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Ventilation Performance in Operating Rooms: A Numerical Assessment
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Sustainable Buildings.
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Surgical site infections (SSIs) remain one of the most challenging postoperative complicationsof healthcare and threaten the lives of millions of patients each year. Current evidence hasshown a positive relationship between the airborne concentration of bacteria-carryingparticles (BCPs) in the operating room (OR) and the rate of infections. The OR ventilation iscrucial for mitigating the dispersion of airborne bacterial contaminants and thus controllingthe risk of SSIs. A variety of ventilation schemes have been developed for OR use. Each haspros and cons and may be better suited than another for operations under certain conditions.The proper functioning of OR ventilation is also affected by external and internal disruptions.By applying Computational Fluid Dynamics (CFD), the present study investigates the airflowand contaminant distribution in ORs under different conditions.The airflow distribution is of critical importance in removing or diluting airbornecontaminants. The conventional mixing ventilation is not able to reliably create an ultracleanenvironment. The usage of mixing ventilation in infection-prone surgery should be limited,especially when a large surgical team is involved. Laminar airflow (LAF) ventilation demandsa sufficient airflow rate to achieve desired performance. Temperature-controlled airflow(TAF) ventilation represents an effective ventilation scheme that can serve as an energyefficientalternative to LAF.Door openings have a detrimental impact on the microbiological cleanliness of the OR. Thetemperature in the OR and adjacent space should be well controlled to minimize the interzonalcontaminant transfer. Temporarily reducing the OR exhaust flow during door operationforms a directional airflow towards the adjacent space, which is found to be an effectivesolution to ensure the isolation.Surgical lamps serve as physical obstructions in the airflow path and significantly deterioratethe performance of LAF ventilation. It is highly recommended to improve the shape anddesign of the lamps in the LAF ventilation. TAF is found to be less sensitive to the presenceof surgical lamps in the airflow path. The buoyancy-driven airflow used by TAF is morecapable of circumventing obstacles than the inertia-driven flow used by LAF. Thermal plumesdeveloped from the surgical equipment in the OR have the potential to distort the buoyancydrivenairflow in TAF.The thesis conducts a comprehensive literature review of important topics in OR ventilation.The present study enhances the understanding of the strengths and limitations of differentventilation schemes and increases the knowledge of the design and usage of OR ventilation.

Abstract [sv]

Postoperativa infektioner tillhör idag de mest utmanande komplikationerna inom sjukvården. De utsätter årligen miljontals patienter för allvarlig hälsofara. Bevis finns för ett samband mellan luftburen koncentration av bakteriebärande partiklar i operationssalen och infektionsfrekvensen. Ventilationen i operationssalen är avgörande för att minimera spridningen av luftburna bakteriella föroreningar och därmed kontrollera risken för postoperativ infektion. För ventilation i operationsrum har olika luftföringsprinciper utvecklats. Dessa har för- och nackdelar och vissa kan vara bättre lämpade än andra under givna förhållanden. Ventilationens funktion påverkas också av yttre och inre störningar. Med numeriska beräkningsmetoder (CFD) undersöks i denna avhandling luftflöden och föroreningsspridning i operationsrum.

Såväl luftflödets fördelning i rummet som luftflödets volym är av avgörande betydelse för eliminering och utspädning av luftburna föroreningar. Konventionell omblandande ventilation har såväl teoretiska som praktiska begränsningar i detta sammanhang och dess användning bör därför begränsas vid infektionsbenägen operation. Detta gäller särskilt vid stora operationsteam. Ventilation med så kallat laminärt luftflöde (LAF) kräver tillräckligt luftflöde för att uppnå önskat resultat. Ventilation med temperaturstyrt luftflöde (TAF) har befunnits vara ett (energi)effektivt alternativ till LAF.

Dörröppningar till operationssalen har negativ inverkan på den mikrobiologiska renheten i rummet. Temperaturen i operationsrummet och angränsande utrymme bör kontrolleras väl för att minimera överföring av föroreningar mellan zonerna. Genom att tillfälligt reducera frånluftflödet i operationsrummet under dörrdrift bildas ett riktat luftflöde mot intilliggande utrymmen som effektiv visat sig säkerställa isoleringen.

Vissa kirurgiska lampor fungerar som fysiska hinder i luftflödesvägen och försämrar avsevärt funktionen vid LAF-ventilation. Därför rekommenderas starkt att inte förbise lampans form och placering. TAF-ventilation har visat sig vara mindre känslig för kirurgiska lampor i luftflödesvägen. Det termiskt drivna luftflödet vid TAF syns mera kapabelt att klara hinder än tröghetsdrivet flöde vid LAF. Värmeplymer som den kirurgiska utrustningen genererar i operationsrummet kan påverka det termiskt drivna luftflödet vid TAF.

