Subglottic Stenosis Position Affects Work of Breathing

Abstract

Objectives: Subglottic stenosis (SGS) is the most common type of laryngeal stenosis in neonates. SGS severity is currently graded based on percent area of obstruction (%AO) via the Myer-Cotton grading scale. However, patients with similar %AO can have widely different clinical courses. Computational fluid dynamics (CFD) based on patient-specific imaging can quantify the relationship between airway geometry and flow dynamics. We investigated the effect of %AO and axial position of SGS on work of breathing (WOB) in neonates using magnetic resonance imaging. Methods: High-resolution ultrashort echo-time MRI of the chest and airway was obtained in three neonatal patients with no suspected airway abnormalities; images were segmented to construct three-dimensional (3D) models of the neonatal airways. These models were then modified with virtual SGSs of varying %AO and axial positioning. CFD simulations of peak inspiratory flow were used to calculate patient-specific WOB in nonstenotic and artificially stenosed airway models. Results: CFD simulations demonstrated a relationship between stenosis geometry and WOB increase. WOB rapidly increased with %AO greater than about 70%. Changes in axial position could also increase WOB by approximately the same amount as a 10% increase in %AO. Increased WOB was particularly pronounced when the SGS lumen was misaligned with the glottic jet. Conclusion: The results indicate a strong, predictable relationship between WOB and axial position of the stenotic lumen relative to the glottis, which has not been previously reported. These findings may lead to precision diagnosis and treatment prediction tools in individual patients.

Monitoring Adult Subglottic Stenosis With Spirometry and Dyspnea Index: A Novel Approach

“… 17 , 19 Computational fluid dynamic studies claim that anatomic variations such as the axial position of stenosis or the cross-sectional subglottic area may affect the perception of breathlessness. 30 , 31 …”

“…17,19 Computational fluid dynamic studies claim that anatomic variations such as the axial position of stenosis or the cross-sectional subglottic area may affect the perception of breathlessness. 30,31 The impact of subglottic stenosis in PFTs has been studied over the past few decades, although they are not routinely used in assessment and follow-up. Most of the test measurements improve postoperatively 14,15,19 ; yet, the EDI was found to be the most reliable parameter in diagnosing subglottic stenosis 12,13 and in monitoring treatment outcomes, [15][16][17][18][19] something supported by our findings.…”

Central airway issues in bronchopulmonary dysplasia

“…As the severity of subglottic narrowing increases, airway resistance and respiratory work increase exponentially. Clearly, the extent of the stenosis is the primary driver, but the length of the stenotic segment and the location of the stenosis in relationship with the glottis also impacts airway resistance 58‐60 . The narrowing and increased airway resistance most commonly manifests with biphasic stridor and increased respiratory effort.…”

Fluid dynamics of the upper airway in pediatric patients with severe laryngomalacia

“…According to Bernoulli's law, the faster the ow velocity, the lower the pressure generated by the uid, and the narrower the airway becomes as the tissue at the supraglottic site absorbs inward[16]. Yang et al suggested that air owing through the narrowing airway forms jets that create turbulent air ow, resulting in energy loss, which increases the respiratory work of the infant patient and can lead to failure to thrive [12].…”

“…CFD is often applied in the study of airway diseases, such as nasal diseases and obstructive sleep apnea hypoventilation syndrome [5,6], vocal cord dysfunction [4,7], and laryngotracheal stenosis [8]. Airway dynamics in infants and children have been less studied, and some studies have used unrealistic symmetric anatomical models to predict air ow dynamics [9,10], while a few reports have reconstructed realistic three-dimensional (3D) anatomical models of the airway from high-resolution computed tomography (CT) or magnetic resonance imaging (MRI) data for hydrodynamic studies of subglottic stenosis and tracheomalacia in pediatric patients [11][12][13]. However, no studies have been conducted on the airway in children with LM based on the hydrodynamics of CT reconstructed 3D models.…”