Comparative study of pressure distribution at the user-cushion interface with different cushions in a population with spinal cord injury

A systematic review of the effectiveness of pressure relieving cushions in reducing pressure injury

This systematic review seeks to gather and analyze the evidence on wheelchair pressure relieving cushions, and report on the optimal materials and designs for reducing pressure injury risk. The following research question guides this study: Which wheelchair cushions best reduce pressure injury risk? PIs continue to impact the health and function of wheelchairs users with significant mobility impairments. Pressure relieving cushions are typically prescribed to provide pressure relief in the pre-wound, wound, and post-wound phases. Presently, no published reviews analyze all of the commonly available cushion materials. Most comparison studies typically address a specific population such as spinal cord injury, or only a few styles of cushion design/materials. Results suggest air-cell cushions provide optimal pressure relief and shear reduction. Furthermore, small sample single cohort studies suggest off-loading cushions provide superior pressure relief beyond that of air-celled cushions but require additional research for greater generalizability.

Battery-Free, Wireless Multi-Modal Sensor, and Actuator Array System for Pressure Injury Prevention

Simultaneous monitoring of critical parameters (e.g., pressure, shear, and temperature) at bony prominences is essential for the prevention of pressure injuries in a systematic manner. However, the development of wireless sensor array for accurate mapping of risk factors has been limited due to the challenges in the convergence of wireless technologies and wearable sensor arrays with a thin and small form factor. Herein, a battery-free, wireless, miniaturized multi-modal sensor array is introduced for continuous mapping of pressure, shear, and temperature at skin interfaces. The sensor array includes an integrated pressure and shear sensor consisting of 3D strain gauges and micromachined components. The mechanically decoupled design of the integrated sensor enables reliable data acquisition of pressure and shear at skin interfaces without the need for additional data processing. The sensor platform enables the analysis of interplay among localized pressure, shear, and temperature in response to changes in the patient's movement, posture, and bed inclination. The validation trials using a novel combination of wireless sensor arrays and customized pneumatic actuator demonstrate the efficacy of the platform in continuous monitoring and efficient redistribution of pressure and shear without repositioning, thereby improving the patient's quality of life.

Hygro-thermo-mechanical performance of wheelchair cushion technologies in the prevention of pressure ulcers and moisture-associated skin damages

This study aims at investigating the effects of three different wheelchair cushion technologies at the patient-wheelchair interface. To this end, eight participants were recruited to remain in an unrelieved seated position on a wheelchair successively equipped with three different cushions (foam, air-cell-based and gel), for a duration of 45 min. Interface pressure, temperature (measured with infrared thermography) and relative humidity were measured at the seat interface, at different timestamps. Experimental results show that foam cushion is significantly more efficient in reducing contact peak pressure (p < .01), while the gel cushion displays higher heat evacuation capabilities. In terms of relative humidity, no significant difference is observed among the three technologies (p > .29): all of them evacuate around only 10% of the total humidity compared to the reference situation (i.e., without cushion). Besides, a complementary numerical simulation corresponding to the steady state of the patient-wheelchair structure clearly highlights the temperature volume field at the underside of the seat, which acts like a thermal barrier and contributes to heat accumulation. Besides, an air flow at the underside of the chair in motion is shown to significantly reduce heat accumulation.

Procedure to categorize wheelchair cushion performance using compliant buttock models

Purpose: Wheelchair cushion prescription often seeks to address tissue integrity in addition to other clinical indicators. Because hundreds of wheelchair cushion models are available, a benefit would result if cushions were classified in a more valid manner to help guide selection by clinicians and users. The objective of this research was to develop an approach to evaluate and classify wheelchair cushion performance with respect to pressure redistribution.

Materials and methods: Two anatomically-based buttock models were designed consisting of an elastomeric shell that models overall buttock form and a rigid substructure that abstracts load-bearing aspects of the skeleton. Model shapes were based upon elliptical and trigonometric equations, respectively. Two performance parameters were defined, pressure magnitude and pressure redistribution. The pressure magnitude parameter compared internal pressure values of the test cushion to a flat foam reference material, resulting in three classifications, superior, comparable, and inferior. Surface sensors were used to distinguish cushions with high, moderate or low pressure redistribution performance. Ten wheelchair cushions were evaluated by both models using two loads that represent a range of body weights expected for 41–43 cm wide cushions.

Results and Conclusion: A classification matrix is proposed using both models and performance parameters. Two cushions met criteria for the highest level of performance, and one cushion was deemed to have inadequate performance for therapeutic value. The proposed method has a sensitivity to discern differences, compatibility with different sized cushions, and a versatility in classification. As such, it stands as an improvement over existing classification approaches.

Follow-Up Study of Subdermal Low-Echoic Lesions in the Ischial Region in Wheelchair Users With Spinal Cord Injuries

Objective:

To follow up patients with spinal cord injuries with subdermal low-echoic lesions in the ischial region for abnormalities after 1 year.

Design

A retrospective cohort study.

Setting

A Japanese rehabilitation center.

Participants

We included patients with chronic spinal cord injuries and subdermal low-echoic lesions who underwent routine inspection and palpation examinations (n = 7).

Interventions

Education on pressure injury and instruction on pressure relief and seating was provided and the patients were followed up for abnormalities after 1 year. Self-reports were obtained on wheelchair sitting time, and interface pressure was recorded while the patients were seated on the wheelchair. Interface pressure measurements at the bilateral ischial regions were recorded with a force-sensitive application pressure mapping system.

Outcome Measures

The primary outcome was the presence of subdermal low-echoic lesions in the bilateral ischial regions on ultrasonography at the 1-year follow-up examination. Secondary outcomes included wheelchair sitting time and interface pressure in the bilateral ischial regions.