Avhandlingen innehåller en omfattande litteraturstudie inom området. Avhandlingen ökar förståelsen för olika ventilationsprincipers funktion och kunskapen om hur ventilation skall användas i sjukhusmiljöer.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019. , p. 79
Series
TRITA-ABE-DLT ; 1939
Keywords [en]
operating room ventilation, bacteria-carrying particles, laminar airflow, mixing ventilation, temperature-controlled airflow, computation fluid dynamics, Lagrangian particle tracking
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering; Civil and Architectural Engineering, Fluid and Climate Theory
Identifiers
URN: urn:nbn:se:kth:diva-263301ISBN: 978-91-7873-338-5 (print)OAI: oai:DiVA.org:kth-263301DiVA, id: diva2:1368003
Public defence
2019-11-27, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20191105

Available from: 2019-11-05 Created: 2019-11-05 Last updated: 2019-11-05Bibliographically approved
List of papers
1. Improving the performance of heat valve ventilation system: A study on the provided thermal environment
Open this publication in new window or tab >>Improving the performance of heat valve ventilation system: A study on the provided thermal environment
Show others...
2019 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 164, article id UNSP 106338Article in journal (Refereed) Published
Abstract [en]

The current study presents and evaluates the performance of two types of supply air terminal devices applied in a heat valve ventilation (HVV) system with regard to the provided thermal environment in a room heated and ventilated by the HVV system. To that end, air temperature and air velocity patterns and local thermal discomfort due to draught were studied both experimentally and numerically. Using numerical simulations, parametric analysis was carried out for investigating the provided indoor thermal environment for a wider range of boundary conditions. The considered parameters included the influence of cold vertical surfaces, supply airflow rate and temperature, and room heating energy demand. The results showed that both of the applied air terminal devices could avoid temperature stratification within the occupied zone. The maximum air temperature difference between 0.1 and 1.8 m above the floor was 2.1 degrees C when using a circular valve placed in the external wall below the window and 2.6 degrees C in the case when the air was supplied through three nozzles located in the wall opposite to the window in the upper part of the room. In general, placing the air terminal device below the window provided more uniform air temperature distribution and contributed to the prevention of downdraught caused by a cold window surface. The outcomes of this study are relevant to selecting and designing ventilation and air heating systems for low-energy buildings.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Air heating, Air terminal device, Thermal environment, Air distribution, Temperature stratification, Draught rate
National Category
Building Technologies
Research subject
Civil and Architectural Engineering, Building Service and Energy Systems
Identifiers
urn:nbn:se:kth:diva-260993 (URN)10.1016/j.buildenv.2019.106338 (DOI)000484515300016 ()2-s2.0-85070748376 (Scopus ID)
Note

QC 20191010

Available from: 2019-10-10 Created: 2019-10-10 Last updated: 2019-11-26Bibliographically approved
2. Numerical study of temperature-controlled airflow in comparison with turbulent mixing and laminar airflow for operating room ventilation
Open this publication in new window or tab >>Numerical study of temperature-controlled airflow in comparison with turbulent mixing and laminar airflow for operating room ventilation
2018 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 144, p. 45-56Article in journal (Refereed) Published
Abstract [en]

Operating room (OR) ventilation is crucial for reducing airborne bacteria-carrying particles (BCPs) concentration and thus preventing post-operative infections. A variety of ventilation schemes have been introduced to ORs. This study explores the effectiveness of a newly developed ventilation scheme, temperature-controlled airflow (TAF), with respect to reducing BCPs distribution and sedimentation in an OR. Comparisons are made with the conventional turbulent mixing and laminar airflow (LAF) ventilation. The study is conducted using Computational Fluid Dynamics (CFD) and Lagrangian particle tracking (LPT), with numerical models validated against literature data. The results reveal that TAF represents reliable and effective ventilation and can serve as an energy-efficient alternative to the LAF systems. The results also show that increasing ventilation rates alone will not always result in better control of BCPs distribution. Airflow patterns play an important role in removing and diluting airborne BCPs, so a specific analysis is necessary to each design of OR ventilation.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2018
Keywords
Operating room ventilation, Bacteria-carrying particles, Temperature-controlled airflow, Laminar airflow, Turbulent mixing ventilation
National Category
Construction Management
Identifiers
urn:nbn:se:kth:diva-238119 (URN)10.1016/j.buildenv.2018.08.010 (DOI)000447484300005 ()2-s2.0-85051404343 (Scopus ID)
Note

QC 20181205

Available from: 2018-12-05 Created: 2018-12-05 Last updated: 2019-11-05Bibliographically approved
3. Impact of door opening on the risk of surgical site infections in an operating room with mixing ventilation
Open this publication in new window or tab >>Impact of door opening on the risk of surgical site infections in an operating room with mixing ventilation
(English)Manuscript (preprint) (Other academic)
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering, Fluid and Climate Theory
Identifiers
urn:nbn:se:kth:diva-263293 (URN)
Note

