TY - JOUR
AU - BSc, Michelle Rae,
AB - Abstract We sought to establish the impact of pressure garment design variables, moisturizer use, and laundry method on the ability of pressure garments to maintain their pressure delivering potential, indicated here by garment tension, over time and use. Twenty-six sets of three replicate pressure garment sleeves were constructed from four powernet fabrics, using three reduction factors and six sleeve dimensions. These pressure garment sleeves were extended for 23 hours on static cylinder models followed by hand or machine laundry up to 28 times. Some sleeves were additionally exposed to moisturizers during their extension. Garment tension and dimensions were measured before and during the simulated wear and wash period to indicate each garment's ability to maintain its tension and therefore pressure throughout a period of “use.” The results of the investigation were analyzed in groups where each group contained only 1 variable, thereby allowing the variables with the most significant impact on tension degradation to be identified. The investigation confirmed that all pressure garments lost tension and therefore pressure delivering ability over time and use. It further revealed that pressure garments designed to exert greater pressures degraded faster than those designed to exert lower pressures. Contact between pressure garments and moisturizers accelerated tension degradation, and machine-washing pressure garments tended to prolong their pressure-delivering properties compared with hand-washing them. To maintain the initial pressure delivered by pressure garments, powernet fabrics should be prestressed before being designed/constructed and they should be machine-washed by patients. It is widely accepted that custom-made pressure garments are the most effective and comfortable method of hypertrophic scar treatment. These pressure garments may be ordered from specialist commercial manufacturers or made in-house by hospital staff. Many pressure garment producers (whether commercial or hospital staff) apply a standard “reduction factor” (typically of 10%, 15%, or 20%) to the patient's circumferential measurements to induce pressure.1,2 The reduction factor used is not normally changed based on the dimensions of the body part being treated or the specific properties of the fabric.1,2 Therefore, pressure garments are unlikely to consistently exert the same pressure.1,2 Further, the pressure applied to scars by pressure garments is known to decrease over time,3 possibly the result of stress relaxation in the fabrics under extension.4 Previous work has established the impact of pressure garment design variables on the pressures that are exerted on underlying tissue.5 Pressure garment designers can increase the pressure that their garment will exert by increasing the fabric tension in the pressure garment. The fabric tension can be increased by constructing the garment from a fabric with an inherently greater tension at a particular extension or by increasing the reduction factor (and thereby the fabric extension) used in pressure garment design.5 In addition to the use of pressure garments it is recommended that patients hydrate and massage their skin daily with moisturizers to improve scar pliability, comfort, and appearance and reduce pruritis and itching.6,7 Many different moisturizers are recommended for hypertrophic scar treatment, ranging from pure oils such as olive oil to water-based creams such as E45,7 and a wide variety of specialist creams, including silicone-based creams (eg, vasogen); liposome-based creams, collagen, corticosteroids, etc. The type of moisturizer used varies according to the experience of local medical staff, advice given by garment manufacturers, internet (or other) recommendations, patient's skin type and preference, etc. Most patients are instructed to massage their moisturizers into their scars after washing and allow the moisturizer to absorb before donning their pressure garments. However, it is inevitable that pressure garments will become tainted with moisturizer to some extent. Therefore, the impact of moisturizers on the ability of pressure garments to maintain tension/pressure over the recommended lifespan of a garment should be known. One previous study6 attempted to address the impact of two different moisturizers on pressure garments, but they did not extend the pressure garments as would occur in wear. Some manufacturers recommend that pressure garments are machine washed,6 but some manufacturers and medical staff and most burn support group websites recommend that patients hand wash their pressure garments daily in mild detergent without wringing.7 Most recommend that pressure garments be air dried flat on a towel or other surface. It is known that the pressure exerted by pressure garments deteriorates over time, but the factors influencing this reduction in pressure have not yet been fully investigated. The aim of this investigation was to establish how the design of pressure garments and their aftercare regimes affected their pressure delivering potential. The garment tension has been measured throughout this study