Oscillometry for lung function testing

Oscillometry is a noninvasive method for assessing respiratory system mechanics during regular tidal breathing. This technique involves the application of a low-amplitude oscillatory flow signal to the lungs while simultaneously recording both the flow signal and the resulting pressure wave developed within the device. The ratio of the measured pressure oscillations to the applied flow oscillations is analyzed across the frequency spectrum of interest to arrive at a complex function of frequency known as the impedance of the respiratory system (Zrs). As the name suggests, impedance reflects all the forces that impede airflow into and out of the lung and is divided into respiratory system resistance (Rrs) and reactance (Xrs). These indices have broad clinical utility in the diagnosis and management of patients with obstructive lung disease, and deeper insights on lung mechanics can be obtained by fitting measurements of Zrs to anatomically based models of the lung.