Children’s cognitive and psychosocial development is influenced by their ability to move independently in their environment.1–5 For children with moderate-to-severe disabilities, powered mobility has been shown to be an effective method to achieve independent mobility as well as improve psychosocial and cognitive developmental skills.6,7 Investigators agree on specific skills as critical to independence in power mobility, such as the ability to drive towards a target, move through doorways, and maneuver around objects.8–11
Selecting the most appropriate power chair is a complicated process for the therapeutic team. Many factors must be considered in making this decision. These include, but are not limited to: the user’s abilities, positioning needs, environmental setting(s), and economic considerations.12 Physical therapists are integral to the wheelchair assessment and prescription process.13 Technology related to power mobility is changing rapidly. New options are available each year, which makes choosing the power wheelchair itself an important part of the prescriptive process. Choosing the wrong chair may lead to frustration and eventually abandonment when functional mobility could have been achieved with a different device.14
Prescription of a mobility device involves a multifactorial approach with both user and technological considerations.15–17 User considerations include motor, sensory, vestibular, cognitive, and visual skills while technological considerations include the chair components, the access method, and the seating system. Two technological factors have been identified as having an effect on power mobility. One factor is the type of control interface, or the means by which the wheelchair is maneuvered, and the other is the electronic system that controls the wheelchair.16 Recent improvements in technology and the production of a variety of drive wheel configurations have complicated the process, and added a third factor. Drive wheel configurations include the traditional rear-wheel drive (RWD; Fig. 1a), front-wheel drive (FWD; Fig. 1b), and mid-wheel drive (MWD; Fig. 1c).
The location of the drive wheel affects wheelchair handling and steering. Axelson and colleagues18 have described the advantages and disadvantages of each configuration. The RWD is historically the oldest model and is the only one in which the drive wheel pushes the chair. The drive wheel is located behind the user, causing the chair to have a large turning radius, making it more difficult to maneuver in small spaces and through doorways. The RWD chair has better traction going uphill than going downhill. The FWD configuration locates the drive wheel slightly in front of the user’s trunk. This drive placement produces a smaller turning radius than the RWD. A disadvantage of this configuration is that the back of the chair swerves at higher speeds. Front-wheel drive chairs have good traction going downhill but can lose traction over sandy or slippery surfaces when going uphill. The MWD is the newest design. The drive wheel is located under the user’s center of gravity. This placement results in a smaller turning radius, compared with the FWD and RWD, without compromising stability. The MWD appears to be the easiest to maneuver in tight spaces, and its navigation on hills is secure both in going uphill and downhill.18 Approximate turning radii for the Invacare adult RWD chair is 33”; the MWD is 23”, and a FWD is 25”. These turning radii are similar to other manufacturers’ specifications. Verification of reported turning radii in our clinic confirmed that measurements were within one inch of those stated in the manufacturers’ literature. Drive-wheel comparisons have not been reported in the literature.
Methods of assessing readiness and functional skills, which are necessary for independent power mobility use, have been published.8,19 Assessment forms, although not standardized, are available to ensure a complete evaluation of users’ needs related to seating components such as cushions and external supports.12 There are also guidelines to document clients’ improvements during the power mobility training process.10 Although these seating and readiness assessment forms are helpful in the decision-making process, they do not offer guidance in choosing the power chair itself.20 Therefore, the purpose of this case report is to describe the clinical decision-making process used to select a power chair for a child with multiple disabilities. We describe the physical therapist’s assessment and training of the child for power mobility using both RWD and MWD power chairs. The clinical decision-making is partially based on evidence-based practice as described by Sackett,21 specifically the weighing of clinical expertise, evidence, and patient values.
Participant and History
Jill was delivered at six months gestation, by Caesarian deliver, weighing one pound, twelve ounces. Shortly after birth, a grade four intraventricular bleed was discovered. Early intervention services were initiated at approximately one month of age, and she was diagnosed with spastic quadriplegic cerebral palsy at six months of age. She lived at home with her parents and an older sibling and began attending school at a cerebral palsy center from the time she was three years old through the time this report was prepared. In the school setting, she received physical, speech, and occupational therapies. Her family was very supportive and wanted her to explore her environment.
