“TcAF ventilation benefits validated using CFD”
(h) Wang. C (2019)
This doctoral thesis investigates the performance of different ventilation technologies using CFC, and confirms the performance of Temperature Controlled Airflow (TcAF).
(g) Wang, C., Sadrizadeh, S. & Holmberg, S. (2018)
In: Proceedings -Roomvent & Ventilation 2018. Aalto University, Espoo, Finland, June 2-5 2018
This study numerically investigated the influence of surgical lamps on the airflow pattern and airborne bacteria concentration in two existing operating rooms equipped with, respectively, a laminar airflow system and a temperature-controlled airflow system. Two different lamp shapes were studied: a closed-shape lamp and an open-shape lamp. The closed-shape lamp obstructs the unidirectional airflow in the LAF ventilated OR and results in an increase in the bacteria concentration. The open-shape lamp, in contrast, creates limited disturbances to the airflow and the desired flow pattern can be achieved. TcAF shows good performance in reducing the concentration of airborne contaminant with both closed-shape and open- shape lamps. In the TcAF system, the cooler air falls down to the surgical site from the supply diffusers, forming a relatively unidirectional flow over the surgical site. This buoyancy-driven downward flow is capable of washing off bacteria carrying particles from their sources and preventing them from reaching the patient.
(f) Aganovic, A., Cao, G., Stenstad, L. I., & Skogås, J. G. (2017)
Impact of surgical lights on the velocity distribution and airborne contamination level in an operating room with laminar airflow system. Building and Environment, 126, 42-53.
The presence of surgical lights disturbs the flow of ultraclean air in operating rooms (ORs) with vertical laminar airflow systems (LAF) by creating a wake downstream of the lights. The wake may be characterized by velocities low enough to directly influence the level of airborne microbe- carrying particles close to the surgical site in an OR, eventually leading to surgical site infections (SSIs). In order to detect microbiological contamination during operating conditions, four mock surgeries were performed mimicking real surgeries on a porcine tissue. Three of the surgeries were performed under different types of surgical lights and one surgery did not include surgical lights at all. The mean velocity under all three surgical lights was significantly lower (≤0.07 m/s) compared with the mean velocity measured when the LAF was not obstructed by lights (0.24 m/s).
(e) Buhl, S., Eschenbecher, N. & Bulitta, C. (2016)
A TAF ventilation system installed in the research operating room of the Ostbayerische-Technische Hochschule Amberg-Weiden in Germany was evaluated using CFD analysis. It was proven to be less influenced by obstacles in the operating room such as operating lamps. According to Swedish standard for microbiological purity in the operating room SIS-TS 39: 2012 active air sampling was performed under real operating conditions and verified that the TAF ventilation system is efficient regarding reduction of airborne bacterial contamination.
(d) Sadrizadeh, S. & Ekolind, P. (2016)
The performance of a TAF ventilation system was evaluated using CFD. The temperature difference between the air supplied from the central and external air showers subdivided a fully equipped operating room into two distinct zones; one in the critical surgical zone that showed a strong unidirectional downward airflow with air velocities high enough to wash of all released bacteria carrying particles above the operating table, and another in the periphery were the external air showers diluted periphery-emitted particles via a mixed airflow. The system proved robust to heat loads as well. A recovery test based on ISO 14644-3:205 showed that the recovery time for the TAF ventilation system is well below the limit proposed by the standard.
(c) Bulitta, C., Magerl, F., Hartwich, R. & Russwurm, B. (2015)
The Technical University of Applied Sciences Amberg-Weiden in Germany is equipped with a fully functioning high-tech operating room. A TAF ventilation system installed in the operating room was subjected to CFD analysis and the temperature and airflow behaviour was examined and compared with experimental data. The results showed good agreement between simulation and measured air velocities as well as temperature distribution which supports the notion of CFD analysis being a good tool to investigate such properties.
(b) Sadrizadeh, S. & Holmberg, S. (2014)
By using computational fluid dynamics, the performance of three different ventilation systems for operating rooms was investigated. The examined ventilation principles were turbulent mixed airflow, laminar airflow and temperature controlled airflow and each system was evaluated in the same operating suite. Using LAF ventilation, a strong reverse flow pattern was observed in the outer edges of the operating room. The TAF ventilation system managed to damp the reverse flow well with the external air showers. Regarding the TMA ventilation, reverse flows occurred in most parts of the operating room as well as airflow stagnation in the corners of the room.
(a) Zoon, W. A. C., van der Heijden, M. G. M., Loomans, M. G. L. C., & Hensen, J. L. M. (2010)
On the applicability of the laminar flow index when selecting surgical lighting. Building and Environment, 45(9), 1976-1983.
Surgical lamps can significantly disturb the flow of clean air. Zoon et al. conducted experimental and numerical studies and found that the infection risk was proportional to the projected area of the surgical lamp. Zoon et al. measured velocities that ranged from 0.10 to 0.20 m/s under three differently shaped and sized surgical lights using hot sphere anemometers in a small scale experimental chamber equipped with LAF. This study also showed that the velocity was lower under closed shaped lights compared with light-heads with openings.
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