New design standards for theatre ventilation

The Netherlands Board for Health Facilities (NBHF) is focused on issues surrounding the accommodation of intramural healthcare. The Board’s work sphere includes hospitals, nursing homes and residential care and mental health facilities. It is an organisation tasked with implementation by the Dutch Ministry of Health, Welfare and Sport.

A permit is required for the construction of new buildings and major renovations in the healthcare sector. The governors of the NBHF consider applications for, and the issuing of building permits. The NBHF staff processes the applications and prepare preliminary decisions.

The NBHF conducts research and reports on the consequences of policy decisions by the Ministry of Health, as well as current developments in the field of planning, technical developments and construction. Research priorities are based on a program of work approved by the Ministry of Health.

Another task for the NBHF is to provide basic quality requirements to describe the minimum functional and architectural quality that health institutions must comply with. Good practice examples are also given as an aid to institutions during the preparation of a construction plan. The NBHF is also recognised as an important provider of expertise, and the knowledge and experience of the Board is widely utilised to support healthcare institutions, and to provide the Ministry of Health, insurers and healthcare offices with information regarding construction for healthcare.

Healthcare legislation [in The Netherlands] is undergoing substantial changes with a new healthcare system to soon be introduced, and the Health Institution Admittance Act replacing the Hospital Provision Act. In general it means that hospital facilities have to operate in a much more market oriented way.

Basic quality requirements

Hospitals
The minimum level of quality for hospitals is described in so called basic quality requirements.

The basic quality requirements for hospitals in a general sense are described in the General Hospital Building Guidelines, in particular in relation to its being reachable, accessible, flexible, its spatial relationships and quality of the environment. Where applicable, these requirements also apply to surgical departments. The above-mentioned building guidelines also deal with the location of the surgical department in the building as a whole.

Surgical departments
As a supplement to the above, this paper lays down the specific basic quality requirements needed for surgical departments, taking into account the care provided in them.

This particularly concerns basic quality requirements in relation to housing, technical installations and working conditions (mainly hygienic aspects and special climatological requirements, but also daylight penetration, view, lighting, noise control). The latter is the case since there is no provision in the Building Guidelines for the indoor environment and technical installations in the healthcare sector.

For specifications in the field of safety and working conditions, we refer to third party regulations such as the National Building Decree and the Working Conditions Act.

When defining the basic quality requirements for a surgical department, a distinction is made between different types of areas in the department. A number of areas in the surgical department do not need to comply with special requirements. These are the areas used for work supervision, personnel accommodation, the holding area and the recovery room (An additional working conditions requirement concerning ventilation applies to the recovery room). The requirements are no different for other areas in the hospital where healthcare activities take place. The basic quality requirements concerning hygienic conditions are described in the Building Guidelines for indoor environment and technical installations in the healthcare sector.

Areas with higher hygienic requirements for air quality.
Areas with high clean-air requirements include the operating theatre, any sterile preparation and pre-operative areas, sterile storage, the anaesthesia and equipment storerooms and the entrances and the exits. The highest clean-air requirements apply to the operation area and the sterile preparation area.

Areas that fall under the working conditions policy regulations.
With respect to air treatment, the operating theatre and a number of adjacent areas have to comply with the provisions of the working conditions policy regulation. This concerns areas where exposure to inhalation of anaesthetic agents is possible, in other words where the patient remains for certain periods of time during and after the anaesthetic, such as the corridors and the recovery room.


Literature studies

In recent years, literature studies were published in which the role of air as a source of infection was investigated. There appears to be little reliable information about the role of air treatment in prevention of post-operative infections in the operation area. There is no evidence in the literature (except in the case of strictly aseptic interventions with introduction of large implants) that the air is a relevant infection hazard in the operation area as a means of contamination for endemic postoperative infections. In the case of operations involving the introduction of large implants, the air appears to be of importance without anyone being able to say explicitly how great this importance is. However, the study does show that air contamination in the immediate vicinity of the operating table and instrument tables can directly or indirectly cause contamination of the operation area.

There are also many indications that contamination of the air during operations can play an important role in relation to postoperative infections. However, this can only be proven in very few cases. Other than this, the literature study revealed no evidence that the air in adjacent rooms or areas located further away influences the risk of post-operative infections.

The highest specifications with respect to the aseptic and protective effect of the air apply to the immediate vicinity in the case of surgical/invasive interventions. From a technical point of view, this protective effect of the air surrounding the patient, operation team and instrument table, can be achieved by installing a large Laminar Air Flow (LAF) device (plenum). This LAF device with a downflow has a surface area of 8 to 9 m2 (e.g. square or octagonal 3 x 3m, rectangular 2.8 x 3.2m).

If aprons are used there is a possibility of combining this with a facility bridge into which all facilities and connections for medical gasses are incorporated. Without aprons, pendants are used, preferably connected to the ceiling outside the air plenum.

The air velocity from the downflow plenum is 24 to 30 cm/sec and flow temperature from the LAF device is 1 to 2°C lower than the ambient air. In this scheme (Fig. 1) the fans for recirculation are placed above the plenum. There is also a possibility to place the recirculation fans outside the OT (lower sound level, construction height can be lower, extra air supply and exhaust ducts)

There are also possible solutions and satisfactory results in environmental control using special LAF devices in which the supplied air has different speeds and temperatures and has also improved the thermal comfort of the surgical team.

In order to be able to safeguard the requisite air quality in the operating theatre, a very large air flow is necessary. A re-circulation downflow system can be installed for this purpose. Part of the air from the downflow system is recirculated via fans to the HEPA filter.

In order to be able to evaluate whether the air system, the air flow profiles and the displacement capacity onto the operating table are correctly functioning, a CFD calculation is recommended at the design stage. This also makes it possible to ascertain whether, at a specific internal heat load, the selected diffused air temperature and the selected air velocity will not lead to an excessively high level of cooling in the operating theatre. This will also reveal at an early stage any short-circuiting between air supplied from the plenum and the site of the intake openings for air recirculation. Assuming that the air from the HEPA filter is sterile, the only possible emission source will be the operation team, the OT staff, the patient, the material used and the equipment.

With respect to the sterile preparation area with direct access to the operating theatres, a higher pressure is recommended compared to all rooms adjacent to this area.

In areas to which high hygienic specifications apply, it is advisable to establish an air pressure hierarchy, whereby more air is supplied than extracted in the “cleanest” area. By installing overflow grids between the rooms, via openings along access doors, a forced air flow is created from the “cleanest” room to less “clean” areas.

This means that the most important basic quality requirements for the technical facilities are:

The reason for having a zoning system in the surgical department is to minimise the risk of micro-organisms from the non-clean sections of the hospital reaching the OT complex. While the zone concept may result in a different air conditioning solution per zone, it means that staff and visitors coming from the ‘dirty’ hospital corridor have to comply with the clothing regulations and rules of conduct applicable to that zone. The incoming and outgoing goods flows also have to comply with a specific protocol. An essential aspect of this zoning and the lay-out of the surgical department is the routing of the operation team, the anaesthesia team, the patients and any visitors, and the sterile and dirty goods flows.

Spatial relationships

The basic quality requirements described in the guidelines particularly concern accessibility, location and size of areas to which patients have access. Minimum requirements are laid down governing the free width of traffic areas and the floor area of operating theatres.

The most important basic quality requirements concerning spatial relationships are: