in the fiber.
Amide linkage - Constitute a defining molecular feature of proteins, the secondary structure of which is due in part to the hydrogen bonding abilities of amides. Formed between the carbon and nitrogen atom. This linkage, which is a single bond, is also characteristic of the amide functional group.
Antibiotic resistance - Occurs when bacteria change in a way that reduces the effectiveness of
drugs, chemicals, or other agents designed to cure or prevent infections. The bacteria survive and continue to multiply, causing more harm.
Antibodies - Large, Y-shaped protein produced mainly by plasma cells (that are white blood
cells that secrete large volumes of antibodies) that is used by the immune system to neutralize pathogens such as bacteria and viruses.
Anticoagulants - Commonly referred to as blood thinners, are substances that prevent or
reduce coagulation of blood, prolonging the clotting time.
Autoclave - Closed vessel where chemical or physical reactions are carried out at high
temperatures and high pressure.
Bactericidal enzymes (lysozyme) - An antimicrobial enzyme produced in the body that forms
part of the innate immune system.
Basic (alkalosis) - When the body fluids are basic, with a pH value greater than 7.45. Bioactivity – Any effect on, interaction with, or response from living tissue.
Biocompatibility - Simply refers to the properties of materials being biologically compatible
by not eliciting local or systemic responses from a living system or tissue.
Carbon - A widely distributed element that forms organic compounds in combination with
Chronic wounds - A wound that does not heal in an orderly set of stages and in a predictable
amount of time the way most wounds do; wounds that do not heal within three months are often considered chronic. Chronic wounds seem to be detained in one or more of the phases of wound healing.
Degree of bacterial contamination - In what amount an environment has been exposed and
attacked by bacteria.
Dendritic cells - A highly specialized white blood cell found in the skin, mucosa, and
lymphoid tissues that initiates a primary immune response by activating lymphocytes and secreting cytokines.
Durability - The ability to withstand wear, pressure, or damage.
Electrostatic forces - Coulomb's law states that: The magnitude of the electrostatic force of
attraction between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them. The force is along the straight line joining them.
Epithelial cell - One of the four basic types of animal tissue. Epithelial tissues line the
cavities and surfaces of blood vessels and organs throughout the body.
Extracellular - Outside the cell.
Exudate - When a wound ooze out, in other word “leaks”. Fibroblasts - A type of connective tissue cell.
Finishing - Coatings on textiles, many textiles used are treated, or finished as it’s called, in
some way. It may include dyeing, anti-wrinkle or flame retardant treatment.
Granulation tissue - New connective tissue and microscopic blood vessels that form on the
surfaces of a wound during the healing process.
Hexamethylenediamine - Organic compound with the formula H₂ N(CH₂ ) ₆ NH₂ . The molecule is a diamine, consisting of a hexamethylene hydrocarbon chain terminated with amine functional groups.
Human microbiota - The microorganisms, both flora and fauna, that inhabit a region (here the
human body), when considered collectively.
Hydrophobic - Having little or no affinity for water.
Hydrogen - A colorless, odorless, flammable gas that combines chemically with oxygen to
form
Hydrogels - A macromolecular polymer gel constructed of a network of crosslinked polymer
chains. Hydrogels are synthesized from hydrophilic monomers by either chain or step growth, along with a functional cross linker to promote network formation.
Lymphocytes - A type of white blood cell having a large, spherical nucleus surrounded by a
thin layer of nongranular cytoplasm (cytoplasm is the material within a living cell, excluding the cell nucleus).
Malignant wounds - The tendency of a wound or medical condition to become progressively
worse.
Microorganism - Any organism too small to be viewed by the unaided eye, as bacteria,
protozoa, and some fungi and algae.
Mitosis rate - The mitosis rate refers to how fast the cells duplicate and split themselves.
During mitosis, the chromosomes, which have already duplicated, condense and attach to spindle fibers that pull one copy of each chromosome to opposite sides of the cell. The result is two genetically identical daughter nuclei.
Moist dressings - A dressing or a patch created to maintain the perfect moist environment for
the wound.
Nitrogen - A colorless, odorless, tasteless gas that is the most plentiful element in Earth’s
atmosphere and is a constituent of all living matter.
Oxygen - A colorless, odorless, tasteless gas essential to living organisms, being taken up by
animals, which convert it to carbon dioxide; plants, in turn, utilize carbon dioxide as a source of carbon and return the oxygen to the atmosphere.
Pressure ulcer/bedsore - An ulceration of the skin and subcutaneous tissue caused by poor
circulation due to prolonged pressure on body parts, especially bony protuberances, occurring in bedridden or immobile patients; decubitus ulcer.
Re-epithelialization - The process of returning to health; the restoration of structure and
Sanies - A thin mixture of pus and blood serum discharged from a wound
Semi-crystalline - Have a highly ordered molecular structure with sharp melt points. They do
not gradually soften with a temperature increase, instead, semi-crystalline materials remain solid until a given quantity of heat is absorbed and then rapidly change into a low viscosity liquid.
Solution spinning - A viscous solution of polymer is pumped through a filter and then passed
through the fine holes of a spinneret. The solvent is subsequently removed, leaving a fiber.
Thermoplastic - A material, usually a plastic polymer, which becomes soft when heated and
hard when cooled. Thermoplastic materials can be cooled and heated several times without any change in their chemistry or mechanical properties.
Weaving & knitting patterns - The pattern of the how the yarn is supposed to be interlaced
1. Background and problem formulation
In the medical care of today, pressure ulcers are calculated as a healthcare injury (SOSFS 2005: 12 (Socialstyrelsen 2005)) and must be reported by the hospital as a deviation. Pressure ulcer is something that affects the majority of elderly and bedridden patients, often these sores develop into chronic wounds (Figure 1). Treating chronic wounds is difficult and they are time consuming to heal, and the options that are available rarely lead to complete healing. (Lindholm, Sophiahemmet Högskola 2016) It has come to a situation where patients seeking care and recover from their initial illnesses turn ill again because of infections caused by sores that develop into chronic wounds during treatment1.
