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

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.

The clinical effectiveness of custom-contoured seating for wheelchair users with neuromuscular disorders: a scoping review

Despite its widespread use, the clinical effectiveness of custom-contoured wheelchair seating for individuals with neuromuscular disorders remains unclear. A scoping review was conducted using PubMed, Scopus, and Web of Knowledge databases in November 2021 and updated April 2022. A total of 17 full text articles were included. Discussion themes were grouped based on three outcomes of interest: (1) posture and musculoskeletal deformity, (2) quantitative measures of body structures and functions, and (3) qualitative perceptions, opinions, and quality of life indicators. This review highlighted the lack of literature exploring the impact of custom-contoured seating on cardiopulmonary function, pressure injury management, and upper limb function; although, there was no indication that risk is increased compared to alternative seating and it performed well in terms of perceived user satisfaction, comfort, and function. The findings also demonstrated immediate benefits to postural alignment, although, the longitudinal effect on progression of musculoskeletal deformity compared to alternative seating is more ambiguous. This review aimed to scope the evidence-base for custom-contoured seating for wheelchair users with neuromuscular disorders to synthesize information from the existing literature, inform current practice, and identify knowledge gaps for further experimental investigation.

Upright vs. supine shape-capturing comparison for custom-contoured cushions

AIMS

This study aims to explore best practices of shape capturing methods for creating custom-contoured wheelchair cushions for the purpose of reducing pressure injury risk.

MATERIALS AND METHODS

Pressure redistribution qualities were measured by peak pressure index (PPI) and compared between custom-contoured seating systems molded in supine vs. upright shape-capturing positions. Subjects consisted of 14 able-bodied participants in a within-subjects comparison.

RESULTS

A Wilcoxon signed-rank test and paired t-test were calculated to compare the mean differences of the PPI between shape-capturing positions. Supine shape-capturing resulted in a statistically significant lower PPI compared to upright (z = 2.040, p < . 05) (t = -2.28, p < .05).

CONCLUSION

Shape-capturing in the supine position provided greater pressure distribution as opposed to an upright position. Creating custom-contoured cushions molded in a supine position can reduce the risk of pressure injury to the patient.

The influence of a contoured seating base on pressure distribution and discomfort

PURPOSE

This research paper examines how contouring of a wheelchair seating base can help prevent pressure sores by distributing pressure over the buttocks. Contouring wheelchair cushioning is already done to some extent and has proved to be beneficial for pressure distribution. We researched the effect of contouring the seating base, and whether contouring the seating base affects effectiveness in pressure distribution and perceived discomfort.

MATERIALS & METHODS

13 healthy participants performed a within-subject experiment with three differently contoured seating bases. Perceived comfort and seating pressure were measured for each condition.

RESULTS

Results indicate that a more contoured base is positive for both comfort and increased pressure distribution.

CONCLUSIONS

Contoured seating bases can provide increased comfort and improved pressure distribution over flat seating bases. Future research should examine the effect of contouring on stability, as well as compare the effects of contoured seating bases and contoured cushions.Implications for rehabilitationWe evaluated the comfort and pressure characteristics of three differently contoured hard seating bases for a wheelchair. The outcomes of the research shows that providing increased contour to seatings could be beneficial to reduce pressure peaks in the buttocks.Contour in the seating is conventionally created by shaping the cushions, this research shows the possibility of using a hard base underneath a cushion to create the desired contour.

Chair design for older immobile people: Comparison of pressure mapping and manual handling outcomes

The number of older adults unable to transfer or ambulate independently is increasing. High support chairs enable people experiencing loss of mobility to be mobile, but current chair designs are associated with global functional loss and pressure ulcers. This pilot study compared the functionality of a traditional design high support chair to a new design of motorised high support chair: 1) a motion laboratory study compared joint angles and pressure at the hip, knee, ankle, elbow and spine when pushing each chair, and 2) a pressure mapping study compared the interface pressure when older people with limited mobility used the chairs. Significant reduction in joint angles for the person pushing the chair (degree difference range -3.6 to 14.2) and decreased seated pressure (w/kg difference range -0.2 to 2.1) for the seated user were identified for the motorised chair. Longitudinal investigations are required to determine if the significant differences identified in this pilot study result in less manual handling injuries and pressure areas.

