Ventilators for Coronavirus: What Are They, How They Work, and When to Use Them Ventilator Associated Pneumonia (VAP) VAP is a subtype of hospital acquired pneumonia or Nosocomial pneumonia which occur in people who are receiving mechanical ventilation. It develops more than 48 hours after tracheal Figure 9 from Common Complications in the Crit ical ly I l l Patient Semantic Scholar What is the definition of hospitalacquired pneumonia (HAP) and how does it differ from ventilatorassociated pneumonia (VAP)?