Each year in the United States, roughly 1.7 million cases of healthcare-associated infections (HAIs) cause an average of 99,000 deaths and cost hospitals around $20 billion, according to Centers for Disease Control and Prevention estimates.

The majority of the literature on this subject focuses on how nursing and physician practices can reduce these rates; however, building environment conditions play a role, too. From design to maintenance, engineering can help prevent HAIs and ultimately improve patient health and satisfaction.

However, design teams must keep in mind that once constructed, hospitals and their mechanical systems have to function optimally for several decades to achieve this goal. To do so, it’s important to first understand how a building will be used and how to meet stringent indoor air quality requirements, and then design all systems to be easily maintained and operated over time.

To fully understand how a facility will be operated after construction, the team of architects, engineers, and contractors should gather all the owner’s project requirements early in the design process. The team must delve into how doctors and nurses will actually use a space. Conducting this robust discovery early on will form a basis of design that meets the on-the-ground needs of hospital staff.

These clinical needs are often outside the confines of codes, though—it’s important to remember that code is always the bare minimum of how a space is to be designed. Particularly for highly critical spaces, design should be closer to best practice (as established by clinical trials) than to the code minimum. And when deciding on whether to invest in creating high-quality environmental conditions, consider what clinical program is being housed in each given space, how critical the space is, and how high the risk is for HAIs.

Air quality
During invasive procedures like surgery, air quality plays a crucial role in protecting the patient from airborne infectious agents, especially in spaces where dirty air can come into contact with an open incision. Good air quality depends on adequate filtration, the volume of new air, and pressurization.

The concept of indoor air quality is relative, depending on location. For example, a surgery unit is more critical than a basic care patient room, which is more critical than an ultrasound room. It’s important to serve each of these spaces with different air handling and distribution systems to minimize the risk of infection while maintaining efficiency.

In surgery units, the clinical environment needs to have a high quantity of clean air at low velocity (to avoid turbulence where the surgeon is working) with a high number of air changes. Less critical spaces need fewer air changes and a higher air velocity is acceptable. Additionally, surgery units need to maintain positive pressure to keep contaminates from entering the surgical suite, while infectious isolation patient rooms must maintain negative pressure so that air crossing patients exits on their far side, protecting the caregiver space.

Additionally, the air filtration needs for each of these systems should be weighed. For the most critical of spaces, where there are immunosuppressed patients, every added layer of filtration can be beneficial. Extremely high levels of filtration (99 percent or greater in captured particulate count) protects immunosuppressed patients in critical spaces such as surgery, burn, or critical care units. Noninvasive patient rooms, on the other hand, may need only 85 percent filtration. Filters are selected based on their efficiency to capture air particulates and as defined by state codes.

New technologies like ultraviolet germicidal irradiation (UVGI) systems are often installed adjacent to air handler chilled water coils and can help improve the quality of the air as it passes through a duct by killing any bacteria in the airstream with UV light.

Choosing filtration levels across an entire hospital is a matter of balancing the specific need of the space versus the efficiency of the system. Generally speaking, the higher the level of filtration, the higher the cost and increased maintenance required. In the end, each decision about air distribution, filtration, and pressurization should be considered in the perspective of the end goal: clean air for the patient and better patient outcomes.

Another important factor that contributes to the transmission of HAIs is humidity. In oxygen-enriched environments like surgery, low humidity creates the risk of static discharge and possible fire. Conversely, if humidity is too high, there’s a risk of growing harmful organisms like mold or bacteria that cause HAIs. Keeping humidity within the ideal range of 20 to 60 percent is extremely important for patient safety.

If the humidistat is located on the surgery room walls, which it generally is, there will be a sharp differential between the actual humidity level at the patient and the humidity level measured at the humidistat.

One solution is to place the humidistat in a location that’s both easily accessible and provides an accurate reading of the patient’s immediate environment. The current best practice is to have the humidistat located in the exhaust/return air duct with an access door for maintaining calibration and service. The sensor would also be connected to the HVAC building automation system and allow for continuous monitoring. Then, if the humidity falls out of range, the system would alert a facilities manager to immediately implement dehumidification or humidification strategies.

Designing for maintenance
Poor maintenance is also a leading cause of environmental conditions that lead to HAIs. Examples include loose filters allowing air to pass by without filtration, old filters not changed until they’re clogged and blocking needed airflow, and dangerous outgrowth of mold on filters that leads to dirty air reaching patients.

Designers have the opportunity to facilitate proper maintenance by understanding how systems will be operated both at the clinical and facilities levels. Specifically, particular attention should be paid to the space that’s being served, the patient population, the size and type of filters required for protection, and how filters and filter racks fit in ducts so there are no gaps. The next move is to create systems that are accessible and easily serviced.

The mechanical room should be easy to access in order to maintain the systems housed there. To inspect and clean the ducts, it’s important to build access panels at critical locations where dust buildup can be expected—such as 90 degree turns or duct transitions—and where each filter is located. Keeping the ductwork clean prevents the opportunity for harmful organisms to contaminate air as it passes through it to the patient treatment areas.

Pay it forward
Designing mechanical systems with a focus on patient outcomes has major benefits. Considering that two criteria for reimbursement from the Centers for Medicare and Medicaid Services are re-admittance rates and patient satisfaction, upfront investments in the environment of care are minor in comparison to the costs avoided and the lives potentially lost. Implementing these strategies are small decisions that can result in positive results that can be magnified over the lifetime of a hospital.

To accomplish this, mechanical engineers and designers must understand the clinical environment and how patient care is provided. Since building codes in the healthcare sector are minimum standards, clinical practices and systems maintenance should anchor designs. Designers must see their role as integral to clinical best practices and the prevention of HAIs to provide easily maintainable systems that protect bo
th caregivers and patients.


Dan Swanson, CEP, CCP, CEM, CPE, is project director at McKinstry (Seattle). He can be reached at dans@mckinstry.com.