Pulmonary function and flow-volume loop patterns in patients with tracheobronchomalacia.

BACKGROUND Patterns of pulmonary function tests (PFTs) and flow-volume loops among patients with clinically important tracheobronchomalacia (TBM) are not well described. Small studies suggest 4 main flow-volume loop morphologies: low maximum forced expiratory flow, biphasic expiratory curve, flow oscillations, and notching. We studied common PFT and flow-volume loop patterns among the largest prospective series of patients to date, undergoing clinical evaluation for symptomatic moderate to severe TBM. METHODS We conducted a retrospective analysis of prospectively collected data from patients who were referred to our Chest Disease Center from January 2002 to December 2008, with respiratory symptoms that were attributed primarily to TBM. The PFT results of 90 subjects with symptomatic moderate to severe TBM were evaluated. RESULTS By PFTs, 40 (44.4%) subjects had an obstructive ventilatory defect, 16 (17.8%) had a definite or highly likely restrictive ventilatory defect, 15 (16.7%) had a mixed defect, and 19 (21.1%) were within normal limits. Among 76 subjects with available flow-volume loops, the most frequent finding was low maximum forced expiratory flow, in 62 (81.6%) subjects, followed by biphasic morphology (15, 19.7%), notched expiratory loop (7, 9.2%), and expiratory oscillations (2, 2.6%). The balance of 13 subjects (17.1%) had no distinctive flow-volume loop abnormality. CONCLUSION PFTs and flow-volume loops are normal in a substantial number of patients with moderate to severe TBM, and should not be used to decide whether TBM is present or clinically important.