2012 Cairo International Biomedical Engineering Conference (CIBEC) Cairo, Egypt, December 20-21, 2012
Improving Operating Theatre Design Using Facilities Layout Planning Mohammed Assem, Bassem K. Ouda and Manal Abdel Wahed Department of Systems and Biomedical Engineering Faculty of Engineering, Cairo University Giza, Egypt
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[email protected], Abstract — Operating theatre (OT) is one of the most critical departments within the hospital. In developing countries, no allocation of sufficient areas for OT, that results in sharing of many services in the same area while ignoring others. Facilities layout planning (FLP) is widely used in industrial engineering for designing block layout plans as it considers the assignment of services to the proper locations. Hence, FLP can solve management and hospital design problems, reduce nursing staff effort and improve overall healthcare environment. The problem presented in this study is an optimization one, which maximizes the subjective closeness rating between different services in the OT considering international standards. Some heuristic approaches have been developed for solving FLP problem; the most successful were based on graph theoretic concepts. This paper proposes a solution by generating an OT layout design based on the graph theoretic approach. It is divided into two subproblems; the first one is the adjacency problem that defines the desirability of locating pair of spaces adjacent to each other. The second one is the block layout problem which was solved by using manual traditional qualitative technique (the spiral technique). The output of the technique was several possible designs and a layout score that was calculated for each design. This allows for selecting the most appropriate design for each end user. Computing the layout score, before and after reallocation of the OT spaces, resulted in an increase by 18.5% in the first hospital. For the second hospital, more services had to be added in addition to the reallocation process, this resulted in an increase in the layout score by 45%. Index Terms — Facility Layout Problem, spiral technique, operating theatre, layout planning & REL Chart.
I. INTRODUCTION Most of operating theatre (OT) layout designs in developing countries have a lot of problems. These problems are differed according to many factors such as: designer education, available resources, project organizer reasoning, insufficient project area and common deficiencies in the medical services quality. OT design mistakes are not accepted, as it has a direct effect on the patient safety. Facilities layout planning (FLP) is widely used in industrial engineering for designing block layout plans for warehouses, factories and offices. This is due to the fact that FLP considers
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the assignment of services to the proper locations. It has an effect on the flexibility of a production plant and thus the material handling cost, all are considered vital factors which directly affect the production. In material handling, the facility layout problem deals with the physical arrangement of spaces to minimize the total cost of moving the required material between the spaces [1]. Facility layout design is used not only in industrial plants, but also in other institutions, such as airports, office buildings, sport centers, police stations, and aircraft’s instrumentation panel. Therefore, facility layout can solve management and hospital design problems to reduce nursing staff effort and improve overall healthcare environment. One of the first studies of this problem is the work of Buffa et al [2] as they allocated the facilities using Computerized Relative Allocation of Facilities Technique CRAFT method. A comparison between performances of twelve heuristic algorithms was made by Andrew Kusiak et al [3], Koopmans et al [4] discussed the assignment of plants to locations. An evaluation of an OT whole design according to an integration of many international design standards using a software package was presented in [5]. The problem presented in this study is an optimization one that is either quantitative or qualitative [1]. The quantitative objective of the FLP is to minimize the material handling cost. On the other hand, the qualitative objective is to maximize the subjective closeness rating by considering vital factors such as international standards. There are a number of heuristic approaches that have been developed for solving FLP problem. The FLP was modeled as a quadratic assignment problem, quadratic set covering problem, a linear integer programming problem, a mixed integer programming problem, and a graph theoretic problem. Seppanen et al [6], Green and Al Hakim [7] discussed how to solve layout problems by graph heuristic approaches. Graph theoretic approach is divided into two sub-problems. The first one is an adjacency problem, which is solved using an adjacency matrix. It defines the desirability of locating each pair of spaces adjacent to each other. The second is the block layout problem. It is a process of driving a layout plan from adjacency matrix [1]. Block layout problem is solved by using