as the indicator of garment pressure. This is appropriate because garment tension (in Nm−1) is directly proportional to the pressure exerted on a particular body or limb5 and garment tension can be measured more accurately and with greater reproducibility than pressure. The impact of the following variables on fabric tension over a period of simulated wear (static extension) and wash cycles were measured: Pressure garment design variables: reduction factor; garment dimensions; different fabrics; Moisturizers; Washing method. The main limitation of this study was that the effect of fabric stress brought about by patient movement was not examined. Because of the inherent variability of textile products and human movements over time, we quickly realized that a laboratory simulation of wear was the only way to establish whether different moisturizers, laundry methods, and garment design variables were impacting on the tension (and therefore pressure) degradation over time and use. We were unable to simulate wear using dynamic models because of the number of variables we wanted to measure and the time constraints on the projects. It should however, be noted that the tension/pressure degradation of pressure garments worn by humans would be greater than those seen in this simulation and the greater the level of activity by the wearer the greater the degradation is likely to be. METHOD This investigation was conducted in two parts. The first part of the investigation established the impact of two pressure garment design variables (reduction factor and sample size) and the impact of contact with a moisturizer on the maintenance of garment tension during a 14-week, 28-cycle wear simulation. The second part of the investigation considered the impact of the fabric used to make the pressure garment, moisturizer choice, and method of laundry on garment tension. The results of the first wear simulation showed that there was no significant degradation in garment tension in any of the samples after 10 weeks of test therefore the simulation period was reduced for the second part of the investigation to a 10.5-week, 21-cycle wear simulation. A total of four powernet fabrics were evaluated during this study, their main determinant characteristics are described in Table 1. Powernet is the most common fabric structure used in the construction of pressure garments1,2 and is warp knitted from nylon and elastane yarns. It has been shown that similarly designed pressure garments made from different fabrics will exert different pressures and that the mass and proportion of nylon to elastane within the structure will influence these pressures.5 Table 1. Main determinant characteristics of powernet test fabrics View Large Table 1. Main determinant characteristics of powernet test fabrics View Large Part 1: Impact of Pressure Garment Design Eight sets of three replicate pressure garment sleeves were constructed from powernet fabric X. The sleeves were constructed following standard pressure garment construction techniques. That is, sleeves were carefully cut so that the elastane yarns in the fabric were parallel to their circumferential dimension and a 3-mm wide BS304 zigzag stitch was used to sew the sleeves with a nonstretch polyester sewing thread. The length and width dimensions of each sewn sleeve were measured in two places to the nearest millimeter to enable calculation of dimensional change throughout the experiment. The (initial) fabric tension of each sleeve was measured at the same extension it would be under when mounted on its cylinder model, see Table 2 for circumferences and extensions. Tension was measured in the sleeves (looped specimens) on a constant rate of extension tensile testing machine (Instron 1122) according to BS 4952:1992, Section 2.2, except that the sleeve dimensions were as specified in Table 2. Table 2. Study parameters, variables, and sleeve/set reference numbers View Large Table 2. Study parameters, variables, and sleeve/set reference numbers View Large Each set of three samples was subjected to two wear and wash cycles per week for 14 weeks, totaling 28 cycles. Each wear and wash cycle involved the sleeves being stretched over the appropriate cylinder model (which was used as a static limb substitute) for 23 hours ± 1 minute. The cylinder models and sleeves were located in a conditioned laboratory with standard atmospheric conditions (20 ± 2°C and 65 ± 2% relative humidity). Samples were positioned and removed at 10-minute intervals to ensure reproducibility and allow time for tension and dimension measurements to be made after the second cycle in any week. After the samples were removed from the cylinder models, they were hand washed together for 2 minutes in 5 liters of 30°C water containing 20 ml of Lux flakes. Samples were rinsed thoroughly in three basins of 30°C water, dried flat on a towel overnight, and left to condition in the laboratory for 24 hours before the next cycle commenced. After alternate cycles the change in each sleeve's dimensions was measured to the nearest millimeter immediately after removal from the cylinder model and then their tension at the cylinder model