FAILURE OF SWITCHES USED WITH ASSISTIVE DEVICES FOR CHILDREN WITH DISABILITIES: A SURVEY STUDY

Paul A. Williams, MS
Research Instructor
Department of Orthopedic Surgery
Loma Linda University School of Medicine
11234 Anderson Street
Loma Linda, CA 92354
Voice/Message: (909) 824-4418
FAX: (909) 824-4820

Donna Anzai, MBA, OTR
Assistant Professor
Department of Occupational Therapy
Loma Linda University School of Allied Health Professions
Loma Linda, CA 92350
Voice/Message: (909) 824-4628, ext. 41343
FAX: (909) 824-4291
e-mail: danzai@ccmail.llu.edu

Clarence B. Starr, MA
Anderson School
San Bernardino County Unified School District
24302 E. 4th Street
San Bernardino, CA 92410
Voice/Message: (909) 388-6311
e-mail: starr.eee.org

Loralee Ward, OTR
11436 Havstad Dr.
Loma Linda, CA 92354
Voice/Message: (909) 478-0658

Mark Glover, OTR
122 Laval Crescent
Saskatoon, SK(Saskatchewan)
Canada S4N4T5
Voice/Message: (306) 931-7748

Darby Parkhurst, OTR
11436 Havstad Dr.
Loma Linda, CA 92354
Voice/Message: (909) 478-0658

Christen Borowicz Freeman, OTR
1688 East Main
El Cajon, CA
Voice/Message: (619) 593-5564
e-mail: otchristen@aol.com

Web Posted on: December 12, 1997

INTRODUCTION

For many individuals with disabilities, assistive devices are essential for accomplishing daily tasks and activities [3,8,15]. This is especially true for children with disabilities [15]. The early intervention of assistive technology with children allows for the development of important cognitive and communication skills [9]. As an example, children learn to interact with their environment through play which contributes to the emotional development of a child by providing a sense of mastery over their own bodies and over the environment [6,7,12]. Thus, assistive devices can play a vital role in a child's overall development [12].

One of the most important components of any assistive device is the interface between the child with a disability and the device [1,11,13,14,15]. This interface is what allows the individual to control or operate the assistive device. Since a switch of some type, in most cases, is the interface for an electronic assistive device it is the critical link between the individual and the device [1,3,11,15]. The importance of the switch can be understood from the human occupation or the environmental domains theoretical perspectives. The model of human occupation (MOHO) consists of three subsystems - motivation, habits, and performance. These subsystems serve as a foundation for human behavior which reinforces a balance of work, play, and rest in a person's societal roles [7]. One of the main occupational behaviors of a child is play. Through the process of play the motivation, habits, and performance subsystems are developed during childhood [7]. At this developmental stage, a child's primary role is that of a student. A child with a disability may have difficulties performing tasks associated with the role of student. Thus, problems may arise when an individual is occupationally dysfunctional because societal demands for productive and playful participation are not met or his or her behavior does not fulfill the urge to explore and master the environment [7]. Through the use of switches, the individual with a disability is enabled in performing the tasks required to fulfill his or her occupational roles, such as activation of a switch to turn on a device (e.g., toy, radio, television)[4,5].

However, to gain the full benefits of using an assistive device, it must be dependable. According to a study by Batavia and Hammer, dependability was identified as one of the four most important factors considered by consumers when purchasing an assistive device [2]. The reliability of an assistive device will be affected by the switch that controls it. If the switch fails, the assistive device will not be dependable, leading to non-use of the assistive device. This non-use may lead to decreased functional abilities and loss of freedom and independence for the child because of his or her ability to interact with the environment [10].

Although some investigators have examined the failure and abandonment of assistive devices, there are very few of these studies and essentially none on switches [10]. Therefore, the purpose of this study was fourfold (1) to identify the types of switches used by a specific group of children with disabilities, (2) to obtain demographic data on the sample population, (3) to determine the incidence of failure for different switch types, and (4) to investigate the possible factors and predictors associated with switch failure.

METHODS AND MATERIALS

Four local area schools were selected for participation in this study. Only thirteen classrooms with students utilizing switches were included in the study. Two surveys (General Survey and Individual Survey), which are described below, were used to collect the data for analysis. Standardized categorization of disabilities and switch types was necessary for proper data analysis. The disability classification system used by the San Bernardino City Unified School District was adopted for classifying the disabilities of the students. A modified version of a classification of switches found in the literature was adopted for the identification of switch types [8]. For each of the thirteen classrooms, the teachers were requested to gather all available switches. Each switch type was identified and counted. Then, each individual switch was tested to verify that it was in working order. In addition, all failed switches were collected, later examined for failure mode, and repaired, if possible.

