VENTILATOR-ASSOCIATED PNEUMONIA - VALUE O F DIAGNOSTIC-TOOLS

The authors analyzed in published studies providing histologic data th e value of diagnostic means of nosocomial bronchopneumonia (NBP) in cr itically ill patients. At least 10 % of patients whose trachea is intu bated and the lungs mechanically ventilated suffer an histologically-c onfirmed NBP. Histology of NBP consists of non systematized foci of in fection, localised in 90 % of cases in the posterior segments of the t ower pulmonary lobes. In fact, small foci are disseminated in both lun gs, usually within large areas of non infectious pulmonary lesions and are often multimicrobial. This may explain why the clinical and radio logical diagnosis is inaccurate in more than 40 % of cases. On chest X -ray, aeric bronchogramm and alveolar infiltrates are suggestive but n on-specific for NBP, as are also fever, leukocytosis and purulent sput um. Therefore, to confirm the diagnosis of infection and to isolate th e microorganisms responsible for NBP, additional investigations are re quired whose interpretation is uneasy. In a simplified manner, bacteri ological inoculum takes a course parallel to the histological bronchop ulmonary lesions: no bacteria in the absence of infection, high bacter ial inoculum in case of confluent NBP, intermediary in case of bronchi tis, however with exceptions when antibiotherapy has recently been mod ified. In fact, neither bronchial protected brushing nor broncho-alveo lar lavage techniques have a perfect sensitivy and specificity. As an exemple, a diagnostic procedure in assessed in calculating the probabi lity of an accurate diagnosis of NBP. It is concluded that diagnosis o f ventilator-associated pneumonia remains still unreliable with the me ans available today.