Change in pulmonary function in chronic obstructive pulmonary disease stage 0 patients.

This study aims to elucidate the change in pulmonary function in stage 0 COPD patients. A total of 48 stage 0 COPD patients and 46 healthy adults were included in the study. The status of their pulmonary function was determined by an impulse oscillometry (IOS) system, and the spirometric indexes such as forced vital capacity, maximum expiratory flow-volume (MEFV) curve, total respiratory impedance (Zrs) and respiratory resistance (Rrs) between the two groups were compared. Significant decreases in the values of forced expiratory flow (FEF) at both 75% and 50% of the vital capacity of the predicted value (EF75/pre and FEF50/pre) were detected in stage 0 COPD patients compared with those in the control (P < 0.05). Significant increases were found in the resonant frequency (Fres) (14.37±3.63 VS 11.26±2.61), total respiratory impedance (Z5) compared with the prediction (Z5/pre) (135.65±19.37 VS 104.69±20.64), total airway resistance at 5 Hz (R5) compared with prediction (R5/pre) (128.46±20.14 VS 100.60±20.98) and peripheral airway resistance (R5-R20) compared with prediction (R5-R20/pre) (282.34±192.83 VS 109.31±80.05) in the study group compared with those in the control(all P < 0.05). The reactance at 5 Hz (X5) (-0.14±0.05 VS -0.08±0.05) in the stage 0 COPD group was markedly lower than that in the healthy group (P < 0.05). Disturbance in the small airway may be detected by the MEFV curve and IOS, and these indexes would be valuable in diagnosing stage 0 COPD.