The General Survey was utilized to establish overall switch usage in each classroom. One General Survey was completed for each classroom based on the available switches at the time. The survey consisted of 11 questions addressing the following for each switch type used in the specific classroom: number of switches available, number of switches being used, number of multiple user units, how often the switch was used, estimated total hours of usage per week, number of units used in the past 2 years, number of units broken in the past 2 years, and number of units abandoned in the past 2 years. In addition to the 11 questions, a section for comments and a clarification section with step-by-step instructions were included in the General Survey. The survey took approximately 10 minutes to complete and at least one member of the research team was present to answer questions and assist with the survey.

For each classroom, one Individual Survey was completed for each student (user) utilizing switches in that classroom. The survey consisted of two sections. The first part of the survey pertained to the user and the second part to the switch(es) being operated by the user. The user section defined the population using the switches (age, gender, race, disability, and manipulation skills). Manipulation skills were classified as smooth and controlled touch, somewhat controlled touch, or uncontrolled smack. The switch section of the Individual Survey consisted of eight questions relating to the switches used by the student. The questions addressed switch failure, whether the switch had been repaired, if it was currently being used, how often it was used, if the switch was being operated by the original user, if the switch was used by other children, and how well the switch performed with the user. If the switch was no longer being used, the survey included an area for an explanation of the reason. Each Individual Survey took approximately 3 to 5 minutes to complete.

RESULTS

In this study, 121 switches were identified and surveyed. Of these 121 switches, 68% were modified microswitches with the remaining 32% consisting of a variety of other switch types. Only four of the 121 switches were single user units with the remainder being multi-user units. The total number of hours of use per week for all of the switches surveyed combined was approximately 289.3 hours with the modified microswitches accounting for about 90% of the total. For all of the switches used during the last two years prior to the study (111) 36% were reported as failing. For the modified microswitches, this two-year failure rate was 32.5% and for all other switch types, the rate was 45.1%.

In this study, the largest age group of switch users was those between the ages of five and nine (38.6%), and the smallest group being those who were twenty years and older (7.1%). The male to female distribution was about equal with 34 males and 36 females. The greatest proportion of students was Hispanic (49%), the smallest proportion was American Indian (3%), with Caucasian being 31%, and Asian-American 4%. The predominant disability classification of the users surveyed in this study was found to be multiply handicapped (65.9%). Approximately 56% of the students in the sample population utilized the switches improperly (uncontrolled smack, grab, throw, twist, chew, pull wire or cable, etc. ).

Of the 17 failed switches collected and examined, 14 were noncommercially assembled or otherwise adapted with the remaining 3 being standard commercial switches. From the investigation of these failed switches, the two components that failed consistently were the switch mounting system, which mechanically supports the switch, and the electrical wiring. In some cases, there was no mechanical system for supporting the switch. In other cases, the mounting had become loose, allowing the switch to move and, thus, preventing the switch from operating properly. The electrical wiring problems included broken wires and poor connections. Of the 17 failed switches, 15 were repairable. Of these 15 switches, five failed due to poor mounting of the switch, seven failed because of poor electrical connections, and two failed by both poor mounting and connections.

DISCUSSION

For the group studied, the failure rate for different switch types varied between 30% and 45%. The most common switch type identified was the modified microswitch (buddy button, Big Red, Jelly Bean, etc.). The modified microswitch also had the lowest failure rate and highest use based on average hours of usage per week (almost three times that of other types). Almost all of the switches (>90%) were used by more than one student. This does present some difficulty in associating failure with different factors relating to specific users, yet it does not prevent some conclusions from being formulated. In a similar study, Phillips and Zhao found an abandonment rate for a wide range of assistive devices of 29.3%. They did not differentiate between failure and abandonment [10]. Using a similar definition of abandonment in our study, we found the abandonment rate to be approximately 34%.

The description of the majority of users for this study would be young (less than 10 years) multiply handicapped Hispanic or Caucasian children. This partially explains the frequency and types of misuse observed since we were dealing with young children with both physical and cognitive disabilities.

