Orthotic-Style Off-Loading Wheelchair Seat Cushion Reduces Interface Pressure Under Ischial Tuberosities and Sacrococcygeal Regions

Introduction: Pressure relief done by a spinal cordinjured patient is of utmost importance in order to prevent pressuresore formation. Some pressure-relieving techniques are describedin previous literature, but their effectivity has not yet been deter-mined on different wheelchair cushions.Null Hypothesis (H0): The null hypothesis (H0) stated for thistudy is that there is no difference in the effectivity of forwardleaning and forward leaning towards the left as pressure relievingtechniques for quadriplegic wheelchair users over the differenwheelchair cushions.Design: An analytical experimental study design using a convenient sample group of ten complete lesion quadriplegics (C6 to T1) was performed at the Physiotherapy Department,University of Pretoria.Method: Interface pressure (in mmHg) over the ischial tuberosities and upper thigh areas was measured using theTalley Oxford Pressure Monitor MKII with a 12-way matrix cell system.Results and Conclusion: The Friedman test for associated observations indicated statistically that the leaning diagonally forward pressure relieving technique is more effective for all three wheelchair cushions used in this study.

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Control Implementation for Real-Time Pressure Adjusting Seat Cushion to Prevent Pressure Ulcers

Volume 6: 14th International Conference on Multibody Systems, Nonlinear Dynamics, and Control ◽

10.1115/detc2018-86210 ◽

2018 ◽

Author(s):

Pavan Nuthi ◽

Wei Carrigan ◽

Charu Pande ◽

Muthu B. J. Wijesundara

Keyword(s):

Real Time ◽

Pressure Ulcer ◽

Time Pressure ◽

Pressure Profile ◽

Health Concern ◽

Ulcer Formation ◽

Interface Pressure ◽

Local Pressure ◽

Seat Cushion ◽

Control Implementation

External mechanical loading is a major contributing factor in pressure ulcer formation and is a major health concern for wheelchair users. Seat cushion technologies are employed to reduce the magnitude and duration of this loading using soft seating surfaces and pressure offloading techniques. However, pressure offloading often results in the creation of new high pressure points which can still lead to pressure ulcer formation. In order to mitigate the issue, a novel closed-loop controlled seat cushion system is developed with sensorized air cell arrays which can continuously monitor pressure profile of a seated person and modulate this interface pressure. This paper presents the control implementation of this seat cushion system using a novel scheduling control algorithm based on bang-bang control as well as the corresponding electronics and pneumatic layout. The effectiveness of the system is demonstrated for real-time pressure mapping, offloading, and redistribution of seating interface pressure and its capabilities of instantaneous local pressure measurement as well as automated pressure modulation are verified.

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Dynamic Seating Interface Pressures during Wheelchair Locomotion: Influence of Cushion Type

The Occupational Therapy Journal of Research ◽

10.1177/153944929801800404 ◽

1998 ◽

Vol 18 (4) ◽

pp. 182-192 ◽

Cited By ~ 2

Author(s):

Thomas W. Kernozek ◽

Jeff E.K. Lewin

Keyword(s):

Repeated Measures ◽

Dynamic Performance ◽

Pressure Fluctuations ◽

Sampling Rate ◽

Interface Pressure ◽

Low Profile ◽

Dynamic Seating ◽

Locomotion Speed ◽

Interface Pressures ◽

Ischial Tuberosities

Seat interface pressure distribution is measured statically in a clinical or research environment with the patient in a fixed position (static) if measured at all. The purpose of this study was to compare the dynamic seat interface pressures between three cushion types [2″ foam, Roho Low Profile (air), and Jay Active (gel)] during wheelchair locomotion. A total of 9 volunteer subjects (7 males, 2 females) participated in a study to determine seat interface pressure fluctuations between each of the 3 different wheelchair cushions. Seat interface pressures were measured with the Novel Pliance System, consisting of a 320×32 sensor matrix mat interfaced with a PC. Each sensor had an area of 1.5 cm2. Sampling rate was fixed at 10 Hz. Average pressures under the ischial tuberosities were determined and the average maxima and minima were calculated from 3 wheelchair locomotion cycles of 3 trials. Wheelchair locomotion speed was constant across trials and conditions (±107). A repeated measures analysis of variance (RM ANOVA) exhibited a main effect for cushion type [F(2, 16)=16.6, p < .05]. A Newman-Keuls pairwise multiple comparison found differences between the 2” foam cushion and both the air and gel cushions, but no differences between the gel and air cushions during wheelchair locomotion. It is important that clinicians and cushion designers understand the dynamic performance characteristics of specific cushion types. Cushion performance may enhance the effectiveness of seating systems in minimizing pressure fluctuations.

