Evidence has been presented that some patients with cystic fibrosis have significant
amounts of obstruction to the ventilation of portions of lung, as indicated by tests of the
distribution of ventilation, but they have little or no evidence of obstruction by conventional
measurements of airway resistance. 1-5 This discrepancy may be attributed to the fact that
various tests of pulmonary function differ in sensitivity with respect to small and large airway
obstruction. It is the purpose of the present Commentary to summarize the evidence for this …