Which lung disease is commonly associated with auto-PEEP?

• A. Asthma
• B. Pneumonia
• C. Pulmonary Fibrosis
• D. Emphysema

Answer: (D)

Intrinsic PEEP, or auto-PEEP, is caused by incomplete expiration before the next breath, leading to breath stacking and higher end-expiratory pressures. This is most likely when there is expiratory flow limitation and airway obstruction, as seen in emphysema. In emphysema, destruction of elastic recoil and narrowing of small airways slow exhalation, so trapped air accumulates, especially with faster ventilator rates or shorter expiratory times. The result is dynamically increased end-expiratory pressure that can complicate ventilation and hemodynamics.

Pneumonia and pulmonary fibrosis tend to create restrictive mechanics with reduced lung volumes and stiffer lungs, which do not typically produce the same pattern of air trapping and auto-PEEP. Asthma can cause significant obstruction and sometimes hyperinflation during severe attacks, but emphysema is the classic, more robust association due to chronic loss of recoil and persistent airway obstruction.