Less infectious by design

Hospital-acquired, or nosocomial, infections affect one in 10 patients admitted to UK hospitals, resulting in more than 5,000 deaths a year and costing the country's National Health Services £1bn. On average, a patient with hospital-acquired infection spends two and a half times longer in hospital, incurring additional costs of £3,000 compared with an uninfected patient.1

Nosocomial infections typically affect patients who are immunocompromised because of age, underlying diseases, or medical or surgical treatments. A strong body of research shows that the built environment in particular influences the incidence of infection in hospitals and that, by careful consideration of environmental transmission routes - surface, air and water - in the design and operation of healthcare facilities, hospital-acquired infections can be reduced dramatically.

This article presents some of the key findings in the US from a recent review of the literature conducted by The Center for Health Design with funding from the Robert Wood Johnson Foundation, linking physical environmental design factors with hospital acquired infections in acute care settings. The complete paper, entitled “The Impact of the Environment on Infections in Healthcare Facilities”, can be downloaded from The Center's website at www.healthdesign.org.

Surface transmission

Most infections are now acquired in the hospital via the contact pathway.2,3 Microbiologically contaminated surfaces can be reservoirs of pathogens. However, these surfaces are generally not associated with the direct transmission of infection to patients or staff.4 It is the hands of healthcare staff that is the principal cause of contact transmission from patient to patient.5 Poor handwashing compliance by healthcare staff (rates in the range of 15%-35% are typical) pose a serious problem in this regard.

Education programmes to improve handwashing compliance among staff have not been successful. Studies show that providing environmental support for handwashing through visual cues (such as posters reminding staff to wash their hands) and the presence of numerous, conveniently located sinks and handwashing dispensers and alcohol rubs may result in an increase in handwashing rates.6 For example, in one study, a combination of bedside antiseptic hand-rub dispensers and posters to remind staff to clean their hands was effective in increasing compliance.7

While most infections are not directly transmitted to patients from environmental surfaces, these surfaces come into contact with the hands of caregivers frequently. Given the low handwashing compliance in healthcare facilities, regular cleaning and disinfection of environmental surfaces as appropriate is critical to controlling surface contact transmission of infections.

Environmental surfaces that are likely to get contaminated by pathogens can be divided into two groups: high touch surfaces - those with frequent hand contact (such as surfaces of medical equipment and high-touch housekeeping surfaces such as doorknobs, bedrails, light switches, wall areas around the toilet in the patient room, and edges of privacy curtains); and low touch surfaces - those with minimal hand contact (e.g. floors and ceilings).

High-contact surfaces in patient-care areas need to be cleaned and disinfected more frequently than minimal contact surfaces. The CDC and HICPAC Guidelines for Environmental Infection Control in Healthcare Facilities provide recommendations for cleaning and maintaining different types of environmental surfaces to prevent the spread of infection.4

Airborne infections

Airborne infections are transmitted from person to person as droplets, and when environmental reservoirs of a pathogen (e.g. soil, water, dust) are disturbed, for example during renovation and construction activities. The importance of good air quality in controlling and preventing airborne infections in healthcare facilities cannot be overemphasised. Providing clean filtered air and effectively controlling indoor air pollution through ventilation are two key aspects of maintaining good air quality.

In this context, HEPA filters that are at least 99.97% efficient for removing particles ?0.3 µm are recommended for special care areas of the hospital such as surgical areas, burn ICU units, and protective environments for immunocompromised patients.

There is convincing evidence that immunocompromised and other high-acuity patient groups have lower incidence of infection when housed in HEPA-filtered isolation rooms.8 In one study, bone-marrow transplant recipients were found to have a ten-fold greater incidence of nosocomial Aspergillus infection, compared with other immunocompromised patient populations, when assigned beds outside of a HEPA-filtered environment.8

Effective ventilation is also important for controlling the level of pathogens in the air. Most ventilation rates for healthcare facilities are expressed as room air changes per hour (ACH). Peak efficiency for particle removal in the air space occurs between 12 ACH-15ACH.4 Air contamination is least in laminar airflow rooms with HEPA filters, and this approach is recommended for operating-room suites and areas with ultraclean-room requirements such as those housing immunocompromised patient populations.8, 9, 10, 11, 12, 13 Laminar flows are very even, smooth, low-velocity airflows that are used in cleanrooms and other settings where high-quality ventilation is critical.

