Flow diagram for VAP definition.

Firstly, a deterioration in ventilation following a period of stability defined according to positive end expiratory pressure (PEEP): ≥ 2 days of stable or decreasing daily minimum PEEP followed by a rise in daily minimum PEEP of ≥ 2.5 cm H₂O, sustained ≥ 2 calendar days; or FiO₂: ≥2 days of stable or decreasing daily minimum fraction of inspired oxygen(FiO₂) followed by a rise in daily minimum FiO₂ ≥ 0.15 points, sustained ≥ 2 calendar days. Secondly, systemic signs of fever >38°C or <36°C or white blood cell count >12×10⁹/L or <4×10 ⁹/L were required. Final criteria was an increased/new purulent tracheal aspirate (TA) samples/tracheobronchial secretions or ≥25 neutrophils per low power field (10 objective) on Gram stain of tracheal aspirate and either new and persistent infiltrates, consolidation, or cavitation as read by two study physicians on chest X-ray, or the decision to commence new antibiotic therapy.