Comparison of lung clearance index determined by washout of N and SF in infants and preschool children with cystic fibrosis.

BACKGROUND

Multiple-breath washout (MBW) has been shown to detect early impairment of lung function in children with cystic fibrosis (CF). Nitrogen (N) or sulfur hexafluoride (SF) can be used as tracer gas for MBW. Recent data indicated higher lung clearance index (LCI) values measured with N-MBW than concurrent SF-MBW in older children and adults, however, a comparison in infants and younger children, as well as to other outcome measures of CF lung disease is pending.

METHODS

N- and SF-MBW were performed consecutively in 31 sedated infants and preschool children with CF (mean age, 2.3 ± 0.8 years) and 20 controls (mean age, 2.3 ± 1.1 years) using the Exhalyzer D system. Children with CF also underwent chest magnetic resonance imaging (MRI).

RESULTS

Mean difference (95% CI) in LCI between N- and SF-MBW was 1.1 ± 0.4 (0.9 to 1.3) in controls and 2.1 ± 1.9 (1.4 to 2.8) in CF. Agreement between N- and SF-LCI was poor in children with CF. N-LCI and SF-LCI correlated with MRI, however N-LCI showed a higher concordance with MRI than SF-LCI. The absolute difference between N- and SF-LCI values increased with the severity of CF lung disease as determined by MRI scores.

CONCLUSION

N-LCI values were higher than SF-LCI values in infants and preschool children with CF and controls. Better concordance of N-LCI than SF-LCI with chest MRI scores point towards of a higher sensitivity of N-LCI to detect early lung disease in children with CF.