The Protected Minialveolar Lavage Technique for the Diagnosis of Nosocomial Pneumonia

Abstract

Nosocomial pneumonia is one of the first causes of fever in mechanically ventilated critically ill patients. Superinfection of the lung parenchyma rapidly complicates non specific alveolar damage following circulatory shock, multiple trauma and sepsis [1, 2]. Because the clinical diagnosis is difficult, the true incidence of nosocomial pneumonia is still uncertain. In a recent pathologic study, the lungs of 60 patients were histologically examined in the immediate postmortem period, and the incidence of nosocomial pneumonia was found as high as 65% [3]. It is generally agreed that critically ill patients with recent fever, increased leukocyte count, new radiologic pulmonary infiltrates and positive tracheal cultures are likely to have nosocomial pneumonia. Although very general and non specific, these clinical criterias are universally accepted and probably adequate enough to assess the incidence of nosocomial pneumonia. We recently examined the lungs of 43 patients who died in the critical care unit after demonstrating the clinical criteria of nosocomial pneumonia: 40 had disseminated foci of bronchopneumonia at microscopic examination [3]. In the mechanically ventilated critically ill, the real challenge does not concern the diagnosis itself, but rather the accurate identification of bacterias infecting the alveolar spaces. Because bronchial infection rapidly occurs within a few hours following endotracheal intubation or tracheostomy, any method designed for obtaining bacteriologic samples representative of lung parenchyma is frequently contaminated. By using markers for this bronchial contamination, uncontaminated samples can be obtained and bacteriologically analyzed. Schematically, either cell criterias or quantitative bacteriological criterias are currently used.