Oscillometry and spirometry derived ratios to assess small airways dysfunction in severe asthma patients taking tezepelumab

Forced oscillometry technique is an effort independent test that imposes varying frequency soundwaves onto normal tidal breathing. This allows the measurement of the pressure/flow relationship of respiratory impedance and thus the calculation of resistance (R) and reactance components (X). Resistance at 5Hz (R5) represents lung resistance throughout the entire airways, whereas resistance at 20Hz (R20) is representative of the larger airways. Thus the heterogeneity between R5 and R20 represents the resistance in peripheral airways.