QC 20191106

Available from: 2019-11-05 Created: 2019-11-05 Last updated: 2019-11-06Bibliographically approved
4. Influence of the shape of surgical lamps on the airflow and particle distribution in operating rooms
Open this publication in new window or tab >>Influence of the shape of surgical lamps on the airflow and particle distribution in operating rooms
2018 (English)In: Proceedings of Roomvent & Ventilation 2018. June 02-05, 2018; Espoo, Finland, 2018Conference paper, Published paper (Refereed)
Abstract [en]

Operating room ventilation plays a significant role in reducing bacteria carrying particles concentration and preventing post-operative infections. The ventilation airflow may be disturbed by objects and heat loads and their effectiveness in reducing bacteria concentration can be compromised. Surgical lamps are one of the major disturbances in an operating room. This study numerically investigated the influence of lamp shapes on airflow patterns and dispersion of airborne bacteria.

Two different shapes of lamps were studied: a closed-shape and an open-shape lamp. The simulation was performed based on the physical configuration of two operating rooms ventilated respectively by laminar airflow and temperature controlled airflow. Results show that the closed-shape lamp severely obstructs the airflow and results in high bacteria concentration in the laminar airflow, whereas the open-shape lamp has a negligible impact on the particle dispersion. The temperature controlled airflow is less sensitive to obstructions and maintains a clean surgical site with both types of lamps.

Keywords
Operating room ventilation, surgical lamp, laminar airflow, temperature controlled airflow
National Category
Architectural Engineering Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-225392 (URN)
Conference
Roomvent & Ventilation 2018. June 02-05, 2018; Espoo, Finland
Note

QC 20180523

Available from: 2018-04-04 Created: 2018-04-04 Last updated: 2019-11-05Bibliographically approved
5. Impact of surgical lamp design on the risk of surgical site infections inoperating rooms with mixing and unidirectional airflow ventilation
Open this publication in new window or tab >>Impact of surgical lamp design on the risk of surgical site infections inoperating rooms with mixing and unidirectional airflow ventilation
(English)Manuscript (preprint) (Other academic)
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering, Fluid and Climate Theory
Identifiers
urn:nbn:se:kth:diva-263296 (URN)
Note

QC 20191113

Available from: 2019-11-05 Created: 2019-11-05 Last updated: 2019-11-13Bibliographically approved
6. Effect of staff number on the bacteria contamination in operating rooms with temperature-controlled airflow ventilation and turbulent mixing ventilation
Open this publication in new window or tab >>Effect of staff number on the bacteria contamination in operating rooms with temperature-controlled airflow ventilation and turbulent mixing ventilation
2019 (English)In: Proceedings of Building Simulation 2019: 16th Conference of IBPSA, 2019Conference paper, Published paper (Refereed)
National Category
Civil Engineering
Research subject
Civil and Architectural Engineering, Fluid and Climate Theory
Identifiers
urn:nbn:se:kth:diva-263298 (URN)978-1-7750520-1-2 (ISBN)
Conference
Building Simulation 2019: 16th Conference of IBPSA,2-4 September Rome Italy
Note

QC 20191106

Available from: 2019-11-05 Created: 2019-11-05 Last updated: 2019-11-06Bibliographically approved
7. Numerical assessment of the influence of heat loads on the performance of temperature-controlled airflow in an operating room
Open this publication in new window or tab >>Numerical assessment of the influence of heat loads on the performance of temperature-controlled airflow in an operating room
2018 (English)In: 39th AIVC Conference, 2018Conference paper, Published paper (Refereed)
Abstract [en]

Airborne bacteria-carrying particles (BCPs) in an operating room (OR) can cause post-operative infections in the patients. The ventilation system in the OR is crucial in removing or diluting airborne BCPs. This study numerically assessed a newly developed OR ventilation scheme – temperature-controlled airflow (TAF), with special focus on the influence of heat loads on the airflow and BCPs concentration. TAF supplies clean air at different temperature levels to different zones and establishes a high-momentum downward airflow pattern over the operating table. The results show that TAF is an efficient ventilation system that can provide good protection for the patients under low to moderately heavy heat loads. When the heat load is further increased to an extremely heavy level, the desired airflow pattern cannot be achieved and TAF becomes less efficient. The numerical results also suggest that the supply air temperature needs to be optimized according to the specific use conditions to maximize the performance of TAF.

National Category
Civil Engineering
Research subject
Civil and Architectural Engineering, Fluid and Climate Theory; Civil and Architectural Engineering, Fluid and Climate Theory
Identifiers
urn:nbn:se:kth:diva-263297 (URN)
Conference
39th AIVC Conference "Smart Ventilation for Buildings", Antibes Juan-Les-Pins, France, 18-19 September 2018
Note

QC 20191120

Available from: 2019-11-05 Created: 2019-11-05 Last updated: 2019-11-20Bibliographically approved

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