extension (shown for each sample in Table 2) was measured according to BS 4952, Section 2.2. Table 2 shows the sleeve reference numbers and test variables for the eight sets of samples evaluated in this part of the study. Note that the sleeve set X1 was the “control” set and therefore appears in all sets. Sample set XE45 had 1 ml of E45 moisturizer applied with a syringe in thin lines along the length of the inside of each sample before they were mounted on their cylinder model. The cylinder model was thoroughly cleaned after the sleeves were removed. Part 2: Impact of Aftercare Regime on Pressure Garments Made From Different Fabrics Part 2 of the investigation measured the tension loss in six sets of three replicate pressure garment sleeves made from each of the 3 powernet fabrics A, B, and C (totaling 18 sets of three replicate pressure garment sleeves). See Table 1 for the fabric's basic determinant characteristics and Table 3a and b for the test variables and sample/set reference numbers. All of these samples were made using a 20% reduction factor for a cylinder model with a 16.9-cm circumference; therefore, the sleeve circumference was 13.5 cm for all samples. Part 1 of the investigation showed that the sleeve length did not influence tension degradation; therefore, sleeves were all cut to 8-cm lengths, allowing two sleeves to be extended on each cylinder model at a time. This procedure allowed more sleeves to be tested and prevented cross-contamination of moisturizer because each cylinder model was assigned to one of the three moisturizers. Table 3a. Sample/set references for all samples to be hand washed View Large Table 3a. Sample/set references for all samples to be hand washed View Large Table 3b. Sample/set references for all samples to be machine washed View Large Table 3b. Sample/set references for all samples to be machine washed View Large Each sample was subjected to two wear and wash cycles per week for a total of 21 wear and wash cycles. All samples were washed (both hand and machine samples) at 40°C in this part of the investigation; otherwise, hand-washing conditions were as described in Part 1. Sample dimensions and garment tension were measured (according to the method previously described) before the first wear cycle and again after 7, 14, and 21 wear cycles. RESULTS Initial Loss of Tension The tension in pressure garments deteriorated more dramatically in the first 5 minutes of extension than at any other time in the entire wear period. The average tension decay (and therefore loss of pressure) was 17.5% in the first 5 minutes of test. All tension measurements and loss of tensions discussed from now on are compared with the initial tension in samples at 5 minutes (after the initial dramatic loss of tension). Part 1: Impact of Pressure Garment Design Reduction Factor. Most garment producers apply a standard reduction factor (most commonly 20%) to patient's circumferential measurements. This reduction factor determines how much smaller the garment is than the body part being treated. In this study, pressure garment sleeves designed and constructed using higher reduction factors had statistically significantly greater tensions (Figure 1) and would therefore exert higher pressures,5 than those designed with lower reduction factors. Figure 1. View largeDownload slide Effect of reduction factor on pressure garment sleeve tension over 14 weeks of wear and wash cycles. Figure 1. View largeDownload slide Effect of reduction factor on pressure garment sleeve tension over 14 weeks of wear and wash cycles. Figure 1 shows that: The tension degraded significantly during the 14-week wear and wash period for all samples. The tension at the end of each period of extension or “wear” was lower than it was before the extension; Washing pressure garments and leaving them to relax for a couple of days allowed them to recover their tension so that they would exert more pressure when they were first put on than they did the last time they were taken off. (The pressure garments shrank slightly when they were washed, which contributed to their ability to recover some of the tension lost during the previous “wear” period.) These effects were observed in all samples regardless of the variable under study. However, the extent of tension degradation during simulated “wear” and recovery during laundry and rest periods varied depending on the variables under test (and were not normally statistically significant) and is most obvious on the 30% reduction factor sleeves shown in Figure 1. Figure 1 shows that pressure garments made with greater reduction factors lost more tension during each pair of 23-hour “wear” periods and the 14-week simulation than those constructed with 10% reduction factors. However, the pressure garment samples made with greater reduction factors still had significantly greater tensions and would therefore still be exerting greater pressures on the skin than those constructed with lower reduction factors. The percent tension loss from initial tension before the first wear period to the end of the last wear period 14 weeks later was 25.3% for the 10% reduction factor pressure garments, 