Your OR can be a great breeding ground and hiding place for infection, as these three cases show.

• Investigators blamed the endophthalmitis that infected four cataract patients on a ventilation system that was turned off over the weekend, long enough for the fungus Acremonium kiliense to grow in the vents. When the ventilation system was brought up to normal operating parameters on Monday morning, the vents released Acremonium into the OR. As you might expect, each of the four infected patients was the first case of the week's first surgical day.
• Six infections caused by Aspergillus spp. over 12 days at another facility was probably related to insulation in HVAC ductwork that had become damp.
• Then there was the case of fungal contamination of saline breast implants. The saline used to fill the implants was stored just below a water-damaged area of the OR ceiling, creating a perfect environment for growing fungal organisms. In addition, the OR where the implant procedures were being done was in negative pressure, and when fungus is dry, its spores can become airborne, especially in a negative pressure room.

Getting environmental recommendations for your OR is easy. From the CDC to the AORN, any number of government agencies, professional societies and infection-control organizations has guidelines at the ready. But you're pretty much on your own when it comes to determining your OR's environment maintenance policies.

For example, how do you know how often to test the air changes per hour (ACH)? What about pressure differentials or filtration for the OR or other critical ventilation areas? And don't forget about the frequency of cleaning ductwork and filters, humidity controls and visitor and other non-clinical personnel restrictions. Hopefully, this rundown of the latest guidelines to consider when setting your OR maintenance policies will help guide you.

1. Maintain your HVAC system.
Surgical facilities need to have data that demonstrate that their ORs have proper and/or effective air conditioning, humidification, airflow direction and filtration. Have a plan for maintaining your HVAC system and documentation that your facility has followed that plan. It's up to you to develop data on your HVAC system for each environmental control. Get input from your infection control personnel.

The CDC's Healthcare Infection Control Practices Advisory Committee (HICPAC) guidelines for environmental infection control in healthcare facilities say, "properly engineered HVAC (heating, ventilation and air conditioning) systems require routine maintenance and monitoring in order to provide acceptable indoor air quality efficiently and to minimize conditions that favor the proliferation of healthcare-associated pathogens." State health department regulations vary by state.

2. Air should flow from clean to dirty.
The general rule in healthcare provider construction is to provide airflow that contributes to a healthy environment. More specifically, this means that air (as well as people and equipment) should always move from clean to dirty - and not the reverse.

Air-quality concerns include odor control, fumes, gases and dust; not just the transmission of airborne infectious agents. Decontamination areas, soiled holding and utility rooms and bathrooms should all be designed for air to flow into the room, not out. Air flowing into a room is simply another way of defining negative pressure; that is, the room air is negative with respect to the adjacent areas. This is accomplished by setting your HVAC system to pull more air out of the room than it introduces to the "dirty" room. The pressure is balanced by letting adjoining areas furnish makeup air. The fact that you weren't aware that bathrooms and utility rooms were negative with respect to the corridor or nearby rooms means that they were probably designed and functioning properly.

You want to ensure that your ORs are under positive pressure with respect to the hallway. A simple positive-/negative-pressure test is to place a thin piece of tissue near any door openings in the room and see which way it blows: If it blows toward you, the room on the other side of the door is under positive pressure; if it gets sucked to the door, the room is under negative pressure. There are more precise ways to verify that all pressure relationships are proper, but that's the job of your facilities management department. It should ensure it has data that at least the critical areas - those that affect patient care and disease transmission, such as the OR, special procedure rooms, sterile-supply preparation areas, and laboratories on the "clean" side and decontam, soiled storage and handling, waste collection areas and bathrooms on the "dirty" side - have proper air changes and directional flow by whatever schedule is required by the organization's own policy manual.

3. Monitor your ACH.
Air changes per hour (ACH) recommendations vary from four ACH in storerooms to 15 ACH in the ORs. The AORN recommends 15 per hour for the OR, three of which should be outdoor air - which is why it's important to consider the source of the incoming air. The duct providing your outside air should not recycle air from another exhaust system and should not be near bird or rodent nests.

Similarly, the air can be exhausted either into the main exhaust system or exhausted through a dedicated system to the outside, again making sure that the exhaust vent is at least 25 feet from any incoming air ducts. Generally speaking, air from any negative-pressure areas should be exhausted either to the outside or through a HEPA-filtered partial re-circulating system.

Monitor ACH regularly to prevent the buildup of dust in the vents and changes to the ambient environment; always do a check after any changes to the air handling system. Some very old systems need to be checked quarterly, but in a new building or with a new HVAC system, twice a year is reasonable.

4. Clean the ducts.
In the American Institute of Architects' (AIA) 2001 Guidelines for Design and Construction of Hospital and Health Care Facilities, paragraph 7.31.D10 reads: "Air handling duct systems shall be designed with accessibility for duct cleaning, and shall meet the requirements of NFPA 90A."

Cleaning of all incoming and outgoing OR ducts must be a part of scheduled preventive maintenance. Make this easy to accomplish through convenient locations of access points into the room and the filters, and with easy-to-remove-and-replace grills. Remember, the grills are only covers for the ends of the ducts - they are not filters - and they are great accumulation points for dust, which can then easily compromise the surgical area.

There is no specific standard regarding scheduling. AIA guidelines prohibit U.S. surgical centers from shutting down their HVAC systems for any reason other than required maintenance, filter changes and construction. You can protect patients and staff during preventive maintenance with intelligent scheduling.

5. Control temperature and humidity.
You can have installed computerized building management systems that measure and adjust temperatures, pressures and humidity to your design parameters. These are great because they have automatic record keeping and alarms to let you know when any of the parameters are exceeded. In addition, humidity readings are sensed in the return air ducts, and the humidifier is adjusted automatically.

The AORN recommends you maintain humidity between 30 percent and 60 percent with temperature between 68'F and 70'F. A 1991 study of a hospital's ventilation system found that, as a hospital's HVAC system was neglected - making any proper humidity and temperature maintenance nearly impossible - infections increased. When a new ventilation system was installed, the ORs once again met these guidelines, and infections returned to baseline rates.

If your facility doesn't have automatic monitoring of these basic recommendations, you'll need to provide daily manual monitoring of these critical measurements. Include this in your procedure manual.

Informed judgment
As you can see, for the most part, good environmental considerations are left up to you. To a large extent, meeting the recommendations depends your facility's age, the type of patients you see, the OR manager's and infection control practitioner's influence, your budget and management's perception of the need for such controls. But by taking these five factors into account, and considering the available recommendations and evidence that they work, you can write a policy that fits your facility.