New Discoveries

Tracking Technologies: A Phase I Study to Validate Efficacy

General clinical consensus is that tracking technology increases power wheelchair driving efficiency… however, this has not been proven in any formal manner. So a phase I study was conducted to determine if, in fact, tracking technologies do increase driving efficiency and to determine if further research is warranted.

What Is Tracking Technology?

Tracking technology has been available on certain complex rehab power wheelchairs for a number of years. This technology is designed to keep the wheelchair “on track” without veering off course due to factors such as slopes and varied terrain.

How do chairs get off course in the first place? After completing a turn, a power wheelchair’s casters are skewed, or facing to one side. When a Forward command is sent (by activating the Forward switch), these casters “pull” the wheelchair to one side before straightening out and moving the chair in a forward direction. The consumer must activate the Left and/or Right directional switches to compensate for this. Varied terrain, slopes and inclines also “pull” the wheelchair off course by turning the casters.

Tracking technology compensates for these influences and keeps the power wheelchair on the course dictated by directional switch inputs. Several distinct technologies are used to achieve this. This tracking technology varies in design, but shares the same goal of increasing driving efficiency, particularly for consumers who use alternative access methods rather than a joystick.

Who Can Benefit from Tracking Technology?

Many people with physical disabilities are unable to self propel a manual wheelchair, control a scooter or use a standard joystick on a power wheelchair. In this case, a variety of alternative access methods is available. Most of these alternative access methods use switches.

Each switch activation moves the power wheelchair in a specific direction. Typically, the consumer uses switches to move the wheelchair Forward, Left, Right and Reverse. If the consumer is able to activate more than one switch at a time, a diagonal movement is achieved (e.g., activating Forward and Left results in diagonal movement between these two discrete directions). Switches can be placed in just about any position on the body where the consumer has control (e.g., hands, head, feet). A wide variety of switches is also available, from mechanical (e.g., plate and pneumatic) to electrical (e.g., proximity and fiber optic).

Improving efficiency in driving a power wheelchair is measured in decreased switch activations and decreased time to drive from one location to another. This is very important for consumers driving power wheelchairs, particularly with alternative access methods.

Reducing switch activations and time has many benefits for consumers. Physically, less motor effort is required, which saves energy and reduces fatigue. For consumers with conditions such as multiple sclerosis, saving energy is vital, as excessive fatigue can lead to loss of function.

For consumers with conditions that lead to increased muscle tone — cerebral palsy, traumatic brain injury — increased motor effort can lead to a further increase in muscle tone and resultant decrease in function. For consumers with muscle diseases — muscular dystrophy, spinal muscular atrophy, ALS — excessive motor effort leads to muscle fatigue and can limit the amount of time the consumer is able to drive. Reducing the amount of time it takes to get from location A to location B is critical for consumers who are students and need to get to that next class on time or who are employees and have to move about the workplace in a timely manner.

The Study Protocol

A protocol was developed and followed on June 20, 2011. A course was marked out on a smooth, level surface — a gym floor — with tape.

Four trials were completed. One volunteer (18-year-old female, no motor, sensory or cognitive limitations) drove in each of the four trials. Invacare power wheelchairs with G-Trac tracking technology were chosen, as the tracking feature on the chairs can be turned on and off with a programmer, allowing the same chairs to be used throughout the trials. Two study coordinators were present: One coordinator digitally recorded and timed each trial, and one coordinator recorded switch activations.

The first trial was with a mid-wheel-drive power wheelchair (Invacare TDX SP) and three AbleNet Jelly Bean mechanical switches (Forward, Left, Right) on a tray. Driving parameters were programmed and remained the same throughout the first trial. The time to complete the course was recorded, as were the numbers of activations of each switch. For each trial, the volunteer wheelchair user completed the course three times without tracking technology and three times with tracking technology. The numbers of switch activations for each of the three runs were averaged, and the averaged results were compared for course completion with and without tracking.

The second trial used the same mid-wheel-drive power wheelchair, but with a head array. The third trial used a front-wheel-drive power chair (Invacare FDX) with three switches on a tray. The fourth trial used the same front-wheel-drive power chair with a head array.

The Observed Results

Comparisons of averaged switch activations required to complete the course showed that significantly fewer switch hits were required when tracking technology was activated (57 to 76 percent less). Comparisons of average course completion times also showed that significantly less time was required when tracking technology was activated (38 to 52 percent less).

Discussion for Future Studies

This project was presented at the 2012 RESNA conference in Baltimore. The participants had a number of comments and suggestions for future efforts.

The subject of this study completed the course first without tracking and then with tracking, so participants were concerned that learning had improved efficiency. Future research should vary the presence of tracking technology.

It was also suggested that more subjects be utilized.

The subject was asked to move through the course while keeping a blue line of tape on the floor in the center of the wheelchair. Participants suggested instead using parallel lines of tape that the wheelchair would drive between, and to include an error count of how many times the wheelchair went over a line.

Participants also suggested that a longer straightaway and different angles be included in a course (the study course included only 90° angles).

Applying These Results to Your Clients

If you are working with a consumer who would benefit from tracking technologies, funding may be an issue if the tracking technology is not a standard feature. You could set up a course and compare driving efficiency with and without tracking to include in your documentation, using similar strategies to those in the study.

Tracking technology does, in fact, increase driving efficiency by reducing compensatory switch activations and time required to move between locations. This efficiency is critical for consumers, as driving efficiency reduces motor effort, energy expenditure and can prevent fatigue, loss of function and increased muscle tone.

Trial 1: MWD, 3 switches on tray

Trial 2: MWD, Head Array

Trial 3: FWD, 3 Switches on Tray

Trial 4: FWD, Head Array

Final Summary

This article originally appeared in the June 2013 issue of Mobility Management.

About the Authors

Lois Brown, MPT, ATP, is the rehab clinical education specialist for Invacare Corp., Elyria, Ohio. She is a frequent presenter on seating & mobility topics at industry events.

Michelle is an occupational therapist with more than 25 years of experience and former Clinical Director of The Assistive Technology Clinics of The Children’s Hospital of Denver. She is a well-respected lecturer, both nationally and internationally, and has authored 6 book chapters and nearly 200 articles. She is the editor of Fundamentals in Assistive Technology, 4th ed. Michelle is on the teaching faculty of RESNA, is a member of the Clinician Task Force and is a Senior Disability Analyst of the ABDA.

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