At nine years of age, Jill was classified at level V of the Gross Motor Function Classification System (GMFCS).22 At Level V of the GMFCS, children between the ages of six and 12 years cannot sit, stand, or walk, and use assistive technology extensively. Jill’s passive range of motion was within functional limits at all joints. She presented with underlying hypotonia of the trunk and, based on the Modified Ashworth Scale,9 grade four spasticity in her upper and lower extremities. Jill’s upper-extremity function, specifically active reaching or grasping, was severely impaired. When she was excited, her limbs postured in extension. Her grasp was nonfunctional bilaterally. She was able to roll independently from prone to supine but required assistance for all other forms of mobility. When prone, she was able to lift her head to midline for periods of up to 10 seconds and, when placed prone on elbows, she was able to attain and maintain her head in midline for up to 10 seconds. She required maximal assistance to maintain sitting, demonstrating poor head control and only attaining neutral alignment for brief periods while tending to keep her head/neck flexed. To maintain a neutral head alignment when fully supported in her wheelchair with a tri-pad headrest, she required physical assistance or verbal cues 20% of the time. When presented with sudden visual stimuli, Jill had a startle-like reflex that caused her to close her eyes and extend her trunk, head, and arms. She was unable to propel a manual wheelchair.
Jill’s educational level, determined by the teacher, was reported to be at a kindergarten level and had not changed in the past two years. She followed two-step commands, rote counted to 10, and recognized colors and simple shapes. A developmental optometrist reported she was unable to sustain fixation, had nystagmus, esotropia, and her best field of vision was looking down at a 45-degree angle. Her speech was dysarthric, and she drooled copiously, requiring two to three bib changes per school day. She was positioned daily in a manual wheelchair with a solid seat and bi-angular back, trunk supports, abductor pommel, shoe holders, tri-pad headrest, and anterior chest harness.
Evaluation: Wheelchair Trial
Jill’s cognitive, physical, and visual impairments interfered with functional mobility. Her family and rehab team (a physical therapist an occupational therapist and a vendor) felt she would benefit from some means of independent mobility. In the absence of evidence from the literature, the therapist used clinical expertise and patient preferences, which in this case were provided by the parents, as the two main sources to inform the clinical decision to initiate mobility training.21 In this case, the parents’ preference was that Jill have independent mobility to advance her social, cognitive, and academic skills. The team agreed that power wheelchair assessment and training should be initiated.
Jill was nine years old when she first participated in the assessment for power mobility. Assessment began with RWD chair as that was the only wheelchair available at the time. Because the team felt her seating needs relative to head control were being met, the assessment began with determination of an access method (see Fig. 2).
Jill was unable to access a switch with her upper extremities, as she would pull into shoulder adduction, elbow flexion, and her hands fisted on attempts at active reaching with either upper extremity. Her posturing accidentally activated the switches placed on her chest. Use of her upper extremities was ruled out as an access method and assessment with a head array was initiated. A head array with three switches (forward, left turn, right turn) was placed on her manual chair. Her ability to move her head to access each of the three switches was assessed. A fourth switch that would be necessary for reverse was not used at this time. She hit the switch for forward and left turn 80% of the time upon request and the right turn switch 50% of the time. A RWD power chair with a head array and seating similar to her manual chair was configured.
Plan of Care and Interventions
Regular practice in a RWD chair with a three-switch head array was incorporated one time a week for 30 minutes or longer as tolerated during physical therapy sessions. Wheelchair mobility goals at this time were to be able to drive straight for 20 feet, stop before colliding with an obstacle, and turn right and left appropriately.
Jill began training in the power wheelchair at age nine years. Two months after the onset of training, she was unable to maintain her head on the access switch for greater than one or two seconds. She showed little interest in driving, indicating it was too hard for her. She was unable to attain a midline head position, so the head array was offset to the left to improve her ability to access the switches.
Jill was unable to stop and avoid a collision because her startle-like reflex, combined with her extensor posture, kept her head in contact with the array. To practice stopping without fear of collisions, training continued in a large open room without obstacles. Games such as requesting her to drive to a favorite object and rewards for success, including frequent verbal encouragement, were used. Despite these strategies, her frustration and the difficulty of learning to drive continued to be an issue. Both the team and the family valued independent mobility and felt she could be successful with practice. Therefore to minimize frustration, training continued on a limited basis of one time a week guided by her willingness to participate.
During the next two years, when Jill was 10 and 11 years old, training continued in this limited manner. She was then able to drive straight for 20 feet and required assistance to consistently turn left and right. Three years after the onset of training at age 12, there was an unexplained change in her attitude towards driving; she became more tolerant of the training tasks, less frustrated, and expressed a desire to be independent in her mobility both at school and home (see Fig. 2).
We speculate the major reason for her change in attitude was a change in her family’s expectations. Her family now encouraged greater independence. Both her physical and cognitive attention to training improved. Training sessions increased to two times a week, and she could avoid obstacles and turn in either direction with greater consistency. Her startle-like reflex was still present; however, she now maintained her eyes open 50% of the time when a collision was imminent. Having achieved this criterion, Jill’s parents were trained, and she tried the chair in her home. Her parents reported moderate success, stating she had hit a table, had trouble negotiating in the hall without hitting the walls, and became frustrated. They believed Jill was nervous and felt her nervousness affected her driving. Both Jill and her parents expressed their desire to continue training.
