Multi-purpose bed tray system applied to hospital beds

Transcription

1 Multi-purpose bed tray system applied to hospital beds Cândida Malça 1 / Pedro Beirão 1 /. Pedro Parreira 2 1 Mechanical Engineering Department, Instituto Superior de Engenharia de Coimbra, Coimbra, Portugal 2 Entrepreneurship Department, Escola Superior de Enfermagem de Coimbra, Coimbra, Portugal candida@isec.pt pbeirao@isec.pt parreira@esenfc.pt Conference Topic CT 22 Abstract The technological development together with innovative methodologies enables the design of products that will benefit a specific population. This approach is particularly relevant when applied to temporarily or permanently bedridden patients whose mobility is significantly restricted. Within this context, the aim of this paper is to describe the design, development and construction of an innovative multi-purpose bed tray system to be applied to hospital beds. It is hoped that this innovating system will result in an optimization of healthcare human resources, and more importantly contribute to a significant improvement in patients quality of life and dignity. Key Words: Bed tray, Hospital bed, Bedridden patients, Healthcare, Patients life quality 1. Introduction Being bedridden has a considerable impact on the way of life of the persons affected by this condition. As a rule, the patient becomes dependent on outside assistance. A study carried out by Creditor (2) showed that three quarters of 75-year-old patients, who were independent prior to their admission to hospital, required assistance once they had been discharged. Zegelin [8] did research on bedriddeness from the perspective of people affected by this condition and he concluded that being bedridden with immobility has a negative connotation on the individual with disadvantageous effects and reduction in cognitive performance. Although this situation has a lot of complications, a survey reported by [1] has demonstrated through several studies (5.777 patients) that bed rest is extensively prescribed. The first larger scale studies on the disadvantageous effects of being bedridden were carried out in the 1940 s. They indicated thrombosis, decubitus problems and pneumonia as the major complications. Several studies described in [4], [6] and [7], among others, analysed the numerous pathological effects of bedridden patients: hypotension, reduction of breathing volumes, stomach secretions and shift of bodily fluids and electrolytes. As a consequence of bone calcium and muscular strength loss atrophy and joint contractures become more frequent. The first changes occur within two days and the consequences for older people are quite dramatic. So it seems important to develop healthcare specific devices that could stimulate the mobilisation and self-satisfaction of basic needs, increasing the autonomy and stimulating personal wellness. As a contribution, this paper describes the design, development and construction of both virtual and physical models of an innovative multi-purpose bed tray system with automated movements to be applied to hospital beds. The purpose is for patients to be able to perform some activities with the minimum or no aid from healthcare professionals. Thus, potential manoeuvrability of patients with disabilities or restricted mobility is valued, by increasing their dignity, autonomy, independence and self-confidence. The implementation of this multi-purpose bed tray system with automated movements aims first, to increase patients dignity and quality of life significantly and second to provide an effective optimisation of healthcare human resources.

