Aaron Greenbaum, Alex Ashoff, Brandon Daveler, Claire Hoelmer, Esteban Ruiz, Eric F Williams, Emma Harbert, Jorge Candiotti, Joseph Corrigan, Lauren Matevish, Nadwah Onwi & Nattasit Wongsirikul.
Most children in poor countries rely on donated, hospital-style wheelchairs that do not meet their basic seating, positioning, or mobility needs. Instead of offering the child numerous benefits, the wrong mobility device is more likely to prevent, delay, halt, or reverse the habilitation process and cause further complications. The goal of the PALM project is to design an adjustable, collapsible, lightweight, pediatric wheelchair platform that will be customizable in order meet the needs of children with a wide range of functional abilities while remaining affordable to families in impoverished areas. The design underwent ANSI/RESNA testing and was thoroughly evaluated by both clinicians and end-users at Teleton in Mexico.
Pediatric wheelchairs represent a unique challenge to wheelchair design, manufacture, and provision. Children with mobility impairments are more likely to have less physical strength, limited range of motion, and expend more energy performing activities than their able-bodied peers (1). A pediatric wheelchair must grow with the child (2), accommodate their need for easy maneuverability (3), and adapt to meet the child’s changing cognitive and functional skills (2, 4). The result of these variables is that a pediatric wheelchair must be lightweight and possess a large range of adjustment and customization. Without adjustability, the pediatric wheelchair may only fit the user for a few months before they outgrow it. All of these factors make proper pediatric wheelchairs expensive, and the more seating and positioning support a child needs, the higher the price. A wheelchair may also need to be replaced every three years due to wear and tear (5). While families in developed countries often have services to offset that cost—many children with disabilities in developing countries only possess healthcare if their family can pay for it out of pocket.
Most adults in developing countries earn less than $300.00 USD annually (6); so purchasing the appropriate wheelchair for themselves or for a family member is often simply impossible. The WHO estimates that 70 million people around the world require a wheelchair to adequately meet their mobility needs, but that only 13% of the people who need one have access to a wheelchair. The study also estimated that current production levels only produce around 3 million wheelchairs to meet an estimated annual need of 23 million wheelchairs (5), suggesting that there is a production gap of 20 million wheelchairs per year. There are a number of charitable organizations that provide free or low cost wheelchairs to people around the world; but due to the overwhelming need, and the high cost of appropriate wheelchairs, many of these organizations often donate hospital style wheelchairs in an effort to serve as many people as possible. Despite numerous studies demonstrating the risks of an ill-fitting wheelchair and the benefits of a proper mobility device, for many children, an improperly sized hospital chair is currently their only option.
A properly fitted wheelchair can help reduce or eliminate flexible postural deformities, and/or prevent fixed deformities from worsening, as well as prevent secondary morbidities. A user in a manual wheelchair that has the appropriate wheel alignment and axle location will see reduced stress on their upper limbs and a lower likelihood of repetitive strain injuries (7). The inclusion of a tilt-in-space seating function on a wheelchair can help prevent pressure ulcers and skin deterioration, reduce postural deformities, discomfort, improve head and trunk orientation, and help promote dynamic seating by the user; and a wheelchair with a reclining seat function can improve line of sight, upper torso control, reduce neck pain, and facilitate transfers to and from the wheelchair (8). The situation is more severe for children who need proper seating and postural support. According to the WHO, early childhood is the most important development period in a person’s life (9), and there is evidence that early interventions can improve many areas of development (10). However, the assistive technology that would serve these children best is far too expensive, and the result is that many children, if they even have a wheelchair, live their lives in an ill-fitting hospital style chair depriving them of many long-term benefits.
The current pediatric wheelchair options that would provide the necessary features for the habilitation and participation of children with disabilities cost more than $1,000, which is too costly for families in developing countries to afford, and too expensive for charitable organizations to distribute in the quantities needed. In addition the large production gap creates a need for wheelchairs to be designed to be mass-producible. Currently, the hospital style wheelchairs that are most economical for distribution are inadequate in their postural support features, have an average lifespan that is less than ten percent that of a rehabilitation wheelchair (11), and their poor design often results in device failure and injury to the user (12) as well as being a significant factor in technology abandonment (13).
The design objective of the PALM project was to create a pediatric wheelchair that could be used by children with a large range of functional and cognitive abilities, and at the same time mass-produced for a cost similar to the wheelchairs currently being distributed to developing nations by charitable foundations, such as the American Wheelchair Mission (AWM). The major design considerations were a large range of sizing adjustment, a full range of postural support and seating functions, and placement of the rear wheel to allow for a self-propel option.
PALM’s interdisciplinary design team (engineers, therapists, and designers), all students at the University of Pittsburgh, relied heavily on end user feedback for all aspects of the PALM project. This included input from clinicians with pediatric seating experience, information from previous focus groups and end-user interviews, as well as benchmarking of current pediatric wheelchairs and similar products (e.g. strollers). Additionally input was received from Chris Lewis, President of the AWM, as well as designers from TiLite and Drive Medical throughout the project. The PALM team utilized a project organization structure to design a pediatric wheelchair from its point of manufacture all the way through a fitting with a future client.
