One of the many challenges involved in completing a successful operating room project is maintaining environmental conditions that meet the demands of the surgical staff and comply with the applicable healthcare requirements. An important step in designing an operating room is to solicit input from the surgeons and surgical staff early in the design process regarding the targeted space temperature and relative humidity conditions. If this input occurs late in the design process, it could lead to a major redesign of the HVAC system(s), which could lead to project delays and budget overruns.
An important step in designing an operating room is to solicit input from the surgeons and surgical staff early in the design process regarding the targeted space temperature and relative humidity conditions. If this input occurs late in the design process, it could lead to major redesign of the HVAC system(s), project delays, and budget overruns.
The sections below address several important considerations when designing operating room environments:
- Operating Room Temperature and Humidity
- When Surgeons Request Lower Temperatures
- Operating Room Ceiling Alternatives
Operating Room Temperature and Humidity
ASHRAE Standard 170-2008, Ventilation of Healthcare Facilities, which is included as part of the 2010 FGI Guidelines for Design and Construction of Healthcare Facilities, defines the acceptable limits for operating rooms as 68°F to 75°F space temperature and 30% to 60% relative humidity (RH).
Addendum d to ASHRAE 170, issued in July 2010, revised the acceptable lower limit of relative humidity to 20%. This lower relative humidity limit has recently been accepted by the Centers for Medicare and Medicaid Services (CMS) through a categorical waiver. Facilities who desire to use the 20% lower limit are required to have documentation stating this fact.
It is important to remember the correlation between space temperature and relative humidity. As the temperature of a room is lowered, the coinciding RH level increases.
This relationship is particularly important in a surgical environment where room space temperatures are targeted to be lower than the 68°F limit identified in ASHRAE Standard 170-2008. It is not uncommon, for example, for surgeons to request room temperatures in the range of 60°-65° F in their operating rooms.
Maintaining space RH conditions below the 60% upper limit at these space temperatures requires special consideration for the HVAC system. Typical HVAC systems cannot adequately dehumidify the supply air during spring and summer operation to meet low space temperature and RH targets.
In order to consistently maintain operating rooms below 68°F, HVAC design solutions may require special applications, including desiccant wheels or low-temperature chilled water systems.
Whether you are planning major operating room renovations or a new operating room suite, it is important to work with the design team and surgical staff to define the target operating room environmental conditions in the early stages of the design process. After the desired environmental conditions are identified, the design team can evaluate what HVAC systems will be appropriate or necessary to obtain the targeted space conditions.
Low-temperature requests from surgical staff are common enough that they warrant a closer look at how these conditions affect HVAC system performance.
When Surgeons Request Lower Temperatures
Our Surgeons Want What Temperature in Their Operating Rooms?
Does this question sound familiar? Every facility manager has probably muttered, or at least thought, this question at some point.
With surgeons performing longer and more complex surgeries, requests for colder operating room temperatures have increased, and it is not uncommon for surgeons to request room conditions that are outside “normal” parameters.
The question here is: what are “normal” operating room space conditions?
The answer is, it depends.
ANSI/ASHRAE/ASHE Standard 170-2013 defines that operating rooms should be designed to maintain space temperatures between 68-75 deg F with space relative humidity between 20-60%.
While many may consider this as “normal”, the reality is that most surgeons are asking for space temperatures lower than 68 deg F, so it is important to understand the impact that these requests have on your HVAC system.
Standard HVAC systems in hospitals are designed to provide 50-55 deg F supply air. At these temperatures, the systems are capable of maintaining approximately 66-68 deg F space temperature while holding space relative humidity below the upper limit of 60%.
If the space temperature is allowed to trend below this range, the space humidity may rise above 60% creating regulatory compliance and patient infection issues.
There are many strategies that can be employed to address low operating room temperature requests.
These options range from having informed discussions with the surgical staff to help them understand the practical limitations of the HVAC system to utilizing specialty HVAC systems that either produce low temperature supply air or utilize desiccant wheel technology to “dry out” the air and maintain lower space relative humidity levels at the reduced space temperature.
Another option that some facilities explore is providing “cool vest” or shirt solutions for surgical staff to keep them cool during procedures without lowering the overall room temperature which limits the operational impacts on the HVAC system.
There are many factors to consider when addressing low temperature and humidity requests from your surgical staff. There is no one size fits all solution so it is important to be armed with a solid understanding of the thermodynamics and psychrometrics involved as well as the myriad of options and approaches that can be implemented.
Having informed and open discussions with your clinical and leadership teams will help you ultimately get to the best value solution for your organization.
Environmental performance is only one component of operating room design. As operating rooms have incorporated more equipment and technology, coordinating everything within the ceiling has become increasingly complex as well.
Operating Room Ceiling Alternatives
For many years the conventional operating room ceiling consisted of a gypsum board or plaster ceiling with openings framed out for lights and diffusers. Openings would be field cut in the gypsum board for overhead surgical light supports, diffusers, general lighting and medical gas columns.
With the advent of hybrid operating rooms, the construction of operating room ceilings has become more complex.
These hybrid rooms contain imaging equipment hung from rails in the ceiling that are supported from the structure above. The imaging equipment is designed to move horizontally along these ceiling tracks.
In addition to this overhead imaging equipment, there are more ceiling booms being provided to support multiple surgical lights, monitors, and medical gas outlet sets.
It becomes very difficult to field fabricate a tightly sealed gypsum board ceiling with all the openings required for the support rails, lights, diffusers and booms.
As an alternative to field fabricating gypsum board operating room ceilings, several manufacturers of operating room type diffusers have developed an integrated ceiling system.
The integrated ceiling system consists of a pre-engineered tee grid system that can be shipped from the factory in pieces and assembled in the field. The grid system is assembled on the floor of the operating room and lifted into place after it is assembled.
The grid has a gasketed framing system that provides a tight seal for diffusers and lights between the ceiling plenum and the operating room.
Framed openings are provided for laminar diffusers, lights, booms and access panels. Blank panels are provided to match the look of the laminar diffusers. These blank panels are used for access above the ceiling as well as for boom supports that penetrate the ceiling.
The material cost of the integrated ceiling system is higher than the field fabricated gypsum board ceiling system, however there is typically a substantial savings in the installation cost.
Other advantages of the integrated ceiling systems are its appearance and the tight seal provided between the ceiling plenum and the operating room.
Additionally, pre-engineered ceiling systems allow designers and constructors to fit all of the necessary support systems in tighter ceiling plenum spaces than a traditional “stick-built” assembly.
Successful operating room design requires early coordination between the design team, facility staff, and surgical staff.
Temperature and relative humidity targets can have significant implications for HVAC system selection and performance, particularly when surgeons request conditions below typical operating ranges. At the same time, the increasing amount of imaging equipment, surgical lights, booms, diffusers, and other overhead systems makes ceiling coordination an important part of the overall operating room design.
Defining these requirements early in the project allows the design team to evaluate the appropriate HVAC and ceiling solutions before they result in major redesign, schedule impacts, or added construction costs.
For more information about operating room design, temperature and humidity control, HVAC requirements, or integrated ceiling systems, please contact us.