2 2. Motivation The percentage of patients that, for medical reasons, need to be at absolute bed rest is high. For example, in Japan, approximately older adults are bed-ridden [3]. Being bedridden is one of the most usual occurrences in nursing that sensorial deprivation is quite closely associated with immobility. As a consequence, lack of stimulation leads to dulling senses and dependence, loss of surface and bodily sensation, role of fear, unfamiliar surroundings and reliance on assistance. Also the restricted space around the patient's bed implies that the placement of furniture to keep their personal items is often out of reach. As a result, patients have limited access to their belongings. The development of specific healthcare devices could, therefore, enhance the mobilisation and self-satisfaction of basic needs, increasing the autonomy and stimulating personal wellness. Hence, patient s independence and autonomy can be improved, thus contributing to a better quality of life. In hospital environment bed trays are a helpful accessory since they provide a stable surface to patients so that they can perform certain activities, such as eating, reading, and writing, among others. Bed trays are characterised by having a low degree of complexity with a simple construction and hence a low production cost. They are usually placed either at the bed side or at the bottom of the bed, taking much space with little flexibility in their use. When to be used by patients, it is sometimes necessary to resort to healthcare staff, which could be reflected in a reduction in human resource productivity. However, since they perform the tasks satisfactorily or which they were created, they are still used in hospitals without ever having undergone major changes. A typical model of a bed tray commonly used in hospitals is shown in Figure 1. Figure 1 Bed tray 3. Virtual model CAD model Prior to the prototype building, the development of a three dimension (3D) virtual Computer Aided Design (CAD) model is advised. The existence of a virtual model helps in fault recognition and in the implementation of improvements. Before be-ginning the design and development of the resulting prototype several initial factors were took into account for, such as: i) maintain the features of the bed tray currently in use, namely simplicity and low cost production; ii) upgrade the bed tray itself with some kind of automated motion system; iii) locate both the bed tray itself and the entire system in a proper place to minimise as possible the occupied space; iv) facilitate the work of healthcare professionals; iv) maintain

3 other features of the hospital beds, in particular the safety bar; v) adjust it to any hospital bed with minor modifications to the bed structure; vi) reduce the physical effort of patients. After studying some hypotheses it was concluded that the best place to couple the entire system would be at one side of the bed, as shown in Figure 2. Figure 2 Multi-purpose bed tray system applied to hospital bed The developed solution minimises the occupied space because both vertical and horizontal linear movements of the bed tray system are done automatically through a car driven inside a U shaped rail coupled alongside the bed structure, as shown in Figure 2. This bed accessory was also designed to perform other tasks, namely as a safety bar to protect the patient from falling off the bed. In addition to other competitive advantages of particular relevance is also the unnecessary presence of an additional bedside support frequently used for to the intake of meals. Since safety and hygiene conditions in hospital environment are quite rigid it is necessary to take into account several aspects, especially lubricants and material selection concerns. Components subjected to relative motions, as in the case of the car driven inside the U shaped rail, must be made with self-lubricating materials, since the use of lubricants is forbidden in hospital environment. Besides and in order to build a lightweight structure, characteristics such as lower density and high mechanical strength must be taken into account in the structure material selection. The automated linear movements of the bed tray system could not be done using hydraulic or pneumatic mechanisms. These systems cause a great deal of noise and they still require a pump, among other disadvantages. Thus the choice relies upon electric motors, as these cause low noise and do not require lubrication. Figure 3 identifies some of the main components of the multi-purpose bed tray system. A comprehensive description is given below. This novel healthcare device, enhanced with automated movements, aims to fulfil three complementary functions: the first one should allow for an automated linear horizontal motion (forward and backward) of the bed tray; the second one should allow an automated linear vertical motion (up and down) of the bed tray and the third one should allow a manual rotation movement of the bed tray. The automated linear movements mentioned above are controlled by the user (not necessarily the patient) through two sets of buttons of a remote control unit. The automated vertical linear movement of the bed tray (1) is performed by the electric motor (6) through the connecting element (2) of the arm (3). Inside the upper shaft (4) and the bifurcated lower shaft (5) although not shown in Fig. 3 there is a vertical threaded rod driven by the electric motor (6). Similarly, the automated horizontal linear movement of the bed tray (1) is done by the electric motor (11) that drives a horizontal threaded rod (10) throughout a car made with two linear guides (9) inside the U shaped rail (7), coupled alongside to the hospital bed by several supporting elements (8).

