Characteristics and lung function of the study groups
| Cystic fibrosis | Healthy controls | |
| Subjects, n | 50 | 65 |
| General characteristics | ||
| Male sex, n (%) | 54.0 (50.3) | 53.8 (50.2) |
| Age years | 9.8±4.1 | 10.1±3.9 |
| Weight kg | 32.3±14.3 | 37.8±17.6 |
| Weight z-score# | −0.1±0.8 | 0.4±0.8 |
| Height cm | 134.4±19.7 | 140.7±23.0 |
| Height z-score# | −0.1±0.8 | 0.4±1.0 |
| Body mass index kg·m−2 | 17.0±2.6 | 17.9±3.1 |
| Body mass index z-score# | 0.0±0.8 | 0.2±0.8 |
| N2-MBW | ||
| Number of trials, n | 137 | 183 |
| Tidal volume mL | 402.9±175.8 | 437.4±199.0 |
| Tidal volume per kg (mL·kg−1) | 12.7±2.8 | 12.0±2.7 |
| Respiratory rate (per minute) | 18.7±4.1 | 18.2±4.8 |
| Minute ventilation mL·min−1·kg−1 | 231.2±46.0 | 215.3±67.6 |
| FRC mL·kg−1 | 40.2±7.8 | 41.4±8.9 |
| LCI 2.5% | 7.8±1.7 | 6.2±0.4* |
Data are presented as mean±sd, unless stated otherwise. N2-MBW: nitrogen multiple-breath washout; FRC: functional residual capacity; LCI: lung clearance index; CDC: Centers for Disease Control and Prevention; WHO: World Health Organization. #: weight, height and body mass index z-scores were calculated according to WHO growth charts. Weight z-scores for children older than 10 years of age were calculated according to CDC growth charts; *: statistically significant difference (p<0.05 using the t-test).