Development and evaluation of a dual-output vocal cord vibration switch for persons with multiple disabilities.

PURPOSE A novel dual-output vocal cord vibration switch is described and evaluated for two individuals with severe motor disabilities and complex communication needs. An evaluative case series was performed to compare the new device to its previously proposed single-output counterpart in terms of accuracy, speed and user fatigue. METHOD In an ABAB design, participants were followed for up to 16 days as they performed several image matching tasks. Custom-written software recorded the average time taken to match each item, as well as the total number of selection errors. Participants reported their fatigue levels using a modified five-point Borg scale. RESULTS For one participant, the dual-output version significantly decreased task completion time and selection error (p > 0.05, Kolmogorov-Smirnov test), thus improving her communication ability. For the second participant, no significant differences were observed between the single- and dual-output systems. Fatigue associated with illness and self-reported stress with school exams were identified as limiting factors. CONCLUSIONS The dual-output vocal cord vibration switch provides a promising new alternative for individuals with severe and multiple disabilities who are able to hum or produce vocalizations. Both participants expressed desire to continue using the device for educational and entertainment purposes.