The temperature and the humidity (30%-60%) play a very important role in maintaining staff and patient comfort. They must be carefully regulated and monitored. In low humidity there is a danger of the production of electrostatic sparks. Ideally, the operating room should be 1ºC cooler than the outer area. This aids in the outward movement of air because the warmer air in the outer area rises and the cooler air from within the operating theatre moves to replace it.
Ideal Air Ventilation System: Air Supply and Exhaust
Positive pressure ventilation with respect to the corridors and adjacent areas in the operating theatre where surgical procedures are performed should be maintained. The number of operating theatres supplied by air handling units (AHUs) should be limited to the number that can be sufficiently supplied to achieve the required air changes. Also, there should be routine maintenance of the AHUs, scheduled calibration of air flow monitors / sensors and these units should not be turned off unless being serviced.
Design features
Parameters to have in place if possible based on available resources are:
• Air changes
Maintenance of 15-20 air changes per hour (depending on code and time of construction), of which at least 3 should be fresh air from outside.
• Filtration
Filter all air with appropriate pre filters (e.g. filtration efficiency of 30%) followed by final filter (e.g. 90%)
• Air supply
Air should enter at the ceiling and be exhausted near the floor (important: furniture or other portable items placed against a wall exhaust at floor level will inhibit the air changeover in a OR and therefore should be monitored and abated).
• Ultraviolet Germicidal Irradiation (UVGI)
Do not use UVGI in the operating theatre to prevent SSI.
• Doors
Keep OR doors closed except as needed for passage of equipment, personnel and the patient.
• Traffic
Limit the number of personnel entering the OR to only those necessary for the surgical procedure. The microbial level in the OR is directly proportional to the number of people moving about in the theatre.
• Laminar flow & ultraclean air
Laminar airflow is designed to move particle free air over the aseptic operating field in one direction. It can be designed to flow vertically or horizontally and is usually combined with high efficiency particulate air (HEPA) filters. HEPA filters remove particles > 0.3 micron in diameter with an efficiency of 99.97%. Ultraclean air can reduce the incidence of SSIs especially for orthopedic implant operations; however, some studies suggest that other interventions such as appropriate timing of preoperative antibiotics and good OR practices such as limiting nonessential traffic can also lower incidence. Therefore, if resources are limited, laminar flow with HEPA filtration is not required for high quality surgical care.
Guidelines for Environmental Infection Control in Health Care Facilities
