The clinical utility of invasive diagnostic techniques in the setting of ventilator-associated pneumonia

Introduction: Despite lack of evidence from randomized trials, bronchoscopy with protected brush catheter (PBC) and bronchoaveolar lavage (BAL) has been advocated for use in critically ill patients with a suspicion of ventilator associated pneumonia (VAP). We conducted a prospective cohort study in ten tertiary care Intensive Care Units (ICU) in Canada to determine the clinical utility of invasive diagnostic techniques. Methods: Ninety-two mechanically ventilated patients with a clinical suspicion of VAP who underwent bronchoscopy were compared to 49 patients with a clinical suspicion of pneumonia who did not undergo bronchoscopy. We compared antibiotic use, duration of mechanical ventilation, ICU stay and mortality. In addition, for patients who received bronchscopy, we administered a questionnaire (pre and post bronchoscopy) to evaluate the effect of PBC or BAL on a) physician perception of the probability of VAP, b) physician confidence in the diagnosis of VAP, and c) changes to antibiotic management. Results: After bronchoscopy results became available, the diagnosis of VAP was deemed much less likely (p<0.001) by the attending intensivist, confidence in the diagnosis increased (p=0.03) and level of comfort with the management plan increased (p=0.02). Following the results of invasive diagnostic tests, in the group that underwent bronchoscopy, patients were on fewer antibiotics (31/92 vs. 9/49, p=0.05) and more patients had all their antibiotics discontinued (18/92 vs. 3/49, p=0.04) compared to the group that did not undergo bronchoscopy. Duration of mechanical ventilation and ICU stay were similar between the two groups but mortality was lower in the group that underwent bronchoscopy with PBC or BAL (18.5 vs. 34.7%, p=0.03). Conclusions: Invasive diagnostic testing may increase physician confidence in the diagnosis and management of VAP and allows for greater ability to limit or discontinue antibiotics. Whether performing PBC or BAL affects clinically important outcomes such as morbidity and mortality requires further study in large, multicenter trials.