Figure 1: Elderly with a wound. Wounds like this can become chronic. Printed with permission from (Pixabay 2017)
Added to this, there is a lot of time in the healthcare used on replacing dressings on existing wounds that might not have to be changed, in doing so the wound is exposed to the external environment risking it to become infected and thus preventing it from healing properly. The reason for the replacement is that the nurses/doctor can't possibly know what's going on under the bandage, so therefore they must put a timeframe on the wound, until they investigate it again. The unnecessary changing of a dressing is not only bad for the wound, it's also a resource wastage, in both time and money. 2
1
I1 2017-05-01 Healthcare interwiev
If a change in the wound´s pH can be detected early, the chance of preventing the occurrence of chronic wounds increases. This because frequent wounds have often been found to have a lower pH than non-healing wounds. Therefore, preventive work and early detection of pH changes are an important part in counteracting chronic wounds. (Landstingen i Jönköping, Kalmar, Östergötland 2009) Measuring pH values in wounds can also facilitate early detection and prevent infections in wounds that have been contaminated. When a wound remains at a pH value of 4.5-5.5 it has the best environment to heal, when it goes above that pH value there is risk of the healing process slowing down. (Schreml 2014)
With a pH detection, it would easier show when a wound needs treatment and a change of dressing. The integration of this application in an adhesive bandage would facilitate
healthcare professionals in their work, helping both them and patients in detecting when the adhesive bandage needs to be lifted off and the wound checked.
The research and the attempts to invent an indicator of pH changes are ongoing on several platforms, where the textile platform has great application value (Guinovart et al. 2014). The only earlier research and product concerning pH change in adhesive bandages found, was one created by the German Fraunhofer Institute, where they had developed a prototype with a similar thought process (Von Schultz 2010). No further information about the project was found and it is not available on the market today. Focus has therefore instead been to identify existing adhesive bandages treating and protecting wounds on today's market and looking at earlier research on possible textile materials that could potentially hold a pH indicator. It is known that wounds often change to a more alkaline pH value when not healing correctly (Stenlund 2016). There exist pH indicators that could indicate pH value changes through color changing (West 1969). There are many ways to create a textile with a special function in it, from finishing and processed to properties already inside the fiber (Kadolph, Langford 2013;2014).
This thesis aims to research the possibilities of textile materials that can respond to pH changes and be used in the healthcare sector as a wound dressing. Therefore, the intention is to start a product development process of a pH adhesive bandage, built on the needs shown in the healthcare interviews3. If this becomes a reality, it can both reduce the number of patients suffering from infected and chronic wounds and facilitate the efficiency of healthcare
workers' work (Guinovart et al. 2014).
1.1 Purpose
The purpose of this study is to create an investigative pilot study on how to develop a textile product that can detect pH values in patients’ wounds, thereby aiding in the work of
preventing the occurrence of chronic wounds.
1.2 Research questions
I. How can a textile material be constructed that holds the function of indicating when the pH value changes in its vicinity?
II. How can a textile patch be designed to indicate pH changes in wounds and fit into the healthcare sector?
1.3 Limitations
The thesis will describe the possibilities of how pH detecting textile theoretically could be used to create a product. This thesis will lay the ground for continued research and
developing which means that the product will not be able to be applied directly to the healthcare sector without further testing and developing, but the healthcare sector requirements and laws has been considered.
The thesis will focus and work from the professional angle; interviewing healthcare personnel and people with knowledge of textile and product development. This means that the thesis not will concern, in any more ways than the comfort and function targeted to them, the patients through interviews. The subject can be a sensitive area and the interviews could do the patients more wrong than help them and since the authors of this thesis has no experience on how to perform an interview of this kind the decision was to remove that kind of focus from the thesis.
Since the thesis is concerned to be a pilot study of the product development of and pH detecting adhesive bandage, there is in this stage no economical or statistical calculations on the profit this bandage could make. What can be mentioned in that subject is that the function is concerned to lower the quantity of patients with chronic wounds and through that the product should save both money and time in the healthcare sector, but the calculations is not performed.
2. Method
In the following chapter the method selected for this thesis will be presented. The method lies on a systematic literature study and qualitative semi-structured interviews, which will be described more thoroughly in their respectively subheading. The thesis seeks to follow a deductive approach, gathering and analyzing data to later draw a fact-based conclusion. (Bryman, Bell 2007)
The following figure (Figure 2) shows the work progress that the research and thesis has followed. The start is presupposed from the theory (step 1, Figure 2) that the wound pH value has a big importance in the healing process, and that the control of this value will help the healthcare staff to heal and aid wounded patients in a better way (Stenlund 2016). The next step (step 2, Figure 2) was to create research questions that aimed the literature studies and data collections in the right direction, also to show the reader and to guide the authors of the thesis towards the purpose of the thesis. The research questions were created by looking at what was known today and what possibilities could be created through the authors.
Subject areas were decided out of the research questions, the most important areas were Healthcare and Textile with many underlying subjects. Data collection and interviews (step 3, Figure 2) (which will be explained more thoroughly further down in this chapter) were
thereafter performed out of the decided subject areas. The data found and interviews
performed gave the research some valuable findings (step 4, Figure 2) that helped the product development process to start. The findings were collected and considered, and thereafter used to create a result (step 5, Figure 2). The result was shown through a hypothetical product, with the most important qualities accounted for and through a summary of the interviews accomplished. After the result were accounted for the analysis (step 6, Figure 2) was made from conclusions and investigations of the results provided together with an analysis about the healthcare markets, profitability and sustainability, revision of the method and future research that we found possible and significant to work further with.
2.1 Literature Studies
Scientific articles have been gathered to understand the subject at hand. It is an extensive topic and to interpret the information right, there has been a selective investigation into the human anatomy, pH, wound care, healthcare sector and medical textile.
Searches has been made in the Primo database linked to the available public and subject databases for Borås Högskola. The searches have been filtered by the option of only showing “articles” and “scientific material”, providing the thesis with scientific articles in the subjects searched for. The selection is thereafter made after reading the abstract to each article and determining the relevance to the subject-matter.
