PFT
Spirometry were performed in the pulmonary function laboratory through Jaeger Master Screen Paed (Jaeger Company, Wurzburg, Germany) by a trained physician and following American Thoracic Society (ATS)/European Respiratory Society (ERS) performance criteria for acceptability and reproducibility[13].
Actual flows (FEV1 in L; maximum mid-expiratory flow 25%-75%, MMEF25%-75% in L/s) and lung volumes(FVC, in L)were normalized according to ethnicity, sex, height and reference equations. The initial data of PFTs in each patient were obtained when they were able to perform the maneuver, median age of 78 months (range: 59-110 months). And PFTs were followed for an average of about 29 months (range: 6-80 months). PFTs were performed when patients had been clinically stable for at least two weeks, at the same place, the same device and by the same physician. Mouth seal around the mouthpiece, breathing patterns even the body position were careful assessed. Prior to the PFTs, long- and short-actingβ2 agonists were with held for 48 and 12h, respectively. According to the ATS/ERS recommendations, the severity of obstructive functional impairment was defined based on the FEV1. The main methods for assessing bronchodilator responses are described in Chart 1. Besides we also analyzed factors that might have influenced the bronchodilator response at the initial PFTs.
Chart 1. Description of different methods (equations) for calculating a bronchodilator response.
Percent variation from the previous (pre-bronchodilator) measurement:
(FEV1 post − FEV1pre)/(FEV1 pre × 100)
Absolute volume change from the previous (pre-bronchodilator) measurement: FEV1post − FEV1pre Post: post-bronchodilator; and pre: pre-bronchodilator. MMEF25%-75% was alike.