Conventional Wheelchair Research Articles

Development of an Omnidirectional Rolling Leg Mechanism for Application in a Locomotion Machine

The wheelchair is a superior assistive apparatus in open and flat spaces; however, in Japanese style houses, the conventional wheelchair has several drawbacks, including difficulty in negotiating tight corners and moving over obstacles such as thresholds, as well as damage to delicate surfaces such as Tatami mats. Therefore, we developed a new six-legged mobility assisting machine. The individual legs are designed to have a semi-circular arced sole, which can be made to roll like a wheel in the stance phase using a cam and crank mechanism. Therefore, the machine can move efficiently without vertical sway and can pass over step-like obstacles twice as high as those that can be passed over in a wheelchair having wheels with the same radius of curvature. Furthermore, the machine can move in any direction while keeping the passenger facing in the same direction. This is accomplished by simultaneously rotating all six legs around their respective vertical axes at the sole contact point. A 2/3-scale prototype machine (hexagon side: 232mm, height: 222mm, leg length: 100mm, and total weight: 8kg) produced smooth movement. The prototype has a velocity of 2.7m/min and a turning speed of 90degree/sec and has a passable step height of 13mm. The machine is easy to control because it is driven by only two motors: one for propulsion and one for turning.

Wheelchair special seating: need and provision

Special seating is needed by people who lack the postural ability to sit unsupported in a standard wheelchair. The majority of users are children and people with neurological impairment. Seating options range from sculpted cushions and backrests designed to be used with a conventional wheelchair, to customized, fully contoured seating systems.

Physiologic comparison of forward and reverse wheelchair propulsion

Objectives: Conventional wheelchair propulsion is physiologically demanding because of the small muscle mass that is used and the low mechanical efficiency of the movement. Previous research has suggested that a reverse wheeling technique might be more economical than conventional forward wheeling. The present study sought to compare the physiologic demands of forward and reverse wheeling techniques. Design: A repeated measures design was used to compare the dependent variables between forward and reverse wheeling techniques in the same subjects. Setting: Human exercise research laboratory. Participants: Ten able-bodied men. Intervention: Subjects completed graded, discontinuous exercise tests on a wheelchair ergometer, using both forward and reverse wheeling techniques. Main Outcome Measures: Oxygen uptake (V̇o 2), ventilation (V̇ E), and heart rate were measured during the last 30 seconds of each 3-minute exercise stage. Blood lactate concentration ([la]) and rating of perceived exertion (RPE) were determined immediately after each stage. Results: Repeated measures analysis of variance demonstrated that V̇o 2, V̇ E, heart rate, [la], and RPE were all significantly greater ( p < .05) with reverse wheeling compared with forward wheeling. Vo 2 values with reverse wheeling averaged 9% higher than forward wheeling at identical power outputs. Conclusions: Reverse wheelchair propulsion is physiologically more demanding than conventional forward wheelchair propulsion and does not appear to offer potential for improving the economy of wheelchair propulsion.

Physical Properties of a New Orthopaedic Supporting Material for Posture Control in Wheelchairs

Providing a support surface with an even pressure distribution for wheelchair occupants is one of the primary objectives in clinical practice. Consequently a new warp-knit fabric has been developed with the aim to provide a more ideal orthopaedic support. The fabric, which has been described in a US patent, comprises a lock-knit stitch with a laid-in yarn and is made by using three guide bars with nylon and elastic yarns. In a clinical trial it was observed that users found this new fabric system to be more comfortable than a conventional wheelchair material. The relationship between relevant fabric properties (including the supporting characteristics of the fabric) and the findings of the clinical trial were investigated. Comparisons of interface pressure were made on 5 nondisabled subjects sitting on a hard surface, a conventional wheelchair seat and the new fabric under different pre-stressed tension loading. Preliminary results indicated that the average pressure under the ischial tuberosities was red...