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Interface pressure and cutaneous hemoglobin and oxygenation changes under ischial tuberosities during sacral nerve root stimulation in spinal cord injury

The Journal of Rehabilitation Research and Development ◽

10.1682/jrrd.2005.08.0135 ◽

2006 ◽

Vol 43 (4) ◽

pp. 553 ◽

Cited By ~ 14

Author(s):

Liang Qin Liu ◽

Graham P. Nicholson ◽

Sarah L. Knight ◽

Ramesh Chelvarajah ◽

Angela Gall ◽

...

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Nerve Root ◽

Interface Pressure ◽

Sacral Nerve Root ◽

Sacral Nerve ◽

Cord Injury ◽

Ischial Tuberosities ◽

Root Stimulation

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Application of Goertzel Algorithm to Piezoresistive Pressure Sensing Fabric for Custom Fitting of Wheelchair Cushions

ASME Letters in Dynamic Systems and Control ◽

10.1115/1.4048934 ◽

2020 ◽

Vol 1 (2) ◽

Author(s):

Justin Trzeciak ◽

James A. Mynderse

Keyword(s):

Low Cost ◽

Sine Wave ◽

Pressure Sores ◽

Interface Pressure ◽

Pressure Sensing ◽

Wheelchair Users ◽

Common Location ◽

Goertzel Algorithm ◽

Ischial Tuberosities ◽

Seating Surface

Abstract Pressure sores are a costly, painful problem for wheelchair users, caused by prolonged periods of mechanical loading. A common location of pressure sores in wheelchair users is the tissue between the ischial tuberosities and the seating surface. The pressure exerted on the tissue, or interface pressure, can be measured using piezoresistive fabric. This work demonstrates the use of the Goertzel algorithm for efficiently acquiring interface pressure data from a fabric assembly consisting of a layer of piezoresistive fabric between two layers of fabric with conducting and non-conducting stripes. The Goertzel algorithm was used to sample sums of sine waves from the conductive columns of the fabric assembly and calculate the amplitudes of each component sine wave corresponding to the local interface pressure. The Goertzel algorithm is more efficient for this application than a fast Fourier transform due to the limited number of calculated frequency bins needed for this application and more freedom in choice of sample size. The algorithm was successfully used to generate two-dimensional, 32 × 32 sensel interface pressure maps once per second. The Goertzel algorithm can be used in tandem with generated sine waves to measure interface pressure from piezoresistive fabric. Low-cost, accurate interface pressure measurements will help lessen the risk of pressure sores in wheelchair users.

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Validation of an indentor system for evaluating truck seat cushions

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1243/095440703321645052 ◽

2003 ◽

Vol 217 (5) ◽

pp. 343-348 ◽

Cited By ~ 1

Author(s):

M Seigler ◽

M Ahmadian ◽

C Boggs

Keyword(s):

Pressure Distribution ◽

Dynamic Testing ◽

Interface Pressure ◽

Dynamic Complexity ◽

Seat Suspension ◽

System Validation ◽

Seat Cushion ◽

Seat Cushions ◽

Heavy Truck ◽

Variable Weighting

The objective of this study was to validate an indentor system—called a cushion loading indentor (CLI)—for use in objectively evaluating seat cushion performance for heavy truck seats. Included in this study is a detailed description of the five-component indentor design, with major components being a polyurethane buttocks mould and a variable weighting system. Validation of the CLI was performed by comparing its interface pressure distribution with five human test subjects for four different seating surfaces. The results demonstrate that the CLI is both more repeatable than the human test subjects and provides similar pressure distribution to that of a seated person. Furthermore, it is shown that the CLI is valid for dynamic testing of heavy truck seat cushions owing to the inclusion of the seat suspension, which significantly reduces the dynamic complexity between the cushion and the seated person.

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