Results

Of the 10 areas that showed subdermal low-echoic lesions on ultrasonography, nine had improved after 1 year. One area that did not improve was an open wound. At the follow-up examination, the pressure duration was reduced in all patients, and the interface pressure could be reduced in 5/7 patients.

Conclusions

This is the first study to follow up with patients having spinal cord injuries and subdermal low-echoic lesions in the ischial region using ultrasonography. The low-echoic lesions improved within 1 year by reducing the pressure duration and interface pressure. Pressure injury prevention in patients with spinal cord injuries relies on the early detection of skin abnormalities, and education and instruction to change self-management behaviors are recommended.

Interface pressure reduction effects of wheelchair cushions in individuals with spinal cord injury: a rapid review

OBJECTIVE

Wheelchair cushion is routinely used to manage the sitting acquired pressure for an individual with spinal cord injury, but which kind of wheelchair cushion performs better in terms of interface pressure management is unclear. This review aims to compare different kinds of wheelchair cushions on their effect of interface pressure reduction in individuals with spinal cord injury.

METHODS AND RESULTS

The databases of MEDLINE, CINAHL, EMBASE and Web of Science were searched. Totally 10 studies were included in this review. Seven of the included studies indicated that air cushions were superior to gel cushions in interface pressure reduction. Three of the included studies reported that gel cushions were superior to polyurethane foam cushions in interface pressure reduction. The variables of measurement duration, measurement focus, measurement devices, cushion covering, sample variations and body positioning of patients may confound the comparison of interface pressure reduction effect of different wheelchair cushions among studies.

CONCLUSIONS

Air cushion was reported more consistently effective in interface pressure reduction than gel and foam cushions. While the variable parameters (measurement duration, focus, devices) and individual conditions (BMI, body positioning) may interfere the comparison among studies. Researches disseminating consistent parameters and clinical prescriptions with individualized evaluation are suggested for the establishment of an evidence-based practice in clinic.Implications for rehabilitationWheelchair cushion is routinely used for an individual post spinal cord injury to manage the sitting acquired pressure.Which kind of wheelchair cushion performs better in terms of interface pressure management is unclear.Air cushion is found more consistently effective in interface pressure reduction than gel cushion and foam cushion.Individualized evaluation of the interface pressure is suggested for the prescription of wheelchair cushion in clinic.

Modelling, design and control of a new seat-cushion for pressure ulcers prevention

Pressure ulcers are a frequent complication in patients having limited activity and mobility (e.g., elderly people, spinal cord injury patients, people with disabilities, etc.). The aim of this work is the conceptual design, modelling and control of a new seat cushion for pressure ulcers prevention. The whole system (constituted by the seat cushion equipped with a real-time pressure mapping with closed-loop control) is designed to identify the critical points on the human skin, before pressure ulcers creation, and to be able to distribute the contact pressure between the human and cushion avoiding wound creation. The seat cushion is constituted by soft air-cells actuated by air flow. To define the shape and size of the soft air-cells, finite element simulations are carried out, analysing the internal volume reduction with external loads application to reproduce the variable stiffness. The data obtained by finite element analysis are used to simulate inflation and deflation of the soft bubble air-cells. Finally, the control systems of a single air-cell and of the whole cushion are designed and simulated. The novelty of our work consists in the conception of a seat cushion able to recognise higher and lower risk zones of pressure ulcer generation on the human skin and to provide compensation automatically. This work can therefore be considered in line with the sustainable development goals recently launched by the EU Commission.

CLINICAL EFFECTIVENESS OF 3D-MODELING-BASED CUSTOMIZED OFF-LOADING PRESSURE-RELIEF CUSHIONS FOR SPINAL CORD INJURY

This study aimed to investigate the effectiveness of a 3D-modeling-based customized off-loading cushion to prevent pressure ulcers in people with spinal cord injury (SCI) using wheelchairs. The study included five people with SCI who use the traditionally manufactured customized off-loading cushions. As part of the test, each subject sat on three types of pressure-relief cushions, and the pressure between the seating surface and cushion was measured for 60[Formula: see text]min. The average measured pressure values were compared, and the change in pressure with time was analyzed to verify the clinical effect. The results showed that the CAD/CAM-based customized off-loading cushion exhibited a better decrease in pressure and pressure distribution effect on the ischial tuberosity and coccyx than the adjustable air cushion but did not differ much from the traditionally manufactured customized off-loading cushion. The clinical and economic effectiveness of the customized off-loading cushion based on the computer-aided design and manufacturing (CAD/CAM) technology was analyzed and tested on people with SCI. An occupational therapist evaluating the client followed by designing the customized off-loading strategy has no difference in terms of clinical effect compared to the traditional manufacturing method. However, time, effort, and cost should be considered when choosing an intervention strategy.

A STUDY OF PRESSURE DISTRIBUTION EFFECT AND USER SATISFACTION OF A CUSTOMIZED OFF-LOADING CUSHION BASED ON 3D MODELING: A COMPARISON WITH CONVENTIONAL AIR CUSHIONS

The study was to compare an off-loading cushion, designed for individuals with spinal cord injury, with air cushion to analyze the effect of pressure on skin injury and user satisfaction. The off-loading cushion can reduce the incidence of pressure ulcers by minimizing the pressure of the ischial tuberosity and coccyx. Because anatomical structures of each participant are different, 3D scanning is used in the customized manufacturing of the cushions. In the 3D modeling, the product is designed so that the ischial tuberosity and coccyx have minimal contact with the cushion’s surface area. The X-sensor was used to confirm the pressure dispersion effect. As a result, maximum pressure of the ischial tuberosity and the coccyx were measured and observed to be lower than that of the air cushion. User satisfaction was compared between two cushions using the QUEST 2.0. The off-loading cushion has slightly higher service and product satisfaction than the air cushion. Based on these findings, this study suggests that off-loading cushions reduce the occurrence of pressure injury compared to air cushions.

