Influence of Pulmonary Bacteriology and Histology on the Yield of Diagnostic Procedures in Ventilator-Acquired Pneumonia

We investigated the influence of pulmonary bacteriology and histology on the yield of diagnostic procedures in a clinically relevant model of ventilator-acquired pneumonia (VAP). Twenty-seven piglets entered a 4-d protocol of ventilatory support under general anesthesia. Endotracheal aspirates (EA), protected specimen brush (PSB), and bronchoalveolar lavage (BAL) were obtained on Day 4. PSB and BAL were performed under bronchoscopic guidance in dependent and nondependent lung segments. Immediately thereafter sternotomy allowed bilateral lung biopsies including the segments studied by bronchoscopic techniques. All respiratory specimens were then processed for microscopic examination and quantitative cultures (QC). In this model where many of the confounding factors often present in human studies were absent, we found that (1) although the local bacterial burden tended to correlate with the presence and the severity of histologic lesions, no definite bacteriologic cutoff could differentiate the histologic p...