Investigation of the effect of a 15-degree tilt-in-space on the fluctuation of shear forces exerted on the buttocks when the back support is reclined

[Purpose] This study aimed to investigate the effect of the combination of 15° tilt-in-space and recline angles on the fluctuation of shear forces exerted on the buttocks. [Participants and Methods] The participants were 11 healthy adult males. The parameters of the shear forces were the parallel and perpendicular forces exerted on the buttocks as measured by a force plate. The two conditions tested were T0R100-130 and T15R100-130. The tilt-in-space angles were set to 0° and 15° in the T0R100-130 and T15R100-130 conditions, respectively. The reclining angles were determined to be 100° to 130° in both conditions. [Results] Upon comparing the two conditions, the parallel and the perpendicular forces exerted on the buttocks in the T15R100-130 condition were significantly lower than those in the T0R100-130 condition in all positions of back support. Upon comparing the fluctuation values of the parallel and perpendicular forces, those applied in the T15R100-130 condition were significantly higher than those in the T0R100-130 condition. [Conclusion] These results suggest that the fluctuation of shear forces exerted on the buttocks could be decreased by using a combination of 15° tilt-in-space and reclining functions.

Computational studies of the biomechanical efficacy of a minimum tissue deformation mattress in protecting from sacral pressure ulcers in a supine position

Sustained soft tissue exposure to localised deformations is a trigger for the formation of pressure ulcers. Immersion and envelopment are critical benchmarks that determine comfort and the pressure ulcer risk mitigation, as they have considerable influence on tissue stress concentrations near bony prominences. In the present study, we developed a computer modelling framework for quantifying the extent by which optimal envelopment disperses tissue stress concentrations near the sacrum. To compare the risk of developing a sacral pressure ulcer while lying supine on a regular foam mattress with respect to lying on a specialised, minimum tissue deformation mattress (which closely conforms to the body contours), we used a three‐dimensional anatomically‐realistic model of the adult female buttocks. The strains and stresses in the subdermal soft tissues reached peak values of 65% and 2.4 kPa for the regular mattress, respectively, but always remained below 45% and 1.2 kPa for the minimum tissue deformation mattress, which indicates longer safe times for supine support on the latter mattress. Our work demonstrates that alleviation of localised, sustained stress concentrations through good immersion and envelopment of the support surface protects from pressure ulcers, and has the potential to relieve chronic pain which is associated with the pressure ulcer risk.

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.

Evaluation of interface pressure and temperature management in five wheelchair seat cushions and their effects on user satisfaction

BACKGROUND

Factors such as the manufacturing materials, shape or even the mechanical and thermal response of sitting Pressure Redistribution Support Surfaces (PRSS) can be potential contributors to pressure ulcers. However, few studies have compared a number of characteristics of the most frequently used devices.

OBJECTIVE

To compare three potential contributors to pressure ulcers in five commercial PRSS: pressure redistribution, temperature and perceived comfort.

METHOD

Study with a cross-over randomized design in healthy volunteer participants. Data was collected in a temperature and relative humidity controlled environment. To assess thermal response, the temperature (Flir-E60) of the region of interest was captured before and after use of each PRSS for further analysis. The region of interest was the gluteal zone. To assess the pressure redistribution a pressure mat (XSensor®) was used between the 5 cushion and each study participant using a standardized method. Finally, a subjective perception questionnaire recorded comfort, adaptability and thermal sensation parameters. Data analysis levels of significance were set at 0.05.

RESULTS

A total of 22 participants completed the assessments. There were no statistically significant differences in baseline temperatures between PRSS (>0.05). Pressure redistribution analysis showed significant differences between all PRSS in all variables evaluated except in the maximum and peak pressure index al sacrum. The subjective assessment suggested no major user-perceived differences between PRSS.

CONCLUSION

Seat cushions made of open cell polyurethane foam blocks of variable hardness and the horseshoe cushion (also open cell polyurethane foam) seem to provide a more effective pressure relief characteristic than those injected with polyurethane foam and gel in most of the studied pressure variables. However, the cushions provide similar thermal response and perceived comfort.

An investigation into the effectiveness of a novel wheelchair seat-cover assembly for the reduction of forces exerted onto the buttocks

Purpose: This purpose was to investigate developed seat-cover assemblies' effect on decreasing the fluctuation of the shear force exerted onto the buttocks as the factors causing decubitus ulcers when the back-support was inclined.Materials and Methods: The participants were 10 wheelchair users. The force plate was used to measure the horizontal force as the shear force. The back-support was inclined at increasing angles, starting from the upright position (IUP), then proceeding to a fully reclined position (FRP), and returning to the upright position (RUP). The experimental conditions were two conditions; the seat-cover assembly conditions and without the seat-cover assembly as the control conditions.Results: The average values in the seat-cover assembly condition were 14.4 ± 3.3, 13.9 ± 2.3, and 17.3 ± 3.3% body weight in the IUP, FRP, and RUP, respectively. The average values in the control condition were 14.8 ± 2.6, 11.4 ± 1.7, and 24.0 ± 6.7% body weight in the IUP, FRP, and RUP, respectively. In the FUP and the RUP, there were significant differences between two conditions (p < .01).Conclusion: These results suggested that the shear force exerted onto the buttocks may to be decreased by using novel seat-cover assembly.Implications for rehabilitationIt is possible to decrease the fluctuations in the shear force by moving the body up and down according the novel seat-cover assembly attached the back-support incline.Disabled, older individuals can be provided with a comfortable life on a reclining wheelchair while preventing decubitus ulcers.

