Tracheobronchial Smooth Muscle Atrophy and Separation

Abstract

We report a case series involving 4 patients with chronic obstructive pulmonary disease who were on an appropriate medical regimen including a high dose of inhaled corticosteroids (ICS). During bronchoscopy, patients were found to have an excessive dynamic collapse of the posterior wall and its separation from the ends of the adjacent cartilaginous rings. This was causing a near-total occlusion of the tracheal and bronchial lumen during exhalation, thereby presenting with an obstructive pattern on the pulmonary functions. We suspect that this was caused by the atrophy of the smooth muscles of the tracheobronchial wall. We reviewed the literature to explore the mechanisms causing atrophy of the bronchial smooth muscle, focusing on the potential role of long-term ICS use.

Tracheobronchopathy From Inhaled Corticosteroids

“…53 Large airway collapse due to a loss of integrity of the airway wall may develop over time with the use of ICSs. 10 The physiological changes observed in the large airways results in limited airflow and decreased flow rates. 54 Tracheobronchomalacia TBM is defined as weakness of the tracheal and bronchial walls due to the softening of supporting airway cartilage and hypotonia of myoelastic elements.…”

“…The authors posit that specific pathologic conditions, such as excessive dynamic airway collapse (EDAC), tracheobronchomalacia (TBM), and tracheobronchial smooth muscle atrophy and separation (TB-SMAS), may be related to increasing overreliance on ICSs. 10 This review highlights potential airway complications of the long-term use of high-dose ICS treatment, which are referred to as "steroid tracheobronchopathy." These conditions range from airway infections to direct effects on the vocal cords, airway smooth muscle, and cartilage (Table 2).…”

Effect of bilateral lung transplantation on excessive dynamic airway collapse

“…A total of seven had central tracheal collapse of pars membranacea, and one had collapse of right main bronchus just distal to the carina. FV loops of 7 out of 8 patients had “inflection point” suggestive of EDAC, and all 8 patients had COPD with mean predicted FEV1/FVC of 37% (range 22%‐70%) and mean predicated FEV1 of 20% (range 9%‐39%).…”

“…Factors associated with the development of EDAC include airway inflammation from smoking, chronic aspiration, prolonged intubation, tracheobronchitis, COPD, asthma, and obesity . Long‐term use of steroids can also cause tracheobronchial smooth muscle atrophy and separation (TBSMAS) and can lead to EDAC . EDAC is associated with respiratory symptoms like chronic cough, dyspnea, stridor, wheezing, asphyxia attacks, and reduced clearance of airway secretions causing recurrent infections refractory to the usual treatment .…”

Are Inhaled Corticosteroids Safe for Large Airways?

“…5 On a similar discourse, a recent publication highlights that long-term use of ICS plays an important role in tracheobronchial smooth muscular atrophy and separation of the smooth muscle wall from the posterior cartilaginous ring (TB-SMAS) leading to excessive dynamic airway collapse of the bronchial wall. 14 Mehta and colleagues published a case series involving 4 patients with this feature observed after chronic use (at least 7 years) of high-dose ICS, notably fluticasone. The cause is the multifaceted role of ICS on bronchial airways, including inhibition of smooth muscle proliferation due to its anticytokine and growth factor effect and smooth muscle atrophy by impairing protein synthesis.…”