Annually in Germany 10 Million patients are transported by emergency services. In a great number of cases the patients have to be transported over diverse obstacles, which is associated with enormous physical effort for the paramedics and longer mission times. In combination with an increasing rate of obese patients the transport is a rising problem for emergency services.
In the context of the project SEBARES a novel mechatronic rescue and transport aid is under development. An innovative self-balancing concept enables high mobility, compactness and speed for the transport of patients. Together with universal stair climbing kinematics, a compact patient chair and a docking interface in the ambulance a universal rescue and transport aid may help to speed up the transport and to reduce the physical effort of paramedics, and therefore improve the working conditions in emergency services.
Detailed information about the status quo in patient transport is essential but not yet available in literature, especially regarding the quantitative occurrence and ergonomic impact of obstacles. Therefore an objective survey at a local emergency medical service provider was conducted and 400 deployments could be quantitatively analyzed. Furthermore we conducted an Ovako working posture analysis (OWAS) to get information about the current physical working conditions and connected these results with the survey. This way we could show that the high physical workloads of paramedics are strongly connected to the frequent occurring obstacles like stairs and relieving transport aids, like the SEBARES system, are necessarily needed to improve the situation of paramedics.
To evaluate the ergonomics of the system in an early state and to get a first notion of the situational improvement for paramedics, a primary user study was conducted with a labtype. The system was evaluated regarding different body sizes, terrains and slopes, while the postures of the different subjects and their applied forces and torques were recorded.
Although self-balancing systems are in general well-analyzed and described, the application as a patient transport system entails several specific requirements. For instance, our field study could show that about 25 % of the patients are not cooperative during transport and therefore might influence the stability of the device control. To analyze this influence a parametric multi-body model was developed and validated experimentally. Simulation of different patient behaviors showed that the patient can critically influence the control loop especially by movements of his torso and introducing external forces such as holding onto a rail. Apart from system design modifications (e.g. for fixation of the patient), advanced control strategies which take possible movements of the patient into account are currently under development and evaluation.
To be able to overcome stairs the transport aid incorporates a stair climbing mechanism which is currently developed based on a comprehensive market and literature analysis. Exemplary scaled down functional models were build and used to conduct first experiments on different staircase models. This way issues and shortcomings could be identified early during the development process.
Different prototypes were set up regarding the stage of development. In an early phase a simplified prototype was used to develop the controller of the self-balancing mechanism on flat terrain. Later, a prototype was designed including the stair climbing kinematics, the developed control scheme, a user interface and patient seat. Finally, a study was conducted with simulated users guiding the system in a transportation scenario with a patient dummy. During the trials, user forces, joint angles and perceived usability were measured. The results showed that long-term acceptable ergonomic limits were met in over 90% of the time. Nevertheless, further developments are needed to improve the system e.g., enhancement of climbing speed.