Designing pressure garments capable of exerting specific pressures on limbs

Pressure garments have been used prophylactically and to treat hypertrophic scars, resulting from serious burns, since the early 1970s. They are custom-made from elastic fabrics by commercial producers and hospital staff. However, no clear scientifically established method has ever been published for their design and manufacture. Previous work [2] identified the most commonly used fabrics and construction methods for the production of pressure garments by hospital staff in UK burn units. These methods were evaluated by measuring pressures delivered to both cylinder models and to human limbs using I-scan pressure sensors. A new calibration method was developed for the I-scan system to enable measurement of low interface pressures to an accuracy of +/-2.5 mmHg. The effects of cylinder/limb circumference and pressure garment design on the pressures exerted were established. These measurements confirm the limitations of current pressure garment construction methods used in UK hospitals. A new method for designing pressure garments that will exert specific known pressures is proposed and evaluated for human thighs. Evaluation of the proposed design method is ongoing for other body parts.     

Pressure garment design tool to monitor exerted pressures

Pressure garments are used in the treatment of hypertrophic scarring following serious burns. The use of pressure garments is believed to hasten the maturation process, reduce pruritus associated with immature hypertrophic scars and prevent the formation of contractures over flexor joints. Pressure garments are normally made to measure for individual patients from elastic fabrics and are worn continuously for up to 2 years or until scar maturation. There are 2 methods of constructing pressure garments. The most common method, called the Reduction Factor method, involves reducing the patient's circumferential measurements by a certain percentage. The second method uses the Laplace Law to calculate the dimensions of pressure garments based on the circumferential measurements of the patient and the tension profile of the fabric. The Laplace Law method is complicated to utilise manually and no design tool is currently available to aid this process. This paper presents the development and suggested use of 2 new pressure garment design tools that will aid pressure garment design using the Reduction Factor and Laplace Law methods. Both tools calculate the pressure garment dimensions and the mean pressure that will be exerted around the body at each measurement point. Monitoring the pressures exerted by pressure garments and noting the clinical outcome would enable clinicians to build an understanding of the implications of particular pressures on scar outcome, maturation times and patient compliance rates. Once the optimum pressure for particular treatments is known, the Laplace Law method described in this paper can be used to deliver those average pressures to all patients. This paper also presents the results of a small scale audit of measurements taken for the fabrication of pressure garments in two UK hospitals. This audit highlights the wide range of pressures that are exerted using the Reduction Factor method and that manual pattern ‘smoothing’ can dramatically change the actual Reduction Factors used.     

New calibration method for I-scan sensors to enable the precise measurement of pressures delivered by 'pressure garments'

Accurate measurement of the pressure delivered by medical compression products is highly desirable both in monitoring treatment and in developing new pressure inducing garments or products. There are several complications in measuring pressure at the garment/body interface and at present no ideal pressure measurement tool exists for this purpose. This paper summarises a thorough evaluation of the accuracy and reproducibility of measurements taken following both of Tekscan Inc.’s recommended calibration procedures for I-scan sensors; and presents an improved method for calibrating and using I-scan pressure sensors. The proposed calibration method enables accurate (±2.1 mmHg) measurement of pressures delivered by pressure garments to body parts with a circumference ≥30 cm. This method is too cumbersome for routine clinical use but is very useful, accurate and reproducible for product development or clinical evaluation purposes.     

Pressure garments for use in the treatment of hypertrophic scars--a review of the problems associated with their use

Pressure garments have been the mainstay of hypertrophic scar treatment since the 1970s. However, there are many problems associated with their use. This is the first in a series of papers on pressure garments that will review the literature published to date on the origins of pressure garments for hypertrophic scar treatment and the problems associated with current pressure garment use.     

Measuring pressure under burns pressure garments using the Oxford Pressure Monitor

Pressure garments are used extensively in the treatment of hypertrophic scarring following burn injuries. The Oxford Pressure Monitor was used to measure garment-scar interface pressure (mmHg) using a number of fabric types over various body parts. The results indicate a wide range of pressure values between different garments and body parts with the greatest pressures found over the dorsum of hands and feet. The problems of achieving 'optimal pressure' over hypertrophic scarring are discussed with emphasis on the need for more accurate measuring equipment.     