The articles being used in this thesis in language will only be in Swedish and English and all the articles have been published between 1969-2016. The reference from 1969 is concerning pH-indicators, a subject that has not been altered in information much since then, the earliest reference after that is from 1993.
2.2 Interviews
Beyond looking from a scientific theory starting point, the theory was immersed with the help of qualitative in-depth semi-structured interviews. Therefore, people with the desired
expertise was contacted. The people is active in different sectors such as healthcare4, textile and finishing5 and product development/process, concerning healthcare products6 . The interviews were done in the language easiest for the interviewed, therefore most for the interviews are in Swedish, with some English exceptions.
The semi structured way to interview was chosen so that the interviewed would have freedom to analyze, communicate their own opinions and reflections over areas of interest. Common for all the interviews was the importance to immerse in a conversation, letting the
interviewed think thoroughly through their answers. (Bryman, Bell 2007) There was no time frame, making the discussion open to new subjects mentioned by the interviewed.
In healthcare interviews the same wide questions were asked. The primary intention was to meet up with the nurses for a face-to-face interview. It turned out it was hard to find time for them to have a personal meeting, and it was decided that they would make contact when they had the time. The interviews were therefore performed over the phone with both interviewers present and taking notes.
The other interviews had some similar questions but many questions were based on the interviewed and their area of knowledge. The interview questions were made on the
4 I1 2017-05-01 Healthcare interview, I2 2017-05-04 Healthcare interview, I3 2017-05-10 Healthcare
interview, I4 2017-05-10 Healthcare interview, I5 2017-05-12 Healthcare interview
5
I6 2017-05-04 textile and finishing interview, I7 2017-03-18 textile and finishing interview, I8 2017- 04-25 textile and finishing interview
6 I9 2017-03-22 product development/process interview, I10 2017-05-03 product
knowledge that the result will be processed qualitatively (Bryman, Bell 2007). By this the thesis wanted to showcase the opinions and perceptions of the person being interviewed. The interview with I107 were executed together with another project group researching the same area. This was mainly done because of the time frame since I10 were visiting Sweden under limited time. The choice to merge the interview with another group made it possible to have a long interview session and to go deep in the medical device development area. These interviews aided in the process of developing a theoretical idea of a product of an adhesive bandage that keeps track of the pH value.
2.2.1 Interview selection
The interviews were separated into three groups to organize the expertise and easier illustrate the different areas that has been the core of the research.
Table 1: Interview group healthcare
Table 3: Interview group development & process
2.3 Product development Process
To create a product, a template for a working process was chosen to support the development. In the creation of a new object there is some certain steps that are beneficial to follow in order not to lose track of the main idea/goal during the whole timespan. The process is gathered from Kenneth Österlin (2010), whose book were recommended to use in this thesis by Industrial designer I98
2.3.1 Start-up
In this step, the goal of the process was discussed. Which frames, resources and economical possibilities are set and needs to be followed? Different working tasks and responsibilities were distributed amongst the participants of the product development. (Österlin 2010)
2.3.2 Analysis and information gathering
Information was gathered of the ergonomic and other demands on the design, which market is possible for the product, possible production possibilities. This information was thereafter analyzed together with material, products partial functions and other conditions. This resulted into a “design requirements specification”. (Österlin 2010)
2.3.3 Sketch/outlining
Here solutions were conceptualized for the different requirements and demands that was set in the design requirements specification. (Österlin 2010)
2.3.4 Processing
The embodiment is decided, built upon the design requirements specification and the analysis of the sketches and concepts created in the previous step. The best part of each concept was gathered, creating the best solution. The concept was fixed and trimmed with exact
measurements and design. The correct material to use was decided. (Österlin 2010)
2.3.5 Follow-up
This step is not included in the thesis, since a prototype never was made. The last step is the detail construction/manufacturing base. The prototype is tested and the production is tried out to check for unexpected events. The last details are polished for the perfect result. The quality is checked repeatedly during the production to make sure that the quality is constant.
(Österlin 2010)
Figure 3: Design development process, drawn with inspiration from the explanation of an industrial product development process (Österlin 2010).
2.4 Reliability and validity
Validity is if the subject/question/theory is relevant for the context. Reliability is
dependability, is the measurements measured in a credible way? And would the result be the same if other students or researchers made the same research? (Bryman, Bell 2007)
Dialogical validity had been used in great extent, whereas the interviews made have had a great amount of time for follow up questions and validation of how the interviewer interpret what the interviewed said, to clear all misunderstandings. Reliability has been considered during the whole thesis as well, the authors of this thesis have aimed at not putting any own emotions or opinions on the interviews. The thesis aims to be clear and transparent to hinder the possibly prejudices behold of the researchers to influence, to strengthen the credibility. Having interviews with as many people as possible and comparing the answers offers reliability to the thesis, this was aimed to be maintained though it was a difficulty in finding people to interview. Information from all the interviews was of use to the thesis and the people interviewed were experts in their fields. Being selective in the work of choosing the people to interview means avoiding misguided information. Here a choice was made to conduct fewer interviews but with reliable information gathered.
2.5 Alternative methods
An alternative method would have been to perform several tests before the surroundings had been analyzed, following an inductive method (Bryman, Bell 2007). As it concerns medical textiles and medical products it was not defensible to attempt to create a product without the necessary knowledge of the area/field and to be aware of the risks that might follow if the product is created wrong (becoming toxic, hazardous etc.). The risk concerned the patients using the plaster as well as the developers behind the product. To put people in harm's way without the qualified testing would not just have been illegal but also unethical, going against the principals of the study.
2.6 Assessment of the methodology
The goal is to thoroughly analyze who the author of the source is, what the source is referring to, who the intended target group is and how that affects the source and how current/actual it is. No matter how carefully the source criticism is conducted there will always be some risk of human error meaning the method is not completely immune to inaccuracy.
The human error can also affect the results of the interviews because misunderstandings and personal relationships can hinder the interview. This has been prevented through thoughtful interview questions and long sessions where the interviewees had the time to motivate and think through their answers. Contact has also been available afterwards, where further questions and uncertainties could be addressed and cleared.
