PURPOSE:To compare changes in tracheal morphology and measurements between inspiration and forced expiration on paired inspiratory-dynamic expiratory CT in healthy volunteers and patients with bronchoscopically proven tracheomalacia.
METHODS:We prospectively studied 20 healthy volunteers (6 M, 14 F mean age 44 (range 26–65), normal spirometry and no history of smoking or risk factors for tracheomalacia. All participants were imaged according to a standard protocol using a 64-detector-row scanner with active respiratory coaching and spirometric monitoring. We retrospectively identified a comparison cohort of 17 patients (5 M, 12 F) mean age 54 (range 36–78) with bronchoscopically proven tracheomalacia who were imaged using a similar protocol without spirometric monitoring. A thoracic radiologist determined the tracheal shape and measured the sagittal and coronal diameters of the trachea 1 cm above the aortic arch at both end-inspiration and dynamic expiration. The tracheal index (ratio of coronal to sagittal diameter) was calculated at end-inspiration and expiration.
RESULTS:All 20 healthy volunteers and 16 (94%) of 17 tracheomalacia patients demonstrated a normal tracheal configuration at end-inspiration. One (6%) of 17 tracheomalacia patients had an abnormal lunate configuration. At forced exhalation, healthy volunteers demonstrated the following changes in the posterior membranous wall: flattening, n = 1 (5%); slight anterior bowing, n = 4 (20%); mild anterior bowing, n = 7 (35%); and moderate anterior bowing, n = 8 (40%). Severe anterior bowing (also referred to as the “frown sign”) was not observed in healthy volunteers, but was seen in 9 (53%) of 17 patients with tracheomalacia at forced exhalation. End-inspiratory tracheal index was 1.0 in healthy volunteers compared to 1.1 for tracheomalacia patients. Forced expiratory tracheal index was 1.4 in healthy volunteers compared to 2.0 for patients with tracheomalacia.
CONCLUSION:Healthy volunteers show a wide range of posterior membranous wall mobility during forced exhalation. Although there is significant overlap with tracheomalacia patients, severe expiratory anterior bowing (“frown sign”) is highly specific for tracheomalacia.
CLINICAL IMPLICATIONS:Severe expiratory anterior bowing is highly specific for tracheomalacia.
DISCLOSURE:Armin Ernst, No Financial Disclosure Information; No Product/Research Disclosure Information