What causes Auto-PEEP in patients with COPD and Asthma?

Auto-PEEP, or auto positive end-expiratory pressure, occurs primarily in patients with COPD and asthma due to prolonged exhalation, which is often a consequence of bronchospasm. When the airways are narrowed, the time it takes for air to be expelled from the lungs is extended. This prolonged exhalation leads to a situation where new air cannot fully enter the lungs before the next breath is initiated, resulting in air becoming trapped in the alveoli. As a result, there is an accumulation of residual air, which increases the end-expiratory lung volume and creates a pressure that mimics positive end-expiratory pressure.

This mechanism is particularly significant during episodes of acute exacerbation of respiratory conditions like COPD and asthma when wheezing and airway obstruction are pronounced. The trapped air can also contribute to hypercapnia—a buildup of carbon dioxide in the bloodstream—because the patient is unable to effectively rid the body of CO2 due to insufficient expiration time. Understanding this process is critical for managing patients with obstructive lung diseases, as it influences ventilation strategies and treatment approaches.