Lung function abnormalities in cystic fibrosis and changes during growth.

Static lung volumes (VC, TLC, FRC, RV), elastic recoil pressure of the 
lungs (Pst(1) at 100, 90, and 60% of TLC), static lung 
compliance [Cst(1)], specific airway conductance at FRC level (Gaw/TGVex), forced expiratory 
volume in the first second (FEV1), maximal expiratory flows (Vmax.) at 
25 and 50% of VC and at 60% of TLC, and 
"upstream" airway conductance (Gus) at 60% of TLC were studied in 
28 patients with cystic fibrosis, 5 to 25 years old, over 
a period of 1 to 5 years. The data were compared 
individually with normal values, related to body height in the form 
of regression equations and expressed in percentage of predicted values. From 
the indices assessing airway function, Vmax. at low lung volumes, Gus 
at 60% TLC, RV and RV/TLC were the functional parameters most 
consistently abnormal. Among the indices characterizing lung elasticity, Pst(1) at 60% 
TLC was the most abnormal. Generally, the values of the majority 
of lung function indices [VC, TLC, FRC, Pst(1)] declined during growth. 
Vmax. at all lung volumes and Gus at 60% TLC did 
not deteriorate with growth probably due to the great abnormality of 
these parameters already in young patients. It was also observed that 
lung function did not change significantly over a period of 1 
to 5 years corresponding to a 10 cm increase in body 
height. However, over that period, lung function improved in some of 
the subjects, did not change in over 50% of the cases 
and deteriorated in the others. 