A STUDY OF PRESSURE DISTRIBUTION EFFECT AND USER SATISFACTION OF A CUSTOMIZED OFF-LOADING CUSHION BASED ON 3D MODELING: A COMPARISON WITH CONVENTIONAL AIR CUSHIONS

The study was to compare an off-loading cushion, designed for individuals with spinal cord injury, with air cushion to analyze the effect of pressure on skin injury and user satisfaction. The off-loading cushion can reduce the incidence of pressure ulcers by minimizing the pressure of the ischial tuberosity and coccyx. Because anatomical structures of each participant are different, 3D scanning is used in the customized manufacturing of the cushions. In the 3D modeling, the product is designed so that the ischial tuberosity and coccyx have minimal contact with the cushion’s surface area. The X-sensor was used to confirm the pressure dispersion effect. As a result, maximum pressure of the ischial tuberosity and the coccyx were measured and observed to be lower than that of the air cushion. User satisfaction was compared between two cushions using the QUEST 2.0. The off-loading cushion has slightly higher service and product satisfaction than the air cushion. Based on these findings, this study suggests that off-loading cushions reduce the occurrence of pressure injury compared to air cushions.

Lateral pressure equalisation as a principle for designing support surfaces to prevent deep tissue pressure ulcers

When immobile or neuropathic patients are supported by beds or chairs, their soft tissues undergo deformations that can cause pressure ulcers. Current support surfaces that redistribute under-body pressures at vulnerable body sites have not succeeded in reducing pressure ulcer prevalence. Here we show that adding a supporting lateral pressure can counter-act the deformations induced by under-body pressure, and that this 'pressure equalisation' approach is a more effective way to reduce ulcer-inducing deformations than current approaches based on redistributing under-body pressure. A finite element model of the seated pelvis predicts that applying a lateral pressure to the soft tissue reduces peak von Mises stress in the deep tissue by a factor of 2.4 relative to a standard cushion (from 113 kPa to 47 kPa)-a greater effect than that achieved by using a more conformable cushion, which reduced von Mises stress to 75 kPa. Combining both a conformable cushion and lateral pressure reduced peak von Mises stresses to 25 kPa. The ratio of peak lateral pressure to peak under-body pressure was shown to regulate deep tissue stress better than under-body pressure alone. By optimising the magnitude and position of lateral pressure, tissue deformations can be reduced to that induced when suspended in a fluid. Our results explain the lack of efficacy in current support surfaces and suggest a new approach to designing and evaluating support surfaces: ensuring sufficient lateral pressure is applied to counter-act under-body pressure.

Effects of seating education and cushion management for adaptive sitting posture in spinal cord injury: Two case reports

RATIONALE

Pressure ulcers can frequently occur in spinal cord injured patients living in wheelchairs. Therefore, to manage the cushion in sitting posture is important for preventing ulcers.

PATIENT CONCERNS

The patients visited seating clinic in rehabilitation hospital for uncomfortable sitting posture. The patients were asked for posture control and cushion air management training in a sitting posture to prevent sores.

DIAGNOSIS

The diagnosis was spinal cord injury.

INTERVENTIONS

Two patients with spinal cord injury were subjected to posture training while the quantity of air in the cushion was being modulated to minimize gluteal pressure by measuring the pressure in the sitting position in the driver's seat using an X-sensor.

OUTCOMES

In Case 1, as a result of air control, contact area showed 1108.06 cm, average pressure 45.20 mmHg, contact area increased, and mean pressure decreased. In Case 2, the contact area 974.19 cm and the average area 41.00 mmHg were measured by applying the change to the ROHO low-Quardro type, showing a decrease in the average body pressure from the initial stage.

LESSONS

From the results of this study, it was found that measurement of body pressure and posture training using a sensor that provides visual feedback is effective in preventing pressure ulcer. Therefore, it is necessary to perform routine control of the sitting pressure in the clinic and management training of the air cell cushion.

Comfort evaluation of a subject-specific seating interface formed by vibrating grains

Sitting is the most common posture for work in offices, and spinal cord injury (SCI) patients who are wheelchair dependent spend 10.6 h per day seated in wheelchairs. Thus, the comfort of subject-specific interfaces is increasingly important for the well-being of patients and office workers. This paper introduces a new method of forming a subject-specific interface, based on vibrating grains. Twenty subjects (10 females and 10 males) participated in the sitting test. Interface comfort was evaluated using the pressure distribution and subjective rating methods. Five seating interface types were compared. The results showed that compared with a flat interface, the interfaces formed by vibrating grains had a significantly reduced peak contact pressure (PeakCP) (by more than 58.03%), and that PeakCP was highly correlated with the comfort rating (R = -0.533) and discomfort rating(R = -0.603). This new method shows promise for guiding the future development of customized seating interfaces.

Developing a process for assessing equivalency of wheelchair cushion pressure redistribution performance

For wheelchair users who are at risk for developing pressure ulcers, cushion prescription seeks to address tissue integrity. Because many designs of wheelchair cushions exist, a need exists to estimate their performance in supporting the body. The objective of this research was to develop an approach to assess the equivalency of cushions with respect to their pressure redistribution performance.Two instrumented compliant buttock models, differing in form, were used in the evaluation. Stress and strain parameters were used to characterize load-bearing performance. A cohort of 8 wheelchair cushions was compared to a standard reference material, HR45 foam. Each cushion was measured using both models under two loading conditions.The use of compliant buttock models that are capable of measuring both stress and strain parameters offer greater capability in measuring load-bearing performance compared to previously described methods. The proposed approach was able to evaluate cushion performance and use a logic-based approach to define whether or not a cushion was equivalent to the HR45 material. Additional study is needed to further validate the approach and to define the thresholds and criteria used to define cushion equivalency.

Pressure Relieving Effect of Adding a Pelvic Well Pad to a Wheelchair Cushion in Individuals With Spinal Cord Injury

Objective

To identify the pressure relieving effect of adding a pelvic well pad, a firm pad that is cut in the ischial area, to a wheelchair cushion on the ischium.