The team decided that power mobility was a viable option for Jill. Her negotiating obstacles and the timing of collisions pointed to difficulty with timing her head movements with the movement of the chair. The team hypothesized that Jill would perform better in a MWD chair compared with a RWD. They felt that a decrease in turning radius would result in driving with fewer collisions and changes in direction. It was also felt that because her center of gravity would be over the drive wheel driving might be more intuitive and congruent with her motions. Specifically, there would be lower cognitive demands than when driving the rear wheel chair. In the traditional RWD configuration, the drive wheel is behind the user so when she needed to turn she actually had to go past the point where she wanted to turn and then command the chair to turn. Clinically, the treating therapist had observed children typically began turning into a doorway too early and therefore collided with the doorjamb.
Jill was 12 years old when a prescription was written for a MWD chair with a head array, trunk supports, abductor pommel, anterior chest harness, and shoe holders. Practice and use of the RWD chair continued in school for six months until the MWD chair arrived. Frequency of RWD use increased gradually, beginning with supervised driving to therapy sessions, the lunchroom, and the bathroom. Jill’s classroom and gym teachers, as well as classroom aide, were instructed in chair use. Within three months, she began using the RWD chair throughout the school day with distant supervision. Once the MWD chair arrived (Fig. 3), she was given a fourth switch mounted by a universal mount placed anterior and to the right of her head. To reverse and put the chair in standby she needed to access this switch by removing her head from the headrest. She quickly grasped the concept of the fourth switch and managed it within the first day of training.
To compare wheelchair configurations and quantify Jill’s driving ability, she performed three tasks8 These included: driving the chair through a standard-width doorway; maneuvering through three cones set three feet apart, and driving the chair through a 100-foot hallway with typical school traffic. The chosen tasks were consistent with those used in the study by Furumasu et al.8 In that study, the authors completed a task analysis on skills commonly trained and evaluated in power training. They then had recognized professionals in the area of power mobility review them for agreement and pilot tested the chosen items.
Testing was performed first in the RWD and one month later on the MWD chair. Jill was given three attempts at each task, completing three trials before progressing on to the next skill. All attempts were completed on the same day with the same evaluator observing and scoring each task. The number of collisions was recorded for each attempt and the average calculated for the final measure (Fig. 4).
Jill was given two weeks to train in the MWD chair before the same tasks were repeated and scored by the same rater. Repeating the tasks was done for two reasons. The first was to confirm the team’s hypothesis that the MWD chair would be more intuitive and less cognitively demanding for Jill thereby making her more efficient and accurate in tasks that required turning. The second reason for repeating the tasks in the MWD chair was to provide evidence to support the use of clinical expertise in the decision making process. In the absences of evidence in the literature, clinical expertise is often relied upon when making decisions regarding patient care. By repeating the tasks and providing evidence of improved performance, it helped to justify the clinician’s decision to prescribe a MWD chair, a decision that was based on expertise rather than scientific evidence. The speed, acceleration, and torques were kept as consistent as possible for the two chairs. However, although the same manufacturer made both the RWD and the MWD chairs, subtle differences in their motors and electronics may have caused differences in their performances.
Results of the two sessions are documented in Figure 4. The number of collisions decreased when Jill used the MWD chair to perform all three tasks. Collisions for moving through a doorway decreased from six collisions to one; for maneuvering through three cones from five collisions to two and in the hallways from six to two.
Approximately one year after completing the tasks in her MWD chair, she was asked to perform the three tasks again in a RWD chair. Her performance at that time also is charted in Figure 4. Her abilities in moving through a doorway and negotiating the school hallway in a RWD chair had improved to a point where they were equal to her skills in the MWD chair. However, her abilities to negotiate around the cones did not improve at all. One year after receiving her MWD chair, Jill completed all three tasks in the MWD chair without any collisions. She also won the obstacle course race in the local Special Olympics even though all the other competitors drove with a joystick.
This case describes the examination and intervention for power mobility of a preadolescent with multiple disabilities. The child’s readiness for the wheelchair mobility emerged approximately two and a half years into the episode of care. The team selected a MWD chair based on reported attributes of the chair and the abilities of the child. Once in the MWD chair, the client rapidly acquired basic mobility skills.
