[Obstructive syndrome in laryngotracheal stenosis].

Pulmonary function studies were carried out in 13 patients in whom the diagnosis of a central (laryngeal or tracheal) stenosis was confirmed by endoscopy. Following lung function tests were performed: static lung volumes (VC, RV, TLC), FEV1.0 and FIV1.0, flow-volume loops of forced expiratory and forced inspiratory vital capacity efforts from which PEFR and PIFR, maximal expiratory (VEmx50) and maximal inspiratory flow at 50 per cent of vital capacity (VLmx50) were measured, Raw, helium mixing time and pharmacological test with acethylcholine. FIV1.0 values and flow-volume loops permitted the classification of the patients into 3 groups: 1. fixed obstruction (6 cases): decrease in about equal proportions of maximal expiratory and inspiratory flows (FEV1.0 and FIV1.0); normal FEV1.0/FIV1.0 ratio; 2. extrathoracic variable obstruction (1 case): predominant decrease in maximal inspiratory flows (FIV1.0). FEV1.0/FIV1.0 ratio is twice as normal; 3. intrathoracic variable obstruction (5 cases): exclusive or predominant reduction in maximal expiratory flows, as in COPD but with the difference that the expiratory limb of the V:V loop showed an excessive reduction in PEFR, a plateau in the midzone of the VC and a terminal portion with normal configuration. Raw was almost always increased, RV sometimes, helium mixing time was prolonged only in presence of COPD or lobar stenosis; pharmacological tests were negative in 3 out of 4 cases. Pulmonary function abnormalities did not allow a prognosis of the nature of the underlying lesion. The severity of the obstruction as evaluated by endoscopic examination was not related to the functional disturbances. In one case no functional alterations were found despite a severe tracheal stenosis.