Air Trapping

Air trapping is a conclusive sign of airway obstruction⁶ and appears as areas of decreased attenuation resulting from the presence of gas retained in the lung parenchyma.⁷ It may be necessary to compare between inspiratory and end-expiratory HRCT scans to determine the extent of air trapping, especially if the degree of air trapping is minimal.⁷ Patients with normal inspiratory scans frequently have signs of air trapping on expiratory scans, suggesting that expiratory scans should be performed as part of a standard evaluation.⁶