The wheelchair examination and intervention process was potentially prolonged because wheelchair readiness was not assessed early in the examination. We did not have access to a wheelchair readiness assessment, such as the one developed by Furumasu and colleagues.8 Had we used the cognitive assessment battery described in their study, training could have been customized to address any deficits. In Jill’s case, the team felt she had the cognitive skills necessary to be functional in a wheelchair. However, they suspected that behavioral issues, such as a low tolerance for any new activity, were a limiting factor.
Although a readiness assessment may have expedited the wheelchair prescription process, time spent in the wheelchair, we speculate, was still beneficial in the final acquisition of wheelchair mobility. It has been shown that level of independence with power mobility for children with severe involvement is correlated to the amount of time spent in the chair but not to IQ or level of motor impairment.6 In Jill’s case, length of training time appeared to be correlated with achieving independence and therefore supports the findings of the literature. However, it cannot be definitively established if it was Jill’s readiness or simply that she needed a significant amount of time training in the chair to achieve independence.
The data in this case are not sufficient to imply a required or even a suggested amount of time to allow for practice. However, it would appear that clinicians should provide many opportunities for wheelchair readiness assessment as well as practice. Jill was able to continue training because her clinical setting allowed therapists extended time and flexibility to work on skills, without constraints placed by third-party payers.
Motivation and level of frustration also were factors in the length of time it took for Jill to achieve independence. Although factors such as personality, age, or maturity level cannot be modified, the team can reduce patient frustration by choosing the appropriate equipment. For example, in this case, when Jill’s team realized she could not maintain a midline head position, they offset the headrest to the left, reducing Jill’s frustration with the task. Introduction of power mobility is often the first opportunity children have to move and explore their environment independently. It is important to motivate them in learning these new tasks. Motivation may take the form of a reward from the parents, making training a game by playing tag or retrieving a favorite toy. Parent participation in the exploration of the environment to acquire wheelchair skills is also important.
The type of wheelchair used for examination and intervention was primarily a RWD; yet, the team prescribed a MWD. At the time, a review of the literature revealed no information on the effects of the different drive configurations. In the absence of evidence from the literature, the team used their clinical expertise and family preferences.22 This approach is consistent with using two of the three sources of information advocated by Sackett,21 that is, patient–family preferences and clinical expertise. The sources of information for evidence-based practice have been more recently updated by Straus.23 From the patient-preference standpoint: the family had consistently expressed their interest in Jill’s independent wheelchair mobility. From the clinical expertise standpoint: the team hypothesized that the center of gravity of the user being directly over the drive wheel would make a significant difference in Jill’s driving ability. Because of her visual dysfunction, having the turning wheel aligned with her head and line of vision would make it easier for her to process and maneuver. In addition, the team felt that driving the MWD chair was more intuitive and less demanding on Jill’s cognitive ability.
We speculate that the team’s hypothesis is partially supported by the speed at which Jill acquired skill in the MWD wheelchair. In the new wheelchair, Jill had identical seating, speed of the chair, and access method and in only two weeks acquired independent mobility. Furthermore, there were no changes in her cognitive status. The major difference in her performance in the MWD chair was her ability to negotiate the cones. This task requires the most turning and readjusting of the chair therefore it best illustrates the affect of the drive wheel being located under the user and the smaller turning radius.
A few questions have been raised by this case. Would it take less time to reach independence if training began immediately in a MWD chair? If the assumption is yes, then the question becomes, should a clinician always start training in a MWD chair? Criteria need to be established to help decide what user characteristics are best suited to MWD chairs and which are suited to RWD chairs. Would the screenings developed by Furmasu and colleagues help clinicians decide which type of chair to train in? The use of Furumasu and colleague’s power mobility readiness and wheelchair independence assessments comparing performance in both a RWD and MWD chair would have strengthened the clinical decision making in this case.
In this case, Jill drove her wheelchair with a head array. A case series of users driving with various access methods would be beneficial to see if performance of the chairs was consistent regardless of access method. This case only addressed indoor mobility in a school setting. Before the benefits of MWD can be fully established or generalized, they must be evaluated in all settings including outdoors and in homes. If the benefits of MWD can be established in a prospectively controlled study, it would have implications for clinicians involved in prescribing power mobility. The results of this case report indicate the importance of clinicians being aware of technological innovations, (in this case MWD chairs); and considering them for clients who may show ability to independently manage a power chair.
This case illustrates the examination and intervention related to wheelchair prescription. Although the child trained in a RWD chair, a MWD chair was prescribed. The selection was made in the absence of evidence, guided by therapist experience and patient needs. This process is consistent with contemporary perspectives of evidence-based practice. Wheelchair readiness, motivation and the type of wheelchair used appear to be salient factors in explaining this client’s acquisition of independent mobility.