Obstruction of the small airways in the spirometric diagnosis of occupational bronchial asthma

The aim of this study was to evaluate spirometric changes after inhalation challenge in steel and tobacco factory workers suffering from bronchial asthma suspected to be of occupational origin. In 49 patients the spirometric changes were analyzed immediately after and 24 h (delayed reaction) after inhalation challenge at work. A decrease in spirometric parameters of 20% compared to baseline was considered significant. The suspicion of occupational bronchial asthma was based on anamnesis and skin patch tests. The atopy features in examined patients were evaluated according to anamnesis, skin prick tests with aeroallergens, as well as total IgE serum level and blood eosinophils. The significant decrease in spirometric parameters after the inhalation challenge at work was confined in 25 (51%) patients. In 16 of them (64%), the decrease of FEV1 value together with the decrease of the MEF 25-75% VC values were noted A significant isolated decrease in the FEV1 was observed in only four (16% ) patients. However in five (20%) patients a significant decrease in MEF 25-75% VC values was only found as a confirmation of airways obstruction. The studies emphasize the diagnostic value of small airways obstruction in the evaluation of inhalation challenge tests in patients suspected of occupational bronchial asthma.