Effects of bronchoalveolar lavage volume on arterial oxygenation in mechanically ventilated patients with pneumonia

Objective: To assess the effect of bronchoalveolar lavage (BAL) volume on arterial oxygenation in critically ill patients with pneumonia. Design: Randomized clinical comparison. Setting: Six-bed respiratory intensive care unit of a 850-bed tertiary care university hospital. Patients: Thirty-seven intubated and mechanically ventilated patients with clinical suspicion of pneumonia. Interventions: Bronchoscopically guided protected specimen brush (PSB) followed by either a "high volume" BAL (n = 16, protected catheter, mean volume: 131 +/- 14 ml) or a "low volume" BAL (n = 21, protected double-plugged catheter, 40 ml volume for all patients). Measurements: Arterial oxygen tension/fractional inspired oxygen (PaO2/FIO2) and mean arterial pressure (MAP) before and up to 24 h after the intervention. Bacterial growth in quantitative cultures. Analysis of variance for repeated measurements with inter-subject factors. Results: All patients showed a lower PaO2/FIO2 ratio and higher MAP after the diagnostic procedure, without differences between the study arms (p = 0.608 and p = 0.967, respectively). Patients with significant bacterial growth (p = 0.014) and patients without preemptive antibiotic (p= 0.032) therapy showed a more profound and longer decrease in arterial oxygenation after the diagnostic procedure. Conclusions: A decrease in the PaO2/FIO2 ratio was observed in all patients after a combined diagnostic procedure, independent of the BAL volume used. A significant bacterial burden recovered from the alveoli and no preemptive antibiotic therapy were associated with a larger and longer-lasting decrease in arterial oxygenation.