In cystic fibrosis, lung clearance index is sensitive to detecting abnormalities appearing at exercise in children with normal spirometry

Symptom-limited incremental cardiopulmonary exercise test was performed in school-age children with clinically stable cystic fibrosis (CF), all with normal spirometry. Physiological parameters were compared between patients with normal lung clearance index (LCI; n = 6) and patients with elevated LCI (n = 6). Dyspnoea ratings during exercise were similar in both groups. Although no patient had significant dynamic hyperinflation, end expiratory lung volumes were higher throughout exercise in patients with elevated LCI. In addition, alveolar arterial oxygen gradient at peak exercise was higher, and SpO(2) was lower in patients with elevated LCI. LCI can thus be regarded as a test performed at rest that predicts some abnormalities appearing at exercise in CF children with normal spirometry.