Introduction: The performance of health care systems in terms of patient flow times and utilization of critical resources can be assessed through queueing and simulation models. This paper provides a tool for studying the capacity, resources, and patient flow time. Materials and Methods: This study was performed in CCU section of the Kosar Hospital, focusing on the impact of outages (preemptive and non-preemptive) on the effective utilization of resources and on the flow time of patients. Two procedures of queueing network solution have been presented; the decomposition and the Brownian motion approaches. Several scenarios have been defined to improve the performances. Simulation has been utilized as a validation tool. Results: Simulation results show that scenario 2 (reduction of time spent on resolving delays) has the lowest waiting times. Scenarios 4 to 6 show that the proportion of time spent on absenteeism is less than the time spent on the resolving delays. Conclusion: The queueing models based on decomposition approaches to Brownian motion Approximation present more accurate results. Decreasing the number of interrupts and reducing the time spent on resolving interrupts decrease flow times. The impact of outages is considered a key managerial challenge.