Dynamic expiratory tracheal collapse in morbidly obese COPD patients.

Morbid obesity may influence several aspects of airway function. However, the effect of morbid obesity on expiratory tracheal collapse in COPD patients is unknown. We thus prospectively studied 100 COPD patients who underwent full pulmonary function tests (PFTs), 6-minute walk test (6MWT), Saint George's Respiratory Questionnaire (SGRQ), and low-dose CT at total lung capacity and during dynamic exhalation with spirometric monitoring. We examined correlations between percentage dynamic expiratory tracheal collapse and body mass index (BMI). The association between tracheal collapse and BMI was compared to a control group of 53 volunteers without COPD. Patients included 48 women and 52 men with mean age 65 ± 7 years; BMI 30 ± 6; FEV1 64 ± 22% predicted and percentage expiratory collapse 59 ± 19%. Expiratory collapse was significantly associated with BMI (69 ± 12% tracheal collapse among 20 morbidly obese patients with BMI ≥ 35 compared to 57 ± 19% in others, p = 0.002, t-test). In contrast, there was no significant difference in collapse between healthy volunteers with BMI ≥ 35 and < 35. COPD patients with BMI ≥ 35 also demonstrated shorter 6MWT distances (340 ± 139 m vs. 430 ± 139 m, p = 0.003) and higher (worse) total SGRQ scores (48 ± 19 vs. 36 ± 20, p = 0.013) compared to those with BMI < 35. In light of these results, clinicians should consider evaluating for excessive expiratory tracheal collapse when confronted with a morbidly obese COPD patient with greater quality of life impairment and worse exercise performance than expected based on functional measures.

Dynamic expiratory tracheal collapse in COPD: correlation with clinical and physiologic parameters.

BACKGROUND: COPD has been described as a risk factor for excessive expiratory tracheal collapse, but its prevalence and clinical correlates have not been fully determined. The purpose of this study is to prospectively determine the prevalence of excessive expiratory tracheal collapse among patients with COPD and to test the hypothesis that clinical and/or physiologic parameters will correlate with the presence of excessive tracheal collapse. METHODS: We studied 100 adults meeting GOLD (Global Initiative for Obstructive Lung Disease) criteria for COPD, who underwent full pulmonary function tests (PFTs), 6-min walk test (6MWT), St. George's Respiratory Questionnaire (SGRQ), and low-dose CT scan at total lung capacity and during dynamic exhalation with spirometric monitoring. We examined correlations between percentage dynamic expiratory tracheal collapse and PFTs, 6MWT distance, and SGRQ scores. RESULTS: Patients included 48 women and 52 men with mean age 65 ± 7 years, FEV1 64% ± 22% predicted, and percentage expiratory collapse 59% ± 19%. Twenty of 100 participants met study criteria for excessive expiratory collapse. There was no significant correlation between percentage expiratory tracheal collapse and any pulmonary function measure, total SGRQ score, or 6MWT distance. The SGRQ symptom subscale was weakly correlated with percentage collapse of the mid trachea (R = 0.215, P = .03). CONCLUSIONS: Excessive expiratory tracheal collapse is observed in a subset of patients with COPD, but the magnitude of collapse is independent of disease severity and does not correlate significantly with physiologic parameters. Thus, the incidental identification of excessive expiratory tracheal collapse in a general COPD population may not necessarily be clinically significant.

Bronchial collapsibility at forced expiration in healthy volunteers: assessment with multidetector CT.

PURPOSE: To assess forced-expiratory bronchial collapsibility in healthy volunteers by using multidetector computed tomography (CT) and to compare the results with the current diagnostic criterion for bronchomalacia. MATERIALS AND METHODS: The institutional review board approved this HIPAA-compliant study. Following informed consent, 51 healthy volunteers with normal pulmonary function and no history of smoking were imaged by using a 64-detector row scanner with spirometric monitoring at total lung capacity and during forced exhalation. The total study population (in whom both main bronchi were imaged) included 25 men and 26 women (mean age, 50 years). Each scan was analyzed at a workstation by a fellowship-trained thoracic radiologist. Cross-sectional area measurements were obtained from end-inspiratory and forced-expiratory CT images for the right main bronchus (RMB), left main bronchus, (LMB), and bronchus intermedius (BI), and the mean percentage of expiratory collapse was calculated for each bronchus. The number of participants who exceeded the current diagnostic threshold level (>50% expiratory reduction in cross-sectional area) for bronchomalacia was calculated. Comparisons of airway dimensions and airway collapse according to bronchial segment and sex were made by using repeated-measures analysis of variance. RESULTS: Mean percentage of expiratory collapse was 66.9% ± 19.0 (standard deviation) for the RMB and 61.4% ± 16.7 for the LMB. Thirty-seven (73%) of 51 participants exceeded the diagnostic threshold level for bronchomalacia. Significant differences were observed in mean percentage of expiratory collapse between the RMB (66.9% ± 19.0) and LMB (61.4% ± 16.7) (P = .0005). Among a subgroup of 37 participants in whom the BI was also imaged, the mean percentage of expiratory collapse was 61.8% ± 22.8, and 27 (73%) participants exceeded the diagnostic threshold level for bronchomalacia. CONCLUSION: Healthy volunteers demonstrate a wide range of forced-expiratory bronchial collapse, frequently exceeding the current diagnostic threshold level for bronchomalacia.