32% for the 20% reduction factor garments, and 35.2% for the pressure garments made with 30% reduction factors. These differences were statistically significant at 95% confidence level. When the tension loss in pressure garment sleeves at the midpoint (14 wear/wash cycles) and end of the simulation (28 wear/wash cycles) were compared with their initial tensions, the correlation was significant at the 99% confidence level. Therefore, greater tension in the fabric led to larger reductions in tension, and therefore pressure, during a period of simulated use. Pressure Garment Dimensions. No consistent and statistically significant relationships were found to suggest that the dimensions of pressure garment sleeves influenced their ability to maintain their tension/pressure during wear and wash cycles. However, the tension in all sleeves reduced over the period of simulated wear in a similar manner to that shown in Figure 1. Table 4 shows the reduction in garment tension and theoretical pressures (calculated according to the Laplace Law2,3,5 based on circumference and tension measurements) during the 14-week wear and wash period. Although the tension and pressure lost during the 28 wear and wash cycles varied between samples, these differences were not statistically significant. Table 4. Reduction in tension and calculated pressure over 28 wear/wash cycles View Large Table 4. Reduction in tension and calculated pressure over 28 wear/wash cycles View Large Table 4 shows that the initial tension in XC22 is greater than that in XC13 (because of the irregularities typical in knitted fabrics and differences in sample size); however, when these tensions were converted into pressures for the different sizes of cylinders, the pressure exerted on the smaller 13.1-cm circumference cylinder model was significantly greater than that exerted by the garments (with slightly higher tensions) made for the 21.9-cm circumference cylinder model. The difference between the initial pressures exerted on cylinder models by samples XC13, X1 and XC22 (shown in the central column of Table 4) are caused by the way in which tension is converted into pressure around different-sized bodies/cylinders. That is, garments designed following similar principles to fit different sizes of cylinders or bodies will exert greater pressures on small cylinders/bodies than on larger cylinders/bodies if the fabric is under the same tension.2,3,5 Effect of Moisturizer on Pressure Garment Tension. Figure 2 shows that when pressure garments came into contact with E45 cream throughout the wear/ wash period, the tension was adversely affected. The greatest decrease in tension for both sets of sleeves was in the first week; thereafter, the reduction in garment tension, and therefore pressure exerted, was less significant. Once again garments recovered their tension during the laundry and relaxing process. Tension loss from 5 minutes after first wear to end of second wear was a mean 21% for garments without moisturizer and 27% tension loss for garments in contact with moisturizer (although this difference was not statistically significant). The initial tension on donning (at 0 weeks) was reduced by a mean 30.5% for the garments that had no contact with moisturizer to 36.5% for the garments that were in contact with moisturizer by the end of the 7th week and by 32% and 38%, respectively, by the end of the wear simulation in the 14th week. These differences between the pressure garment sleeve sets that had been in contact with E45 and those that had not were statistically significant at both 7 and 14 weeks of wear/wash simulation. Figure 2. View largeDownload slide Effect of contact with E45 moisturizer on pressure garment sleeve tension. Figure 2. View largeDownload slide Effect of contact with E45 moisturizer on pressure garment sleeve tension. The main conclusions of this part of the study were that contact between pressure garments and E45 moisturizer and high fabric tension caused by high reduction factors had a significant detrimental effect on maintenance of garment tension (and therefore pressure) during a period of simulated use. Therefore, part 2 of the study aimed to establish which of the most popular moisturizer types used would have the least detrimental effect on pressure garment tension and whether increasing garment tension by using powernet fabrics with inherently different tensions would affect the maintenance of tension/pressure delivering properties. The impact of washing conditions was also investigated. Part 2: Impact of Aftercare Regime on Pressure Garments Made From Different Fabrics Choice of Moisturizer. Figure 3 shows that olive oil tended to have the least detrimental impact on the pressure garments' ability to maintain their tension (and therefore pressure) during 21 wear and wash cycles. E45 and vasogen had a greater and similar effect on most of the garments' ability to maintain tension during the test period. However, these noticeable trends were not statistically significant because of the relatively high standard deviations of sleeve sets (SD ranged from 0.2 to 6.5, typically between 2 and 3.5). The only exception to