Central airway collapse is related to obesity independent of asthma phenotype

Abstract

Background and objective Late‐onset non‐allergic asthma in obesity is characterized by an abnormally compliant, collapsible lung periphery; it is not known whether this abnormality exists in proximal airways. We sought to compare collapsibility of central airways between lean and obese individuals with and without asthma. Methods A cross‐sectional study comparing luminal area and shape (circularity) of the trachea, left mainstem bronchus, right bronchus intermedius and right inferior lobar bronchus at RV and TLC by CT was conducted. Results In 11 lean controls (BMI: 22.4 (21.5, 23.8) kg/m2), 10 lean individuals with asthma (23.6 (22.0, 24.8) kg/m2), 10 obese controls (45.5 (40.3, 48.5) kg/m2) and 21 obese individuals with asthma (39.2 (35.8, 42.9) kg/m2), lumen area and circularity increased significantly with an increase in lung volume from RV to TLC for all four airways (P < 0.05 for all). Changes in area and circularity with lung volume were similar in obese individuals with and without asthma, and both obese groups had severe airway collapse at RV. In multivariate analysis, change in lumen area was related to BMI and change in circularity to waist circumference, but neither was related to asthma diagnosis. Conclusion Excessive collapse of the central airways is related to obesity, and occurs in both obese controls and obese asthma. Increased airway collapse could contribute to ventilation abnormalities in obese individuals particularly at lower lung volumes, and complicate asthma in obese individuals.

Obesity and Asthma

“…23 Obesity is associated with expiratory dynamic airway collapse of the central airways, even in otherwise healthy people with obesity, which may also contribute to respiratory symptoms. 24 The reason for this central airway collapse is not known but may be related to loss of airway-parenchymal tethering in obesity. Obese individuals also breathe at lower lung volumes (measured as lower functional residual capacity and expiratory reserve volume), close to the closing volumes of the small airways.…”

Clinical advances in the evaluation of patients with excessive central airway collapse: a narrative review

“…The degree of ECAC is worse in COPD patients with BMI >35, and is associated with reduced exercise capacity and worse symptom burden (13). In a study looking at the relationship of obesity and asthma on central airway collapse, BMI was shown to be the strongest factor (21). Choo et al suggests that anatomic changes associated with obesity include diaphragm elevation and the downward movement of the chest wall, which results in foreshortening and reduced rigidity of the trachea and increased pleural pressure (22).…”

Airway to Lung Volume Ratio on CT is Associated with Pulmonary Function Transition from Obstructive to Restrictive Pattern in Obesity

“…Previous CT/MRI studies showed that obesity adversely affects both the airway tree and lung volume [4,12]. However, their data did not elucidate the effects of obesity on the interaction between airway and lung sizes, which is essential for maintaining lung mechanics and pulmonary function [13].…”