Ventilator-associated pneumonia (VAP) is defined as a pneumonia in a patient on mechanical ventilator support (by endotracheal tube or tracheostomy) for > 48 hours.VAP is the major cause of infection in critically ill patients and continues to complicate the course of 8 to 28% of patients receiving mechanical ventilation. Mortality rate for VAP ranges from 24 to 50% and can reach 76%in some specific settings or when lung infection is caused by high-risk pathogens.The predominant organisms responsible for infection are Enterobacteriaceae, Pseudomonas aeruginosa and Staphylooccus aureus, but causative agents widely differ according to the population of patients in an intensive care unit, duration of hospital stay, prior antimicrobial therapy and local epidemiological conditions. Since an appropriate antimicrobial treatment of patients with VAP significantly improves outcome, more rapid identification of infected patients and accurate selection of antimicrobial agents represent important clinical goals. However, VAP is difficult to diagnose and consensus on appropriate diagnostic, therapeutic, and preventive strategies for VAP has yet to be reached. Most often used diagnostic procedures of VAP are reviewed, including radiological diagnosis, clinical criteria, microscopic assessment, endotracheal aspiration sampling, blinded invasive procedures (blinded bronchial sampling, minimal bronchoalveolar lavage, blinded sampling with protected specimen brush) and bronchoscopic invasive procedures (bronchoalveolar lavage, protected specimen brush). Accuracy, advantages and risks of various methods are discussed. At the present time, it seems to be clear that endotracheal aspirate sampling is most sensitive, while bronchoscopic sampling is most specific and exactness of mentioned quantitative procedures is influenced by previous antibiotic exposure. The authors are of the opinion that diagnosis of VAP and decision whether to initiate antibiotic therapy or not, should be based on combination of the clinical likelihood of pneumonia (purulent tracheal secretion, pulmonary infiltrates, temperature, leukocytosis, alteration of gas exchange) with the results of examination of respiratory secretion specimens (Gram stains, qualitative and if indicated quantitative results) and the clinical severity of the systemic response to infection.

        Key words: ventilator-associated pneumonia – epidemiology – etiology – pathogenesis – diagnostic procedures