Pulmonary Function
All patients underwent spirometry with bronchodilator testing. Forced
expiratory volume in 1 second (FEV1), forced vital
capacity (FVC), FEV1/FVC ratio, and forced expiratory
flow at 25–75% of FVC (FEF25–75) were calculated. A
positive bronchodilator response was defined as an increase in the
FEV1 of ≥ 12% from baseline (15 minutes after
inhalation of 400 mcg of salbutamol by metered-dose inhaler plus
spacer). Where available, total body plethysmography and lung diffusion
by the single breath diffusion method were performed, and the following
parameters were collected: total lung capacity (TLC), functional
residual capacity, residual volume (RV), RV/TLC ratio,
diffusing capacity of the lung for
carbon monoxide (DLCO), and DLCOadjusted for alveolar volume (KCO). All parameters were
expressed as a percentage of the predicted value (%pred) and as a
z-score, except for the RV/TLC ratio, which was only expressed as a
percentage. The FEV1/FVC and RV/TLC ratios were also
expressed as actual values (percentages). The Global Lung Function
Initiative equations12,13 were used as references for
spirometry and diffusion, while equations from Rosenthal et
al14. were used for plethysmography. All measurements
were performed according to American Thoracic Society/European
Respiratory Society guidelines15-17.