[Small airway function tests; techniques of measurements. Review of the literature]

It is usually agreed that obstructive lesions in small airways are the first abnormalities in patients with chronic bronchitis. Consequently, there is now a great interest in the early detection of airways obstruction. Three techniques are described: frequency dependence of compliance, flow-volume curve and closing-volume. The results obtained in healthy subjects and in patients with obstructed airways are discussed.