Online & Oslo, Norway
21-23 June 2021
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Session 6: Ventilation and IEQ in healthcare facilities
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1:00pm - 1:12pm
Thermal comfort in hospital isolation room – A laboratory study
Turku University of Applied Sciences, Finland
Ventilation and air distribution are important in hospital environments, especially in isolation rooms, where they have an essential role in protecting healthcare workers e.g. from patient-exhaled contaminants. In optimal case the supply air distribution should be able to mix and dilute the air close to the source (patient). However, this is not always the case with traditional mixing ventilation systems.
Previous studies have shown that local downward ventilation above the patient’s bed is effective in reducing the healthcare workers exposure close to the patient. However, it is very challenging to provide thermally comfortable downward ventilation towards patient with low activity level. There is a need to gain more information of the perception regarding thermal environment while lying in patient bed in isolation room having downward ventilation.
The aim of this study is to examine perceived thermal comfort, air movement, symptoms, such as eye-irritation and headache, and measured heart rate-based activity level of persons lying in patient bed in hospital isolation room.
The experiments were done in autumn 2020 in Turku University of Applied Sciences’ (TUAS) HVAC laboratory, where a climate chamber representing a full-scale hospital isolation room was built. 8 volunteers (7 male and 1 female) participated in two different ventilation conditions (1 hour per condition, Troom=23 °C): 1) baseline overhead mixing ventilation and 2) local downward ventilation over the patient bed with background mixing ventilation. All volunteers wore a standard hospital clothing and laid in hospital bed during the whole session. They answered several times in questionnaire regarding thermal comfort, symptoms and perception of air movement. Participants´ heart rate was monitored and activity level was calculated according to standard EN ISO 8996 (2004).
Tentative results show that there were differences in the perceived thermal environment between the test conditions. There were discrepancies in the perceived air movement between the test conditions. Also measured activity levels appeared to vary notably. Detailed analysis will be provided in the conference paper.
This study is part of dECOnhealth (Demand Controlled Ventilation in Healthcare Settings) -project. The objective of the project is to develop feasible demand controlled ventilation methods and control strategies for hospital environment without compromising staff, patient and visitor safety and health.
1:12pm - 1:17pm
Experimental investigation of the local air exchange behind an obstacle in laminar flow
Technical University of Berlin, Hermann-Rietschel-Institut, Germany
This study presents two methods to study the wake area of a round plate (Ø=400 mm) in a cleanroom. First, visualizations were conducted, in which the air in the wake area behind the plate was made visible by theatre fog. Second, the local air exchange was studied by comparing the mean aerosol concentration below the plate and the decay time for varying velocities of the air supply. The particles’ decay times below the plate decrease with increasing air flow velocity.
1:17pm - 1:29pm
Experimental study on the thermal plume from a surgeon in an operating room with mixing ventilation during COVID-19 pandemic
1Norwegian University of Science and Technology, Trondheim Norway; 2Norconsult AS
In 2003 there were severe cases of SARS (SARS-CoV), after this outbreak, few researched the possibility of negative pressure operating rooms by using CFD simulation. Outside the OR, a reduction in the circulation of the virus is best achieved with a negative pressure environment inside the OR. Following the outbreak of COVID-19 in 2019 studies on how to best prepare for and perform surgery on infectious patients have been conducted, conclusions were made with good results in protecting the surgical staff from patients infected by COVID-19 in operating rooms with negative pressure. However, it is unclear whether the surgeon´s thermal plume can have an impact on the transport of contaminants up to the breathing zone and thus cause infection. The aim of this study is to quantify the thermal plume in front of the main surgeon in an operating room with mixing ventilation under different pressures. The measurements of the thermal plume will be performed in a full-scale operating room laboratory, which has an area of approximately 61 m2, with a mixing ventilation system and for three different cases: positive pressure of 20 and 10 Pa, and negative pressure of -5 Pa. Measurements results will show if the pressure inside the operating room has an impact on the thermal plume and airflow distribution in front of the main surgeon. The knowledge from this study can help to consequently prevent the spread of particles to exposed areas, and also reduce the risk of adverse side effects for the medical team from surgical patients with infectious disease.
1:29pm - 1:41pm
Experimental study on the surgical microenvironment in an operating room with mixing ventilation under positive and negative pressure
1Norwegian University of Science and Technology, Trondheim, Norway; 2Norconsult AS, Sandvika, Norway; 3The Arctic University of Norway, Tromsø, Norway
Due to the outbreak of Covid-19, negative pressure operating room (NPOR) are strongly recommended to be applied to prevent spreading virus from infected patients to adjacent rooms during surgery procedures. However, there have been few experimental studies on the effect of OR pressure difference on the surgical microenvironment. This study aims to experimentally investigate the airflow distribution in the surgical microenvironment in an OR under different pressure conditions. All measurements were performed in a full-scale laboratory, which has an area of 62 m2, and a mixing ventilation. The air velocity and temperature in the surgical microenvironment of a lying patient were measured under positive pressure of 5 Pa, 10 Pa, 15 Pa and negative pressure of -5 Pa, -10 Pa and -15 Pa. The effect of heat generated by operating lamps was also considered. The results show that the airflow distribution around the surgical wound is dominated by thermal plume from the patient under the condition of both positive and negative pressure. In other areas of the surgical microenvironment, regardless the pressure difference conditions, the room airflow distribution by ventilation system is the dominant factor on surgical microenvironment. Variations in differential pressure can affect the temperature distribution around the surgical site, with a smaller differential pressure producing a slightly larger vertical temperature gradient.