3. Theory
This chapter intends to explain the theoretical ground on which the thesis and product development is built upon.
Attachment O1 shows an overview over the theory covered in the thesis. The first subjects are explaining about the human skin, how it's built and what happens when it's torn (when a wound is created). After this the theory focus on pH and how it's connected to the body and its functions, why pH is important in wound care and which pH indicators there exist that has the same pH range as the body.
The theory thereafter explains how wounds are treated in healthcare and touches down in basic facts about the needed hygiene inside the healthcare sector.
Lastly the textile area is covered, with theory about different textile materials used in
healthcare, processed and finishing’s together with laws and requirements applied on textiles when created to be of medical use. In the end of the chapter, the most important theory will be summed up, pinpointing the most important parts of the theory.
3.1 The skin anatomy and its basic functions
The skin it is the biggest organ of the body and is protecting us from the surroundings consisting of bacteria, chemical and physical substances and climate changes.
The skin is made of organic material and is therefore consistently decomposing in greater or lesser extent. This makes the function of a continuous renewal of the skin barrier of highest importance. (Henriksson, Rasmusson, Lyons, Högskolan Kristianstad, Sektionen för hälsa och samhälle 2007).
The anatomy of the skin is divided into three main parts (Figure 4); epidermis (scarfskin),
dermis (true skin) and lastly the subcutaneous fat. The different layers are good for different
reasons. The layer you can see with your eyes, here called the first layer, is called epidermis and is the main protection from the surroundings. Dermis, second layer, primary function is to act as a cover with favorable mechanical properties, thus making it easier to move. The third layer, subcutaneous fat is isolating and helps the body to control the temperature. Together, these three parts creates the “skin” and work together to protect the body. (Forslind, Forss 1998)
The skin consists of a network of a specific type of cells (dendritic cells) that are capable of capturing microorganisms, which are then taken care of by lymphocytes. There are always a variety of bacteria on the skin, the bacteria that are not pathogenic are said to belong to the “human microbiota”. Bacteria of human microbiota are good for the skin because they are there to hinder the propagation and growth of the pathogenic bacteria. To the skin, sweat and sebum are secreted, which contains bactericidal enzymes (lysozyme), antibodies (used by the body's immune system to detect and identify foreign substances such as viruses, bacteria or parasites) and lactic acid, which gives the skin an acidic pH value. All these features are essential for the skin to function at its best. (Henriksson, Rasmusson, Lyons, Högskolan Kristianstad, Sektionen för hälsa och samhälle 2007)
Figure 4, Skin layers drawn with inspiration from (Landstinget i Jönköping, Kalmar, Östergötland 2009)
3.2 Healing process
The wound healing process begins when the skin barrier is broken and then continues for several years after the wound looks "healed". However, the healed wound never gets its original strength back completely. (Myles 2006)
The superficial wounds are healed by re-epithelialization (Figure 5). Epithelial cells
(specialized cells building a type of tissue covering the surfaces of the body; epithelium), hair follicles and sweat pathways migrate into the wound and the mitosis rate (an estimate of how fast the cells break) in the underlying epithelial layer increases. For this epithelialization to occur, cells should bind to different types of protein. The wound healing process is usually divided into four phases, which flow into each other and have varying length of time. (Landstingen i Jönköping, Kalmar, Östergötland 2009)
Figure 5: Re-epithelialization drawn with inspiration from (Landstingen i Jönköping, Kalmar, Östergötland 2009)
3.2.1 Wound healing phases
A wound is defined as a breach in the epidermis and/or dermis that initiates a healing process. Wounds can be subdivided into three categories: acute, chronic and postoperative wounds (Hansen 2001). They can all be in different level of complexity and therefore all require different appropriate evaluations and diagnosis. (Myles 2006).
The target of this thesis is chronic wounds, a chronic wound is one that remains unhealed for more than 8 weeks despite optimal and general treatments. Typical examples are leg ulcers and pressure ulcers, malignant wounds and diabetic foot ulcers. (Myles 2006) Examples of chronical wounds that rarely occur in clinical practice includes burning (thermal, chemical, electrical) and frostbite wounds (Skórkowska-Telichowska, Czemplik, Kulma, & Szopa. 2011). The chronic wound gets stuck in the destructive phase and stops to heal and therefore does not develop further into next phase (Hansen 2001). The phases listed below is
Step 1. Acute inflammatory/Coagulation Phase (0-3 days): In case of acute direct wounds
the blood will coagulate to stop the blood flow. This phase causes the body to not bleed out and is essentially not pertinent for this study. (Landstingen i Jönköping, Kalmar, Östergötland 2009)
Step 2. Destructive phase (2-6 days): The permeability of the blood vessels increases and
allows leakage of protein-exudate (which is a medium for cells whose main function is to eat bacteria and worn-out bodily cells; phagocytic cells) (Henriksson, Rasmusson, Lyons, Högskolan Kristianstad, Sektionen för hälsa och samhälle 2007) and different proteases (A group of enzymes that catalyze the degradation of the linkages between amino acids in proteins). Cells with various important functions interact to strengthen the wound and stop the growth of bacteria and inflammations. (Landstingen i Jönköping, Kalmar, Östergötland 2009)
Step 3. Proliferative phase (3-24 day): The wound is filled with newly formed blood
vessels which together with fibroblasts and newly formed collagen constitute the granulation tissue (the tissue covering the healing surface of a wound) (Myles 2006).
Step 4. Maturation phase (3 weeks to months or years): After 6-10 days, the maturation
phase begins. During this time, the granulation tissue draws together. The amount of water and the number of vessels decreases in the wound and the granulation tissue is converted into scar tissue. (Myles 2006)
Figure 6: Drawn with inspiration from the theory of the 4 phases of wound healing (Landstingen i Jönköping, Kalmar, Östergötland 2009). Since its a hypothetical sketch the height of the arcs has no importance.
