[The routine diagnosis of the distal obstructive syndrome (DOS)].

The diagnosis of distal obstructive syndrome (DOS) is based on the test of lung ventilation function. The tests applied (FEF25-75, MEF50, MEF25) are more sensible than in the routine spirography exploration (FEV1, FEV1.0 x 100/VC), because they evaluate the efficiency of ventilation in those conditions in which the force of the respiratory muscles plays a secondary part and, therefore, cannot hide a flow decrease caused by the obstruction of small pathways (less than 2 mm in diameter). FEF25-75 is measured on the same forced maximum expirogram as FEV1.0. MEF50 and MEF25 are parameters derived from the flow-volume curve. The introduction of these tests into the routine exploration of pulmonary ventilation will improve considerably the diagnosis of early COPD forms.