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manual traditional qualitative technique called spiral technique [8]. The Spiral technique generates a layout block plan from the adjacency matrix, and then a layout score is calculated to facilitate the selection of the best alternate design. The higher layout score indicates the better design. This research proposes an efficient solution by generating an OT layout design based on a mathematical approach. There is no need to have definitive knowledge about the international design standards to start using the proposed model to generate a better OT layout design matching the international design standards [9]. This model submits a proposal to reallocate the spaces in an existing OT to reach better layout plan. Also, adding more OT services in the same OT area. The next section presents the methods used to reach the proposed model. For testing the model it was applied to hospitals that were having a reallocation problem. II. METHODOLOGY A. Adjacency Problem Adjacency problem is solved using an adjacency matrix, which defines the desirability of locating each pair of spaces adjacent to each other. The adjacency matrix of a finite graph G that has n vertices is n × n matrix where the non-diagonal entries aij equals the number of edges from vertex i to vertex j. The vertices represent the spaces within facility and the edges represent the “adjacencies” The adjacency coefficients are as follows: a- Fully adjacent (takes value 1): Two spaces are fully adjacent in a layout if they only share one wall. In this application, the spaces are fully adjacent when they are facing each other directly. b- Partially adjacent (takes value 0.5): In this application, the values of partially adjacent are proposed to be 0.5 or 0.75; in addition of adding new conditions, two spaces are partially adjacent in a layout if these spaces are together in the same area. The nearest space to the selected space will take a value of 0.75 and the farthest space will take a value of 0.5. c- Non-adjacent (takes value 0): If the spaces don’t share any point. In this application, the spaces are non-adjacent when they can’t be seen together in the same area (they are separated by a door or curtain). Let aij [0, α, 1]: Adjacency coefficient between activities i and j will be as follows:
B. Block Layout Problem It is a process of deriving a layout plan from adjacency matrix. This matrix contains the spaces to be included in the design and each space will be represented by a vertex. The problem now is how to select and insert the vertices one by one to complete an initial layout planar graph. This problem can be
solved using the Spiral Technique. [1], [8]. Spiral Technique is a manual traditional qualitative technique used to construct an initial layout plan based on relationship. The model proposed in this paper reallocates services in medium and small OTs that are more common in developing countries. Three basic steps are done to generate different block layouts. These steps are: 1) Insertion of vertices. 2) Generation of block plans. 3) Scoring of the generated layout. 1) Insertion of Vertices Inserting the vertices into the initial block plan should be done by using the following five steps Creating a scaled paper cutout for the spaces to start the partial layout. Calculating the total closeness rating (TCR) [7], [9]. This rating is used to determine the closeness rating for each space to other spaces; it is defined as the summation of all the rating-values of all edges linked with the space defined by AEIOUX rating system. AEIOUX Rating System was defined as, A = absolutely necessary and takes value of 4, E = especially important and takes value of 3, I = important and takes value of 2, O = ordinary closeness and takes value of 1, U = unimportant and takes value of 0, X = undesirable and takes value of -1 or -2 or -3. According to the infection control constraints, OT is divided into three distinct areas; namely restricted, semi-restricted and unrestricted. TCR is proposed to be a summation of the adjacency coefficient of each row of the adjacency matrix. It represents an ordered preference for closeness. Inserting the lower order spaces one by one. TCR gives the priority of vertices insertion where the space with a high rating value should therefore be at the center of the partial layout. This placement makes it close to all other spaces. Inserting vertices at the partial layout according to order sequence in the layout center. (Note: if there are two or more spaces have the same TCR, the space in the same physical area is proposed to be selected (restricted, semirestricted and unrestricted)). Repeating the previous step until all vertices have been placed in the partial layout (bubble plan). There are many restrictions proposed to affect the insertion process such as: - Entrances and exits of OT. - Plumbing services. - Windows which are permitting daylight. - HVAC system. - Concrete columns. - Available areas. 2) Block Plan Construction Two steps were followed to construct the initial block layout plan:
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Applying each space block at its vertex.
Selecting the best fitting feasible shape for this space and placing it at an appropriate location along the partial layout periphery. 3) Layout Scoring The weights of the edges must be firstly defined to calculate the layout plan score. They represent the benefit of having two adjacent spaces, then classifying the weights between spaces according to AEIOUX rating system [1], [9]. Relationship chart (REL chart) can be used to facilitate the calculations [10], [11]. The REL chart represents M(M-1)/2 symmetric qualitative relationships, where M is the number of spaces at the OT. The relationship degree can be described by AEIOUX rating system. There are two ways to compute layout score [1], [8]:
Fig.1. First case study present OT layout plan.
