For all patients included as study case following data was recorded: age, gender, clinical presentation, dates of admission and discharge. Time period of ICU stay prior to initiation of ventilation, duration of mechanical ventilation, duration of ICU and hospital stays were also recorded. Date of suspicion of VAP and number of episodes of VAP were also noted. Chest radiographs at the time of admission, on initiation of ventilation and at the time of clinical suspicion of VAP were also recorded.