this trend was that olive oil caused the greatest reduction in garment tension for the hand washed set of samples made from fabric A. Figure 4 also shows that fabric A was more affected by its contact with all 3 moisturizers than fabrics B or C this effect will be discussed further under the section entitled “Impact of fabrics.” Figure 3. View largeDownload slide Effect of moisturizer on % tension loss during 21 wear and wash cycles. Figure 3. View largeDownload slide Effect of moisturizer on % tension loss during 21 wear and wash cycles. Figure 4. View largeDownload slide Effect of laundry method on % tension loss during 21 wear and wash cycles. Figure 4. View largeDownload slide Effect of laundry method on % tension loss during 21 wear and wash cycles. Machine Wash or Hand Wash. Figure 4 shows that machine washing pressure garments resulted in less tension degradation than hand washing in seven of nine sets of pressure garment sleeves. However, these differences between the tension lost when sleeves were hand washed and machine washed were only statistically significant in 1 sample set (COM). Therefore, although the results of this study cannot claim to show that machine washing pressure garments maintains their pressure delivering properties significantly longer than hand washing them, it can dispel the popularly held belief that pressure garments should be hand washed. This is useful because laundering pressure garments in washing machines is more convenient than hand washing for most patients. Impact of Fabric Used in the Construction of Pressure Garments. Most pressure garments are made from powernet fabrics (which are warp knitted from nylon and elastane filaments).2 Although these fabrics often look similar, their performance can vary enormously depending on the specific manufacturing techniques used in their construction. Figure 3 and 4 show that the fabric used to construct the pressure garment sleeves affects their ability to maintain tension (and therefore pressure) over the duration of the simulated wear period. Fabric A lost significantly more tension in every experiment than fabrics B and C. Table 5 shows the relationship between initial fabric tension and percent tension loss during the course of 21 wear and wash cycles. There was a statistically significant correlation (at 99 or 99.9% levels) between high mean initial fabric tension (before any wear and wash testing had been done) and the increased loss of tension (%) during both 14 and 21 wear and wash cycles. This confirms the trend noted in the section “Reduction Factor” that pressure garments that are under greater tension during use will lose a greater percentage of their initial tension than garments under less strain. There was also a significant correlation between the initial tension of fabrics X, A, B, and C (all of which had been exposed to 1ml of E45 each “wear” and hand washed) during the first 14 wear/wash cycles. Therefore, regardless of how tension was induced in the pressure garment (whether through garment design or fabric design) garments with higher tension showed a greater % deterioration over “use.” Table 5. Impact of initial fabric tension on tension loss over 21 wear and wash cycles View Large Table 5. Impact of initial fabric tension on tension loss over 21 wear and wash cycles View Large CONCLUSIONS Pressure garments designed to exert higher pressures lost their tension and therefore pressure-delivering ability at a greater rate than pressure garments designed to exert lower pressures (this was true regardless of whether the high pressure was achieved by using fabrics with inherently high tensions or by inducing high tensions using high reduction factors). However, pressure garments designed to exert significantly greater pressures will still be exerting greater pressures than those designed to exert low pressures at the end of similar periods of wear. Pressure garments that are in contact with moisturizers during use will lose their tension and pressure delivering ability more quickly than pressure garments that do not come into contact with moisturizers. In this study, olive oil appeared to have less impact on pressure garment tension than E45 cream or vasogen, but this trend was not statistically significant. This study showed that there was no benefit to hand-washing pressure garment sleeves in terms of maintaining their tension and pressure-delivering ability. Therefore, unless there are non-machine washable wires, fastenings, or linings in pressure garments, we recommend that pressure garments made from powernet fabrics composed of nylon and elastane (as they nearly always are) should be machine washed and not hand washed if this is more convenient for patients. The fabrics used to construct pressure garments should be pretreated during finishing to pre-stress the fabric and therefore reduce the dramatic initial decline in garments' pressure delivering abilities during use. Where this is not possible pressure garments could be designed to exert higher than “ideal” pressures and be issued to patients with instruction to pre-stretch and wash their pressure garments two or three times before commencing