###### Abstract  
Planning and scheduling critical resources in hospitals is significant for better service and profit generation. The current research investigates an integrated planning and scheduling problem at different levels of operating rooms, intensive care units, and wards. The theory of constraints is applied to make plans and schedules for operating rooms based on the capacity constraints of the operating room itself and downstream wards. A mixed integer linear programming model is developed considering shifting bottleneck resources among the operating room, intensive care unit, and hospital wards to maximize the utilization of resources at all levels of planning. Different sizes of planning and scheduling problems of the hospital, including small, medium, and large sizes, are created with variable arrivals and surgery durations and solved using a CPLEX solver for validating the developed models. Later, the application of the proposed models in the real world to develop planning systems for hospitals is discussed, and future extensions are suggested. operating room; intensive care unit; ward; theory of constraints; planning and scheduling  
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[PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], H. Modeling of Multi-Level Planning of Shifting Bottleneck Resources Integrated with Downstream Words in a Hospital  
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[PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], H. Modeling of Multi-Level Planning of Shifting Bottleneck Resources Integrated with Downstream Words in a Hospital  
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[PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], H. Modeling of Multi-Level Planning of Shifting Bottleneck Resources Integrated with Downstream Words in a Hospital  
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[PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], H. Modeling of Multi-Level Planning of Shifting Bottleneck Resources Integrated with Downstream Words in a Hospital
Planning and scheduling problems in healthcare facilities are divided into three different levels including strategic, tactical, and operational level planning [2]. Strategic level planning is also called higher-level planning and is based on forecast and surgical demands, where the operating room time is allocated to different surgical specialties. Tactical level planning is also termed medium-level planning, and it involves the division of allocated time for different surgical specialties and preparing a master surgery schedule. Operational level planning is also termed lower-level planning, where the daily plans of the operating room are made and patients are sequenced within the allocated operating rooms. Some articles investigate decision-making regarding operating room planning and scheduling in hospitals at four hierarchical decision levels: strategic, tactical, offline operational, and online operational. The offline operational level deals with assigning patients to dates and sequencing the patients in the operating rooms and involves monitoring and controlling the schedule execution [3,4]. The literature contains studies of the different levels of planning and scheduling problems to improve the performance of healthcare facilities [5, 6, 7]. For example, [PERSON] and [PERSON] [8] studied case mix planning decisions for higher-level planning and proposed a mixed integer linear programming model to solve this problem. [PERSON] et al. [9] proposed an iterative approach for case mix planning decisions. They developed mathematical models to generate a pool of candidate solutions and used a simulation method to evaluate the effectiveness of each candidate solution for higher-level and lower-level performance measures, i.e., the overutilization of operating rooms and utilization of downstream wards. The case mix planning problem was also investigated by [PERSON] et al. [10]. They developed a stochastic model to find the optimal case mix of patients considering surgery duration, length of stay, and arrival time as uncertain variables. Medium-level planning problems have also been studied in the literature.