The diagnosis of ventilator-associated pneumonia using non-bronchoscopic, non-directed lung lavages

Objectives: (1)To assess the diagnostic utility of quantitative cultures of non-bronchoscopic lung lavage (NBL) in ventilator-associated pneumonia and evaluate the role of the Bacterial Index; (2) To assess the predictive value of NBL surveillance quantitative cultures in ventilated patients; (3) To evaluate the Clinical Pulmonary Infection Score (CPIS) system in ventilated patients. Design: A prospective comparison of NBL with bronchoscopic bronchoalveolar lavage and protected specimen brush. Setting: Three intensive care units in academic tertiary care centres. Patients: 145 adults ventilated for 72 h, with and without clinical signs of pneumonia. Interventions: Sampling of lower airway secretions by NBL, bronchoalveolar lavage and protected specimen brush. Main outcome measures: Diagnostic reliability of quantitative cultures, Bacterial Index and CPIS. Results: 34 episodes of clinical ventilator-associated pneumonia were documented in 32 patients. 9 episodes were confirmed by concordant blood/pleural culture or post-mortem lung examination. Qualitative concordance of the predominant pathogen between sequential NBL: bronchoalveolar lavage and protected specimen brush was 83%. Sensitivity and specificity of non-directed bronchial lavage at a threshold of 104 CFU/ml were 68%and 70% respectively (p = 0.003) and were comparable with the bronchoscopic methods. However, the low positive predictive value of NBL indicates that quantitation in the absence of clinical signs is unlikely to be useful. Bacterial Index did not improve discriminatory power of quantitation compared with bacterial load of predominant organism. Mean CPIS for confirmed pneumonia cases was 8.4 - 1.01, significantly higher than for non-pneumonia observations (p = < 0.0001). Conclusion: NBL is a simple, safe, cheap, readily-available method of diagnosing ventilator-associated pneumonia with comparable diagnostic accuracy to bronchoscopic techniques. Quantitation of respiratory tract cultures can exclude pneumonia in patients with equivocal clinical signs. The diagnostic threshold should vary depending on the length of ventilation, likelihood of pneumonia and antibiotic administration. The Bacterial Index is a flawed mathematical device that has no contributory role in pneumonia diagnosis. The CPIS has some diagnostic role in selected cohorts of ventilated patients.