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.