The Operating Theatre: HVAC Commissioning to Fight Airborne Particles and Bacteria
Patients face significant risks from infection during surgery, the threat is airborne.
Bacteria lurks… The issue is microscopic, but the impact on a patient can be devastating. Infections from surgery affect 1 in 10 patients worldwide, 3% will not survive. That’s 8 million people annually, or the entire population of Switzerland lost, year after year.
When ourselves or our loved ones are laying on the operating theatre table we need the confidence that as many risks as possible have been removed.
WE NEED TO PROTECT OUR PATIENTS.
How do we reduce the risks through HVAC?
- Unidirectional laminar flow design
- Positive air pressure to surrounding spaces
- A minimum of 20 air changes per hour at 50% outside air
- HEPA filters
- Operating table air velocities in the range of 0.2m/s and 0.3m/s
- Cross-flow air velocities to a minimum of 0.4m/s at 1 metre from the ceiling outlet
What is unidirectional laminar flow?
Airflow is directed from the ceiling to the floor, creating a downward flow of air that helps to keep the surgical field sterile. The air is drawn out of the room through outlets located at or near floor level.
What if we do not achieve laminar flow?
Turbulent air carries foreign particles and bacteria picked up from the floor and other areas into the protection zone.
How do we commission an Operating theatre?
- Room Integrity testing: The test ensures all airflows to the Operating Theatre room are controlled, and the HVAC system can create critical positive pressure needed in the space. It’s an important first step in the commissioning process and should be completed prior to any other works (on a new build its best performed before any plasterboard is installed)
- Airflow test and balance: Setting the Supply, Return, Outside and Exhaust air to the design values while the room is in a completed state are foundations for achieving the bacteria-free environment. This process involves some minor deviation from laid out design flows to achieve zone pressure differentials
- Table velocity test: The supply air flowing down from the ceiling to the patient on the operating theatre, which creates the protection zone, must be tested to ensure it meets a minimum and maximum velocity of between 0.2m/s and 0.3m/s
Contact us for more information in relation to design, testing, or require testing services.
Institutions within Australia that provide the relevant standards and guidelines in this post:
Statistics and useful topic related links:
Infection and the extended patient stay time: https://www.cdc.gov/nhsn/pdfs/pscmanual/9pscssicurrent.pdf
Mortality rates because of infection:
https://www.who.int/teams/integrated-health-services/patient-safety/research/safe-surgery
Incidents of SSI (Surgery site infection) Statistics:
https://www.sciencedirect.com/science/article/abs/pii/S1743919121002715#:~:text=The%20incidence%20of%20surgical%20site,83)