Auto-PEEP and dynamic hyperinflation

This diagram shows the presence of auto-PEEP and dynamic hyperinflation with and without expiratory flow limitation. The diagram on the left displays the circumstance of expiratory flow limitation as reflected in proximal airway collapse ("choke point"). In the diagram on the right, expiratory flow limitation has not taken place although the patient manifests auto-PEEP and dynamic pulmonary hyperinflation as a function of increased expiratory resistance from the endotracheal tube, exhalation valve, and bacteria filter. The application of PEEP in the patient with expiratory flow limitation would be expected to improve expiratory airflow. However, in conditions without the presence of expiratory limitation, the application of PEEP would potentially worsen dynamic hyperinflation and increase the risk of barotrauma.