A Pediatric Knee Exoskeleton With Real-Time Adaptive Control for Overground Walking in Ambulatory Individuals With Cerebral Palsy.

Gait training via a wearable device in children with cerebral palsy (CP) offers the potential to increase therapy dosage and intensity compared to current approaches. Here, we report the design and characterization of a pediatric knee exoskeleton (P.REX) with a microcontroller based multi-layered closed loop control system to provide individualized control capability. Exoskeleton performance was evaluated through benchtop and human subject testing. Step response tests show the averaged 90% rise was 26 ± 0.2 ms for 5 Nm, 22 ± 0.2 ms for 10 Nm, 32 ± 0.4 ms for 15 Nm. Torque bandwidth of P.REX was 12 Hz and output impedance was less than 1.8 Nm with control on (Zero mode). Three different control strategies can be deployed to apply assistance to knee extension: state-based assistance, impedance-based trajectory tracking, and real-time adaptive control. One participant with typical development (TD) and one participant with crouch gait from CP were recruited to evaluate P.REX in overground walking tests. Data from the participant with TD were used to validate control system performance. Kinematic and kinetic data were collected by motion capture and compared to exoskeleton on-board sensors to evaluate control system performance with results demonstrating that the control system functioned as intended. The data from the participant with CP are part of a larger ongoing study. Results for this participant compare walking with P.REX in two control modes: a state-based approach that provided constant knee extension assistance during early stance, mid-stance and late swing (Est+Mst+Lsw mode) and an Adaptive mode providing knee extension assistance proportional to estimated knee moment during stance. Both were well tolerated and significantly improved knee extension compared to walking without extension assistance (Zero mode). There was less reduction in gait speed during use of the adaptive controller, suggesting that it may be more intuitive than state-based constant assistance for this individual. Future work will investigate the effects of exoskeleton assistance during overground gait training in children with neurological disorders and will aim to identify the optimal individualized control strategy for exoskeleton prescription.

An organosynthetic soft robotic respiratory simulator.

In this work, we describe a benchtop model that recreates the motion and function of the diaphragm using a combination of advanced robotic and organic tissue. First, we build a high-fidelity anthropomorphic model of the diaphragm using thermoplastic and elastomeric material based on clinical imaging data. We then attach pneumatic artificial muscles to this elastomeric diaphragm, pre-programmed to move in a clinically relevant manner when pressurized. By inserting this diaphragm as the divider between two chambers in a benchtop model-one representing the thorax and the other the abdomen-and subsequently activating the diaphragm, we can recreate the pressure changes that cause lungs to inflate and deflate during regular breathing. Insertion of organic lungs in the thoracic cavity demonstrates this inflation and deflation in response to the pressures generated by our robotic diaphragm. By tailoring the input pressures and timing, we can represent different breathing motions and disease states. We instrument the model with multiple sensors to measure pressures, volumes, and flows and display these data in real-time, allowing the user to vary inputs such as the breathing rate and compliance of various components, and so they can observe and measure the downstream effect of changing these parameters. In this way, the model elucidates fundamental physiological concepts and can demonstrate pathology and the interplay of components of the respiratory system. This model will serve as an innovative and effective pedagogical tool for educating students on respiratory physiology and pathology in a user-controlled, interactive manner. It will also serve as an anatomically and physiologically accurate testbed for devices or pleural sealants that reside in the thoracic cavity, representing a vast improvement over existing models and ultimately reducing the requirement for testing these technologies in animal models. Finally, it will act as an impactful visualization tool for educating and engaging the broader community.

Digital Wings: Innovations in Transition Readiness for Adolescent and Young Adult Transplant Recipients [corrected].

The Johns Hopkins University School of Medicine organized 2 multistakeholder symposia on February 2, 2018 and January 11, 2019 to address the problem of high graft failure in adolescent and young adult (AYA) solid organ transplant (SOT) recipients. Participants included international experts in transplantation, behavioral psychology, patient/parent advocacy, and technology. The objectives of the symposia were as follows: (1) to identify and discuss the barriers to and facilitators of effective transfer of care for AYA SOT recipients; (2) to actively explore strategies and digital solutions to promote their successful transfer of care; and (3) to develop meaningful partnerships for the successful development, evaluation, implementation, and dissemination of these digital solutions. Additionally, data were collected from 152 AYA SOT recipients demonstrating a substantial gap in how this population uses technologies for health-related activities, alongside an increased interest in an app to help them manage their transplant.

Design Advancements toward a Wearable Pediatric Robotic Knee Exoskeleton for Overground Gait Rehabilitation.

Exoskeleton assisted gait training in children with cerebral palsy (CP) offers the potential to increase therapy dosage and intensity compared to current approaches. Here, we report the design and characterization of a pediatric knee exoskeleton for gait training outside of a clinical environment. A multi-layered closed loop control system and a microcontroller based data acquisition system were implemented to provide individualized control approaches and achieve device portability for home use. Step response tests show the averaged 90% rise time was 45 ms for 5 Nm, 35 ms for 10 Nm, 40 ms for 15 Nm. The gain-limited closed-loop torque bandwidth was about 9 Hz with a 9 Nm amplitude chirp in knee flexion and extension. The actuator has low output impedance (<0.5 Nm) at low frequencies expected during use. Future work will investigate the long term effects of providing children with CP knee extension assistance during daily walking on gait biomechanics with, and without, the device.