218 A PHYSIOLOGICAL COMPARISON OF FORWARD vs REVERSE WHEELCHAIR ERGOMETRY

The purpose of this study was to compare metabolic and cardiopulmonary responses for forward wheelchair ergometry (FOR) and reverse wheelchair ergometry (REV) at equal power outputs (PO) levels. Moderately active able-bodies (N = 21) subjects exercised at 3-min stages at PO levels of 15, 20, 25, and 30 W for each mode of ergometry. Oxygen uptake (VO2), pulmonary ventilation (VE), respiratory exchange ratio (RER), heart rate (HR), percent net mechanical efficiency (ME), revolutions per minute (RPM) and strikes per minute (SPM) were determined at each PO level. With the exception of RER, all the physiological responses (VO2, VE, and HR) were higher for FOR exercise (P < 0.05) than REV exercise. ME increased with PO and was higher (P < 0.05) for REV than FOR at each PO level. SPM values for the REV were lower (P < 0.01) by almost half of that for the FOR exercise, although RPM remained constant between modes during all four stages. In general, these data suggest that reverse wheelchair ergometry is physiologically more efficient than conventional wheelchair ergometry and should be studied further as an alternative method for wheelchair ambulation.

Effect of Wheelchair Design on Posture and Comfort of Users

The canvas sling seat and backrest incorporated into a conventional wheelchair provide a seating system which fails short of many basic ergonomic requirements, which may compromise the comfort, health and level of dependency of the user. The high incidence of back pain among able-bodied people gives rise to much concern. Yet although there are indications that a similar proportion suffer, back pain in the disabled population receives less specific attention. Two prospective studies were undertaken involving a total of 58 subjects. The first evaluated the effects of wheelchair design on posture and the second looked at the effects that this had on the comfort of the user. Posture was recorded using a technique for measuring spinal curves, and data on the comfort of each seat were collected by questionnaire. The studies evaluated three different seating systems. The first was that of a conventional model 8BL wheelchair; the second and third were experimental rigs incorporated into an 8BL frame. One rig had cushions chamfered to fit the concavities of the canvas seat and backrest and the second had a rigid base on which was mounted cushioning material. The unmodified 8BL was shown to encourage a kyphotic posture and caused discomfort in both able-bodied and disabled subjects especially in the neck and back. The two experimental rigs promoted an acceptable degree of lordosis and, although both proved more comfortable than the canvas seat, of the two the hard-based seat was preferred. The canvas sling seat and backrest incorporated into a conventional wheelchair provide a seating system which fails short of many basic ergonomic requirements, which may compromise the comfort, health and level of dependency of the user. The high incidence of back pain among able-bodied people gives rise to much concern. Yet although there are indications that a similar proportion suffer, back pain in the disabled population receives less specific attention. Two prospective studies were undertaken involving a total of 58 subjects. The first evaluated the effects of wheelchair design on posture and the second looked at the effects that this had on the comfort of the user. Posture was recorded using a technique for measuring spinal curves, and data on the comfort of each seat were collected by questionnaire. The studies evaluated three different seating systems. The first was that of a conventional model 8BL wheelchair; the second and third were experimental rigs incorporated into an 8BL frame. One rig had cushions chamfered to fit the concavities of the canvas seat and backrest and the second had a rigid base on which was mounted cushioning material. The unmodified 8BL was shown to encourage a kyphotic posture and caused discomfort in both able-bodied and disabled subjects especially in the neck and back. The two experimental rigs promoted an acceptable degree of lordosis and, although both proved more comfortable than the canvas seat, of the two the hard-based seat was preferred. Biography: Michele Harms qualified as a physiotherapist in 1982 and worked for four years at The Royal Free Hospital. During this time she spent six months in Cape Town at Groote Schuur Hospital on a working exchange. This study was initiated as a result of her interest in improving posutre and lessening the back pain felt by wheelchair users. Since completing this project she has been working as a superintendent research physiotherapist in the Bloomsbury Health District.

Microprocessor-based weight shift monitors for paraplegic patients.

The prevention of pressure sores for patients with spinal cord injuries includes pressure relief through the patient shifting position and, thus, weight. We have designed a microprocessor-based device to mount on the seat of a conventional wheelchair. This device has applications in hospital rehabilitation programs for improving patient care and in research to study the cause and prevention of pressure sores. It can use audible alarms, which can be disarmed, to train patients to regularly shift weight. The device stores in its memory data on the interval between and the duration of weight shifts. The contents of this memory can be transmitted to a laboratory microcomputer system and displayed in tabular, graphical, or histogram formats. This device is more versatile than previous timer-based systems, not only because its timer and alarm parameters easily can be reprogrammed, but especially because it can store and play back detailed data on the patient's performance. The device is powered by rechargeable NiCad batteries, which can last several days without recharging.

