Current place of impulse oscillometry in the assessment of pulmonary diseases

In 1956, a diagnostic tool using the forced oscillation technique (FOT) was developed to examine respiratory functions. A modification of this method is impulse oscillometry (IOS). In the latter, a loudspeaker delivers to the respiratory system a regular, square pressure wave at a constant frequency from which all other individual frequencies are derived using spectral analysis. The usefulness of IOS has been examined in relation to COPD, asthma, interstitial lung diseases, obstructive sleep apnea, and other conditions. The greatest advantage, most notable in children, is the ability to monitor the course of a disease and to assess the response to therapy in a simple way, i.e., minimal requirements for the cooperation of the patient, rapid and reproducible measurements. The IOS shows similar or even higher sensitivity than spimmetry in detecting small airways dysfunction (SAD). The most well-known result observed in peripheral airways disease (PAD) is the frequency dependence of resistance. Importantly, the abnormal resistance at a specific frequency may occur with normal spirometry in those with early PAD. Moreover, IOS is particularly useful if the patient cannot perform effort dependent exhalation. Despite its advantages, the technique is still poorly found in official worldwide recommendations. Nonetheless, considering the promising results of many studies, an increase in interest in IOS is expected, and it could soon be on par with standard pulmonary function tests. The aim of this work is to present the basics, current views, and various aspects of IOS. To carry out our analysis, we searched for relevant publications on PubMed, Web of Science. Original and review articles were selected and discussed.