3.3 pH in the body and skin
3.3.1 Wound healing phases as regard to pH
First and foremost; pH is used when measuring acidity and alkalinity, and indicates the concentration of hydrogen ions (H +). The range is from 1 to 14, whereas pH value 7 is considered at “neutral” and is also the value for pure water. (Kumar, Pramod, Honnegowda, Thittamaranahalli 2015) The cells within our bodies operates best with a pH value of 7.40 in our body fluids. The skin's surface, however, has a more acidic pH value of around 4 - 5.50. The body fluids are basic (alkalosis) if the pH value is higher than 7.45. At a lower pH value than 7.35 exists acidosis, which means that the body fluids are acidic.
During the four healing phases the pH value of the wound will differ. The first stage is consisting of blood reaching the wound surface, which will leave the wound in a pH value as the blood: about 7,4. After this, the pH value will differ and change during the whole healing period depending on the circumstances around the healing process. After approximately two weeks after the wound is considered “healed”, the pH is restored to the same value as the skin. (Epstein, Singer, Clark 1999)
Different circumstances affecting the pH value and the healing phases are: inflammation, release of oxygen into the wound bed, vasodilation, contamination and how well the body's own cells perform the re-epithelialization, how the body fluids and tissues is stabilized by the different protein buffering systems (as mentioned before in chapter 3.2 and 3.2.1) (Kumar, Pramod, Honnegowda, Thittamaranahalli 2015).
3.3.2 The body's own mechanisms of action
Studies have been done on the body's mechanisms of action, which provides that sanies has a pH value that shifts toward increasing acidity to counter the growth of some bacteria.
However, a causal relationship between the measured pH value and the degree of bacterial contamination or the nature of the contaminating bacteria in the wound has not been determined so far. (Schneider et al. 2007)
The outer skin (epidermis, scarfskin) is an acidic environment. This environment is disturbed when wounds are created and the basic body fluids comes in contact with the skin and threat to change the pH value. The most relevant human pathogenic bacteria that cause diseases have a requirement pH value above 6, and their growth can therefore be decelerated at lower pH value. Investigations have shown that infected wounds are neutral or faintly alkaline, pH 7-8.5, unlike a healthy skin which has a pH value of 5-5.5 pH. (Schneider et al. 2007) When a wound remains at a pH value of 4.5-5.5 it has the best environment to heal, when it goes above that pH value there is risk of the healing process slowing down (Figure 7). (Schreml 2014)
Figure 7: Shows the pH range regarding to the skin healing. When the pH value is 6 and under the skin is
3.4 pH indicators
PH indicators are used for detection, identification and analysis of chemical, biological or medical processes or conditions, changing in physical appearance when shifting between acidity and alkalinity, usually through an alteration in color. (West1969).
The pH indicators of interest are the ones who have a reaction in the same range of values as the skins 4.4 - 6.8. 4 pH indicators were fitting for this use (Figure 8).
One pH-indicator Bromocresol Purple, an anionic sulfophtalien dye, is a indicator used in an aqueous solution in the region pH 5.2 where the color will turn yellow to a pH of 6.8 where the color shifts to purple (Van der Schueren et al. 2010).
Other pH indicators active in similar pH region is: Methyl red (active in the region pH 4.4 (red) to pH 6.2 (yellow), Litmus/Azolitmin (active in the region pH 4.5 (red) to pH 8.3 (blue) and Bromothymol blue (active in the region pH 6.0 (yellow) to pH 7.6 (blue)
Figure 8: Drawn to easier show the range of the different pH indicators and the color they change in.
3.5 Healthcare and care hygiene
In this chapter details of the hygiene that should exist in healthcare is looked at, because the bandages are mainly applied to patients with wounds that are at risk of infection. Also described is how chronic and infected wounds are treated in the healthcare now.
Patients are exposed to health-related infections in healthcare, even if not everything can be avoided, there have been research showing at least 20% could be averted. If the right routines are created the risk can be lowered. A problem in today’s healthcare is antibiotic resistance, that is a threat in public health. Components that worsen the situation is lack of resources and equipment. (Weston 2013)
3.5.1 Sample procurement
If a wound shows sign of infection it should be tested with swab samples. If this test would be taken on routine in a wound, especially a chronic wound, it could disrupt the environment and hinder the healing. Restriction and caution should be taken into consideration when swabbing a wound. But when a swab test is needed it should be directly from the infected or inflamed area not surrounding skin to ensure the right area is tested. (Weston 2013)
Because of increased antibiotic resistance in many organisms it is essential that infections are treated in the most suitable way, to do this swab are taken for microbiological analysis. (Ferguson 2005)
To retrieve a good, test the sampling stick needs to be rolled in a zigzag motion over the wound. Removal of soluble organic residues should be done for the wound to heal properly, because the organic residues may consist of bacteria not ideal for the infected microorganism and for that reason it could harm the healing process. (Weston 2013)
3.5.2 Principles of care hygiene
To maintain a strict hand hygiene routine and removal of microorganisms from hands among healthcare staff is crucial to keep a sterile environment to the greatest extent possible, since it is mostly through touch that infections is spread. Research shows that factors contributing to poor compliance to hand hygiene are lack of time, inadequate resources, lack of knowledge about the spread of infection and lack of knowledge about healthcare guidelines. (Weston 2013)
3.5.3 Treatment of chronic wounds
To treat a chronic wound there needs to be cooperation between the patient and the physician. It is a intricate and systematized process. In the proliferation stage, it is important to give the recently formed tissue the ultimate humidity. If the wound were to get too dry the cells would die which would slow down the healing. In the stage of wound closure and scar formation, ultimate humidity is also of importance along with the right temperature, pH value and oxygen. These qualities are essential for the cell migration to take place. (Skórkowska-Telichowska et al. 2011)
There exists a strategy called TIME proposed by The European Wound Management Association, which focus was put on strengthening the natural healing processes and
eliminating aggressive and proliferation-inhibiting activities. (Skórkowska-Telichowska et al. 2011)
The method contains:
- T (tissue management)
- I (infection or inflammation), inhibiting infection - M (moisture balance)
- E (edge of the wound, epithelialization support) (Werdin, Tenenhaus, & Rennekampff 2008)
Treating a chronic wound relies a great deal on choosing the appropriate dressing,
considering localization, character, depth and area of the injury, the level of exudates, any infection, the healing stage and the skin type. (Skórkowska-Telichowska et al. 2011) The perfect dressing will give the guarantee to physical continuity of the wound, actively cleaning the wound, absorbing excess exudates, protecting against infection and external factors, providing the perfect pH, thermoregulation, gas exchange and humidity, cooperating with wound-healing processes, preventing rejection reactions, not being allergenic,
comfortable for user and not damaging to the edges of the ulcer. (Skórkowska-Telichowska et al. 2011)
There has been documentation showing moist dressing (dressings keeping the environment of the wound moist) are appropriate for managing wounds. In that it has shown moist dressing to lower the pain and increase healing rate. But all wounds can look extremely different from each other, making it hard to give one wound dressing to treat all wounds. What is known is that a dressing should protect the wound from the environment around consistent of bacteria and particles. (Korting, Schollmann,White, Schoellmann 2011)
3.6 Textile in healthcare
This chapter is to display the different parts that is needed to produce a textile product of this quality. The chapter starts with the explanation of the difference between natural,
manufactured regenerated fibers and synthetic fibers. Following is information on materials used in bandages today. Techniques and manufacturing processes are thereafter explained in the areas important for this thesis.
3.6.1 Material
Textile materials can be defined as any flexible material that is made of thin films of polymer or fibers, yarns or fabrics or products made of films, fibers or fabrics. Textile fibers can be categorized in 3 main groups with subgroups.
3.6.1.1 Natural fibers and healthcare uses
Plant based textile materials are natural cellulosic fibers that are classified as the plant component from which they are removed ex. seed, stem or leaf. Among the most common fibers are cotton and flax. Some properties generally known for cellulose fibers are that they are hydrophilic fibers meaning they react readily with moisture, dyes and many finishes. But they can get damaged from use of chemicals as chlorine bleach. The fibers have good
absorbency, can be flammable, be harmed by mineral acids, but gets minimal damage by organic acids and they have moderate resistance to sunlight. (Kadolph, Langford 2013;2014) Another natural fiber group is protein fibers who are of animal origin, most of the protein fibers come from wool, being hair and fur of animals. Silk is an exception since it's the secretion of the silk caterpillar. Properties of protein fibers are that they are resistant to wrinkling (with wrinkles disappearing between uses), hygroscopic, they protect from humidity in cool damp climate, the fiber becomes weaker when it gets wet, it is harmed by alkali and oxidizing agents and has high flame resistance. (Kadolph, Langford 2013;2014) 3.6.1.1.1 Cotton
Cotton is a natural cellulose fiber, and one of the most widely known fibers in the world. The cotton fiber is mostly used in apparel but it is also a big part in many other industries. With properties such a comfort, high absorbency, good washability/easy care, low static build up and durability the fiber is a great choice also in the healthcare sector. Cotton can be
The good absorbency of cotton make it perfect for moist absorbent and to be drenched in other substances that will help the wound environment to be antibacterial or healing. Examples are aloe vera extract in nanocapsules that adds to the cotton fabric, using the healing qualities of aloe vera enter the wound and keep the environment good. (Ghayempour, Montazer, Mahmoudi Rad 2016)
3.6.1.2 Manufactured regenerated fibers and healthcare uses
Manufactured regenerated fibers need processing before being a ready fiber, meaning they do not occur naturally as fiber and needs to be processed first to become a fiber form in which to later make the yarn and fabric. Cellulose and protein fibers are used as the base material, with cellulosic fibers being the most commonly used to produce regenerated fibers. Some
examples of regenerated fibers are rayon, viscose and lyocell. (Kadolph, Langford 2013;2014)
3.6.1.2.1 Alginate fibers
Alginate is a natural rapidly developing copolymer derived from the oceans brown algae. The interests for alginates are mainly from their nontoxicity, good biocompatibility, high
absorbance and the fact that they are capable of being decomposed by other organisms. (Wang et al. 2013)
The fibers are substantially used in wound-care applications and management because the previous mentioned inherent biocompatibility, nontoxicity, and potential bioactivity. (Wang et al. 2013) A moist gel is formed when the alginate fibers interact with the wound exudates. This gel removes fibers entrapment in the wound, which is a major cause of patient trauma at dressing change. (Lv et al 2012)
One of the examples for when alginate fibers are used in healthcare is when it's used as a woven compress that turns into gel when the wound exudates, keeping the wound moist (Mölnycke Health care AB 2017c). Another is when mixed together with sodium and calcium to create an even more healing non-woven product that is highly absorbent (this product is placed inside big wound openings) (Mölnycke Health care AB2017b). Other qualities can be ad to the alginate fibers such as alginate containing silver where the silver is added for its beneficial antimicrobial properties. (Leaper 2012)
3.6.1.2.2 Viscose
The viscose fibers consist of regenerated cellulose and have the same advantageous health and security properties as natural cellulose fibers has. Viscose fibers are manufactured from natural wood pulp in a chemical process, in which natural variations of the raw material are even out. (Wimmer, Zacharias 2015)
To produce viscose the cellulose fiber must first be treated with a caustic soda solution forming alkali cellulose, this is later treated with carbon disulphide forming sodium cellulose xanthate. This makes a solution, that is pushed through a spinning process, that coagulate in relatively high temperatures, forming strands of fibers. (Kauffman, George 1993)
Viscose is of good use in healthcare because of its excellent absorbent qualities which helps to keep the wound in a moist climate but also makes it possible to add substances into the fiber (Mölnycke Health care AB 2017a). Viscose impregnated in sodium chloride is for example used as a dressing where the sodium is released from the fiber when it meets the wound exudate and through this helps to effectively stimulate the cleaning of the wound. (Mölnlycke Health care AB 2017d)
3.6.1.3 Synthetic fibers and healthcare uses
Synthetic fibers are as regenerated fibers also manufactured or man made with the biggest difference being that synthetic fibers are petroleum-based chemicals or petrochemicals using complex procedures. Properties common to synthetic fibers; heat-sensitive, resistant to most chemicals, static cling may occur, low moisture absorbency, pilling. (Kadolph, Langford 2013;2014)
Both synthetic and regenerated fibers can have different cross-sections giving each filament a different functionality. The most common and used one is a round cross section (Figure 9, circular), but different shapes are providing the new surface physical characteristics. The fiber cross section can change the fiber wicking ability (Figure 9, Triangular), abrasion resistance, isolation (Figure 9, Square with voids), pilling and so on. (Bueno,
Aneja, Renner 2004)
Figure 9: 3 different cross sections is shown, showing some of the many options available.