Low cost wheelchair.

This wheelchair is a new concept in wheelchair design, made entirely of readily available plastic materials and rear bicycle wheels. The chair does not require a cushion, weights only 12 kg with 100 mm front castors or 13 kg with 175 mm castors. It is easy to manoeuvre. The design allows this wheelchair to be used as a conventional wheelchair and a shower/commode chair. Side arms and brakes can be attached if required. The necessary materials are relatively inexpensive and generally available in most countries.

Modular seating for paralytic scoliosis: design and initial experience.

The conventional wheelchair sling seat provides little or no support to the spine of a child with myopathy or neurogenic muscular weakness. As the spinal muscles become weaker scoliosis may develop with associated deformity, pain and restriction of cardio-respiratory function. If muscle weakness is severe, the resultant fully developed deformity is virtually impossible to treat. Slowing the rate of increase of the deformity is, therefore, the most hopeful avenue of attack. This work addresses the hypothesis that custom moulded seating can increase sitting comfort and slow the rate of progression of spinal curvature in children with paralytic scoliosis, and further, that a range of standard or modular seats can achieve these goals at less cost. Previous work on this problem has ranged from simply padding the armrest, in order to distribute force over the rib cage, through to custom moulded seating. Our initial experience with custom moulding, using the bean bag evacuation and consolidation technique, produced several comfortable seats although the technique was labour intensive and therefore costly. This led us to attempt to develop a method of providing comfortable seating that would help control spinal deformity at reasonable cost. This paper describes the design of a standardized seating system for school age children with myopathy or neurogenic muscular weakness. Preliminary results indicate that this technique may have advantages over alternative methods of treatment. The radiological study is continuing.

Versatile wheelchair control system

An electric wheelchair control system is described that offers an increased ease of operation to conventional wheelchair users and makes it possible for persons with severe pathologic hand movements to control wheelchairs in a safe and satisfactory manner. The control system is designed so that its characteristics are easily adjusted by the therapist to match the patient's control abilities. Chair acceleration, maximum speed and joystick-position averaging are adjusted by means of plug-in modules. There is only a disconnect relay that is activated when the joystick is grasped or addressed with a mouth stick. This relay functions as a ‘deadman control’ by applying dynamic braking when the joystick is released. The absence of other relays results in noise-free operation. Cruise control is included to permit the drive motors to develop full torque automatically when required, regardless of the joystick position. This control system can be applied to any existing wheelchair that uses two motors for steering/propulsion, provided two batteries are used to provide a +6, 0, −6 or +12, 0, −12V supply. The design focused on portability so that the control system does not interfere with folding the wheelchair.

Workload and energy expenditure during wheelchair propelling.

In this investigation it was tried to evaluate the workload of wheelchair driving in physical units, i.e. watts or meter kg./sec. For this reason an ergometer was adapted so that subjects sitting in wheelchairs with fixed brakes, could hand frank it. They were asked to perform at a standard workload of ½ watt/kg. body weight and at 1 watt/kg. body weight for 5 minutes each. During this time heart rate, CO2 elimination, O2 uptake, minute volume of respiration and the RQ were continuously recorded or calculated. In a second procedure these subjects were asked to drive a conventional wheelchair 5 to 6 minutes at a convenient speed. During the last 2 minutes the V was measured with the Korfryani-Müller spirometer and samples of expired air were taken for O2 and CO2 analysis. The heart rate was recorded by telemetry. In a third procedure the subjects drove their wheelchairs for 5 minutes on platforms equipped with rollers so that the above mentioned parameters could be measured continuously. The data collected in the second and third parts of the experiment were projected on the graph of performance of ergometric experiments, and plotted along the X-axis to estimate the workload in watts. By this method it was possible to calculate the physical workload of wheelchair driving within a range of approximately ±5 watts.