The diagnosis of a lung function anomaly requires the evaluation of pulmonary function by spirometry. However, some patients (e.g. children, elderly, or diseased individuals) may have difficulty performing the related forced maximal respiratory maneuver correctly. Forced Oscillation Technique (FOT) measures lung impedance during tidal breathing, requiring minimal patient cooperation. The purpose of this study is to establish the diagnostic accuracy of FOT parameters alone or in combination with lung volumes in detecting lung function anomalies as compared with spirometry and with the diagnosis made by the physician.

Purpose and Rationale The diagnosis of a lung function anomaly requires the evaluation of pulmonary function by spirometry. However, some patients (e.g. children, elderly, or diseased individuals) may have difficulty performing the related forced maximal respiratory maneuver correctly. FOT measures lung impedance during tidal breathing, requiring minimal patient cooperation. The within-breath calculation of impedance allows separating the contribution of inspiration and expiration to the measured parameters. The purpose of this study is to establish the diagnostic accuracy of FOT parameters alone or in combination with lung volumes in detecting lung function anomalies as compared with spirometry and with the diagnosis made by the physician.

Objectives Primary: To compare the diagnostic accuracy of FOT with spirometry to detect a lung function anomaly (i.e. an obstructive and/or restrictive respiratory disease).

Secondary: To compare the diagnostic accuracy of FOT with the final diagnosis made by the physician (i.e. the diagnosis based on current guidelines) to detect a lung function anomaly (i.e. an obstructive and/or restrictive respiratory disease).

Study Design This will be a multi-center prospective study of consecutive subjects attending the pulmonary function test laboratory for pulmonary function tests (PFT) or randomly taken from the clinical site's records among those with symptoms with two separate study phases, an Identification Phase and a Validation Phase. Subjects will undergo the same study procedures in both phases. After signing the Informed Consent, a medical history will be obtained, a physical examination performed, and PFT (FOT, spirometry and, if required by the physician to reach a final diagnosis, additional lung function measurements) will be performed.

Identification Phase: Subject data will be used to identify two separate rules based on abnormal lung volumes and impedance (FOT) parameters that will maximize the accuracy in identifying a lung function anomaly. For the primary objective, the reference test for the determination of such lung anomaly will be spirometry. For the secondary objective, the reference test for the determination of the presence of a lung function anomaly will be the final diagnosis made by the physician.

Validation Phase: A separate and independent dataset of subjects will be used to test the accuracy of the rules identified from analysis of the Identification Phase in detecting a lung function anomaly.

Study Duration Subject participation will be completed in 1 day. Study duration is expected to be 7 months

Inclusion Criteria:

• All subjects ≥3 years old attending the pulmonary function laboratory with an order for PFT or
• Subjects ≥3 years old randomly chosen from a database of subjects having respiratory symptoms at the time of inclusion into the database.

Exclusion Criteria:

- Subjects unable to provide written Informed Consent (or not provided by the participant's parent/guardian) and Assent Form (where applicable).

The following age groups will be considered:

• Preschool children (3-5 years old)
• School-age children (6-11 years old)
• Adolescents (12-17 years old)
• Adults (>= 18 years old)