What is ventilator associated pneumonia? Medtecs Group Abstract Background and Aims: Ventilator associated pneumonia (VAP) is a major cause of morbidity and mortality among patients in the Intensive Care Units (ICUs) and results in added healthcare costs. One of the Ventilator associated pneumonia (VAP) ()? is a lung infection that can cause serious health complications, especially in patients with weakened immune systems. When a patient is Ventilator Associated Pneumonia (VAP): Why is it so difficult to define? In real world practice: The diagnosis of VAP remains more an exercise in clinical integration than strict adherence to criteria.