Reproducibility of repeated measurements with the Kikuhime pressure sensor under pressure garments in burn scar treatment

This study investigated the reproducibility of repeated measurements with the Kikuhime pressure sensor under two different types of pressure garments used in the treatment and prevention of scars after burns. Also efficiency of garments was assessed in clinical circumstances by assessing pressure loss and residual pressure after 1 month. Intra- and inter-observer reproducibility and repeated measurements with 1-month time lapse were examined on 55 sites in 26 subjects by means of intra-class correlation coefficients and standard error of measurements. Results showed good to excellent ICC and low SEMs in the two conditions. There was a significant difference in pressure after 1 month between elastic tricot and weft knit garments, although evolution of pressure loss after 1 month was similar. Concerning different locations, there was a significant difference in pressure loss after 1 month between gloves and sleeves with the largest pressure loss for sleeves. Considering these results we concluded that the Kikuhime pressure sensor provides valid and reliable information and can be used in comparative clinical trials to evaluate pressure garments used in burn scar treatment. Secondly, elastic tricot garments in our study tended to have higher clinical pressures but both types of garments had similar pressure loss over time.     

Compression therapy: effects of posture and application techniques on initial pressures delivered by bandages of different physical properties.

OBJECTIVE: To define the pressures and gradients achieved by different bandages when applied by alternative bandaging techniques. METHODS: An experienced bandager applied six bandages to the same leg of a volunteer using three application techniques. Pressure measurements were taken at the ankle, gaiter, calf and upper calf in three postures. RESULTS: All bandages gave consistent pressures with all standard deviations falling below 7 mmHg. The percentage increase in pressure from resting leg to standing was inversely related to bandage elasticity. Pressures were similar at the upper calf among the bandages for each application technique in each posture (differences <10 mmHg). Small differences in pressure among the bandages (4-15 mmHg) occurred at the ankle for the resting leg with a reduction in pressure between 6 and 63% at the upper calf compared to the ankle. These differences in ankle pressure were more marked on sitting (differences 15-18 mmHg) and standing (differences 15-27 mmHg), which resulted in substantial differences in gradients. CONCLUSIONS: Striking variations in pressures and gradients were observed between bandages of different physical properties applied using alternative application techniques. In order to achieve clinical benefits without tissue damage, it is essential that the therapist appreciates how a bandage will react with a specific application technique.     

The assessment of erythema and thickness on burn related scars during pressure garment therapy as a preventive measure for hypertrophic scarring

The aim of this study was threefold: (1) Assess the pressure loss of two types of pressure garments that are used in the treatment of hypertrophic scars after burn injury, (2) investigate the influence of two different levels of compression on erythema and thickness of burn scars and (3) examine the association between erythema and thickness. The study was a prospective trial in which 76 burn scars in 60 patients were objectively assessed with the Minolta Chromameter CR-300 for erythema and with the Dermascan C for thickness of the scar over a period of 3 months. Each patient was randomly assigned to a "normal" or "lower" compression class treatment, with respectively mean values of 15 and 10 mmHg pressure after wearing the garment for 1 month. Measurements for both parameters were taken at 0, 1, 2 and 3 months of treatment. Pressure garments with "normal" compression did lose significantly more compression over 1 month (4.82 mmHg) than did the garments from the low compression class (2.57 mmHg). Scars that were treated with garments from a "normal" compression class did score significantly better for thickness compared to the "low" compression class. The difference in thickness was most evident at 1 month. Thereafter no further significant improvement between the two different treatments over time could be obtained. This difference was not found for erythema. Positive correlations could be found between erythema and thickness values at all of the three test points while changes in erythema and thickness only correlated significantly after the first month. The pattern of change of both parameters correlated at a high level of significance after 3 months of treatment. These data suggest that pressure garments that deliver a pressure of at least 15 mmHg pressure tend to accelerate scar maturation and that measurements of the pattern of change of the erythema can be used to predict changes in scar thickness and vice versa.     

12-Year within-wound study of the effectiveness of custom pressure garment therapy

Pressure garment therapy is standard of care for prevention and treatment of hypertrophic scarring after burn injury. Nevertheless there is little objective data that confirms effectiveness. The purpose of this study was to determine the effectiveness of pressure garment therapy with objective data obtained with a randomized within-wound comparison. We enrolled consecutive patients with forearm injuries over a 12-year period. The subjects wore custom garments with normal and low compression randomized to either the proximal or distal zones. Hardness, color and thickness of wounds were objectively measured using appropriate devices; clinical appearance was measured by a panel masked to the identity of the pressure treated area. Wounds treated with normal compression were significantly softer, thinner, and had improved clinical appearance. There was no interaction of any effect with patient ethnicity. However, these findings were clinically evident only with moderate to severe scarring. We conclude that pressure garment therapy is effective, but that the clinical benefit is restricted to those patients with moderate or severe scarring.     

