Ventilator-associated pneumonia (VAP) is the most frequent intensive care unit (ICU)-acquired infection among patients receiving mechanical ventilation.1 In contrast to infections of other frequently involved organs (e.g., urinary tract and skin), for which mortality is low, ranging from 1% to 4%, the mortality rate for VAP, defined as pneumonia occurring more than 48 hours after endotracheal intubation and initiation of mechanical ventilation, ranges from 20% to 50% and can even be higher in some specific settings or when lung infection is caused by high-risk pathogens.1–3 Although the attributable mortality rate for VAP is still debated, it has been shown that these infections prolong both the duration of ventilation and the duration of ICU stay.1,2 Approximately 50% of all antibiotics prescribed in an ICU are administered for respiratory tract infections.4 Because several studies have shown that appropriate antimicrobial treatment of patients with VAP significantly improves outcome, more rapid identification of infected patients and accurate selection of antimicrobial agents represent important clinical goals.2 Consensus, however, on appropriate diagnostic, therapeutic, and preventive strategies for VAP has yet to be reached. In this chapter, we summarize published studies on epidemiology, diagnosis, treatment, and prevention of nosocomial pulmonary infection in critically ill patients mechanically ventilated in the ICU, and present our experience with this infection.
Accurate data on the epidemiology of VAP are limited by the lack of standardized criteria for its diagnosis. Conceptually, VAP is defined as an inflammation of the lung parenchyma caused by infectious agents not present or incubating at the time mechanical ventilation was started. Despite the clarity of this conception, the past three decades have witnessed the appearance of numerous operational definitions, none of which is universally accepted. Even definitions based on histopathologic findings at autopsy may fail to find consensus or provide certainty. Pneumonia in focal areas of a lobe may be missed, microbiologic studies may be negative despite of presence of inflammation in the lung, and pathologists may disagree on the findings.5 The absence of a “reference standard” continues to fuel controversy about the adequacy and relevance of many studies in this field.
Incidence of Ventilator-Associated Pneumonia
The exact incidence varies widely depending on the case definition of pneumonia and the population being evaluated.6–10 All studies, however, have confirmed that nosocomial pneumonia is considerably more frequent in ventilated patients than in other ICU patients, with an incidence increasing by as much as sixfold to 20-fold in this subset of patients.11,12 VAP occurs in 9% to 27% of all intubated patients and its incidence increases with duration of ventilation.10,13 The risk of VAP is highest early in the course of hospital stay and is estimated to be 3% per day during the first 5 days of ventilation, 2% per day during days 5 to 10 of ventilation, and 1% per day beginning from day 11.13 Because ...