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. What is Pneumonia: Symptoms, Causes, Diagnosis & Treatment Artemis Hospital ()? is a lung infection that can cause serious health complications, especially in patients with weakened immune systems. When a patient is What is the definition of hospitalacquired pneumonia (HAP) and how does it differ from ventilatorassociated pneumonia (VAP)?