The PALM team utilized an iterative form of Ulrich and Eppinger’s “Complex System Development Process” throughout the project (14). Benchmarking and end user feedback were used to determine that the chair had to be lightweight, adjustable, collapsible, have both tilt-in-space and recline functions, elevating leg supports, the option for independent propulsion, and it needed to be constructed of materials easily found in developing countries. Models were constructed in SolidWorks after the initial chair design was completed. Weekly meetings kept teammates updated of new information, expected changes in how different aspects of the chair were going to interact with each other, and allowed for collaborative problem solving of challenging pieces of the puzzle. The Human Engineering Research Labs (HERL) machine shop staff and faculty were consulted on ease of manufacture, expected manufacturing processes, and estimated cost of manufacture. This constant feedback loop was invaluable and resulted in cutting out many of the unique, and potentially expensive, parts from the PALM’s current design.
After the design was finalized, the prototype was manufactured and assembled in the HERL machine shop; an activity that provided invaluable insight into the actual time and processes involved in the construction of the pediatric wheelchair. A total of two prototypes were built: one was taken to one of Teleton’s Children’s Rehabilitation Centers (CRIT) in Irapuato, Mexico for end user and clinician feedback, and the other underwent ANSI/RESNA testing to ensure that the PALM was a robust and viable design. Visiting one of the centers where the PALM would potentially be distributed allowed the design team to see their facilities, the extent of their shop capabilities, and obtain a concrete understanding of the actual need. Feedback gathered in Mexico and results from the standards testing have formed the basis for future work on the PALM project that will include refining the seating and positioning features as well as minor modifications to the frame itself.
The majority of the feedback received from clinicians and end-users at CRIT regarding the PALM design was positive. The CRIT center staff all felt the PALM’s ability to adjust to the size of the child, by either cutting or replacing tubes, would significantly lower what the center spent on new wheelchairs as their consumers outgrew previous chairs. PALM’s postural support features, including the tilt-in-space, the reclining back support, the elevating leg supports, and the cushions were also well received. In addition, the PALM’s ability to fully collapse the frame is essential because it significantly increases the odds of the child being able to attend school.
The biggest stakeholder critique was the placement of the PALM’s rear wheel. The design team struggled with a solution that would allow proper placement of the rear wheel for independent propulsion while keeping a tilt-in-space function and a collapsible frame. Most of the reviewers felt that the consumers would be better served if the PALM were available in both a self-propel and an attendant propelled model. They felt that many of the features essential to children with limited functional ability only add weight and additional modes of possible failure to a wheelchair designed for self-propulsion. The clinicians, while pleased with the chair’s adjustability, also requested modifications to make such adjustments quicker and easier. Their final critiques focused on upgrading the user securement system to a four point belt, adding clothing guards, lateral supports, including Velcro on the seat cushion for attaching a pommel, and increasing the length of the leg supports.
In addition to the end-user and clinician reviews, the PALM team also gained valuable feedback on the design through ANSI/RESNA standards testing. The PALM design was put through the full cycle of Section 8 Static, Impact, and Fatigue benchmarking tests. The PALM passed all of the static and impact tests with the exception of the rubber covers on the handles which did not adhere well enough to the metal. While undergoing Double Drum testing the spring pins that hold the back support sheered off successively a number of times (Type II Failure) and that resulted in an overall failure for the PALM. However, because the team was interested in the overall integrity of the design, the pins were replaced with bolts and testing continued. Once the spring pins were replaced, the PALM was able to successfully complete both the Double Drum test (200,000 cycles) and the Curb Drop test (6,666 cycles) with a 60 kg test dummy. In addition to finding an acceptable replacement for the spring pins, the team would also like to test future prototypes with both heavier weights and thinner gauges of steel to optimize the PALM’s performance.
The current PALM design will be refocused as an attendant-propelled pediatric wheelchair. The design team will focus on clinician and end user feedback including quicker and easier adjustment features, a more refined solution to collapse the frame, and the need for additional accessories. However, a major design consideration of this future work will be creating a platform using many of the same parts and pieces, which can be quickly and easily converted into a mass customizable pediatric wheelchair that is more appropriate for children who have the functional ability to self-propel. In addition, preliminary talks between the AWM and a factory in Irapuato, Mexico may lead to localized production of the final design and generate a model for the local manufacture and distribution of the PALM to CRIT centers throughout Latin America. Overall, the PALM design shows great promise for becoming a real solution that can provide the proper seating and postural support for less than a quarter of the cost of current market options.
The team would like to acknowledge the support they received from their Professor, Dr. Pearlman, and his two Teaching Assistants, Mary Goldberg and Maria Toro Hernandez, Dr. Rory Cooper, Garrett Grindle and the shop staff at HERL, Dr. Patricia E. Beeson our Provost, as well as Chris Lewis of the American Wheelchair Mission, Ricardo Guzman Director of Irapuato’s CRIT Center, Drive Medical, and TiLite.
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University of Pittsburgh/Human Engineering Research Laboratory
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