Adherence to pressure garment therapy in adult burn patients

Pressure garment therapy (PGT) is a generally accepted procedure to prevent hypertrophic scarring after severe burns. Wearing pressure garments is uncomfortable and challenging for the patient and, consequently adherence is low. In order to improve adherence, precise knowledge about the advantages and disadvantages of PGT is necessary. In this study we investigated specific aspects which inhibit or reinforce the application of PGT on the patients’ part. Twenty-one patients participated in a semi-structured interview concerning their experiences with PGT. The complaints most frequently mentioned were ‘physical and functional limitations’ caused by the garments, ‘additional effort’ created by the need to care for garments and ‘perceived deficiencies’ of the treatment. At the same time, most of the patients reported coping strategies used to persevere with the therapy. Coping can be categorised into ‘behavioural’ and ‘cognitive coping strategies’. Besides the ‘expectation of success’, ‘emotional’ as well as ‘practical support’ and experiencing ‘good outcome’ were motivating factors for the patients. Based on the analyses of limitations and resources, recommendations for future interventions enhancing adherence are outlined.     

Reverse mid-dilution: new way to remove small and middle molecules as well as phosphate with high intrafilter convective clearance.

BACKGROUND: The removal of small and middle molecules has a relevant impact on haemodialysis (HD) patient survival. Mid-dilution (MD) is a technique combining ease of use with high diffusive-convective clearances. However, MD may increase the intrafilter blood pressure due to the high filtration fraction. We devised a new filter configuration, reverse MD, with an inverted blood inlet and outlet. We compared biochemical and technical performances of reverse MD vs standard MD. METHODS: Eight HD patients underwent one standard MD treatment and one reverse MD. Samples for instantaneous clearance and total mass removed from dialysate spilling (urea, phosphate, beta2-microglobulin, angiogenin) were obtained. Dialysate and blood pressures in the circuit were monitored every 15 min. The reinfusion rate was set at 6 l/h for both treatments. RESULTS: Absolute removals were very high and statistically comparable in both the configurations. Pressures were significantly lower with the reverse compared with the standard MD: inlet blood pressure was 731+/-222 and 595+/-119 mmHg in the standard and in the reverse MD, respectively. The transmembrane pressures were lower in the reverse compared with the standard MD (422+/-90 and 611+/-136 mmHg for 1st stage; 188+/-54 and 307+/-56 mmHg for 2nd stage). CONCLUSIONS: Reverse MD could be an ideal technique for high ultrafiltration routine treatments without any external fluid reinfusion. It allows a very high removal of small and middle molecules, with relatively lower intrafilter pressures.     

A novel technique to determine pressure in pressure garments for hypertrophic burn scars and comfort properties

Current recommendations state that pressure garments should be worn for up to 2 years for hypertrophic burn scars. Thermo-physiological properties of pressure garments were assessed by the thermo-physiological tests and a comparison of the fabric with a sportwool which is a single-jersey knitted fabric was performed. In this novel technique, it was aimed to determine the exact pressure of pressure garments on the applied body part. For the theoretical part of this study, the Laplace equation was used with an optimum pressure of 20 mmHg and a relationship between change in length versus circumference was calculated. To determine the change in length a ruler was prepared for each predetermined circumference value using this relationship. Grid printed fabric samples were prepared with an interval of 2 cm in width direction to be used for the calculation of mean pressure on a Mannequin Leg. The resultant mean pressure calculated experimentally on Mannequin Leg as 24 mmHg was compared to the optimum pressure of 20 mmHg. It was observed that the two values were not statistically significantly different.     

Carbon dioxide pneumoperitoneum-related liver injury is pressure dependent: A study in an isolated-perfused organ model

Background Disturbed liver function tests are associated with the pneumoperitoneum applied for biliary and non-biliary laparoscopic surgical procedures. The extent, duration and reversibility of such an injury are unknown. An isolated organ model was used to assess reversibility of liver injury in a CO₂–pneumoperitoneum-like environment. Methods Rat livers (n = 63) were isolated and perfused within a chamber pressurized at 0, 3, 5, 8, 12, 15 or 18 mmHg for 60 minutes. Pressure was annulled during the ensuing 61–90 minutes in one-half of the groups and markers of liver function were measured and recorded. Results Inflow pressure level, flow rate, effluent partial O₂ and CO₂ pressures, O₂ extraction rate, lactate dehydrogenase level, lactic to pyruvic acid ratio, and total xanthine oxidase and dehydrogenase levels became abnormal, starting at 15 minutes after a pressure >5 mmHg was applied in the chamber. Signs of injury slowly reversed towards baseline values in all groups except for the 15 mmHg and 18 mmHg-pressurized ones, even after pressure had been annulled for 30 minutes. Conclusions CO₂-pneumoperitoneum-like conditions directly injured rat liver tissue to a degree which correlated with the amount of applied pressure. Damage caused by pressure ≥15 mmHg was no longer reversible if it had been applied over a 60-minute period.     

