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- Sadeghian, Parastoo
(author)
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Computational fluid dynamics application in indoor air quality and health
- 2022
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Doctoral thesis (other academic/artistic)abstract
- Indoor air quality directly affects the comfort, performance, and well-being of occupants. Indoor pollution can cause immediate or long-term health effects and has been responsible for 4.1% of global deaths in recent decades. In operating rooms, providing a high indoor air quality is especially critical as surgical site infection can occur in patients due to air contamination in operating rooms.Surgical site infections due to antibiotic resistant bacteria may threaten the safety and lives of millions of people each year. To moderate and reduce indoor contamination, it is necessary to select a proper ventilation strategy.Improving ventilation system performance requires a deep understanding of airflow patterns and contamination distribution.This thesis adopted computational fluid dynamics to evaluate airflow patterns and the spread of airborne contaminations in indoor environments. Moreover, we sought to provide an approach to facilitate transferring the obtained knowledge to medical experts and decisionmakers to reduce the infection risk after the surgery.The use of warming blankets has raised the concern about surgical site infections. Warming blankets are used to prevent hypothermia in patients during surgery. However, our results showed that these warming blankets reduce the bacteria-carrying particles level at the wound due to warm upward airflows.Surgical lamps can block the airflow and generate a low-velocity area under the lamp that increases the accumulation of contaminants. The simulation results revealed that a novel fan-mounted surgical lamp reduced the contamination level to an acceptable range for infection-prone surgeries. This novel surgical lamp successfully reduced contamination in the operating room supplied with both turbulent mixing and laminar airflow ventilations.In another study, we implemented a protective curtain and showed that this strategy could significantly reduce the exposure level of the medical team to a patient with infectious respiratory disease. This novel protective curtain is located between the patient’s upper body and the lower part during surgery. We found a 57% reduction in bacteria-carrying particle concentration at the wound by adopting this curtain. Thus, using this protective curtain can reduce the exposure level of both patient and surgical team in the operating room.Besides investigating the performance of ventilation systems in hospitals, we investigated the application of diffuse ceilings ventilations in clinics, especially waiting rooms. Diffuse ceiling ventilation systems are common air distribution systems in offices and schools. Based on simulation results, a diffuse ceiling with a central opening and evenly distributed heat loads resulted in the highest cooling capacity and thermal comfort in clinic waiting rooms.We have visualised the airflow field and airborne particles in operating rooms with the help of virtual reality techniques. We found the virtual reality environment more engaging to understand the airflow field and particle movements in operating rooms.
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| 2. |
- Sadeghian, Parastoo
(author)
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A new generation of hospital operating room ventilation
- 2020
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Licentiate thesis (other academic/artistic)abstract
- Surgical site infection is responsible for 38 percent of reported infections after surgery. This infection increases mortality and treatment costs, and prolongs the hospitalization of patients. Bacteria-carrying particles are the main cause of surgical site infection and one of the main sources of these particles is skin fragments released from the surgical personnel during an ongoing surgery. Ventilation systems reduce the concentration of bacteria-carrying particles by supplying clean air in the operating room. The performance of operating room ventilation systems is affected by internal disruptions such as medical equipment, surgical lamps, number of staff and their behaviour during the surgery.Using computational fluid dynamics, this thesis investigates the airflow behaviour and distribution of the contamination in the operating room under the presence of various internal disruptions. In this regard, three common ventilation systems are considered: laminar airflow, turbulent mixing and temperature-controlled airflow ventilations. This study tries to overcome the weaknesses of the ventilation systems by providing sustainable solutions and continuously being in contact with design companies.It is common to use warming blankets to prevent reduction in the core body temperature of the patient during major surgeries. However, there is a major concern that these blankets disrupt the supplied airflow, which results in rising contaminant concentration. Most of the studies about warming blankets are clinical works and it is still not clear whether or not these blankets should be used. The results of the present study show that using warming blankets had no impact on increase of contamination level at the surgical zone. However, one common type of warming blanket – a forced-air warming blanket – can considerably increase the concentration of bacteria-carrying particles at the wound area if it becomes contaminated.The simulated results of the airflow field and particle tracking showed that the laminar airflow ventilation system was disturbed more easily by the local heat loads than overall heat loads in the operating room.Surgical lamps are considered as an obstacle in the supplied airflow path. These lamps create a stagnant area above the operating table and increase the contamination level. In this regard, a novel design of surgical lamp, a fan-mounted surgical lamp, was introduced to operating rooms.This device was used in the operating rooms equipped with laminar airflow and mixing ventilation system. The simulated results revealed that this lamp significantly reduced the contamination level at the operating table.Visualization techniques were adopted to teach and improve the understanding of surgical personnel about transmission of contaminated particles in operating rooms. Here, a virtual and augmented reality interface was used to visualize the impact of differences in ventilation principle, surgical staff constellation and work practice.
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