Table 3

 Lung function results compared by diagnosis

Cystic fibrosis (n = 39)Healthy controls (n = 21)Mean (95% CI) difference*p Value
FEF, mid-expiratory flow; FEV, forced expiratory volume; FVC, forced vital capacity; LCI, lung clearance index; FRC, functional residual capacity.
FRCMBW corrected for equipment and mask deadspace.
Results are expressed as mean (SD) unless specified otherwise.
*Difference calculated as cystic fibrosis−control.
†According to prediction equation by Ranganathan et al.27
‡According to the prediction equations for He dilution by Stocks and Quanjer.24
Respiratory rate (per min)38.2 (9.7)32.0 (5.2)6.2 (2.3 to 10.0)0.009
Respiratory rate (Z score)†0.8 (1.4)–0.3 (0.9)1.1 (0.4 to 1.8)0.002
Tidal volume (ml)70.3 (24.2)71.3 (14.3)–1 (–12.5 to 10.6)0.865
Minute ventilation (ml/min)2524 (543)2235 (374)287 (22 to 554)0.035
FRCMBW (ml)170 (54)156 (38)14 (–13 to 41)0.295
FRCMBW (Z score)‡–0.27 (1.0)–1 (0.9)0.7 (0.3 to 1.2)0.004
LCI8.4 (1.5)7.2 (0.3)1.2 (0.7 to 1.7)<0.001
FEV0.5 (Z score)–1.6 (1.4)0.1 (0.9)–1.7 (–2.3 to –1.1)<0.001
FVC (Z score)–1.2 (1)–0.1 (0.8)–1.1 (–1.6 to –0.6)<0.001
FEF75 (Z score)–1.8 (1.5)–0.3 (0.9)–1.4 (–2.1 to –0.8)<0.001
FEF25–75 (Z score)–1.9 (1.5)–0.4 (1)–1.5 (–2.2 to –0.9)<0.001
FEV0.5/FVC (Z score)–0.43 (1.26)0.27 (0.81)–0.70 (–1.23 to –1.16)0.011