Real-world effects of tezepelumab on small airway dysfunction in severe refractory asthma

Small airway dysfunction (SAD) involves narrowing of the airways to less than 2 mm in caliber between generations 8 and 23 of the bronchial tree.1 It can be defined using airway oscillometry (AO), an effort-independent test that superimposes sound waves on top of tidal breathing. This, in turn, measures resistance (R) and reactance (X) components of respiratory impedance. Frequency-dependent heterogeneity of resistance between 5 Hz and 20 Hz (R5-R20) greater than or equal to 0.1 kPa/L/s reflects abnormal peripheral lung resistance.