Airwave oscillometry (AOS: Tremoflo, Thorasys, Montreal) is a modern forced oscillation technique (FOT) using a vibrating mesh to superimpose forced oscillations of sound waves on top of normal tidal breathing to measure respiratory impedance as lung resistance (R) and reactance (X), whereas the older impulse oscillometry (IOS: Jaeger Masterscreen, Carefusion Hoechberg, Germany) uses a loudspeaker source. Airwave oscillometry measurements strongly correlate with IOS1,2 and quantify the degree of small airways dysfunction (SAD) as either peripheral airway resistance in terms of heterogeneity (AOS: R5-R19; IOS: R5-R20) or peripheral reactance (ie, compliance) as area under the reactance curve (AX).

Kuo CRW, Lipworth B. Airwave oscillometry and patient-reported outcomes in persistent asthma. Ann Allergy, Asthma Immunol. 2020;124:288–99.