Methods

Medical records of 77 individuals with SCI, who underwent interface pressure mapping of the buttock-thigh area, were retrospectively reviewed. The pelvic well pad is a 2.5-cm thick firm pad and has a cut in the ischial area. Expecting additional pressure relief, it can be inserted under a wheelchair cushion. Subjects underwent interface pressure mapping in the subject's wheelchair utilizing the subject's pre-existing pressure relieving cushion and subsequently on a combination of a pelvic well pad and the cushion. The average pressure, peak pressure, and contact area of the buttock-thigh were evaluated.

Results

Adding a pelvic well pad, under the pressure relieving cushion, resulted in a decrease in the average and peak pressures and increase in the contact area of the buttock-thigh area when compared with applying only pressure relieving cushions (p<0.05). The mean of the average pressure decreased from 46.10±10.26 to 44.09±9.92 mmHg and peak pressure decreased from 155.03±48.02 to 131.42±45.86 mmHg when adding a pelvic well pad. The mean of the contact area increased from 1,136.44±262.46 to 1,216.99±255.29 cm².

Conclusion

When a pelvic well pad was applied, in addition to a pre-existing pressure relieving cushion, the average and peak pressures of the buttock-thigh area decreased and the contact area increased. These results suggest that adding a pelvic well pad to wheelchair cushion may be effective in preventing a pressure ulcer of the buttock area.

Experts' opinion on manual wheelchair adjustments for adults with diabetes

Diabetes is a global health concern that can lead to mobility limitations necessitating a wheelchair. However, there are currently no guidelines for wheelchair adjustments tailored to the diabetic population.

PURPOSE

To describe relevant manual wheelchair adjustments for adults with diabetes, and to explore how these adjustments apply to populations living in less-resourced countries.

METHODS

Semi-structured interviews were conducted with 13 wheelchair experts from five different countries working with adult with diabetes. Interviews were analyzed using the constant comparison method.

RESULTS

The most frequently mentioned wheelchair adjustments were related to neuropathies, skin integrity, decreased strength and amputations. Air cushions were preferred for managing seat sores. Lightweight wheelchairs could be advantageous for people with decreased strength and endurance. In less-resourced settings, wheelchair adjustment decisions prioritized durability and low maintenance.

DISCUSSION

The recommendation of lightweight wheelchairs for adults with diabetes may be limited by the lack of adjustment possibilities compared to regular weight wheelchairs. In less-resourced settings, prioritizing durability and low maintenance may limit prevention and management of conditions associated to diabetes.

CONCLUSION

This study represents a first step towards the development of guidelines for manual wheelchair adjustments specifically tailored to adults with diabetes, in a global health context. Implications of rehabilitation When prescribing manual wheelchairs to persons with diabetes, expert clinicians agree that skin integrity, neuropathies and decreased strength are their primary concerns. Compromises are often necessary when adjusting a wheelchair for a person with diabetes, due to the complexity of their symptoms: same modification can be indicated for one symptom but contraindicated for another. Diabetes prevalence is high in less-resourced settings. There is a need for increased availability of affordable wheelchair equipment that is durable, reliable and adapted to persons with diabetes.

Comparing the interface pressure redistribution after applying three different types of cushions: differences according to cushion type

[Purpose] The purpose of this study was to compare the interface pressure redistribution when sitting after applying three different types of cushions and on a firm surface in individuals in their 20s and those older than 60 years old. [Subjects and Methods] Healthy 100 elderly (60 years and older) subjects and 111 college students participated in this study. Interface pressure redistribution while sitting on a firm surface or honeycomb, air, and memory foam cushions, examined in that order. [Results] For all groups, significant differences were found in the total pressure mean among sitting states. When the hip and thigh interface pressure among sitting states were compared within each group, significant differences were found in the mean right hip pressure, mean left hip pressure, peak right hip pressure, peak left hip pressure, right hip pressure ratio, and left hip pressure ratio. [Conclusion] Our data indicated that the type of cushion should be considered and fit for individuals when recommending appropriate interface pressure redistribution cushions.

Comparing the interface pressure redistribution of three different types of cushions: differences according to age groups and cushion preferences

[Purpose] The purpose of this study was to analyze the change in interface pressure redistribution of three different types of cushions sat on by individuals in their 20s and older than 60 years old. [Subjects and Methods] One hundred and eleven college students and 100 persons than 60 years old were recruited. Sitting pressure redistribution was measured while subjects sat without cushions or on honeycomb, air, and memory foam cushions in that order. Subsequently, the cushion preference was measured. After obtaining all measurements, the mean total pressure and each quadrant's mean and peak pressure were analyzed. [Results] The mean hip and the peak pressures were low in the group of females aged 60 years or older, and the highest in the group of males in their 20s. The hip pressure ratio was low in the groups of females in their 20s and 60 years or older, whereas the thigh pressure ratio was high in the same groups. The analysis of cushion preference showed that the groups of males (42.0%) and females (40.0%) in their 20s mostly preferred air cushion. The men (55.1%) and women (50.0%) aged 20 years or older selected honeycomb and air cushions as the first and third preferred cushions with a high response rate. [Conclusion] Our results indicate that gender and age should be considered when recommending appropriate pressure redistribution cushions.

Seat pan and backrest pressure distribution while sitting in office chairs

Nowadays, an increasing amount of time is spent seated, especially in office environments, where sitting comfort and support are increasingly important due to the prevalence of musculoskeletal disorders. The aim of this study was to develop a methodology for chair-specific sensor mat calibration, to evaluate the interconnections between specific pressure parameters and to establish those that are most meaningful and significant in order to differentiate pressure distribution measures between office chairs. The shape of the exponential calibration function was highly influenced by the material properties and geometry of the office chairs, and therefore a chair-specific calibration proved to be essential. High correlations were observed between the eight analysed pressure parameters, whereby the pressure parameters could be reduced to a set of four and three parameters for the seat pan and the backrest respectively. In order to find significant differences between office chairs, gradient parameters should be analysed for the seat pan, whereas for the backrest almost all parameters are suitable.

