José Laparra Hernández; Enrique Medina Ripoll; Amparo López Vicente; Juan Giménez Pla; Francisco Fos Ros; Ricard Barberà i Guillem; Juan V. Durá Gil; Rafael Mengual Ortolá; Pablo Iscar Perelló, Ignacio Bermejo Bosch*; L. Francisco Roldán Atienza;
Laura Martínez Gómez
Instituto de Biomecánica (IBV)
Universitat Politècnica de València
Camino de Vera s/n. Edificio 9C
46022 Valencia, España
* The IBV Health Technology Group, Bio-engineering, Biomaterials and Nanomedicine CIBER (CIBER-BBN)
The Instituto de Biomecánica (IBV) has been the technical leader of the European PUMA project for the development of an intelligent system for detecting and preventing pressure ulcers. The PUMA solution has been integrated into a wheelchair and consists of a system to detect the risk of ulceration based on smart textile sensors and a prevention system that is able to redistribute local pressures thanks to a dynamic cushion, to release pressure zones by the repositioning of the chair and to increase blood flow through functional electrical stimulation. These systems are controlled from a simple mobile application. The prototype has been validated with patients with spinal cord injury and professionals, yielding impressive social and healthcare results."
INTRODUCTION
Approximately 85% of people with spinal cord injury who depend on the use of a wheelchair (380,000 in Europe with more than 11,000 new cases each year) will develop a pressure ulcer (PU) during their lifetime. PU accelerate the deterioration of their health, lead to social exclusion and reduce their independent lifestyle. In addition, treatment costs exceed two mil millions euros per year in Europe alone.
PU are injuries on the skin and/or tissue caused by a reduction in blood flow. Excessive pressure or a pressure applied for a long time on bony prominences (e.g. the ischium) limits blood flow, setting off a vicious circle that is difficult to stop/revert and can reach until bone tissue (Figure 1).
Figure 1. Process of generation of pressure ulcers.
PU is a common problem forpeople with spinal cord injury because they lack the natural mechanisms that prevent their formation, such as adequate sensory perception, the ability to perform postural movements or appropriate compensation responses by the Autonomous Nervous System.
While 95% of all PU are considered preventable, 38.5% of them appear when the subjects are using devices to prevent ulcers such as pressure reliefe cushions. The fundamental limitations of current solutions can be divided into two groups. In the first place, the prevention strategies that these systems apply do not take into account the characteristics of the user, the level of risk and the context of use. Secondly, the few devices that are adapted to the user’s situation are based on the measurement of pressures, when the decisive parameter for knowing the real risk of emergence of a PU is the viability of the tissue[1].
Furthermore, today there is still a nonalignment between the user and technology, which hinders the acceptance of the current solutions by users, because they do not adequately meet their needs.
In this context, the objective of the PUMA project was to develop a definitive solution for the prevention of PU in wheelchair users. To achieve this objective, the system had to be able to reproduce the natural mechanisms of healthy users (persons without functional limitations) in order to prevent the occurrence of pressure ulcers.
Due to the complexity of the project, it was necessary to call on experts in smart textiles, electrostimulation, assistive technologies, biomechanics, ICT, etc. For this reason, the PUMA project has been led technically by the IBV with the collaboration of the PERA technological center in the UK and the CENTEXBEL technological center in Belgium. In addition, the companies QIMOVA (Denmark), BERKEL BIKE (Holland) and SENSING TEX (Spain) have participated by providing their business insight. Finally, the National Hospital of Paraplegics in Toledo and ILUNION have contributed by providing the vision of professionals and involved users.
Over the two years of the project, having a multidisciplinary team (engineers, designers, therapists, rehabilitation staff, social workers etc.) has been of key importance; as has our being able to permeate the design and the development of the product by leaning on People Driven Innovation (PDI) Methodologies.
METHODOLOGY
The work plan was organized in 7 phases over two years; the most important activities in each one of them are highlighted below.
The objective of Phase 1, led by IBV, was to define the concept of the PUMA solution (Figure 2). On the one hand, we collected the needs of the users, we characterized the tissues of patients with spinal cord injury and we analyzed strategies for repositioning users without functional limitations, that allow them to maintain their tissues in optimal conditions. The IBV also conducted a study to select the most appropriate sensors for assessing the risk of a PU, that were suitable for everyday use. To this end we analyzed sensors based on the measurement of the blood flow and the concentration of oxygen in the blood.
Figure 2. Concept of the PUMA solution.
During Phase 2, led by IBV, we defined the requirements of the various systems of the PUMA product. We also carried out risk analysis and we selected the trials that were necessary to obtain the CE mark of health products for what would be the final solution.
On the basis of the results of these two phases, we then undertook three phases in parallel, in order to develop the different components.
During Phase 3, two prototypes were developed:
1. A smart textile embedded in the cover of a dynamic cushion in order to obtain a map of pressures and to detect the areas of greatest risk.
2. Textile sensors to measure the impedance of the skin, which is related to the blood flow, and to measure temperature and humidity, thereby obtaining a reliable measurement of the viability of the tissue. These sensors were embedded into a pair of shorts together with textile electrodes by which to apply electrical stimulation.
IBV designed the distribution of the sensors and electrodes and the measurements of the shorts so that they should cover the variable anthropometric forms of wheelchair users and so that this population group would find it easy to fit and remove them.
During Phase 4, led by IBV, we developed all the components associated with the wheelchair:
1. A dynamic cushion that allowed independent control of the different areas of the cushion and reproduced the micro-movements made by subjects without functional limitations in order to prevent PU.
2. A system to incline the chair that made it possible to reproduce the repositioning of these subjects in order to prevent PU.
