small airway disease
- related: Pulmonary Diseases
- tags: #literature #pulmonology
Overview
Small airway disease includes airways between big airways (trachea, main carina, down to 4th generation) and alveoli (14th).
It has the highest cross sectional area and least amount of airway resistant in healthy patients.
Bronchiolitis is diseases that affect small airways (bronchioles). It includes everything except COPD and asthma related small airway disease. Bronchiolitis can happen two ways:
- complete occlusion
- mucous
- fibrous tissues
- narrowing of airway
- extrinsic compression
- smooth muscle hypertrophy
- cell infiltration
- airway wall thickening
Small Airway Disease Types
There are 5 overarching types of small airway diseases:
- COPD/asthma
- cellular bronchiolitis: characterized by cellular infiltration
- proliferative bronchiolitis: characterized by connective tissue proliferation
- constrictive bronchiolitis: characterized by concentric bronchiole narrowing
- diffuse panbronchiolitis: happens in asian nonsmokers. Rare
Details
- Cellular bronchiolitis
- neutrophil predominant: usually in acute infections and children
- lymphocytic: follicular bronchiolitis and LIP (lymphoid interstitial pneumonia LIP etiologies are typically autoimmune)
- granulomatous: IBD, HP, sarcoid, NTM
- eosinophilic: aka hypereosinophilic obliterative bronchiolitis
- respiratory bronchiolitis: in smokers, tan pigmented macrophages, exists in continuum with RB-ILD.
- proliferative bronchiolitis: aka bronchiolitis obliterans and BO organizing pneumonia (BOOP)
- BO if in airway. OP if in alveoli
- causes: CTD, drug, environment, infections
- COP cryptogenic organizing pneumonia
- constrictive bronchiolitis: can have a lot of etiologies
Diagnosis
- look for decreased FEF 25%-75% (highly variable)
- hyperinflation and gas trapping, especially in patients without large airway obstruction
- bronchiolar wall thickenin on CT chest
- tree in bud nodules
- mosaic attenuation worsening on expiratory image (differentiates from pulmonary vascular disease)
Treatment
- Generally, treat the underlying etiology.
- Azithromycin may be helpful in inflammatory bronchiolitis