Incidence

Currently, incidence of VAP has decreased to approximately 10-15% or to an incidence density of 5-10 cases per 1000 ventilator days. Notably, in the last decade, the hospital data from the National Healthcare Safety Network have reported a steady decline in VAP [3, 4], likely due to better implementation of preventive bundles. Yet, these encouraging numbers should be interpreted with caution. Indeed, the true incidence of VAP is difficult to ascertain, particularly due to the well-known diagnostic challenges. Thus, as described in the next paragraphs, VAP incidence may be either overestimated when only diagnostic clinical signs are used, or underestimated when invasive diagnostic methods are used to sample distal pulmonary regions. Also, it is worthy to mention that epidemiology data from other reliable sources in the United States, i.e., the Medicare Patient Safety Monitoring System - which attains medical records from a random sample of hospitalized patients - have reported a steady incidence of VAP of approximately 10%, without any decrease throughout the years [5].

As for the incidence of VAP in patients with ARDS, several studies have consistently reported higher rates, ranging from 15 to 60% (Table 20.1). In particular, Chastre and collaborators [6] used cultures of bronchoalveolar lavage (BAL) fluids to diagnose VAP and found an incidence of 28% in patients without ARDS. Conversely, in patients with ARDS, VAP incidence increased up to 55%. Other investigators reported much lower VAP rates, sustaining disagreement in this field. Indeed, in a study by Sutherland et al., VAP incidence rate was 15%, likely, due to the use of broad-spectrum antibiotics, prior to BAL sampling. In conclusion, as reported in Table 20.1, it seems that ARDS patients, in comparison with other critically ill mechanically ventilated patients, are at higher risk for developing VAP.

Table 20.1 Epidemiology of ventilator-associated pneumonia in patients with acute respiratory distress syndrome

ARDS acute respiratory distress syndrome, NA not available, VAP ventilator-associated pneumonia