1:41pm - 1:53pm
Performance assessment and clinical validation of Operating Room ventilation systems
Ostbayerische Technische Hochschule Amberg-Weiden, Germany
BACKGROUND: To date there still is substantial discussion in the scientific community which ventilation system provides the most effective and economical respectively efficient control of microbial risk factors during surgery. This is especially im-portant as most standards do not require a performance assessement of the operating room (OR) ventilation, but rather rely on tests “at rest” in empty room. This might be an explanation for the conflicting results regarding infection preven-tive effects of different OR ventilation systems as well as the ambiguous data for infection rates.
AIMS: Thus, we aimed to evaluate how different widely used qualification techniques as well as several operational parame-ters impact OR ventilation performance assessement. We specifically studied the desired effect of reducing microbio-logical air burden and infection rates under routine clinical conditions. Therefore, we evaluated the performance of a temperature controlled ventilation system (TcAF) during surgery and its impact on surgical site infections.
RESULTS: Clothing, workflow, setup/positioning, staff behaviour and measurement technique (particle versus active and passive cfu measurement) showed to have significant impact on the performance assessment of OR ventilation systems. Nev-ertheless, most international standards only measure at rest situations during system assessement and thus do not take these critical parameters into account. We could also show that therefore active air sampling is to be preferred. TcAF showed to reliably and robustly provide "ultra-clean" air (<10 CFU / m3) in the entire operating room demon-strating its capability to reduce the risk of airborne microbial transmission during surgery. In a further retrospective analysis of 1000 consecutive patients undergoing total joint replacement (hip, knee) in an operating room with a TcAF system compared to 1000 consecutive cases in an operating room with mixing ventilation showed that TcAF was as-sociated with a decrease in mean postoperative hospital stay, a decrease in percentage of hospital length of stay, and a decrease of infectious complications from 3% to 1%.
CONCLUSIONS: Our results show that performance testing is essential for a proper assessment of OR ventilation systems. Moreover, we demonstrated that TcAF systems are able to reliably and robustly ensure "ultra-clean" air (<10 CFU / m3) in the entire operating room demonstrating its capability to reduce the risk of airborne microbial transmission during sur-gery. The retrospective analysis of clinical patient data shows positive impact of TcAF on key clinical outcome pa-rameters in line with previous research by Charnley and Lidwell.
1:53pm - 2:05pm
Visualizing bacteria-carrying particles in the operating room: exposing invisible risks
KTH Royal Institute of Technology, Sweden
Surgical site infections occur due to contamination of the wound area by bacteria-carrying particles during the surgery. There are many surgery preparation conditions that might block the path of clean air in the operating room, consequently increasing the contamination level at the surgical zone. The main goal of the current study is to translate this knowledge into a perceivable tool for the medical staff by applying state-of-the-art simulation and visualization techniques. In this work, the results of numerical simulations are used to inform visualization. These results predict the airflow fields in the operating rooms equipped with mixing, laminar airflow and temperature-controlled airflow ventilation systems. In this regard, the visualization uses a virtual reality interface to translate the computational fluid dynamics simulations into usable animations. The results of this study help the surgical and technical staff to update their procedures by using the provided virtual tools.
2:05pm - 2:17pm
Thermal comfort level of patients and surgical staff in operating rooms at a Nordic hospital
1Tallinn University of Technology, Estonia; 2Norwegian University of Science and Technology, Department of Energy and Process Engineering
In healthcare facilities and hospital environment, it is essential to enable thermal comfort for occupants. Unstable thermal conditions in the operating room (OR) will influence the performance of surgical staff and the infection possibility of patients. In this study, the thermal comfort of patients and surgical staff was measured with two ventilation solutions at St. Olavs hospital ORs in Trondheim, Norway. Research methods include thermal environment measurements during mock (imitation) surgery, a survey among surgical staff, and observation during a real operation. The results show that the mean air velocity near occupants in mixing ventilation (MV) OR was low (max 0,08 m/s) and in laminar air flow (LAF) ventilation OR considerably higher, 0,36 m/s. In conclusion, there was good general thermal comfort of surgical staff in LAF OR, but the surgical staff felt mainly uncomfortable in MV OR.
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