Construction guidelines in hospitals

An infection control team member should participate on the planning team for any new hospital construction or renovation of existing facilities. The role of infection control in this process is to review and approve construction plans to ensure that they meet standards for minimizing nosocomial infections (Walker et al., 2007).
Considerations will usually include selection of the site of hospitals which should be away from overcrowded public areas especially for hospitals managing infectious diseases as TB, SARS, meningitis and pandemic influenza. Considerations also include proper ventilation, isolation room design, proper traffic flow and appropriate access to hand washing facilities (Lateef, 2009).

a. Ventilation:
Of all the possible engineering techniques that can be employed to control airborne pathogens, good ventilation is probably the most effective. Although most people are familiar with the general concept of ventilation, very few understand the principles on which it is based. The term ventilation should therefore only be applied to the supply of outside air to the room space (Crimi et al., 2005).
Dilution ventilation:
Most ventilation systems push large quantities of ‘clean’ outside air into occupied spaces so that any contaminants in the room space are diluted and flushed out to atmosphere. To function properly good mixing of the air in the room space is essential (McLarnon et al., 2006).
Laminar and displacement ventilation:
This is based mainly on directing airflows to displace the contaminated air so that it is ‘pushed’ out of the room space. In this way the contaminated air is continually being replaced by clean air. With this type of ventilation system it is undesirable to have any air mixing and so ‘laminar’ streams of air are often used. Such ventilation systems are frequently used in operating theatres and isolation rooms (Abdulsalam et al., 2010).



Pressure differences ventilation:
By controlling the airflows within a building it is possible to create ‘high’ and ‘low’ pressure regions. This can be used to great advantage in isolation rooms, which can be negatively pressurized space so that airborne pathogens are unable to escape. These negative pressures can be achieved by supplying less air to an isolation room than is extracted. It is recommended that a positively pressurized anteroom be placed between the corridor and the isolation room according to fire regulations (Crimi et al., 2005).
Natural ventilation:
Many hospital buildings, especially older facilities, rely heavily on natural ventilation. In many ways the natural ventilation of clinical spaces is a good solution. However, reliance solely on natural ventilation has a number of drawbacks such as ventilation rates will be variable and are greatly dependent on the outside climatic conditions. Also, Pathogens such as Aspergillus spp. which is widespread in the outdoor environment can easily enter ward spaces (McLarnon et al., 2006).
b. Room air cleaning devices:
There are a variety of room air cleaning devices currently available, incorporating technologies such as high efficiency particulate air (HEPA) filters and ultraviolet germicidal irradiation (UVGI) lamps. These devices are intended to be mounted within a room space and are designed to reduce the microbial level in the room air. They have the advantage that they are relatively cheap and can be strategically positioned to protect vulnerable patients and staff (Crutis, 2007).

High efficiency particulate air (HEPA) filters units:
HEPA filter units are readily available machines that can be used any where to provide clean air. These units are especially useful in settings that may have inadequate or no ventilation and limited funds for upgrades. HEPA filters exhibit very high efficiencies (i.e. 99.9 % efficient for particles 0.3µm in diameter). HEPA filter unit will provide cleaned air to dilute infectious particles and will also remove airborne particles. HEPA filter units are available in a variety of sizes and configurations. All consist primarily of pre-filter to remove coarser particles and thereby prolong the life of the HEPA filter, a fan to circulate the filtered into the room and controls, such as an on/off switch and fan speed control (Liao et al., 2008).
The most common types of units are portable, free standing and permanent devices. Ceiling-mounted and wall-mounted units are also available. Portable units have the advantage of greater flexibility and ease of installation and service (Eckmanns et al., 2006).
Ultra-violet (UV) germicidal irradiation:
The germicidal properties of UV light have been known about for many years; in the pre-antibiotic era. UV lamps were used extensively in tuberculosis (TB) wards to control the spread of infection, but with the development of anti-bacterial drugs and, in some countries the introduction of vaccination against TB, UV air disinfection fell out of favour. However, in recent years, with the global rise in TB, there has been renewed interest in its use as an infection control measure and several research programmes have been initiated in this field (Kujundzic et al., 2006).
The activation spectrum peaks in the range 260 to 270 nm is similar to the absorption spectrum of nucleic acids, thus deoxyribonucleic acid (DNA) is the main target. UV light at this wave length is absorbed by nucleic acids with the formation of pyrimidine dimers, resulting in damage to the DNA of the micro-organism which is lethal. Conventional low and medium pressure mercury discharge UV lamps have a strong spectral emission at 253.7 nm, close to the peak of the action spectrum and can be used as an effective bactericidal agent (Rudnick and First, 2007).
C. Isolation room design:
The interest in the use of airborne isolation rooms has increased due to the occurrence of new emerging diseases such as severe acute respiratory syndrome (SARS), avian influenza and multi-drug resistant tuberculosis (MDR-TB). The recognition of the possibility of pandemic outbreaks of influenza has required authorities to put in place “emergency planning” for dealing with infected patients that may require isolation (Walker et al., 2007).
Isolation rooms can be used to limit the spread of small-particle aerosols, which may play a role in all isolated diseases. Mechanically ventilated isolation rooms can be classified in to standard, source and protective isolation room according to the ventilation pressure as shown in table (5) (Hoffman et al., 2004).

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