Other than providing good quality air and ensuring adequate ventilation in patient-care areas, instituting effective prevention and control measures during construction and renovation is critical. Effective measures include using portable HEPA filters, installing barriers between the patient-care and construction areas, using negative air pressure in construction/renovation areas relative to patient-care spaces, and sealing patient windows.

Single rooms are an effective infection control strategy. The evidence from many different studies suggests that providing single rooms might be a critical strategy for reducing nosocomial infection in hospitals.

Three studies have been identified that suggest that providing single-patient rooms with a conveniently located sink in each room reduces nosocomial infection rates in ICUs, such as neonatal intensive-care or burn units, compared with when the same staff and comparable patients are in multibed open units with few sinks.6

Further, single-bed rooms are clearly superior to multibed rooms in preventing the transmission of airborne pathogens from one patient to others because of the ease in isolating a patient and providing high-quality HEPA filters, negative room pressure to prevent a patient with an aerial-spread infection from infecting others, or maintaining positive pressure to protect an immunocompromised patient from airborne pathogens in nearby rooms.

Compared with single-bed rooms, multibed rooms are far more difficult to decontaminate thoroughly after a patient is discharged, and, therefore, worsen the problem of multiple surfaces acting as pathogen reservoirs. Because different staff members who enter a room can touch the same contaminated surfaces, the risk of a nurse unknowingly becoming contaminated should be greater in multi-occupancy rooms.6

Water-borne sources

Water-borne infections spread through direct contact (e.g. for hydrotherapy), ingestion of contaminated water, indirect contact, and inhalation of aerosols dispersed from water sources. Water-borne infectious pathogens such as Legionella enter healthcare facilities most often through aerosols generated by cooling towers, showers, faucets, respiratory therapy equipment, and room-air humidifiers. Point-of-use fixtures, such as sinks, showers, aerators and toilets, may serve as reservoirs for pathogens such as Legionella. Many studies have linked aerosols from shower heads and aerators with the outbreak of infection including Legionnaires' disease among immunocompromised patients.14, 15, 16, 17

In this context, the use of decorative fountains in hospitals has often been opposed by staff and infection control specialists. On the other hand, such features serve as landmarks or wayfinding elements and create positive distractions. There are no documented cases of hospital-acquired Legionnaires' disease or any other water-borne infectious diseases that resulted from the indoor placement of a water fountain or water feature in hospital spaces.18

The only such documented outbreak of Legionnaires' disease was among a group of older adults in a hotel. This was associated with a decorative water fountain that was not properly maintained and was lit by submerged lighting that caused the water to become warm - providing the ideal condition for the growth of legionella bacteria.19

Regular cleaning, maintenance, and testing of water systems and point-of-use fixtures is important for preventing the spread of water-borne infections such as Legionnaires' disease. Another important aspect of preventing contamination through the water supply involves designing the water supply system to minimise stagnation and back flow as well as provide temperature control to prevent growth of bacteria.

To summarise, some key considerations for preventing and controlling the spread of nosocomial infections include the following:

• Careful design and maintenance of the HVAC system including incorporation of HEPA filters reduces the threat of airborne diseases.
• Proper precautions during design and construction activities are also critical to preventing the spread of airborne infections.
• Single-bed rooms are strongly recommended - it is easier to isolate infectious pathogens and disinfect single-bed rooms than multioccupancy rooms once a patient has been discharged. The threat of infections spread through contact transmission of pathogens is also reduced in single-bed rooms.
• An important aspect of reducing infections spread through surface contact involves providing environmental support for handwashing - visible, conveniently placed sinks, handwashing liquid dispensers and alcohol rubs.
• Regular cleaning, maintenance, and testing of water systems and point-of-use fixtures is important for preventing the spread of waterborne infections such as Legionnaires' disease.