Abstract
Introduction
Operating theatre airflow can be measured using pulsed lasers (particle image velocimetry) but the process is difficult to do in 3D. Cup, vane or hot wire anemometers provide only 2D information. 3D measurements enable better understanding of airflow.
Patients/Materials & Methods
We used a Windmaster ultrasound 3D anemometer (Skyview systems), which uses three ultrasound transmitters to measure velocity in XYZ planes, with a sampling rate of 32 Hz. Post processing was done using MATLAB.
An operating theatre with an Howorth Exflow canopy was studied. Equipment, including lights, was moved. A 50 cm grid was marked, and measurements were made at intervals up to the ceiling.
Door opening was observed within the clean zone and the peripheral zone, next to the door and on the opposite side of the room.
Anaesthetic screens were studied during operating. Airflow was visualised initially using video of smoke puffs and subsequently measured using the aeronometer.
Results
In the upper part of the ultraclean canopy air velocity was 0.34 m/s with a standard deviation of 0.02 m/s, indicating an almost constant velocity. In the periphery there was more turbulence and horizontal air movement.
Door opening had no effect on air movements in the clean zone. In the periphery there was an increase in horizontal airflow when the doors are closed.
There is a pattern of upward airflow against an anaesthetic screen. This is unlikely to be caused by warming blankets. If the partial wall of the enclosure is lowered this results in a fast washout of air towards the anaesthetist.
Discussion
Traditional anaesthetic screens may interfere with airflow. Door opening is a lesser effect.
Conclusion
The 3D anemometer enables detailed mapping of airflow within an ultra clean air operating theatre. The data obtained will enable the construction of more accurate computational fluid dynamic models of operating theatres.