Survey of national and local practice of compression therapy timing for burn patients in the United States

ObjectiveCompression therapy (CT) has been an important, but debated, treatment for burn scars. To better understand one source of variation in observed outcomes after CT, an evaluation of CT timing of application is needed.Materials and MethodsFollowing IRB approval, 126 burn centers were contacted to complete a 17-question survey regarding the center’s practice pattern for compression garment therapy. Locally, study subjects were identified between March 1, 2014 and December 31, 2015 and medical records examined for timing of garment ordering, delivery and fitting.ResultsThe majority believed that compression therapy is beneficial. Most centers reported using custom-fit and pre-fabricated garments, and a goal time of application between 2–4 weeks (42%) and 4–6 weeks (36%). After the garments are ordered, 61% of centers estimate that it takes 2–4 weeks for them to arrive. No significant differences in practices were found among centers treating pediatric patients only, adults only or both. Locally, the mean number of weeks between the date of original injury and garment order placement was 9.1 weeks with an additional 8.7 weeks between the date of order and date of delivery.ConclusionsThe current study identified that although the national reporting of time to garment application is estimated to be between 2–6 weeks at the majority of burn centers including our own, we found our center to be well in excess of 17 weeks. The findings offer an opportunity for local improvement, and raise the possibility of similar incongruity between goals and practice at other centers.     

Comparison between the portable pressure measuring device and PicoPress® for garment pressure measurement on hypertrophic burn scar during compression therapy

PurposeThe current standard treatment for hypertrophic scars following burn injury is pressure garment therapy. The experimenters developed the novel portable pressure measuring device using silicon piezoresistive sensors. As PicoPress® is the most accurate (i.e., lowest variation and error) manometric sensor for pressure measurement, we sought to compare and examine the accuracy of the novel device regarding in vitro pressure measurements at the hypertrophic scar–pressure garment interface.MethodsThe novel device was designed to operate in non-corrosive media, such as air. The device can use up to six pressure sensing points and was developed to adjust the number of pressure sensors according to the size of the scar. Pressure measurements were acquired through a readout circuit consisting of an analog-to-digital converter, a microprocessor, and a Bluetooth transmission module for wireless data transmission to an external device. All signals were converted into mean pressure expressed in millimeters of mercury (mmHg). The mean pressure values measured by the sensors were compared to those obtained from PicoPress®. 55 garment pressures recordings were obtained from the sensors over this study conducted in 2018–February 2020. We then analyzed the test–retest reliability using the intraclass correlation coefficients (ICC). PicoPress® was also employed in the same pressure garments for obtaining similar measurements. A two way random effects model ICC with 95% confidence intervals was used to compare the mean pressure values obtained from the silicon piezoresistive sensors to the PicoPress® measurements.ResultsThe test–retest reliability of the pressure sensors was close to the acceptable level for clinical use regarding stationary interface pressure measurement (ICC = 0.99, 95% CI 0.990−0.997). The mean pressure obtained from the silicon piezoresistive pressure sensors showed an accordance with the measurements from PicoPress® (ICC = 0.97, 95% CI 0.947−0.985).ConclusionThe novel device may present a viable alternative to PicoPress® for garment pressure measurements. In addition, the novel device improves adaptability to the hypertrophic scar shape and size. Complementary characteristics such as wireless transmission to an external device may allow burn patients to continuously wear the device for real-time measurements during pressure garment therapy, thus improving existing devices including PicoPress®.     

Variability of pressure at the pressure garment-scar interface in children after burn: A pilot longitudinal cohort study

Background

Current consensus for the ideal pressure range at the pressure garment to scar interface is 15–25 mmHg. Interface pressure variability has been reported at new pressure garment fitting in children. Pressure reductions up to 25% have been recorded over one month in adults.