Effects of different seat cushions on interface pressure distribution: a pilot study

[Purpose] The purpose of this study was to evaluate pressure redistribution on the supporting area of healthy volunteers when using different cushions. [Subjects and Methods] Twenty healthy individuals ranging in age from 19–23 years old and 20 older adults age 60 or above participated in the study. All participants lived in urban communities in South Korea. Group differences according to gender, age, and cushion types were analyzed with one-way analysis of variance and post-hoc analysis. [Results] Statistically significant differences in peak pressure and mean pressure were identified between age, gender, and cushion types. Peak pressure and mean pressure were higher on firm surfaces and on the air cushion than other cushion types. The pressure ratio was lower when an air cushion was used in the buttock area and was higher when it was used under the thighs compared to that in other conditions. [Conclusion] This study showed that interface pressure can be distributed differently depending on what cushions are used. Therefore, when using seat cushions, individuals should seek advice to help them choose the appropriate cushion for their needs.

The Effects of Body Mass Composition and Cushion Type on Seat-Interface Pressure in Spinal Cord Injured Patients

Objective

To investigate the effects of body mass composition and cushion type on seat-interface pressure in spinal cord injured (SCI) patients and healthy subjects.

Methods

Twenty SCI patients and control subjects were included and their body mass composition measured. Seat-interface pressure was measured with participants in an upright sitting posture on a wheelchair with three kinds of seat cushion and without a seat cushion. We also measured the pressure with each participant in three kinds of sitting postures on each air-filled cushion. We used repeated measure ANOVA, the Mann-Whitney test, and Spearman correlation coefficient for statistical analysis.

Results

The total skeletal muscle mass and body water in the lower extremities were significantly higher in the control group, whilst body fat was significantly higher in the SCI group. However, the seat-interface pressure and body mass composition were not significantly correlated in both groups. Each of the three types of seat cushion resulted in significant reduction in the seat-interface pressure. The SCI group had significantly higher seatinterface pressure than the control group regardless of cushion type or sitting posture. The three kinds of sitting posture did not result in a significant reduction of seat-interface pressure.

Conclusion

We confirmed that the body mass composition does not have a direct effect on seat-interface pressure. However, a reduction of skeletal muscle mass and body water can influence the occurrence of pressure ulcers. Furthermore, in order to minimize seat-interface pressure, it is necessary to apply a method fitted to each individual rather than a uniform method.

Reliability of the special support system for sitting pressure redistribution

[Purpose] This study investigated the reliability of the Special Support System. [Subjects and Methods] Eighteen female and 14 male volunteers participated in this study. Participants were asked to sit on the Special Support System with their chins tucked in, spines straight, pelvis neutrally positioned, and their hands placed on their thighs. They were also asked to flex their hips, knees, and ankles to approximately 90 degrees and to put their feet flat on the floor. The total contact area, mean total pressure, as well as mean and peak pressures of each quadrant were each measured 15 times. Test-retest reliability was analyzed for inflated air pressure, and pressure redistribution values by using intraclass correlation coefficients. [Results] The intraclass correlation coefficient was greater than 0.89 for inflated air pressure and greater than 0.92 for total contact area, mean total pressure, and each quadrant’s mean and peak pressure. [Conclusion] The findings suggest that the Special Support System is reliable and can be used as an alternative method for redistributing sitting pressure.

Support surfaces for pressure ulcer prevention

BACKGROUND

Pressure ulcers (i.e. bedsores, pressure sores, pressure injuries, decubitus ulcers) are areas of localised damage to the skin and underlying tissue. They are common in the elderly and immobile, and costly in financial and human terms. Pressure-relieving support surfaces (i.e. beds, mattresses, seat cushions etc) are used to help prevent ulcer development.

OBJECTIVES

This systematic review seeks to establish:(1) the extent to which pressure-relieving support surfaces reduce the incidence of pressure ulcers compared with standard support surfaces, and,(2) their comparative effectiveness in ulcer prevention.

SEARCH METHODS

In April 2015, for this fourth update we searched The Cochrane Wounds Group Specialised Register (searched 15 April 2015) which includes the results of regular searches of MEDLINE, EMBASE and CINAHL and The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2015, Issue 3).

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-randomised trials, published or unpublished, that assessed the effects of any support surface for prevention of pressure ulcers, in any patient group or setting which measured pressure ulcer incidence. Trials reporting only proxy outcomes (e.g. interface pressure) were excluded. Two review authors independently selected trials.

DATA COLLECTION AND ANALYSIS

Data were extracted by one review author and checked by another. Where appropriate, estimates from similar trials were pooled for meta-analysis.

MAIN RESULTS

For this fourth update six new trials were included, bringing the total of included trials to 59.Foam alternatives to standard hospital foam mattresses reduce the incidence of pressure ulcers in people at risk (RR 0.40 95% CI 0.21 to 0.74). The relative merits of alternating- and constant low-pressure devices are unclear. One high-quality trial suggested that alternating-pressure mattresses may be more cost effective than alternating-pressure overlays in a UK context.Pressure-relieving overlays on the operating table reduce postoperative pressure ulcer incidence, although two trials indicated that foam overlays caused adverse skin changes. Meta-analysis of three trials suggest that Australian standard medical sheepskins prevent pressure ulcers (RR 0.56 95% CI 0.32 to 0.97). 

