Investigating the Challenges of Managing Coexisting Subglottic Stenosis and Bronchopulmonary Diseases Medically Using Computational Modeling

Introduction: Patients with laryngotracheal stenosis may experience coexisting conditions with other respiratory pathologies, e.g bronchopulmonary diseases; managing this is challenging due to different anatomical locations in the airway. Via computational modeling, this study investigates efficacy of topical delivery with orally inhaled medications targeting both subglottic stenosis and the bronchopulmonary segment.

Methods: Anatomically normal airways from mouth to bronchi were reconstructed from CT-images, and digitally modified at the subglottis to mimic 8 different models representing combinations of Stage I (5mm) and II (15mm) stenotic lengths from McCaffrey system with Cotton-Myer system stenotic constrictions of Grade I (10% and 30%), Grade II (60%), and Grade III (90%). Oral inhalation at 15 L/min and inhaler characteristics for ciclesonide (CIC; particle velocity 4.26 m/s; 1-4 µm particle sizes) and fluticasone (FP; velocity 9.19 m/s; 1-8 µm sizes) were simulated. Drug depositions in the subglottis and the lower airway were calculated.

Results: In airway models with Grade 1 stenosis, Inhaler CIC and FP had <=0.1% subglottic and >80% lower airway deposition regardless of stenotic length (Stage I or II). Subglottic depositions improved marginally with Grade II-Stage I stenosis (CIC=0.1% and FP =0.6%) while lower airway depositions remained unchanged. Subglottic depositions were much greater with Grade III-Stage I stenosis (CIC=0.3% and FP =2.1%). Lower airway depositions were: CIC=70% and FP =34% (Grade III-Stage I), and CIC=35% and FP =41% (Grade III-Stage II).

Conclusions: Our preliminary findings highlight the challenges of managing coexisting airway conditions medically with the disease at different locations of the airway. Subglottic depositions were < 1% for milder stenosis severity. Inhaler characteristics for CIC demonstrated superior airway deposition for milder stenosis severity coexisting with bronchopulmonary diseases, while FP may be preferred for elevated stenosis severity.