Ventilator-associated pneumonia (VAP) refers to pneumonia that develops at least 48 hours after the initiation of mechanical ventilation [1,2]. It is probably caused by aerodigestive tract colonization, followed by aspiration of contaminated secretions into the lower airways (figure 1). Many of the risk factors for VAP increase the risk of pharyngeal colonization and aspiration (table 1), while most of the interventions to prevent VAP reduce colonization and aspiration (figure 2) [3-8].
The role of the ventilator circuit in VAP is reviewed here. The pathogenesis, risk factors, clinical presentation, diagnosis, prevention, and treatment of VAP are discussed separately. (See "Clinical presentation and diagnosis of ventilator-associated pneumonia" and "Epidemiology, pathogenesis, microbiology, and diagnosis of hospital-acquired, ventilator-associated, and healthcare-associated pneumonia in adults" and "Risk factors and prevention of hospital-acquired, ventilator-associated, and healthcare-associated pneumonia in adults" and "Treatment of hospital-acquired, ventilator-associated, and healthcare-associated pneumonia in adults".)
ROLE OF THE VENTILATOR CIRCUIT IN VAP
The ventilator circuit refers to the tubing that connects the ventilator to a patient, as well as any device that is connected to the tubing. The most common devices include humidifiers, filters, suction catheters, and nebulizers.
The ventilator circuit appears to have only a small effect on the development of VAP, assuming that reasonable infection control practices are followed. This view is supported by several pieces of evidence:
●Aspiration of contaminated pharyngeal secretions is the predominant cause of nosocomial pneumonia, not inhalation of aerosols containing bacteria [4,6,9].