Pressure garments for use in the treatment of hypertrophic scars -- an evaluation of current construction techniques in NHS hospitals

The purpose of this investigation was to establish the variety of pressure garment construction methods and materials used in UK hospitals. This paper reports an investigation conducted in two parts. First, a survey of pressure garment practitioners was conducted and second, 15 of the fabrics currently used in UK hospitals were tested. The results showed that the pressures exerted by pressure garments constructed in UK hospitals were likely to range from ineffectively low to dangerously high.     

Carpal tunnel pressure alters median nerve function in a dose-dependent manner: a rabbit model for carpal tunnel syndrome.

BACKGROUND: An in vivo animal model for carpal tunnel syndrome (CTS) is presented which allows for graded application of pressure to the median nerve within the carpal canal. We hypothesized that such pressure would cause electrophysiologic changes in the median nerve in a dose-related manner, with NCS/EMG changes consistent with CTS in humans. METHODS: In 40 New Zealand white rabbits, ranging from 2 to 2.5 kg, angioplasty catheters were placed in the carpal tunnel in the forepaws and pressures ranging from 50 to 80 mmHg applied to one side while the contralateral side served as the control and remained uninflated. Pressure was applied until a 15% increase in distal motor latency was obtained for 2 consecutive weeks by nerve conduction studies. RESULTS: All the experimental limbs exhibited a 15% increase in distal motor latency. None of the control limbs showed a significant increase in distal motor latency. In the experimental animals the 15% delay was achieved in approximately 4-5 weeks in the 50-70 mmHg groups and in approximately 1 week in the 80 mmHg group. CONCLUSION: This new animal model for CTS demonstrates a direct cause and effect relationship between carpal tunnel pressure and median nerve dysfunction. We anticipate that this in vivo model with clinically relevant outcomes will facilitate identification of injury mechanisms, and will serve as a basis for future development of novel interventions and treatments.     

Pressure therapy for scars: Myth or reality? A systematic review

BackgroundHypertrophic scarring is a deviate occurrence after wound closure and is a common burn sequela. The mainstay of scar treatment consists of a trifold approach: hydration, UV-protection and the use of pressure garments with or without extra paddings or inlays to provide additional pressure. Pressure therapy has been reported to induce a state of hypoxia and to reduce the expression pattern of transforming growth factor-β1 (TGF-β1), therefore limiting the activity of fibroblasts. However, pressure therapy is said to be largely based on empirical evidence and a lot of controversy concerning the effectiveness still prevails. Many variables influencing its effectivity, such as adherence to treatment, wear time, wash frequency, number of available pressure garment sets and amount of pressure remain only partially understood. This systematic review aims to give a complete and comprehensive overview of the currently available clinical evidence of pressure therapy.MethodsA systematic search for articles concerning the use of pressure therapy in the treatment and prevention of scars was performed in 3 different databases (Pubmed, Embase, and Cochrane library) according to the PRISMA statement. Only case series, case-control studies, cohort studies, and RCTs were included. The qualitative assessment was done by 2 separate reviewers with the appropriate quality assessment tools.ResultsThe search yielded 1458 articles. After deduplication and removal of ineligible records, 1280 records were screened on title and abstract. Full text screening was done for 23 articles and ultimately 17 articles were included. Comparisons between pressure or no pressure, low vs high pressure, short vs long duration and early vs late start of treatment were investigated.ConclusionThere is sufficient evidence that indicates the value of prophylactic and curative use of pressure therapy for scar management. The evidence suggests that pressure therapy is capable of improving scar color, thickness, pain, and scar quality in general. Evidence also recommends commencing pressure therapy prior to 2 months after injury, and using a minimal pressure of 20–25 mmHg. To be effective, treatment duration should be at least 12 months and even preferably up to 18–24 months. These findings were in line with the best evidence statement by Sharp et al. (2016).     

Effect of facial pressure garments for burn injury in adult patients after orthodontic treatment

Pressure garments are commonly used to prevent and control hypertrophic scar tissue. Complications are unusual, though in children with facial burns, pressure garments may lead to skeletal and dental deformities. Studies in adolescents and adults are sparse. We describe a 24-year-old woman who sustained facial burns. Prior to injury, the patient had undergone premolar extraction in preparation for orthodontic treatment. Her post-burn care consisted of application of a Jobst pressure garment. After 2 months treatment, severe deformation of the dental-alveolar structure was observed. This reports suggests that adults after dental extraction are at a high risk of dental-alveolar deformities from pressure garments and might benefit from the use of occlusal wafers.