Respiratory Filters and Ventilator-Associated Pneumonia: Composition, Efficacy Tests and Advantages and Disadvantages

Respiratory filters are devices with a high capacity to prevent the passage of microorganisms. The use of respiratory filters interposed in respiratory circuits to avoid ventilator-associated pneumonia (VAP) was proposed after reports between 1952 and 1972 of several outbreaks of respiratory infections attributed to contamination of anesthesia machines; however, none of the reports presented a bacteriological demonstration of a cause-and-effect relationship. The use of respiratory filters has not decreased the incidence of VAP in patients on anesthesia machines and in critically ill patients. Besides, respiratory filters could have some undesirable effects such as the increase of resistance to inspiratory airflow, increase of resistance to expiratory airflow and increase of dead space in the breathing circuit. Thus, the use of respiratory filters is not routinely necessary; however, they should be used in patients with suspected or confirmed highly communicable respiratory infections (such as bacillary pulmonary tuberculosis) and who require mechanical ventilation).