Pneumonia during mechanical ventilation complicates the course of 50% of patients requiring minimally three days of mechanical ventilation. Pneumonia is responsible for an increase in 20–40% of relative risk of mortality. The predominant potentially pathogenic micro-organisms are Streptococcus pneumoniae, Staphylococcus aureus sensitive to methicillin in the previously healthy host,and Pseudomonas aeruginosa, aerobic Gram-negative bacilli,and methicillin-resistant Sta-phylococcus aureus in the host with underlying disease.Approximately85%of pneumoniasareendogenous, i. e.,due to bacteria present in the patient’s oropharyngeal flora. Bacteria present on admission cause primary endogenous pneumonia (55%), whilst bacteria acquired on the unit lead to super-carriage or secondary carriage and subsequently secondary endogenous pneumonia (30%). The remaining 15% are exogenous, i. e., the bacteria causing pneumonia are not carried by the patient. The diagnosis is usually based on clinical, radiological and microbiological criteria using the non-invasive method of tracheal aspirate, yielding >105 micro-organisms. Six randomised trials have evaluated two non-antibiotic prophylactic manoeuvres: subglottic drainage (4 trials) and semi-recumbent position (2 trials). The impact on pneumonia was mixed, mortality not being changed. Selective digestive decontamination, using parenteral and enteral antimicrobials age agents to control the three types of pneumonia, has been evaluated in 53 trials and shows an absolute mortality reduction of 8%. Therapy of pneumonia relies on five basic principles: 1. surveillance and diagnostic cultures to identify the micro-organism; 2. immediate and adequate antibiotic treatment to sterilise the lower airways; 3. the source of potential pathogens requires elimination for recovery of the original infection and prevention of relapses and/or superinfections; 4. removal or replacement of ventilation tube; 5. surveillance samples are indispensable to monitor efficacy.

        Key words: pneumonia – pathogenic micro-organisms – pathogenesis – diagnosis – ventilation