AUTHORS' CONCLUSIONS

People at high risk of developing pressure ulcers should use higher-specification foam mattresses rather than standard hospital foam mattresses. The relative merits of higher-specification constant low-pressure and alternating-pressure support surfaces for preventing pressure ulcers are unclear, but alternating-pressure mattresses may be more cost effective than alternating-pressure overlays in a UK context. Medical grade sheepskins are associated with a decrease in pressure ulcer development. Organisations might consider the use of some forms of pressure relief for high risk patients in the operating theatre.

The effect of seat shape on the risk of pressure ulcers using discomfort and interface pressure measurements

BACKGROUND

It is clinically known that shape is important when selecting or designing a wheelchair support surface for the prevention of pressure ulcers (a £ 2 billion annual cost to the National Health Service, UK); however, the effect of different levels of shape contouring has not been adequately studied.

OBJECTIVES

To investigate the effect of seat shape on the risk of pressure ulcers using discomfort and interface pressure measurements.

STUDY DESIGN

Randomised, repeated trial.

METHODS

Thirty able-bodied participants sat with restricted movement for 30 min in three sessions to evaluate two cushion shapes against a flat baseline surface. Visual Analog Scaling and pressure mapping were used to measure surrogates for pressure ulcer risk, discomfort and interface pressures, respectively.

RESULTS

Linear regression revealed a reduction in discomfort (p < 0.05) on the custom contoured shapes. Interface pressures measured were also lower (p < 0.05) on the custom contoured shapes, and a negative Pearson's correlation (p < 0.05) indicated an association between smaller hip widths and increased discomfort for the commercially shaped cushion.

CONCLUSIONS

The results of this study confirm that custom contoured shapes were effective at reducing pressure ulcer surrogate measures in the participants of this study and therefore suggests that the contribution of a cushion's three-dimensional contours on pressure ulcer risk should be further researched.

CLINICAL RELEVANCE

The measurement of seat shape, discomfort and interface pressure in surrogate participants can help inform the design of wheelchair seating for individuals who are insensate or otherwise at risk of developing pressure ulcers. This knowledge can now be implemented using modern three-dimensional shape acquisition, analysis and fabrication technologies.

An alternating pressure sequence proposal for an air-cell cushion for preventing pressure ulcers

The distribution and release of pressure on ischial regions are two important parameters for evaluating the effectiveness of a cushion; especially the release of pressure over time on ischial tuberosities, which is significant for preventing pressure ulcers. The aim of this work is to evaluate the effect on interface pressure through the application of a proposed alternating pressure sequence for an air-cell cushion. Six healthy volunteers were asked to sit on the air cell cushion, in static and alternating modes, as well as on a typical foam cushion for 12 minutes. Interface pressure was monitored with a matrix sensor system. Interface pressure values on ischial tuberosities, user contact area and pressure distribution were analyzed. Results showed that IP on IT tends to increase in both foam and static cushions, while in alternating cushion IP on IT tends to decrease. User contact area was significantly larger in alternating cushion than in static or foam cushions. Moreover, there is a better pressure re-distribution with alternating cushion than with the other cushions. The goal of the alternating sequence is to redistribute pressure and stimulate the ischial regions in order to promote blood flow and prevent pressure occurring in wheelchair users.

A Comparison of the Average Sitting Pressures and Symmetry Indexes between Air-adjustable and Foam Cushions

[Purpose] The purpose of this study was to determine the best adjustable cushions, for the maintenance of normal sitting balance by healthy persons in wheelchairs, from a foam cushion, and a newly-developed air-adjustable cushion. [Subjects] Eighteen healthy participants (9 men, 9 women) were recruited. [Methods] Participants were evaluated using the Force Sensing Array System to assess average sitting pressure and the symmetry index of chair sitting under the following conditions: no seat cushion, a foam cushion, and a newly-developed air-adjustable cushion. [Results] The results show that there were no significant differences among the average sitting pressures which were measured on the hard surface of a chair, a foam cushion, and the newly-developed cushion. The air-adjustable cushion's symmetry index turned out to be closer to 0 than those of the foam cushion and the hard surface of the chair. [Conclusion] We suggest that the newly-developed air-adjustable cushion contributes to a more symmetrical sitting posture than the basic foam cushion or no seat cushion.

Is a computer-based measurement method superior to a recommended manual method by the ROHO(®) Group to assess pressure in the sitting position?

BACKGROUND

In clinical practice, a manual-based assessment is standard procedure to adjust the air pressure in the ROHO(®) cushion in seated position. Recently, a computerized pressure system method was developed to support the clinical adjustment of air in the ROHO(®) cushion to reduce the pressure in the seated position. To our knowledge, no studies have investigated the reliability between the manual method mostly used in clinical practice and the alternative computer-based assessment of the pressure in the seated position.

AIM

The objective was to test intra-tester and inter-tester reliability and evaluate if a computer-based measurement method is superior to a manual method to reduce pressure in the seated position. The cushion used was a Roho Quadtro select(®) high profile.

METHODS

An intra-tester and inter-tester reliability study was conducted in 2010 at the Department of Occupational Therapy and Physiotherapy, Aalborg Hospital, Aarhus University Hospital, Denmark. Subjects included were two occupational therapists and 20 healthy subjects. The outcome measures were obtained using a pressure imaging system that could register pressure distribution in the sitting area.

RESULTS

The study did not show high intra-class correlation coefficients neither in the intra-tester nor in the inter-tester reliability for manual or computer-based methods in reducing pressure in the seating position.

CONCLUSIONS

The current company-recommended air pressure adjustment procedure seems unreliable. The technical superiority of the computer-based method over the manual method has not been established.

