Related Experiment Video
Updated: Feb 18, 2026
Drug-Induced Sleep Endoscopy DISE with Target Controlled Infusion TCI and Bispectral Analysis in Obstructive Sleep Apnea
Published on: December 6, 2016
Relationship between degree of obstruction and airflow limitation in subglottic stenosis
Emily L Lin1,2, Jonathan M Bock2, Carlton J Zdanski3
1Department of Biomedical Engineering, Marquette University & The Medical College of Wisconsin, Milwaukee, Wisconsin, U.S.A.
Insights
Subglottic stenosis (SGS) severity in children can be estimated using airway resistance calculations based on anatomical measurements. This study validates computer models for predicting airflow limitation in SGS patients.
Area of Science:
- Pediatric Otolaryngology
- Computational Fluid Dynamics
- Respiratory Physiology
Background:
- Subglottic stenosis (SGS) is a common pediatric airway disorder.
- Current severity assessment relies on the Cotton-Myer scale, which uses cross-sectional area (CSA) reduction.
- The relationship between upper airway resistance and subglottic CSA is not well understood.
Purpose of the Study:
- To investigate the relationship between subglottic cross-sectional area and airway resistance in pediatric SGS.
- To test the applicability of the Bernoulli Obstruction Theory to subglottic stenosis.
- To develop and validate computational models for assessing SGS severity.
Main Methods:
- Created 3D respiratory tract models from CT scans of healthy subjects and SGS patients.
- Simulated SGS by digitally inserting constrictions into healthy models.
- Utilized computational fluid dynamics (CFD) to compute airway resistance in simulated and actual SGS models.
Main Results:
- Airway resistance was more sensitive to constriction diameter than length.
- Simulated SGS models confirmed the Bernoulli Obstruction Theory (R ∝ A⁻¹).
- Airflow limitation correlated directly with CSA reduction in severe constrictions (Q% = k * A%).
Conclusions:
- Computer simulations suggest anatomical measurements alone can estimate airflow limitation in SGS.
- The developed models accurately represent airway resistance in SGS patients.
- Further validation in larger patient cohorts is recommended.
Objectives:
Subglottic stenosis (SGS) is one of the most common airway disorders in pediatric patients. Currently, treatment decisions rely primarily on the Cotton-Myer scale, which classifies SGS severity based on percentage reduction in airspace cross-sectional area (CSA). However, the precise relationship between upper airway resistance and subglottic CSA is unknown. We hypothesize that airway resistance can be described by the Bernoulli Obstruction Theory, which predicts that airway resistance is inversely proportional to airspace CSA ( R∝A-1) in cases of severe constriction.
Methods:
Computed tomography (CT) scans of six healthy subjects and five SGS patients were used to create three-dimensional models of the respiratory tract from nostrils to carina. Cylindrical segments of varying lengths and varying diameters were digitally inserted in the subglottis of the healthy subjects to create simulated SGS models. Computational fluid dynamics simulations were run, and airway resistance was computed in the simulated SGS models and actual SGS models.
Results:
Constriction diameter had a greater impact in airway resistance than constriction length. In agreement with the Bernoulli Obstruction Theory, airway resistance in the simulated SGS models was well represented by the power law R=aAb, where a is a constant and the exponent b ranged from -0.85 to -1.07. The percentage reduction in airflow (QOBSTRUCTIONQHEALTHY) at a constant pressure drop was found to be directly proportional to the percentage reduction in CSA (AOBSTRUCTIONAHEALTHY) in the limit of severe constrictions, namely QOBSTRUCTIONQHEALTHY=kAOBSTRUCTIONAHEALTHY, where k=2.25 ± 0.15. Airway resistances in the simulated SGS models were similar to resistances in models based on CT scans of actual SGS patients, suggesting that our simulated SGS models were representative of airway resistance in actual SGS patients.
Conclusion:
Our computer simulations suggest that the degree of airflow limitation in SGS patients may be estimated based on anatomic measurements alone. Future studies are recommended to test these predictions in larger cohorts.
Level Of Evidence:
4. Laryngoscope, 128:1551-1557, 2018.
Related Concept Videos
01:19Factors Affecting Pulmonary Ventilation
Alveolar Surface Tension
The alveolar fluid lines the luminal surface of the alveoli and exerts a force called surface tension. This force is caused by the polar water molecules in the liquid being more strongly attracted to each...
01:20Chronic Obstructive Pulmonary Disease-II: Pathophysiology
Chronic Inflammation
01:22Trachea
Anatomical Features:
Location: About half of the trachea is situated in the neck, anterior to the esophagus, and extends from the larynx (at the level of...
01:24Chronic Obstructive Pulmonary Disease
Smoking is a primary risk factor for COPD, with over 80% of patients having a history of it. Patients typically experience progressive dyspnea or labored breathing, frequent coughing, and recurrent pulmonary infections. Many eventually succumb to respiratory failure, characterized by...
01:20Chronic Obstructive Pulmonary Disease-I: Introduction
01:21Tracheostomy Decannulation
Description of the Procedure
Decannulation refers to the permanent removal of the tracheostomy tube, signaling the resolution of the condition that initially necessitated the tracheostomy. The process requires a well-coordinated interplay between...