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