A NEW CUSTOM-CONTOURED CUSHION SYSTEM BASED ON FINITE ELEMENT MODELING PREDICTION

High internal stress in the deep tissues adjacent to bony prominences can cause deep tissue injuries. Therefore, internal stress in the soft tissue should be considered when the performance of anti-decubitus cushions is evaluated during cushion design. This paper reports on a custom-contoured cushion (CCC) system incorporated with a three-dimensional (3D) slice subject-specific finite element (FE) model to investigate the internal stress distribution in the soft tissues. This stress distribution was used to transform the interface pressure into the carving depth of the fabricated cushions based on the biomechanical characteristics of the cushion materials. The internal stress in the soft tissues was investigated using an FE model of buttocks and cushion made from three cushion materials. The cushion design was optimized according to the properties of the material. The simulated interface stress between the buttocks and the cushion (18 kPa) was consistent with the measured interface pressure of the CCC (17.1 kPa). The 3D FE model predicted the internal stress and displacement of the soft tissues and cushion. Additionally, it efficiently optimized the selection of cushion material. Fifty subjects (25 subjects with spinal cord injuries (SCI) and 25 healthy subjects) were recruited to investigate the interface pressure and perform subjective comfort evaluation. The CCC decreased the interface pressure under the buttocks and simultaneously increased the subjective comfort and stability. The effectiveness of the cushion materials was predicted by the CCC system, which also validated the clinical performance of decreasing interface pressure.

A robust wheelchair pressure relief monitoring system

It is essential to prevent pressure ulcers for people with spinal cord injuries (SCI). Pressure ulcer is likely to develop when there is excessive pressure on the body tissue for lengthy durations. Therefore, persons with SCI, who usually spend long time sitting in wheelchairs, are advised to perform regular pressure reliefs in their daily lives. This paper proposes a system for the monitoring of wheelchair users' pressure relief behaviors. The system utilizes piezo resistive sensors beneath a wheelchair cushion to monitor pressure, and employs supervised learning techniques to classify a wheelchair user's pressure relief status. Key features of the system include robustness and not interfering with cushion performance or the daily activities of wheelchair users. The system works well on different types of cushions, and achieves 91% sensitivity and 89% specificity based on tests on different wheelchair users.

Influence of different types of seat cushions on the static sitting posture in individuals with spinal cord injury

STUDY DESIGN

Cross-sectional study.

OBJECTIVES

To evaluate the efficacy of the Postural Assessment Software PAS/SAPO in the posture analysis of individuals with spinal cord injury (SCI) during sitting position and to analyze if the use of different types of seat cushions-gel and foam, with no cushion-can interfere in the individual's posture during sitting position.

SETTING

Centre of Rehabilitation at the University Hospital (FMRP-USP), Ribeirão Preto, Brazil.

METHODS

Eight individuals, four paraplegics and four tetraplegics with SCI and 20 healthy individuals participated in the study. Photos were taken of individuals in the sitting position using foam, gel cushions and with no cushion. They were analyzed using the PAS/SAPO. The alignment of the anterior-superior iliac spine (ASIS) and the posterior pelvic tilt were evaluated from the angle formed between the ASIS and the greater trochanter of the femur.

RESULTS

The group of healthy individuals presented the best postural alignment when compared with the group with SCI, both for the ASIS alignment (P<0.05) and for the degree of posterior pelvic tilt (P<0.05). No significant differences were found in the variables analyzed when the seat cushions were compared.

CONCLUSION

The different types of cushions did not alter the sitting posture; however, individuals with SCI showed worse postural alignment than the healthy individuals. PAS/SAPO was demonstrated to be useful for postural assessment.

Prevention of pressure ulcer: interaction of body characteristics and different mattresses

We analysed the effect of different body features on contact area, interface pressure and pressure distribution of three different mattresses. Thirty-eight volunteers (age ranged from 17 to 73 years, 23 females) were asked to lie on three different mattresses in a random order: I, standard hospital foam mattresses; II, higher specification foam mattresses (Viscorelax Sure® ); III, constant low pressure devices (CareMedx® , AirSystems). Measurements were performed in supine position and in a 90° left- and right-sided position, respectively, using a full-body mat (pressure mapping device Xsensor X2-Modell). Outcome variables were contact area (CA) in cm(2) , mean interface pressure (IP) in mmHg and pressure distribution (PD) estimated as rate of low pressures between 5 and 33 mmHg on each mattress in percent. Mean CA was lowest in the standard hospital foam mattresses and increased in the higher specification foam mattresses and was highest in the constant low pressure device (supine position: 491 ± 86 cm(2) , 615 ± 95 cm(2) , 685 ± 116 cm(2) ). Mean IP was highest in the standard hospital foam mattresses and lower but similar in the higher specification foam mattresses and the constant low pressure devices (supine position: 22·3 ± 1·5 mmHg, 17·6 ± 1·7 mmHg, 17·6 ± 2·2 mmHg). Models were estimated for CA, IP and PD including the independent variables height, weight and waist-to-hip-ratio (WHR). They show that body morphology seems to play a minor role for CA, IP and PD, but very thin and tall patients and very small and obese people might benefit from different mattresses. Our data show that CA increases with increasing specification of mattresses. Higher specification foam mattresses and constant low pressure devices show similar IP, but constant low pressure devices show a wider pressure distribution. Body morphology should be considered to optimise prevention for single patients.