use. DISCUSSION Pressure garments should be designed and constructed5 to exert the most effective pressures for scar treatment. Often, these “most-effective” pressures will be relatively high and will be generated by using fabrics with high tension profiles and/or high reduction factors in the design process. This study has shown that pressure garments with greater pressure delivering properties loose them more quickly than those designed to exert lower pressures and that this effect is unavoidable using traditional techniques. However, this study has also shown that the tension/pressure degradation effect is most dramatic in the first wear cycle. Therefore, it is possible that pressure garment manufacturers or fabric suppliers could reduce this problem by pre-stressing the fabrics or garments before supplying them to patients. Further work would be necessary to determine the optimum finishing conditions that would provide fabrics and garments with flatter tension degradation curves and result in pressure garments being supplied to patients that would lose significantly less tension/pressure over time and use. In the simplest case practitioners may be able to design or request garments to be supplied with higher pressures than those required for the patient. These garments could be laundered and stretched on an expandable mannequin or other former (larger than the body they are designed to fit) until the required tension/pressure was achieved, before being supplied to patients. This investigation has also shown that the tension/pressure profile of pressure garments was affected by the aftercare regime that would be used by patients. This study has shown that contact with moisturizers hastens the pressure degradation effect. Therefore, patients should apply small quantities of moisturizer to their skin/scars and allow it to absorb fully before donning their pressure garments. Anything that could be done to improve moisturizer absorption and/or remove it more efficiently at the end of the wear period would be likely to prolong the useful service life of pressure garments. Contrary to popular advice, there was no evidence to suggest that hand-washing pressure garments offers any benefit in terms of maintaining garment pressure over periods of extended use compared with machine-washing them. Further, although not statistically significant, there appeared to be a consistent benefit associated with machine-washing pressure garments noted from two of three fabrics tested. Therefore, in the interests of convenience, thorough removal of moisturizing creams/oils, effective cleaning, and maintenance of pressure, we recommend that pressure garments be machine washed (at 40°C) after each use. The washing machine should be loaded according to the machine manufacturer's instructions with pressure garments and other household textiles. However, patients should be instructed not to wash their pressure garments with anything that might snag or tear the garment during the laundry cycle (such as zips, Velcro, hooks/eyes), nor should they machine wash their pressure garments if the garment itself contains components that may be dislodged in the washing machine. Patients may wish to further protect their pressure garments by ensuring that any Velcro or zip fastenings are properly closed and place their pressure garments into a net laundry bag during the machine wash cycle. REFERENCES 1. Macintyre LM, Baird MR. Pressure garments for use in the treatment of hypertrophic scars—a review of the problems associated with their use. Burns 2006;32:10–15, and all references contained therein. 2. Macintyre LM, Baird MR Pressure garments for use in the treatment of hypertrophic scars—an evaluation of current construction techniques in NHS hospitals. Burns  2005; 31: 11– 4. Google Scholar CrossRef Search ADS PubMed  3. Cheng J, Evans J, Leung K, Clark J, Choy T, Leung P Pressure therapy in the treatment of post-burn hypertrophic scar —a critical look into its usefulness and fallacies by pressure monitoring. Burns  1984; 10: 154– 63. Google Scholar CrossRef Search ADS   4. Ng-Yip F Medical clothing—the stress relaxation and shrinkage of pressure garments. Int J Clothing Sci Technol  1994; 64: 17– 27. Google Scholar CrossRef Search ADS   5. Macintyre L Designing pressure garments capable of exerting specific pressures on limbs. Burns  2007; 33: 579– 86. Google Scholar CrossRef Search ADS PubMed  6. Gallagher JM, Kaplan S, Hills Maguire G, et al.   Compliance and durability in pressure garments. J Burn Care Rehabil  1992; 132: 239– 43. Google Scholar CrossRef Search ADS   7. Life after a burn—booklet for patients of all ages, parents, relatives and friends.  Milton Keynes, UK: Beiersdorf Medical; 1989. Copyright © 2007 by the American Burn Association
TI - The Impact of Design Variables and Aftercare Regime on the Long-Term Performance of Pressure Garments
JF - Journal of Burn Care & Research
DO - 10.1097/BCR.0B013E318148C999
DA - 2007-09-01
UR - https://www.deepdyve.com/lp/oxford-university-press/the-impact-of-design-variables-and-aftercare-regime-on-the-long-term-CixChCxar4
SP - 725
EP - 733
VL - 28
IS - 5
DP - DeepDyve
ER -