Considerations on isolation rooms and alternative pressure ventilation systems.

The health-care facility environment is involved in disease transmission in essentially two different situations: 1. in cases where patients are immunocompromised and require protection from infections; 2. in cases of inadvertent exposure to environmental or airborne pathogens that can aggravate patients' existent disease and cause illness among health-care personnel. Environmental infection-control strategies and engineering controls can effectively prevent transmission of these infections. In particular the ventilation system is fundamental to the control of the concentration of airborne contaminants within a hospital isolation room because it establishes and maintains appropriate pressure differentials within special care areas of the building. Thus the incidence of health-care-associated infections can be minimized by adherence to ventilation standards suggested in the guidelines for specialized care environments such as Airborne Infection Isolation rooms (AII, as in situation 2 above), and Protective Environments (PE) rooms (as in situation 1 above). This report is a comparative review of the principal guidelines and strategies existing in the international scientific literature for the prevention of environment-associated infections in healthcare facilities using pressure differentials (positive pressure for PE rooms, negative pressure for AII rooms). The purpose of the review is also to investigate the state-of-the-art use of the "alternative pressure rooms", i.e., areas furnished with a ventilation system capable of switching pressure from positive to negative according to patients' needs. The results of the present analysis indicate an unenthusiastic reaction to these "alternative pressure rooms", although there is no scientific evidence against their use.