1School of Textiles and Design, Heriot-Watt University
Pressure garments have been used to help treat and prevent hypertrophic burn scars since the early 1970s. Pressure garments are made from elastic fabrics that are cut smaller than the patient’s body in order to exert pressure. The difference in size between the body and garment is often referred to as the ‘reduction factor’. The reduction factor and inherent fabric properties determine the Tension in the material when worn. The Tension and patient’s body size (specifically radius of curvature) determine the pressures that are exerted at each point on the body and can be calculated using the Laplace Law.
The recently published ‘development of a best evidence statement for the use of pressure therapy for management of hypertrophic scarring’ by Sharp et al in JBCR noted some useful evidence based do’s and don’ts of pressure therapy alongside some ‘insufficient evidence for …’ they note that it is not practical to use pressure sensors or pressure mapping devices clinically and suggest that monitoring pressure using trained fingers and the ‘pull test’ is sufficient, but they also recommend that 20-30mmHg be delivered. Since the tension in the fabric is only one of the two major factors contributing to the pressure exerted on the patient, the pull test can never determine the actual pressure, regardless of the level of training.
A surprising number of hospitals and companies still use a ‘standard reduction factor’ (the same reduction factor for all garments regardless of material properties or body size) to make all or some of their pressure garments and as repeated research has shown this results in very variable pressures on the skin (ranging from less than 5 to 55mmHg). Thus it is not possible for these pressure garment manufacturers to deliver garments that consistently deliver pressures in the range of 20-30mmHg. If the pressure ‘dose’ of these garments is variable and unknown we should be unsurprised that the results of this type of pressure therapy is variable.
A pressure garment design tool based on a recently tested fabric is an efficient way to ensure that pressure is, at least initially, consistent for all patients. The pressure garment design tool (or Company specific equivalent) uses the Laplace Law to calculate pressure garment dimensions based on input patient dimensions and input desired pressure (or graduated pressures) and the tension profile equations for the specific fabric to be used in garment construction. Thus, if all fabrics were tested prior to use and their particular tension profile used to calculate garment dimensions then initial mean compression values would be known and this would eliminate the most important device-based variables impacting pressure therapy. Human variables would still exist but using devices that delivered a consistent theraputic benefit would surely make outcomes more consistent and build a useful body of evidence, if collected and shared.
The tools for improving the consistency of pressure therapy exist and are not expensive, let’s use them to gather the evidence we need to improve patient experience.
Lisa is an academic at the School of Textiles and Design, Heriot-Watt University. She has been lecturing in textile technology and researching medical compression garments for more than 20 years. She was awarded her PhD in Pressure garments for hypertrophic scar treatment in 2004 and won best paper at the BBA conference in 2004 for this work. Although most of her pressure garment research has been directed to burn scars, she has also applied her understanding and research methods to other conditions for which compression is useful (including DVT prevention, scoliosis and currently lipoedema). She is a member of the UK Pressure Garment Interest Group (therapists making pressure garments in NHS hospitals), has published several papers on pressure garments in Burns and the Journal of Burn Care Research, designed the Pressure Garment Design tool (to optimise pressure garment construction methods and enable evidence gathering for most effective pressures) and regularly undertakes consultancy on pressure garment testing and fabric sourcing for a number of UK and international pressure garment companies.
Lisa has undertaken research projects funded by the MRC CiC, Textile Future Forum, Worshipful Company of Framework Knitters, Innovate UK, AHRC and Industry. She teaches undergraduate and postgraduate courses on textiles, product specification/testing and research methods and supervises student research projects at all academic levels. She has been the Director of Research, a programme director and is currently the School Director of Postgraduate Research Study.