Air Trapping in Respiratory Conditions

Pathophysiology and Clinical Significance

Air trapping is the abnormal retention of air in the lungs due to airway obstruction, particularly in small airways, resulting in areas of hyperinflation that fail to empty properly during exhalation, as noted by the American College of Radiology 1
The European Respiratory Society suggests that air trapping occurs through several mechanisms, including small airway luminal narrowing caused by inflammation and remodeling, leading to increased airway resistance and reduced expiratory flow 2
Air trapping has significant clinical implications, including association with lung function impairment in patients with small airways disease, including asthma and COPD, as reported by the American College of Radiology 1
The European Respiratory Society indicates that air trapping contributes to dyspnea, especially during exertion, as gas trapping worsens with exercise due to hyperventilation-related reduction in expiratory time 2

Computed tomography (CT) is the primary method for visualizing air trapping, as stated by the American College of Radiology 1
Chest radiography may show lung hyperinflation, hyperlucent areas in the lungs, peripheral trimming of vascular markings, according to the American Journal of Respiratory and Critical Care Medicine 3
Pulmonary function tests, such as decreased FEV1/FVC ratio indicating airflow obstruction, can be used to detect air trapping, as noted by Thorax 4

Air trapping in COPD results from small airway narrowing, loss of elastic recoil, and premature airway closure, as reported by the European Respiratory Journal 2
Air trapping can be seen in patients with a history of COVID-19 infection, as well as other small airways disease subtypes, according to the American College of Radiology 1

Inspiratory and expiratory CT chest may have a specific role in evaluating air trapping, as stated by the American College of Radiology 1
Xenon-MRI has shown promise in demonstrating impaired ventilation in patients with COPD, COVID-19 history, and small airways disease, as noted by the American College of Radiology 1