User-centered practicability analysis of two identification strategies in electrode arrays for FES induced hand motion in early stroke rehabilitation.

BACKGROUND: Surface electrode arrays have become popular in the application of functional electrical stimulation (FES) on the forearm. Arrays consist of multiple, small elements, which can be activated separately or in groups, forming virtual electrodes (VEs). As technology progress yields rising numbers of possible elements, an effective search strategy for suitable VEs in electrode arrays is of increasing importance. Current methods can be time-consuming, lack user integration, and miss an evaluation regarding clinical acceptance and practicability. METHODS: Two array identification procedures with different levels of user integration-a semi-automatic and a fully automatic approach-are evaluated. The semi-automatic method allows health professionals to continuously modify VEs via a touchscreen while the stimulation intensities are automatically controlled to maintain sufficient wrist extension. The automatic approach evaluates stimulation responses of various VEs for different intensities using a cost function and joint-angles recordings. Both procedures are compared in a clinical setup with five sub-acute stroke patients with moderate hand disabilities. The task was to find suitable VEs in two arrays with 59 elements in total to generate hand opening and closing for a grasp-and-release task. Practicability and acceptance by patients and health professionals were investigated using questionnaires and interviews. RESULTS: Both identification methods yield suitable VEs for hand opening and closing in patients who could tolerate the stimulation. However, the resulting VEs differed for both approaches. The average time for a complete search was 25% faster for the semi-automatic approach (semi-automatic: 7.3min, automatic: 10.5min). User acceptance was high for both methods, while no clear preference could be identified. CONCLUSIONS: The semi-automatic approach should be preferred as the search strategy in arrays on the forearm. The observed faster search duration will further reduce when applying the system repeatedly on a patient as only small position adjustments for VEs are required. However, the setup time will significantly increase for generation of various grasp types and adaptation to different arm postures. We recommend different levels of user integration in FES systems such that the search strategy can be chosen based on the users' preferences and application scenario.

A user-centered design approach in the development of rehabilitation devices after stroke.

Involving users in iterative development processes is to be shown to increase the quality of health care devices and to prevent refusal. Successful use can only be achieved provided that the devices are accepted by its users. In this study potentials of user satisfaction surveys in the development of stroke rehabilitation devices are presented. The two arm-training devices Reha-Slide (RS) and Bi-Manu-Track (BMT) are assessed for patient satisfaction. The aim is to detect the satisfaction with the current state of certain aspects of the devices to obtain incentives for technical optimisation. Correlation analyses from the data of 18 patients show significant positive correlations between satisfaction with the introduction and the personal well-being during training with both devices, whereas no significant correlations are found between satisfaction with the introduction and the perceived safety. In the RS sample, a higher satisfaction with the training also correlates with a higher feeling of improvement. The results are used to derive improvement suggestions tailored to the systems and its users. The surveys are conducted as a method for improving the ongoing design process of innovative technical devices developed in the BMBF (Federal Ministry of Education and Research) funded project "BeMobil".