Excessive dynamic airway collapse: A condition behind the veil

Table 1 Etiological factors of excessive dynamic airway collapse

Congenital/primary causes
Mounier-Kuhn Syndrome
Acquired/secondary causes
Irritant inhalation (smoking, air pollution)
Gastroesophageal reflux disease
Recurrent chest infections
Obstructive airway diseases (chronic obstructive pulmonary disease, asthma)
Drugs (corticosteroids, beta-agonists)
Others (obstructive sleep apnea, obesity)

Table 2 FEMOS classification of excessive dynamic airway collapse

Components	Grade
	I (normal)	II (mild)	III (moderate)	IV (severe)
Functional class	Asymptomatic	Symptomatic on exertion	Symptomatic with regular activity	Symptomatic at rest
Extent	No abnormality	Focal	Multifocal	Diffuse
Morphology	Crescent
Origin	Idiopathic or secondary
Severity	0%-50% EAC	50%-75% EAC	75%-100% EAC	100% EAC with airway walls making contact

EAC: Esophageal adenocarcinoma.

Table 3 Diagnostic evaluation tools for excessive dynamic airway collapse

Diagnostic evaluation tools
Pulmonary function testing
Bronchoscopy
Dynamic computed tomography scan
Dynamic magnetic resonance imaging
Endobronchial ultrasonography
Others: Vibration resonance imaging; pH or impedance probe testing