Combining low-frequency oscillometry and spirometry measurements in relation to asthma control and exacerbations in moderate-to-severe asthma

Respiratory oscillometry is an effort-independent pulmonary function test that can assess respiratory impedance over a range of frequencies, comprising resistance (R) and reactance (X) moieties. Governed by Poiseuille’s law, airway resistance is largely determined by airway caliber and length, whereas reactance comprises elastance and inertance components and can be used as a measurement for lung stiffness at various frequencies. Low-frequency sound waves penetrate further down the airways and hence reflect changes in the whole lung.