Evaluation of a simple approach to modify the supporting property of seating foam cushion for pressure relief

Model construction and analysis of ride comfort for high-speed railway seat cushions

BACKGROUND

More and more people choose to travel by high-speed railway. The seats in these vehicles are an important contact point and comfort of the seat cushions needs attention.

OBJECTIVE

The aim of this study is to choose among three seat cushions, the one that creates most comfort for a high-speed train.

METHODS

Twelve healthy volunteers were selected to participate in the experiment. Three different surface shape models of high-speed railway seat cushions were used. The Seat Pressure Distribution Index (SPD%) was calculated and analysed. A 7-point Likert scale questionnaire was applied for subjective evaluation.

RESULTS AND CONCLUSION

The evaluation is based on subjective and objective data. The results showed that the front protruding cushion made the pressure distribution more even, while the flat cushion had the smallest SPD% and the static pressure was most evenly distributed. This knowledge was beneficial for the design of comfortable high-speed railway seat cushions.

Quantifying Dynamic Changes in Plantar Pressure Gradient in Diabetics with Peripheral Neuropathy

Diabetic foot ulcers remain one of the most serious complications of diabetes. Peak plantar pressure (PPP) and peak pressure gradient (PPG) during walking have been shown to be associated with the development of diabetic foot ulcers. To gain further insight into the mechanical etiology of diabetic foot ulcers, examination of the pressure gradient angle (PGA) has been recently proposed. The PGA quantifies directional variation or orientation of the pressure gradient during walking and provides a measure of whether pressure gradient patterns are concentrated or dispersed along the plantar surface. We hypothesized that diabetics at risk of foot ulceration would have smaller PGA in key plantar regions, suggesting less movement of the pressure gradient over time. A total of 27 participants were studied, including 19 diabetics with peripheral neuropathy and 8 non-diabetic control subjects. A foot pressure measurement system was used to measure plantar pressures during walking. PPP, PPG, and PGA were calculated for four foot regions – first toe (T1), first metatarsal head (M1), second metatarsal head (M2), and heel (HL). Consistent with prior studies, PPP and PPG were significantly larger in the diabetic group compared with non-diabetic controls in the T1 and M1 regions, but not M2 or HL. For example, PPP was 165% (P = 0.02) and PPG was 214% (P < 0.001) larger in T1. PGA was found to be significantly smaller in the diabetic group in T1 (46%, P = 0.04), suggesting a more concentrated pressure gradient pattern under the toe. The proposed PGA may improve our understanding of the role of pressure gradient on the risk of diabetic foot ulcers.

Evaluation of pressure and durability of a low-cost wheelchair cushion designed for developing countries

Pressure sores are a medical problem for wheelchair users worldwide. In developing countries this problem is more critical because of lack of access to specialized technologies and medical assessment. Seat cushions to relieve pressure represent one of best ways to prevent pressure sores for people with spinal cord injury, amputation, cerebral palsy, and other disabilities that require use of wheelchairs for long periods of time. The purpose of this study was to evaluate the performance of a low cost cushion, called the Tuball, designed for low-income communities in developing countries. The Tuball is made from bicycle inner tubes and plastic balls. Its durability and pressure-relieving characteristics were compared with the ROHOTM cushion and the foam cushions now used in Brazil. A sample of 30 participants tested the three cushions: 15 persons with paraplegia and 15 matched able-bodied persons evaluated the capacity of the cushions to distribute pressure. This study also addressed the use of samples of persons without disabilities to test wheelchair cushions.The Tuball cushion provided significantly better pressure distribution than the foam cushion. A t-test was used to compare disabled persons and non-disabled persons as samples in testing cushions. No difference between pressure distribution between non-disabled and disabled participants was found in testing the ROHO cushion or the foam cushion. However, both capacities of pressure distribution and HICPR varied between non-disabled and disabled participants for the Tuball cushion. To determine the useful life of the Tuball cushion, a fatigue test was conducted to simulate sitting and transfer. Both the Tuball and ROHO cushions withstood the equivalent of at least 1 year of use, whereas the foam cushion broke down.

Analysis of pressure distribution at the body-seat interface in able-bodied and paraplegic subjects using a deformable active contour algorithm

In this paper, a semi-automatic method for segmenting pressure distribution image-based data at the body-seat interface is presented. The purpose of this work was to estimate the surface and the load supported by the ischial tuberosity (IT) region. The proposed method involves three steps: (1) detecting the IT region using a pressure-distribution image gradient; (2) estimating the contour of the IT region by an iterative active contour algorithm and finally (3) estimating the percentage of the surface and the weight-bearing of the IT region in a group of able-bodied (AB) and spinal-cord injury (SCI) subjects. It was found in this study that the weight bearing on the IT for the spinal-cord injured group is distributed on half the surface in comparison with the AB group or the powered wheelchair users groups. The findings of this study provide insights concerning pressure distribution in sitting for the paraplegic and able-bodied.

Analysis of sliding and pressure distribution during a repositioning of persons in a simulator chair

This study was undertaken to investigate the effect of system tilt and back recline angles on sliding and pressure distribution of seated subjects. Ten able-bodied subjects adopted successively 12 postures on a multiadjustable simulator chair. The system tilt angle was varied from 0 degrees to 45 degrees posterior tilt, while the seat to back angle varied from 90 degrees to 120 degrees. A maximum of 40.2% of weight shift was found when combining a system tilt angle of 45 degrees to a seat to back angle of 120 degrees. Maximum value of 74 mm of sliding was observed for the acromion marker during repositioning. Significant weight shift at the level of the seat is obtained only when the system tilt angle exceeds 15 degrees in a posterior direction. We can put forward here that a small tilt < or =15 degrees can be used to adjust back pressure distribution, whereas large posterior tilts are used for an effective weight shift at the seat level. The peak pressure gradient remains in general in the interval of +/-30% from the neutral posture for the able-bodied subjects and is fairly constant at 15 degrees of tilt. A significant amount of displacement along the back and seat reference plane were found for the shoulder and hip markers, but this displacement does not necessarily correspond to a pure translation motion of the pelvic segment.