pulmonary disorders
Ventilator Associated Pneumonia
Diagnosis of Ventilator Associated Pneumonia
Chest x-ray and clinical criteria (limited accuracy) Sometimes bronchoscopy or blood cultures Diagnosis is imperfect. In practice, ventilator-associated pneumonia is often suspected on the basis of the appearance of a new infiltrate on a chest x-ray that is taken for evaluation of new symptoms or signs (eg, fever, increased secretions, worsening hypoxemia) or of leukocytosis. However, no symptom, sign, or x-ray finding is sensitive or specific for the diagnosis, because all can be caused by atelectasis, pulmonary embolism, or pulmonary edema and may be part of the clinical findings in Acute Hypoxemic Respiratory Failure (AHRF, ARDS) . Gram stain and semiquantitative cultures of endotracheal aspirates, though not definitive for identifying infection, are recommended for guiding treatment in VAP. Bronchoscopic sampling of lower airway secretions for quantitative culture yields more reliable specimens that can differentiate colonization from infection. Information gained from bronchoscopic sampling reduces antibiotic use and assists in switching from broader to narrower antibiotic coverage. However, it has not been shown to improve outcomes. Measurement of inflammatory mediators in bronchoalveolar lavage fluid or serum has not been shown to be reliable in deciding on initiation of antibiotics. The only finding that reliably identifies both pneumonia and the responsible organism is a pleural fluid culture (obtained via thoracentesis in a patient with pleural effusion) that is positive for a respiratory pathogen. Blood cultures are also relatively specific if a respiratory pathogen is identified but are insensitive. 