**2. Pulmonary function tests and previous studies**

Pulmonary function refers to how the lungs perform gas exchange. Pulmonary function testing is a practical application of Respiratory Physiology and is necessary for understanding abnormalities in lung function and the effects of treatments. Pulmonary function tests help to determine the severity of functional impairments or defects and the extent to which treatments restore normal function (62). In this section we first review two important pulmonary function tests: Spirometry and Impulse Oscillometry. We then perform a literature review of several studies that have been carried out in previous years to compare several Pulmonary Function Tests (PFTs) to assess the ability of FOT and IOS to measure pulmonary function and to discriminate between impaired and non-impaired conditions.