Influence of back support shape in wheelchairs offering pelvic support on asymmetrical sitting posture and pressure points during reaching tasks in stroke patients

Many poststroke hemiplegic patients have an asymmetrical wheelchair-sitting posture. This study aimed to investigate the impact of different back support shapes on asymmetrical sitting posture and pressure points among poststroke hemiplegic patients during an activities of daily living–related reaching task. This study included 23 poststroke hemiplegic patients who performed tasks that involved the movement of objects using the unaffected upper limb to the affected side while sitting in a conventional wheelchair (C-WC) with a flat back support or a wheelchair providing pelvic and thoracic support (P-WC). Body alignment angles from video images and pressure distribution on supporting surfaces were measured using a two-dimensional motion analysis software (Dartfish) and a pressure mapping system (FSA). Regarding movement performance, although postural asymmetry increased in both wheelchair types, the degree of postural variation was smaller with P-WC use than C-WC use (p < 0.05), with partly reduced postural asymmetry. With P-WC, one-sided ischial asymmetrical pressure was significantly less after the movement (p < 0.05). In conclusion, P-WC’s back support shape contributed to a decrease in postural asymmetry for pelvic girdle support both at rest and during movement. This highlights the importance of a wheelchair back support shape and may help to increase the quality of activities of daily living movement in poststroke hemiplegic patients in wheelchairs.

Manufacturing custom-contoured wheelchair seating: A state-of-the-art review

BACKGROUND

Custom-contoured wheelchair seating lowers risk of pressure injury and postural deterioration while custom-contoured wheelchair seating lowers risk of pressure injury and postural deterioration while increasing the stability and functional activity of the wheelchair occupant. Producing custom-contoured seating systems has historically been a labour-intensive process custom-contoured seating systems is historically labour-intensive.

OBJECTIVES

Evaluate the strengths and limitations of current manufacturing processes for custom-contoured wheelchair seating to suggest potential future manufacturing processes.

STUDY DESIGN

Literature review of the state of the art.

METHODS

Research conducted through a literature review focused on the performance of different types of custom-contoured wheelchair seating products and processes over the last 40 years. Recent literature in orthotics and prosthetics was also consulted to assess future trends in seating.

RESULTS

There are five main manufacturing processes currently used to produce custom-contoured wheelchair seating systems. No single process is yet suitable for all wheelchair users, but many manufacturers are transitioning to computer numerical controlled (CNC) milling to reduce manual labour. Adjustable micro-modular seating and moulded seat insert manufacturing are also prevalent and offer alternative seating to soft foam carving.

CONCLUSION

There is a need in the custom wheelchair seating sector for processes that are fast, cost-effective, produce little to no material waste, and that can effectively maintain a comfortable seating micro-climate. Additive manufacturing may meet these criteria, but further evaluation is required.

CLINICAL RELEVANCE

This review suggests that the custom-contoured wheelchair seating manufacturers are moving away from labour-intensive processes towards digital techniques, like CNC foam milling. Additive manufacturing is a potential new process that may reduce overall costs, the lead time in preparing seats and has the potential to better manage the seating micro-climate.

Development and evaluation of a self-regulating alternating pressure air cushion

PURPOSE

To investigate the effect of alternating air cells of a newly developed dynamic cushion on interface pressure and tissue oxygenation levels.

METHOD

This cross-over experimental study included 19 healthy volunteers. The dynamic cushion used has an automatic self-regulating alternating pressure air-cell system with 35 small and four large air cells for maintaining posture while seated. This cushion also has 17 bottoming-out detectors that automatically inflate the air cells to release a high interface pressure. To assess the effect of this alternating system, participants sat on the new cushion with an alternating system or static system for 30 min and then performed push-ups. The interface pressure was monitored by pressure-sensitive and conductive ink film sensors and tissue oxygenation levels were monitored by near-infrared spectroscopy. A reactive hyperaemia indicator was calculated using tissue oxygenation levels as an outcome measure.

RESULTS

The peak interface pressure was not significantly different between the groups. The reactive hyperaemia indicator was significantly higher in the static group than in the alternating group.

CONCLUSIONS

An alternating system has beneficial effects on blood oxygenation levels without increasing interface pressure. Therefore, our new cushion is promising for preventing pressure ulcers with patients with limited ability to perform push-ups. Implications for Rehabilitation A dynamic cushion was developed, which consists of a uniquely-designed air-cell layout, detectors for bottoming out, and an alternating system with multiple air-cell lines. The alternating system did not increase interface pressure and it significantly reduced reactive hyperaemia after 30 min of sitting in healthy volunteers. This cushion is a new option for individuals who require stable posture but have limitations in performing scheduled push-ups for prevention of pressure ulcers.