The impact of patient room design on hospital airborne infections

The Affordable Care Act’s many provisions designed to transform the healthcare delivery system include financial incentives for medical centers to reduce and eliminate hospital-acquired infections (HAI) and “never events,” the kinds of major, preventable medical errors groups like the National Quality Forum have declared must never happen.

By limiting reimbursement to hospitals for services required for hospital-acquired infections, the ACA creates an incentive to promote infection control and coordinated care.

One particularly important HAI concern is preventing the transmission of airborne diseases within healthcare facilities, due both to the reduction in funding from insurance companies for HAIs as well as the economic impact of infectious outbreaks within a hospital. While design guidelines have focused on recommending appropriate ventilation rates, they generally disregard the impact of room layout relative to the delivery of conditioned air to occupied spaces. Supplied ventilation is designed to positively contribute to air-mixing and distribution, improvement of thermal comfort, and air quality conditions. Unfortunately, air distribution also contributes to airborne pathogen transmission.

Working with a colleague, Dr. Adil Sharag-Eldin an associate professor of Architectural Sciences at the College of Architecture and Environmental Design at Kent State University., I recently completed a study of the important but overlooked role that room design plays in how successfully ventilation systems remove contaminated air from patient rooms to reduce the risk of airborne disease transmission.

What we learned, as I’ll describe more fully below, is that decisions about whether to locate entrances to bathrooms in patient suites along hallway walls or exterior walls, or next to the heads or feet of patients’ beds, can have a significant impact on the performance and effectiveness of the air-ventilation system. Depending on where a bathroom is to be sited in a patient room, adjustments to the standard placement of air ducts and returns may prove necessary to maximize healthy air.

Among the organizations that set standards for the prevention of disease transmission are Facilities Guidelines Institution and the American Society of Heating Refrigeration and Air-Conditioning Engineers (ASHRAE). Standards for healthcare facilities require fresh air continuously enter spaces through the effective maintenance of heating, cooling, and ventilation requirements within acute patient rooms. The standard of measurement is “air changes per hour” or ACH, or the number of times per hour the volume of air within a room is replaced by ventilated air. ASHRAE’s standard is that non-critical patient rooms should receive six ACH, with a minimum of two of those complete air changes coming from outdoor air brought inside. However, the standard does not suggest how to effectively remove contaminated air that may be caught in dead zones affected by room design.

The design of patient rooms has gone through a great change in the past 10 years. While once multi-bed wards were common, now single patient rooms with private bathrooms are the standard. It is important to understand the impact that the configuration of the room has on all users including the patient, visitors, nurses, doctors, therapists and cleaning staff. The new ACA financial incentives and reimbursement deductions are pushing architects and designers to promote improved waste management, patient safety, staff efficiency, circulation, infection control, patient consideration, and family amenities.

Many factors can influence the layout of patient room. A primary concern during design is the placement of the bathroom within the patient room. The bathroom can either be located on the headwall, or foot wall. Besides where the bathroom is located in relation to the patient’s head or feet, the bathroom may be located on the façade wall of the building (outboard) or the interior corridor wall (inboard).

Each configuration has benefits to the patient and caregiver as well as negative impacts. While caregivers may prefer the outboard configuration, because it is easier to see patients from the hall, patients may feel their privacy is diminished. There is a significant lack of empirical evidence to support one layout over another. Many layouts are chosen by stakeholder perspectives, not necessarily on viable research. Design teams must choose configurations that promote clients’ goals while understanding the implications these layouts can have on all use groups.

As Dr. Sharag-Eldin and I found in our research, room configuration plays a large factor in airflow patterns and “air age’’¬–how long has it been since air in a specific spot in a patient room was replaced by ventilated replacement air. In a 6 ACH room, in theory, no zone would have air with an “air age” of more than 10 minutes. Our study found, however, that depending on the configuration of a room and its ventilation, average air age in various spots could range from 9 minutes to as much as 15.5 minutes, which significantly increases the risk of the spread of airborne infections like influenza A because they, in effect, sit in the room longer before being flushed out by ventilation exposing a greater number of physicians, nurses, staff, visitors, cleaners, who enter the room. In addition, because air supply outlets are typically located above patients’ beds, often the least-effectively-ventilated zones of the rooms are those where family and visitors sit, increasing their susceptibility to infection.

The ASHRAE standards do not take into consideration the causal relationship between the room configuration and ventilation efficiency. Our study did not lead to a firm conclusion that certain configurations of bed, bathroom, and family space within patient rooms are best and others should be avoided–only that depending on configuration, the typical placement of fresh air supply over a patient’s bed should be carefully evaluated. With new emerging airborne threats and the potential for older airborne threats to resurface, the standards should no longer just consider ACH to achieve well mixed spaces, but also how the space itself influences the airflow and dispersion of possible pathogens. The standard does require the use of High Efficiency Particulate Air (HEPA) filters, which prevent outside pathogens from entering rooms as these systems are typically applied to inlet air ducts. However, it does not consider pathogen transmission from internal sources like patients, staff and visitor, a risk that increases the more a given room is failing to meet the six ACH standard.

The impact of transmissible airborne diseases in the healthcare system is a large concern, especially when acquired in the hospital. Tuberculosis is known to spread rapidly as an aerosolized particle and consequently has been a factor in hospitals initializing HEPA filters in ventilation systems, as well as Ultraviolet Germicidal Irradiation (UVGIs).

Some pathogens’ main route of transmission is by contact or droplet spread, but they can occasionally become airborne as well. The relative impact of airborne dissemination is challenging to measure due to the large number of factors that have been found to influence airborne transmission. These include temperature, humidity, and survival rate of microbes. Regardless of the many factors that can influence the survival rate and transmission of airborne infections, they are seen as a growing and predominate threat in healthcare settings. The potential for outbreaks and pandemics due to mutating strains like that of influenza and other infectious airborne diseases need to be addressed with preventative action including active design strategies that can help negate virus transmission.

Mechanical ventilation contributes to air temperature, distribution, thermal comfort, air quality, and the possibility of airborne pathogen transmission within a space or spaces. Airflow patterns of existing rooms can influence pathogen transmission due to pre-existing relationships between location and type of supply diffusers, supply airflow rates, supply temperature, air return location and size, infiltration, furniture arrangement, heat sources and location of the patient and others in the room. These patterns need to be understood by the design team in order to thoughtfully design room layouts, and mechanical placement for the safety of caregivers and patients alike.

Despite the ability of ventilation to dilute pathogen density, it can also cause detrimental airflows that may create stagnant air and increase risk of infection. Many factors must be considered in order to fully understand the transmission of certain airborne infectious diseases as well as the inactivation of them. To fully comprehend how to prevent transmission, a multi-level team should comprehensively address ventilation, patient and others’ movement, design factors, and the possible pathogen threats themselves individually as well as in relation to each other.

The key takeaway from our research: Meeting standards for air movement at the HVAC system level is not enough to prevent airborne infections and the public-health and financial challenges they pose for hospitals. Design teams and all stakeholders–healthcare facility managers, architects, engineers, hospital staff and patients–need to understand more completely the roles that room design, bathroom location relative to patients and hallways, and details as granular as the locations and movements of specific doors can play in affecting the performance of ventilation systems and the spread of infectious disease. It is not enough to simply focus on new air requirements provided by air delivery systems, as this does not adequately control the spread of airborne diseases.

Alexa Copeland, is a Project Coordinator at E4H Environments for Health Architecture, where specializes in healthcare infection control. She is certified in Evidence-Based Design (EDAC.) Alexa can be reached at acopeland@e4harchitecture.com.

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