Pneumonia complicating the acute respiratory distress syndrome

Ventilator-associated pneumonia (VAP) complicating the course of acute respiratory distress syndrome (ARDS) is one of the most challenging diagnostic and treatment dilemmas in critical care medicine. The VAP incidence rate ranges from 37 to 60% in ARDS patients, significantly greater than for other causes of respiratory failure. Although the normal risk factors for VAP are the same in ARDS patients, multiple aspects of the underlying disease and its management increase the risk compared with non-ARDS patients. Multiple mimics of the clinical symptoms and signs make the clinical diagnosis of VAP very nonspecific in the setting of ARDS. The multilobar but predominantly lower lobe pattern of pneumonia in ARDS makes use of quantitative cultures of lower respiratory secretions (sampled by various techniques) very accurate to confirm the presence of pneumonia. VAP in ARDS patients is usually late-onset and therefore caused by highly antibiotic-resistant microorganisms. Somewhat surprisingly, the mortality of ARDS patients with VAP is not significantly greater than that of ARDS patients without VAP, although subsequent duration of mechanical ventilation is consistently prolonged in patients with VAP.