Settling down time following initial sitting and its relationship with comfort and discomfort

This study examined the subjective rating of wheelchair comfort and discomfort (numerical rating scale questionnaire) and the duration of objective in-chair movement reduction "settling down time" following initial contact with the seating surface. Healthy young subjects (n = 22) sat for 5 min on contoured foam or wood cushion surfaces fitted to otherwise identical wheelchairs. Force sensing resistors attached to each quadrant of the sitting interface measured the relative movements of the subjects over time. A significant correlation was found between settling down time (SDT) and reported leg/feet discomfort (p = 0.003; correlation co-efficient = 0.44); and a significant negative correlation was found between SDT and overall comfort (p = 0.015; correlation co-efficient = -0.36). When comparing cushion surfaces: SDT was significantly longer (p < 0.0001) for subjects sitting on wood (5.8 s) compared to contoured foam (3.9 s); Leg/feet discomfort was significant higher (p = 0.007) for subjects sitting on wood (1.1 out of 10) compared to contoured foam (0.3 out of 10); Overall discomfort was significant higher (p = 0.009) for subjects sitting on wood (1.3 out of 10) compared to contoured foam (0.5 out of 10); Comfort was significantly lower (p = 0.001) for subjects sitting on wood (6.5 out of 10) compared to contoured foam (8.3 out of 10); Support was significantly lower (p = 0.001) for subjects sitting on wood (6.4 out of 10) compared to contoured foam (8 out of 10). The results of this study suggest that the shape and firmness of the surface at the buttock-wheelchair interface can affect a subject's SDT following initial contact with the seat as well as their perception of comfort and discomfort. In addition, there appears to be a relationship between longer SDT's and increased discomfort ratings, and shorter SDT's and increased comfort ratings. Therefore, testing for SDT's may be useful in the indirect objective assessment of wheelchair cushions and possibly other types of seating surfaces with design differences that aim to improve comfort and minimize discomfort.

Comparison of the pressure redistribution qualities of two air-filled wheelchair cushions for people with spinal cord injuries

BACKGROUND/AIM

People with spinal cord injuries are at high risk of developing pressure ulcers. Wheelchair cushions that redistribute pressure are one prevention strategy to reduce the risk of pressure ulcers in this population. Currently, therapists have only limited evidence concerning the pressure redistribution qualities of wheelchair cushions to guide their cushion selection in clinical practice. The aim of this study was to compare the pressure redistribution qualities of two air-filled cushions currently recommended for people with spinal cord injuries.

METHODS

A series of single case studies, based on the methodology used in a previous study, was undertaken on three inpatients with complete spinal cord injury. Interface pressure readings were compared between a Roho® and Vicair® cushion using the Xsensor® Pressure Mapping System. The Roho® cushion is comprised of a series of soft, flexible, inter-connected air cells, and the Vicair® cushion contains separate, sealed cells of air.

RESULTS

The Roho® cushion recorded significantly fewer cells with pressures ≥100 mmHg than the Vicair® cushion for the three participants.

CONCLUSION

This study has provided evidence that the Roho® cushion has superior pressure redistribution qualities than the Vicair® cushion for a small sample of patients with complete spinal cord injury.

Support surfaces for pressure ulcer prevention

BACKGROUND

Pressure ulcers (i.e. bedsores, pressure sores, decubitus ulcers) are areas of localised damage to the skin and underlying tissue. They are common in the elderly and immobile, and costly in financial and human terms. Pressure-relieving support surfaces (i.e. beds, mattresses, seat cushions etc) are used to help prevent ulcer development.

OBJECTIVES

This systematic review seeks to establish: (1) the extent to which pressure-relieving support surfaces reduce the incidence of pressure ulcers compared with standard support surfaces, and, (2) their comparative effectiveness in ulcer prevention.

SEARCH STRATEGY

For this third update we searched: the Cochrane Wounds Group Specialised Register (searched 8 December 2010), The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, Issue 4); Ovid MEDLINE (1950 to November Week 3 2010); Ovid MEDLINE (In-Process & Other Non-Indexed Citations December 07, 2010); Ovid EMBASE (1980 to 2010 Week 48); EBSCO CINAHL (1982 to 3 December 2010), and the reference sections of included studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-randomised studies, published or unpublished, that assessed the effects of any support surface for prevention of pressure ulcers, in any patient group or setting which measured pressure ulcer incidence.Studies reporting only proxy outcomes (e.g. interface pressure) were excluded. Two review authors independently selected studies.

DATA COLLECTION AND ANALYSIS

Data were extracted by one author and checked by another. Where appropriate, estimates from similar studies were pooled for meta-analysis.

MAIN RESULTS

One new trial was included, bringing the total of included studies to 53.Foam alternatives to standard hospital foam mattresses reduce the incidence of pressure ulcers in people at risk (RR 0.40 95% CI 0.21 to 0.74). The relative merits of alternating- and constant low-pressure devices are unclear. One high-quality trial suggested that alternating-pressure mattresses may be more cost effective than alternating-pressure overlays in a UK context.Pressure-relieving overlays on the operating table reduce postoperative pressure ulcer incidence, although two studies indicated that foam overlays caused adverse skin changes. Meta-analysis of three trials indicated that Australian standard medical sheepskins prevent pressure ulcers (RR 0.56 95% CI 0.32 to 0.97). 

AUTHORS' CONCLUSIONS

People at high risk of developing pressure ulcers should use higher-specification foam mattresses rather than standard hospital foam mattresses. The relative merits of higher-specification constant low-pressure and alternating-pressure support surfaces for preventing pressure ulcers are unclear, but alternating-pressure mattresses may be more cost effective than alternating-pressure overlays in a UK context. Medical grade sheepskins are associated with a decrease in pressure ulcer development. Organisations might consider the use of some forms of pressure relief for high risk patients in the operating theatre.

Fiber optic pressure sensing with conforming elastomers

A novel pressure sensing scheme based on the effect of a conforming elastomer material on the transmission spectrum of tilted fiber Bragg gratings is presented. Lateral pressure on the elastomer increases its contact angle around the circumference of the fiber and strongly perturbs the optical transmission of the grating. Using an elastomer with a Young's modulus of 20 MPa, a Poisson ratio of 0.48, and a refractive index of 1.42, the sensor reacts monotonically to pressures from 0 to 50 kPa (and linearly from 0 to 15 kPa), with a standard deviation of 0.25 kPa and maximum error of 0.5 kPa. The data are extracted from the optical transmission spectrum using Fourier analysis and we show that this technique makes the response of the sensor independent of temperature, with a maximum error of 2% between 25°C and 75°C. Finally, other pressure ranges can be reached by using conforming materials with different modulii or applying the pressure at different orientations.