4 Figure 3 Main components of the multi-purpose bed tray system Figure 4 highlights the assemblage between the electric motor (11), responsible for the automated horizontal linear movement of the bed tray, and the horizontal threaded rod (10) that passes through the linear guides. Figure 4 Detail of the assembly between the electric motor and horizontal threaded rod Figure 5 details one of the two linear guides, showing the inward threaded sleeves (13) that make up the revolute joint (12). As stated above, the horizontal threaded rod passes through this component. Two linear guides were used to increase the structure strength when submitted to forces in specific positions. Additionally, vibrations related to the linear movements of the whole structure are diminished. Figure 6 shows the position occupied by the bed tray system when not in use. Figure 5 Detail of the linear guides

5 Figure 6 Rest position of the multi-purpose bed tray system As Figure 7 illustrates, the bed tray can also be used in a different position. Patients not fully bedridden can use it when seated sited on a chair. To obtain this alternative position it is necessary to remove the arm of the upper shaft and rotate it 180 degrees. Figure 7 Alternative position of the multi-purpose bed tray system A numerical analysis of critical structural components was performed using an automatic computational tool based on the finite element method. The multi-purpose bed tray system numerical model, directly obtained from the CAD representation and depicted in the top picture of Figure 8, was automatically divided into linear solid tetrahedral elements. The bottom picture of Fig. 8 illustrates, as an ex-ample of numerical analysis results, the maximum stress obtained for the bed tray support when a load of 350 N is applied on each one of its fixation points. Figure 8 Bed tray support stress distribution field

6 4. Physical model Prototype For a sustainable development and a better analysis of any project, the construction of a prototype is a fundamental task. Prototypes are helpful to implement and validate a given solution. Hence, one of the goals was to design and build a prototype able to demonstrate its features. With this prototype it will be possible to prove its viability and to define what can be corrected in the future from an optimisation point of view [5]. At this development stage there is no need to fully comply with the final design specifications, namely in what concerns the final choice of materials or the design. The essential issue is to test its functionality and analyse the behaviour of its several components. The physical assembly of the prototype was carried out in the Workshop Technology Laboratory of the Mechanical Engineering Department at the Coimbra Polytechnic Engineering Institute. The finished prototype is presented in Figure 9. To confirm that there were no interferences between the prototype operation and the bed itself a partial structure was built similar to the ones used on hospital beds, and the prototype was coupled to it. Figure 9 Prototype of the multi-purpose bed tray system 5. Conclusions Being bedridden has as considerable impact on the way of life of the persons affected by this condition. Despite being associated to numerous pathological effects, there are numerous clinical situations in which bed rest is recommended. An overall description concerning the design, development and construction of both virtual and physical models of a multi-purpose bed tray system was de-scribed throughout this paper. The implementation of this novel healthcare de-vice, enhanced with automated movements, aims to contribute to a significant increase in the dignity and quality of life of the totally or partially bedridden patients and to provide an optimisation of healthcare human resources. References [1] Allen, C., Glasziou, P., Del Mar, C.: Bed rest: a potentially harmful treatment needing more careful evaluation Lancet, 354 (1993), pp [2] Creditor, M.D.: Hazards of hospitalisation of the elderly Ann. Intern. Med., 118 (1993), pp [3] Futamura, M., Sugama, J., Okuwa, M., Sanada, H., Tabata, K.: Evaluation of comfort in bedridden older adults using an air-cell mattress with an automated turning function: measurement of parasympathetic activity during night sleep J. Gerontol. Nurs., 34 n º 12 (2008), pp [4] Harper, C.M., Lyles, Y.M.: Physiology and complications of bed rest J. Am. Geriatr. Soc., 36 (1988), pp

7 [5] Malça, C., Beirão, P. Application of disinfection system to hospital curtains. In: Silva Gomes, J.F., Vaz, M. (eds.) Proceedings of 15th Int. Conf. Exp. Mech. ICEM 15, Porto, Portugal, [6] Olson, E.V.: The hazards of immobility Am. J. Nurs., 90 (1990), pp [7] Rubin, M.: The physiology of bed rest. Am. J. Nurs., 88 (1988), pp [8] Zegelin, A.: Tied down the process of becoming bedridden through gradual local confinement J. Clin. Nurs., 17 nº 17 (2008), pp