3.6.1.3.1 Polyamide
Polyamides are the current leaders on the world polymer market. When looking at the extensive picture of polymers, polyamide-6 (PA 6) stands out as the most predominantly used, with being used in production of industrial textile fibers and thread. (Kazantseva, Ustinova, Artemenko 2003)
Producing polyamide 6.6 (PA 6.6) fibers comes from adipic acid and hexamethylenediamine and polyamide is one of the most consumed synthetic textile fibers used for garments. They are hydrophobic meaning they do not absorb liquid and that can make dyeing difficult and may affect wearing comfort. (Kisner et al. 2013)
3.6.1.3.2. Nylon
It was in the 1920’s that the chemical company, DuPont, opened a laboratory on the research and development of artificial materials in the US. The focus was to create a synthetic
substitute for silk because of trade relations between US and Japan (main provider of silk to the US’s) were tense. (Nylon 2005)
It was from combining two different monomers, a diacid and a diamine, namely
hexamethylene diamine and adipic acid, and using the condensation polymerisation process that they succeeded and the invention of a new material named fiber 6-6 was born. The first number was linked to the carbon atoms in the diamine and the second was the number in the acid. (Nylon 2005)
Nylons are polyamides, containing the elements carbon, oxygen, nitrogen and hydrogen. It is manufactured in such a way that the fiber-forming substances is any long-chain, synthetic polyamide were less than 85% of the amide linkage are attached directly to two aromatic rings. It is a fiber with considerable durability and elastic recovery. (Kadolph, Langford 2013;2014)
The greater part of nylons is semi-crystalline and with their high molecular weight they create tough materials that have high thermal, chemical and abrasion resistance. They are capable of absorbing moisture content as high as 10%, and this increases their resistance and flexibility. (Nylon 2005)
There are parts of the nylon that is amorphous that endorse elasticity and other parts that is lamellar crystals which add properties like strength, rigidity, wear resistance, chemical resistance and thermal resistance to the fiber. (Ploszajski 2014)
3.6.1.3.3 Polyurethane
Polyurethane (PU) is a thermoset and thermoplastic polymer. In biomedical applications, it is an enticing material for its advanced elasto mechanical and biological properties.
Thermoplastic polyurethane is often used as film or foam in wound dressing functions, this is because of its rare properties, including its blood compatibility, air permeability,
well-supported barrier, durability, elasticity and acceptance or tolerance in the body during the healing. (Hacker et al.2014)
Polyurethanes have considerable structure diversity and it’s because of this it is one of the most bio- and blood compatible materials known today. It can be designed to moderate and strengthen the acceptance and healing of the device or implant at hand. There are many inventive processing technologies that are used to fabricate functional devices, making it to feel and behave like natural tissue. (Zdrahala, Zdrahala 1999)
3.6.1.3.4 Polyvinyl alcohol (PVA) fiber
Because of their excellent comprehensive properties, the high strength and high modulus polyvinyl alcohol fibers are extensively used in high-tech areas. But as of now the preparation of the fiber is mainly based on solution spinning. (Wu et al. 2012).
To be used in wound dressing polyvinyl alcohol, a hydrophilic polymer, has great potential for its excellent strength, water absorption and water retention properties. These functions have given polyvinyl alcohol a lot of attention in the field of biomedical applications, to be used as hydrogels and fibers. (Aytimur et al. 2015)
3.6.1.3.5 Polypropylene
Polypropylene is a widely used synthetic fiber, and belongs to the textile raw materials that is commonly used in many (often disposable) products. The synthetic polymer is inexpensive and holds low surface energy, it is water resistance, has excellent strength, toughness and low liquid and gas permeability. These abilities work both with and against polypropylene
concerning its use in healthcare. (Calhoun 2016) (Stawski, Bellmann 2009)
The fiber is used in form of disposable shoe covers, face mask, head covers, surgical gowns, drapes etc. For polypropene to be used in more advanced wound care there is a need for more research on how to circumvent the fact that the inherent hydrophobicity makes it hard to apply and impart any properties in the polypropylene fiber and it also makes the moist absorption minimal. (Nithyakalyani et al. 2013) The usage of the fiber is good for protection, as the outer layer of a plaster or for the strength, mixed with other more absorbent materials. (Lohmann-rauscher 2017)
3.6.2 Manufacturing processes
3.6.2.1 Electrospinning
With electrospinning one can produce fibers with diameters typically one to two orders of magnitude lower than by extrusion and conventional solution-spun fibers. One trait making electrospinning appealing is its ability to produce highly porous nanofibrous membranes with structural integrity.
In the 1930s the idea of electrospinning was invented but it has only been in the last 15 years that it has seen revived interest, both in academic purpose and by the industry. (De Vrieze et al. 2010) Electrospun material have numerous possibilities for medical applications such as tissue engineering drug release, wound dressing, enzyme immobilization etc. (Werdin, Tenenhaus, & Rennekampff 2008)
The electrospinning system is composed of a high voltage power generator, a syringe, a collector made of a metallic material and a dosage pump. The composite polymer solutions prepared is taken into syringes. The negative electrode is connected to a metallic stationary collector wrapped with aluminum foil and served as a counter electrode and spun under10–20 kV. The working distance between the tip of the syringe needle and the collector is 9–13 cm. Composite fibers are collected on an aluminum foil. The fibers obtained are then dried in an oven at 70 C for 12 h (Figure 10). (Aytimur et al. 2015)
For the technique to work an electrostatic force must be present between the tip of the nozzle and the collector plate. This electric field encourage a distortion of the polymer solution from a spherical pendent drop to a Taylor cone. (Van Der Schueren, Mollet, Ceylan, De Clerck 2010)
A key parameter for nozzle electrospinning to be a success lies in the steady state condition, where the polymer fiber comes out in an unchanging condition, in long separated strands and not unsystematically. (De Vrieze et al. 2010)
Figure 10: The drawing shows the electrospinning process. Number Explanation: 1, Syringe pump. 2, Syringe. 3, Solution. 4, Needle. 5, Voltage supply. 6, Collector. Drawn with inspiration from (Kiennorka, Nakhowong, Chueachot, Tipparacha 2015).