To calculate the layout score, three steps are applied: First Step: Generating an adjacency matrix from the previous existing OT layout plan figure 1, by considering adjacency coefficient definitions.
1. Layout score based on distance M 1 M
LS d
V (r ) d
i 1 j i 1
ij
ij
(1)
Second Step: Extracting the spaces found at figure 1 to generate a REL chart from reference REL chart. See table 1. TABLE 1. EXTRACTED REL CHART
Where dij = distance between activities i and j. V (r) ij is the cost per unit distance of flow between activities i and j 2. Layout score based on adjacency M 1 M
LS a
V (r ) a
i 1 j i 1
ij
ij
(2)
Where aij [0, 1]: adjacency coefficient between activities i& j. V (r)ij is a weighting factor. Layout based on adjacency (equation 2) was applied in this study.
Third Step: Calculating the layout score by using equation 2 and replacing the values of AEIOUX rating system as mentioned before, B. Layout Scoring After Applying the Proposed Model
III. RESULTS AND DISCUSSION The proposed method is applied on two secondary hospitals. The first case study is an Orthopedics OR. It includes many services shared in the same space. The available area of OT is very small compared with the international standards recommendations. This method is applied to reallocate OT spaces and services. The second case study is a general OR. The challenge of the proposed method is getting an efficient solution for OT designers to reallocate OT spaces and services according to international standards. Case Study Assessment of the new model is done by calculating:
A) Extracting the adjacency matrix with the same spaces found at figure 1. Notes: 1. TCR (Total Closeness Ratio) is a summation of an adjacency matrix for each row. 2. Order column, represent the priority of inserting this space in the proposed layout plan, table 2. TABLE 2. EXTRACTED ADJACENCY MATRIX
A. Layout scoring of the present OT layout design. B. Layout scoring after applying the proposed model A. Layout Scoring of the Present OT Layout Design Figure 1, shows the first case study of a present OT layout plan.
B) Using the extracted reference REL chart, as table 1. C) Implementation of the spiral technique as mentioned in the previous section. Generating a bubble plan as shown in figure 2, the resulted modified initial layout plan is shown in figure 3. D) Calculating the layout score by using equation 2
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The resulted layout score of the proposed design is 49.25. This score is raised by 18.5% (the layout score of the present design was 40), leading to enhancement of OT layout design. Layout problems like traffic pattern in the staff change room which is not supporting one way traffic, present of two semi-clean corridors and two clean corridors (inefficient allocation) and operating rooms are not adjacent together to share many services (HVAC, Medical Gas, Electrical system….etc), are removed in the new design. Fig. 5. Second case study modified OT layout plan after adding more services.
IV. CONCLUSION
Fig. 2. Bubble plan
Fig. 3. First case modified OT layout plan.
Figure 4 shows an actual layout plan of OT for the second case study.
Reallocation of OT spaces was done by a graph theoretic heuristics. Adjacency matrix was used to reflect the closeness rating of the spaces in OT. Manual qualitative technique called spiral technique was used to derive initial layout block plan. Satisfactory results were obtained. OT layout designs were improved up to 45%. The Analysis of the results reflects the lack of infection control awareness and a misunderstanding or un-realization of the role of the clinical engineer in OT design and healthcare facilities design as whole. Some countries do not have a national reference standard for OT design and the ministry of health approves the OT design without applying the international standards. This proposed model has many benefits, such as, reducing the percentage of errors that may result from human being design, in addition to time and effort savings. Using of this model doesn’t need a definitive knowledge about international design standards. As future work, we intend to expand our model to cover modern OTs, study the restrictions effect on the operation of the proposed algorithm, and to generate a software program to handle all problems concerning OT layout design, with more considerations such as area, distance, flow, cost and time. REFERENCES
Fig. 4. Second case study present OT layout plan.
Following the same steps as the first case study, only that after step C (completing layout block plan), some spaces that were not found at figure 5 were added, this needs general background about OT design. By using the proposed priority list, the resulting score of the OT layout present design was 40, and after reallocation process and services addition it was 72 (figure 5), thus the score was raised by 45%.
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