Expiratory computed tomographic techniques: A cause of a poor rate of change in lung volume

Abstract

Ninety-nine patients (29 males and 70 females; mean age, 57.1 years; range, 22-81 years) were included in this study to evaluate the factors affecting smaller lung volume changes in expiratory high-resolution computed tomography performed to depict air trapping. All patients underwent inspiratory and expiratory chest thin-section CT examinations and pulmonary function tests. Air trapping on CT images was graded subjectively. All variables (age, sex, diagnosis, pulmonary function index, and air trapping score) were compared with the degree of change in lung volume between the inspiratory and expiratory CT examinations. The variables affecting a lower degree of volume change were vital capacity, forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1.0), and the FEV1.0/FVC ratio. Bronchiolitis obliterans was the dominant diagnosis in patients with insufficient degrees of breath holding and in patients with negative air trapping scores despite an abnormal air trapping index. An insufficient degree of lung changes between inspiration and expiration on CT examinations represented bronchiolitis obliterans, which resulted in low FEV1.0 and FEV1.0/FVC values. Changes in the time gap from the announcement of exhalation and breath holding to the start of scanning most effectively indicated air trapping in patients with bronchiolar disorders.

Increased Expiratory Computed Tomography Density Reveals Possible Abnormalities in Radiologically Preserved Lung Parenchyma in Idiopathic Pulmonary Fibrosis

“…Lobulated areas of lower attenuation, which represent retained gas in the secondary pulmonary lobules, are translated as an obstruction of the expiratory airflow, seen in many obstructive diseases, such as asthma, emphysema, bronchiolitis, and many others. 17,26 Although expiratory CT scans are routinely performed for the aforementioned lung diseases, no such approach exists for patients with IPF. It is still debated when an expiratory CT scan should be acquired in terms of additional information gained as well as radiation concerns, varying between volumetric and noncontiguous CT scans.…”