Available techniques for the assessment of bronchial airways by size (small vs. large airways)

MethodSmall airway functionLarge airway function
1. SpirometryFEF25–75%, FVC, FVC/SVCFEV1, FEV1/FVC
2. IOSR5–R20, X5, AX, Fres Δ X5 in-espR20
3. Single or multiple breath nitrogen washout (SBNW/MBNW) testSlope phase III, CV, CC, Sacin, Scond
4. Body plethysmographyRV, RV/TLC
5. High resolution CT (HRCT)Air trapping, airway wall thicknessAirway wall thickness
6. Nuclear medicine (scintigraphy, SPECT, PET)Regional ventilation defects
7. 3He-MRINon-ventilated lung volume
8. BronchoscopyTransbronchial biopsy, BALEndobronchial biopsy
9. Sputum inductionLate phase sputumEarly phase sputum
10. Exhaled nitric oxide (eNO)Alveolar eNO
11. CT and computational fluid dynamicsChanges in airway volume and resistance

AX: reactance area; Fres: resonant frequency; FEV1: forced expiratory volume in 1 s; R5: resistance at 5 Hz; Sacin and Scond: acinar and conductive airways ventilation heterogeneity; TLC: total lung capacity; FEF25–75%: forced mid-expiratory flow; SVC: slow vital capacity; X5: reactance at 5 Hz; esp: espiratory; CV: closing capacity; CC: closing volume; SPECT: single-photon emission CT; PET: positron emission tomography; BAL: broncho-alveolar lavage

Note. Adapted from “Small airway dysfunction and poor asthma control: a dangerous liaison,” by Cottini M, Licini A, Lombardi C, Bagnasco D, Comberiati P, Berti A. Clin Mol Allergy. 2021;19:7 (https://clinicalmolecularallergy.biomedcentral.com/articles/10.1186/s12948-021-00147-8). CC-BY.