Towards a performance assessment methodology using computational simulation for air distribution system designs in operating rooms

Abstract

One of the important performance requirements for an air distribution system for an operating room (OR) is to provide good indoor environmental conditions in which to perform operations. Important conditions in this respect relate to the air quality and to the thermal conditions for the surgical team and the patient. Previous research has shown that some types of air distribution systems used in ORs may contribute to the reduction of surgical site infection (SSI). However, despite improved efficiency of air distribution systems, combined with new methods of infection control, technological developments in medical equipment and use of antibiotics, SSI is still a real risk and remains relatively high for certain types of surgery. One of the identified causes is inadequate performance of air distribution systems. Although various air distribution systems/strategies are available for application in ORs, no general assessment methodology is available to objectively compare different systems for a given design problem on the basis of identified performance indicators. This may result in the application of inadequately designed systems, affecting the health, safety and comfort of the patient and surgical team. The focus in this research, therefore, is on the design decision support information. The objective is to develop a methodology to support designers in the objective performance assessment of air distribution system designs for ORs, with a further focus on the application of computational simulation in this design assessment. To reach this goal, a number of measures were taken, briefly comprising of: extensive literature review; interviews with designers and hospital decision makers; observations in ORs; and a survey among experts in the field of heating, ventilation and air-conditioning (HVAC) and computational simulation. The Basis for the general research methodology applied in this work is the Design Research Methodology. The more specific methodology developed to assess air distribution systems combines the Performance Based approach with the Building Evaluation Domain Model. The latter method provides structure to the design problem by identifying different building levels and stakeholders. In this structure, the performance approach resulted in the definition of performance requirements and a listing of important performance indicators (mainly) related to the indoor air quality and thermal comfort in ORs. Computational simulation, such as building energy simulation, air flow network models and computational fluid dynamics, coupled or stand-alone, are introduced and recognized for their potential to assess the performance of air distribution systems in the design phase. Their application in practice, however, is still limited. Within the context of the developed methodology, use of computational simulation is indispensable. Some significant barriers to the current use of computational simulation have been identified. However, research is still in the process of addressing these areas. Besides a listing of performance indicators with respect to air distribution systems for ORs, an evaluation procedure for deciding on the appropriate evaluation method to predict the performance indicators is proposed. The evaluation procedure comprises five steps. First, selection of the zones of interest to be evaluated (e.g., workstation, instrument table and breathing zone); Second, identification of the boundary conditions to calculate the performance indicators; Third, identification of the airflow dynamic in the zone(s) of interest; Four, sensitivity analysis to verify the accuracy of the evaluation method chosen; Finally, identification of the robustness of the design solution by performing uncertainty and parameter sensitivity analysis. Based on this analysis, the designer will be able to verify if the air distribution system design performs properly and meets the client´s needs. The final stage of this research consisted of verifying if the proposed approach realizes the intended objectives, and if the method can be used in practice. A survey among researchers with expertise in building HVAC systems and computational simulation was used as a means for this evaluation. The results of this initial investigation indicated a positive reaction towards the general set-up of the procedure and towards its principal ideas to arrive at a design support methodology with respect to the evaluation of air distribution systems for operating rooms. However, the step between theory and practice still has a number of barriers. The complexity of the procedure, followed by resource constraints (time, knowledge and financial) were mentioned as barriers for its current complete application. The extent to which these barriers will prevent (or not) the use of the developed approach in practice should be explored. Options and directions for improvements are specified. The conclusions also indicate the need for further confirmation of the actual design improvement possible by applying the approach in a practical case.