The forced oscillation technique (FOT) is a relatively new, non-invasive method to assess airway function. It involves the delivery of oscillatory signals into the respiratory tract during tidal ventilation. It is a novel and sensitive diagnostic tool for early detection of small airway changes, for example, in smokers.
It requires minimal effort on the part of the patients, making it useful for younger children and the elderly who cannot perform spirometry. It is useful to diagnose respiratory diseases, especially asthma in children and chronic obstructive pulmonary disease (COPD) in the elderly. It is a very useful measure of small airway dysfunction in smokers, obese individuals, and other causes with suspected airway disorders.