From the 17 failed switches that were collected and examined a few conclusions can be developed. Because less than 20% of the retrieved failed switches were commercially availed devices, it can be suggested that the commercial switches had better survival than those that were noncommercial. Examination of the data from the General Survey revealed that commercial, unaltered switches did have a lower failure rate than noncommercial switches. An engineering review and analysis of the retrieved failed switches discovered that most of the noncommercial switches that the designs were reasonably sound, but that the construction and fabrication were normally poor. Most of the mistakes found represented lack of sufficient knowledge and understanding of good fabrication and construction principles.

SIGNIFICANCE

From an occupational therapist's perspective the importance of this study is threefold. First, prescribing the switch type is very critical and can directly impact switch failure. By taking a preventive posture to failure of switches, the occupational therapist can anticipate and attempt to minimize breakage by selecting the most appropriate switch for specific student problems and abilities. Secondly, switch placement can also directly affect switch failure. With this in mind, there must be a balance between the location of the input device and its attachments with the cognitive and motor abilities of the student. Thirdly, the occupational therapist needs to be cognizant of the various products which offer alternative solutions. The creative application of this technical knowledge is important in order to be resourceful to meet the needs of the individual.

The significance of this study for the classroom educator focuses on the two concerns of switch cost and downtime. Clearly, the need to obtain new switches to replace broken ones is problematic. The process for the securing of funding to buy new switches can be very time-consuming. Secondly, when switches are nonfunctional, teaching "downtime" is created and the student skills cannot be improved. However, there are proactive strategies that can be developed that can be drawn from this study that can minimize these problems for the educator. Vigilance as a classroom tactic works in several ways. Constant awareness of student-switch interaction is paramount. Further, if switches are not in use, proper storage reduces potential accidents or misuse of the switch. Another approach is to secure loose switch fastenings by taping or clamping of wire inserts. Lastly, just prior to switch use, make sure all switch adapters are tight and working correctly.

The technical engineering issues resulting from this study involve the areas of education, design, and use of the switches. Educating rehabilitation professionals involved in the use of assistive devices with children in switch fabrication and modification can aid in reduction of failure. The assistive device designers and manufacturers can significantly reduce the likelihood of failure of switches by implementing designs and construction methods that will reduce the harmful effects of switch misuse. Furthermore, providing information on the selection, proper altering, and mounting of a switch can aid in preventing failure. Finally, practical engineering advice can be provided in a meaningful fashion to educators and allied health professionals.

REFERENCES

[1] "Input modes: their importance in the clinical application of electronic aids for disabled persons", (1979), Arch. Phys. Med. Rehabil., 60:516-521.

[2] "Toward the development of consumer-based criteria for the evaluation of assistive devices", (1990), J. Rehabil. Res. and Dev., 27(4):425-435.

[3] "Technology", (1993), Willard and Spackman's Occupational Therapy, Lippincott Co., pp. 325-340.

[4] "A comparison of the use of adaptive microswitches by students with cerebral palsy", (1987), Am. J. Occupational Therapy, 41(11):739-744.

[5] "Issues in the assessment of assistive devices in relation to functional performance of children with disabilities", (1990), Rehabilitation Engineering, CRC Press, pp. 80-86.

[6] "Play and Leisure", (1993), Willard and Spackman's Occupational Therapy, Lippincott Co., pp. 260-267.

[7] Model of Human Occupation: Frames of Reference for Intervention, (1993), SLACK Incorporated, pp. 145-175.

[8] "Technology, disability, and professional services", (1995), Assistive Technology for Persons with Disabilities, AOTA, pp. 5-32.

[9] "Using assistive technology for play and learning: children, from birth to 10 years of age", (1995), Assistive Technology for Persons with Disabilities, AOTA, pp. 131-161.

[10] "Predictors of assistive technology abandonment", (1993), Assistive Tech, 5(1):36-45.

[11] "Switches - the vital link", (1981), Special Education: Forward Trends, 8(4):11-13.

[12] "The child and technology", (1987), Advances in Clinical Rehabilitation, 1:77-114.

[13] "Interface modalities of technical aids used by people with disability" (1983), Am. J. Occup. Ther, 37:761-765.

[14] "Control units for operation of computers by severely physically handicapped persons", (1986), J. Med. Eng. Technol, 10:21-23.

[15] "Augmentative Input Interfaces for Handicapped Children", (1993), Ruston, Louisiana.