Pulmonary function tests (PFTs)
First visit: Children underwent spirometry and DLCO/DLNO
measurement (Medisoft, Hyp’Air Compact, Belgium) to calculate the
membrane diffusion (Dm) and capillary blood volume (Vc), as recommended
(a finite specific conductance in the blood for NO (θNO) was assumed),
as previously described.5 The breath-hold time of this
DLCO/DLNO measurement was 4 seconds.
Second visit: Children underwent spirometry and DLCO measurement
(without DLNO) according to international recommendations. The
breath-hold time of this DLCO measurement was 10 seconds.
The predicted values were those of Global Lung Initiative, taking into
account ethnicity for spirometry, and those of Caucasians for DLCO. The
results of KCO and DLCO are given without and with correction
(KCOcorrected, DLCOcorrected) for
hemoglobin concentration, as recommended. The changes in DLCO and KCO
from visit 1 to visit 2 were calculated as visit 1, % predicted value
minus % predicted value of visit 2.