Exam (analysis) that serves to measure pulmonary volumes and flows, component of respiratory functional exploration.
Spirometry is used to diagnose various chronic bronchial and lung disorders (asthma, obstructive chronic bronchitis, interstitial pneumonitis, emphysema) to assess their severity and to track their development.
The subject first breathes normal, then inspires and expires deeply. The volumes of air contained in his lungs at different moments of breath are measured by a measuring apparatus (spirometer)
Depending on the inspired or expired air flows, a graphic is called a flow-volume curve.
The forced vital capacity (total expired air volume after a deep breath) and the maximum expiratory volume per second (the volume of air expired during the first second of forced exhalation following a deep inspiration) can be measured. Adding to the spirometer a complementary circuit that uses helium allows to calculate total pulmonary capacity (the maximum volume that lungs can contain).
The abnormalities found are classified as obstructive syndrome (abnormally low flow rates), restrictive syndrome (abnormally small volumes), and mixed syndrome (association of the two disturbances).