[Significance of maximal midexpiratory time and F-V curve configuration in testing small airway function for smokers]

To evaluate the clinical significance of maximal midexpiratory time (MET) in testing small airway functions for smokers, the routine ventilatory functions, MET and F-V curve configurations were studied in 116 passive and light, heavy active smokers. Routine ventilatory functions and F-V curve configuration were determined with LR80 flow volume recorder. The MET was measured with FJD80 spirometer. The results showed that the distribution of convex type rose with the degree of smoking. In heavy smokers, the MET elongated to 127% of the predicted value and in the convex type F-V curve, it elongated to 120% of the predicted value; both were consistent with the decrease of corresponding V50, V25. This implied when MET elongated to 120%-130% of the predicted value in smokers, there had been slight disturbances in small airway functions. It is therefore suggested that MET and convex type F-V curve both are sensitive indices for testing small airway functions, thus it should be of clinical significance and be appropriate for general application.