3.6.2.2 Weaving, knitting, non-woven and film technologies
Knitting, weaving and non-woven technologies comes with many variations inside them. The differentiation can for example be the kind of material that is used to create the fabric, with which machine (or by hand) the fabric is created and the variety of different binding
techniques and pattern designs. The different options provide different qualities that will change how the fabric will appear and function. (Kadolph, Langford 2013;2014)
To create a woven fabric one needs a warp and a weft/filling yarn brought together by intertwining the two in numerous ways to form a fabric. There are three basic weaves; plain weave (Figure 11), twill and satin weave. (Kadolph, Langford 2013;2014)
Knitted fabrics are instead assembled of interloping one or more sets of yarns, with two main procedures of knitting: weft/filling knitting (Figure 12B) where yarn is carried back and forth under needles to form a fabric while warp knitting (Figure 12A) is a process in which the yarn move in an upwards zigzag fashion. (Kadolph, Langford 2013;2014)
Figure 12.A
Figure 12.B
Figure 12: A, shows warp knitting and B, weft knitting. To easy understand how the threads lie in relation to the other threads, follow the red “thread”. Drawn with inspiration from (Kadolph, Langford 2013;2014)
Non-woven fabrics includes all textile-sheet structures bonded my entanglement (mechanical) to create fibrous webs. There are different alternatives to create the
entanglement such as forming chemical complexes, resin or thermal fusion. Similar to the construction of non-woven is paper, but non-woven is much greater in flexibility. Non-woven is the cheapest textile to create and is widely used for technical uses. (Kadolph, Langford 2013;2014)
There are also films, made directly from the polymer solutions. The films can be processed for example into plain film, supported films or expanded films. The surface of the film can be formed into different structures, e.g. on a bag made of film colored and structured to look like snake skin. Films are excellent to protect surfaces since it extremely water and soil repellent. The negative qualities are that it can become stiff or harden in very cold or very warm environments. (Kadolph, Langford 2013;2014)
3.6.2.3 3D-textile
Textile materials all have an internal 3D-structure of fibers, but most are formed as a single layer, planar or occasionally as cylindrical 2D sheets. Nowadays talking of 3D fabrics usually means a fabric with an overall 3D shape or more of an intricate internal 3D-structure,
sometimes both. They can include the forms of: - Single-layer materials with an overall shape
- Multilayer hollow materials
- Solid planar materials with multiple layers
- Solid multilayer materials with an overall 3D shape
3D fabrics could be woven, knitted, braided or non-woven etc. One can find uses for 3D-textiles in medical devices or large engineering structures but also in production of clothes in knitting a garment in one piece. (Chen, Bogdanovich, Textile Institute Content Provider 2015)
In medicine and wound dressing 3D-textile creates an opportunity to merge different layers with different functions something that is of importance in wound management. In a wound dressing the layers necessary for controlling the wound in the best way are usually; wound surface contact layer, one-way fluid resistance layer, odor management (antibacterial layer), absorption and moist management. When using 3D-textile technique all the layers can be produced in one go with one machine. (Chen, Bogdanovich, Textile Institute Content Provider 2015)
3.7 Laws & requirements for textile in healthcare
To define a medical textile one can look at the definition of a medical device as it is the same. In that way “A medical textile is any textile product manufactured with the intention to be used to diagnose, prevent, monitor, treat or alleviate disease, to compensate an injury or handicap, to investigate, replace or modify the anatomy or a physiological process or to control conception” (Weston 2013).
Therefore, when the intention is to treat a wound it becomes a medical textile and needs to fulfill the set requirements to be able to be used in the healthcare sector.
To introduce a medical textile into the healthcare sector there are certain regulations that must be followed. In this chapter those are brought to light to understand what must be done to release a medical device or textile on the market.
3.7.1 European Union
In 1998, the European Union came together to develop a directive like the United States FDA, named Medical Devices Directive (MDD). They took the directive to protect patients but also to lift trade barriers. Before the initiative was made it was relatively easy to introduce a new medical device because it mostly depended on plans made between the producers and surgeons. (Eikelboom, Duijst 1996)
Today the European Union only allows clinical application of medical devices which has a CE mark. For a manufacturer to collect a CE mark they must abide to the requirements of MDD. The device will have to prove to be on a specific level of safety and performance. They will need to go through Notified Bodies, these are test houses that deal with quality assurance audits. A company wanting to hold a CE mark for their product may choose a Notified Body in any European Union country. There are two critical points that the Notified Body look at; the certification of the manufacturer’s Quality Assurance System and
supporting test data on the device. This is so not only the device is tested but also the manufacturing process. (Eikelboom, Duijst 1996)
3.7.2 Sweden
Since Sweden is a part of EU, Sweden follows EU's laws and requirements. Even so, there are some Swedish agencies worth mentioning that is important to know off when creating and developing a new product.
3.7.2.1 Medical Product Agency
Looking at Medical Product Agency´s directive there's all the information needed on how to proceed to get your medical technical product out on the market. There are several criteria’s that must be fulfilled such as knowing in which class your product is divided into. The classes go from class1 to class4 where class4 is highly regulated and class1 is for the safer/easier products. Inside every class there is also subclasses. For example; inside class1 there is 1m and 1s, where 1m is if the product has a measuring function and 1s if the product is supposed to be sterile. The CE marking is important, as well as the legal manufacturer that has all the responsibility over the product from the creation until it has been used by the customer. The legal manufacturer has an obligation to report to the Medical Product Agency if there's any possible problems with the product or if any incident has happened.
