Laminar Air Flow in Operating Rooms

In order to reduce the concentration of germs and particles in the operating rooms, previously conditioned air is passed through HEPA filters at the end-use point and given to the environment. The air distribution system is important for the air quality in the operating room. For this purpose, air distribution devices that will provide laminar flow or create the least turbulence in the environment have been developed. Air distributors deliver the air at a lower temperature than the environment to the operation area, allowing the dirty air to be displaced towards the exhaust vents. In addition, with the HEPA filters they contain, it prevents germs and particles from being delivered to the operation area. Laminar flow enters turbulence when it encounters any obstacle or temperature difference due to its characteristics. On the one hand, low velocity air supply prevents cold air from falling directly in the operation zone, on the other hand, it makes the flow more sensitive.

External factors that disrupt the laminar air flow cause the clean air to mix with the room air and rapidly increase the concentration of microbes and particles in the operation zone. The factors that disrupt the air flow can be listed in detail as the physical and thermal effects of the operating team and their location in the operating room, the location of the medical devices and surgical materials, the operating table lamp position and its thermal effect. The position of the team performing the surgery during the operation and the lighting of the operating table cause turbulence in the air flow zone. Heat loads emanating from people cannot be reduced. The turbulence created by the operating table lighting and the air flow of medical devices can be reduced by improving the aerodynamic design. The aim of the improvement is to obtain an operating system with stable, laminar cold air that does not allow direct drop of air flow, combined with operating table lighting that causes as little turbulence as possible, and displaces germs and particles from the operation zone.

Although the velocity of the cold and laminar air increases downward in the vertical within the air throw distance, it does not create discomfort effect as long as the flow remains laminar. Laminar flow is provided smoothly downward at an air outlet speed of 0.15 m / sec. The supply air temperature should be 0.5 to 4 K below ambient temperature. In isothermal situations or in warm blast air the flow is not laminar. In addition, the purpose cannot be achieved since it will interfere with the ambient air.

While the area with laminar flow is created around the operating table, which is called a clean zone, in the area where this zone is in contact with the ambient air, the blowing air and ambient air are mixed in an unavoidable way and the mixing zone is formed. Because it is not possible to separate the operating table with any hanging curtains or similar equipment. Filtered and particulate-free supply air is provided around 0.5 m of the operation zone.
should be controlled and the mixture zone should be prevented from being in this area. However, if a 1.4 m wide laminar flow unit is used, filtered, particle-free air is provided around 0.5 m around the operating table. “Mixing Zone” is outside this area.

Source: Dipl.-Eng.F.Masuhr
Translated by: Aylin GÜLPINAR