3. A mobile application that makes it possible for spinal cord injuries to interact with the system; and for social and healthcare professionals to control the system easily, to alert the user and to customize the system.
During Phase 5, we developed the electronic and the control systems necessary for the management of the analysis and prevention systems included in the PUMA solution. Specifically, IBV’s activity focused on developing an algorithm based on the different sensors for the detection of PU risk and the intelligent management of prevention strategies depending on the risk, the user and the context.
Once the development phases were completed, we moved on to Phase 6, the integration of the final prototype and its technical validation. Among other validations, IBV was responsible for the regulatory validation that is applicable to health products associated with wheelchairs and cushions.
Finally, IBV led Phase 7 in which the validations of the different systems were performed both in the laboratory and in a real context in order to check their effectiveness and usability.
It should be noted that the users (people with spinal cord injury and social and healthcare professionals) have been involved throughout the project in such activities as the analysis of needs and the characterization of prevention strategies, the definition of requirements, the validation of the conceptual design, the validation of usability and acceptance and the final clinical validation. In fact, more than 100 users with different levels of spinal cord injury and more than 40 professionals involved in the social healthcare of this population group have participated in this project.
This important level of involvement has been possible thanks to the participation of the National Hospital of Paraplegics in Toledo and to ILUNION and to IBV’s experience in PDI methodologies in this area, combining in this project both subjective and qualitative techniques (daily studies, discussion groups, brainstorming, "thinking aloud", innovation workshops, etc.) with objective and quantitative techniques (pressure and blood flow measurements, analysis of movements, etc.).
RESULTS
The main outcome of the PUMA project has been a functional prototype integrated into an electric wheelchair that reproduces the behavior of users without functional limitations through three processes (Figure 3): (a) Real-time measurement of the condition of the tissues based on skin impedance, pressure, temperature and humidity, all performed by textile sensors embedded in a pair of short pants and in the cover of the cushion; (b) Assessment of the risk of PU and proposals for a set of strategies in terms of risk, the characteristics and preferences of the user and the context thanks to an intelligent system; (c) Optimal combination of chair repositioning, the movements of the dynamic cushion and electrical stimulation.
Figure 3. Final prototype and graph of functioning of the system.
The objective of the first process ("feel") is to collect key information with which to assess the viability of the tissue. To do this, the system registers the pressure, the impedance of the skin, the temperature and the humidity in the areas of risk through sensors incorporated into the cover of the dynamic cushion and the smart pants (Figure 4).
Figure 4. Systems for evaluation of the risk of PU by means of smart textiles.
The second process ("analyze and decide") is based on an algorithm developed by the IBV whose purpose is to assess the level of risk of PU depending on the condition of the tissue and the characteristics of the user. This algorithm proposes a set of strategies that reduce the risk of PU, endeavoring to alter as little as possible the daily tasks of the user and to adapt the strategies to their preferences.
As can be seen in figure 5, the mobile application developed by IBV allows the user to control the system easily, alerting him or her to the level of risk and offering the most appropriate prevention strategies to reduce the risk without affecting the everyday performance of their activities
Figure 5. App to interact with the system and to notify the risks and strategies used to prevent PU.
The objective of the third process ("Act") is to implement strategies that combine the 3 elements used to prevent PU (Figure 6): the movements of the dynamic cushion, the repositioning of the wheelchair and the application of electrical stimulation by electrodes embedded in the pants.
.Figure 6. Systems used to prevent PU: repositioning of the wheelchair, dynamic cushion and electrical stimulation.
The results obtained in the different phases of validation have allowed us to fine tune the system until we have achieved optimum functionality and adjustment to the real needs of users. In fact, during the clinical validation in a real context (Figure 7) we managed to keep the level of risk of PU in low levels during a week without affecting the daily life of users.
Figure 7. Validation of the system PUMA in real context.
In addition, patients and professionals have given us a remarkably high usability and acceptance evaluation, as shown in figure 8, with the exception of the aesthetic aspect where there is room for improvement, given that we worked with functional prototypes during the project.
Figure 8. Valuation of the usability and acceptance for the patients and the professionals. Scales of 1 (minor) to 5 (major).
We are currently working towards the launch of the commercial solution and we have patented the solution for its industrial exploitation. It should be noted that the commercial price of the system will be similar to the current cost of an electric wheelchair in the medium to high range, which makes it a highly competitive product, taking into account the extra functionalities and the intelligence inherent in the system.
The system can be seen in operation in the following video:
CONCLUSIONS
The work carried out during the past two years has enabled us to reach the following conclusions:
♦ The combination of measurements to evaluate blood flow together with the measurements of pressure makes it possible to reliably identify the level of risk of pressure ulcers using the algorithm developed by IBV.
♦ We have been able to combine in the best possible way, strategies for preventing pressure ulcers (the inclination of the chair, the movements of the dynamic cushion and the implementation of electrostimulation) depending on the risk, the context of use and user preferences.
♦ The PUMA system has received a warm welcome from wheelchair users and from social and healthcare professionals.
♦ The system is controlled in a simple and intuitive way by a mobile application that meets accessibility and usability requirements.
♦ The involvement of users through PDI techniques and the experience that IBV has accumulated with these population groups have been key to achieving a final product that meets user expectations.
All this allows us to affirm that the prevention of pressure ulcers is feasible from a technical perspective and potentially profitable from a market point of view.
For more information, visit: http://puma.ibv.org
ACKNOWLEDGEMENTS
This project has been funded by the European Union within the 7th Framework Program, under code FP7-SME-2012-315114.
To all users and professionals who have participated in the project.
[1]Tissue viability: The condition of the tissue at the level of oxygenation, nutrients, temperature, etc., related to the ease with which ulcers occur in the event of external factors such as prolonged pressure.
