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.