TABLE 1

Comparison of multiple-breath washout devices, cystic fibrosis (CF) and healthy control (HC) demographics and lung clearance index (LCI) results

CF (n=47)HC (n=42)
Female24 (51%)26 (62%)
Age years16.05 (5.9–63.7)24.32 (5.7–56.1)
Height cm, Z-score154.6±52.2, −0.07±1.1158.4±17.9, −0.79±1.1
Weight kg, Z-score52.2±18, 0.60±1.159.7±20.6, −0.27±1.2
FEV1 % pred, Z-score72.9±16.8, −2.29±1.43Not done
SF6InnN2ExDDifference p-valueSF6InnN2ExDDifference p-value
LCI2.59.5±2.3 (8.82 to 10.19)14.0±3.7 (12.88 to 15.14)−4.5 (−5.2 to −3.8), p=<0.00016.3±0.5 (6.12–6.5)7.3±0.72 (7.03–7.48)−0.9 (−1.1 to −0.7), p<0.0001
LCI56.8±1.4 (6.38 to 7.23)7.9±1.7 (7.31 to 8.32)−1.01 (−1.2 to −0.8), p<0.00015.1±0.4 (4.97 to 5.20)5.1±0.3 (5.01 to 5.20)−0.02 (−0.12 to 0.08), p=0.709
FRC2.5 L1.9±0.6 (1.73 to 2.09)2.5±0.9 (2.23 to 2.78)−0.6 (−0.7 to −0.5), p<0.00012.3±0.8 (2.05–2.55)2.5±0.9 (2.25–2.84)−0.2 (−0.3 to −0.2), p<0.0001
CEV L18.4±7.7 (16.1–20.8)38.5±18.7 (33.9–44.2)−20.1 (−23.9 to −16.3), p<0.000114.5±5.6 (12.8–16.2)19.8±7.9 (17.4–22.3)−5.3 (−6.4 to −4.2), p<0.0001
SF6InnMean LCI difference 3.2±0.4 (2.5 to 3.9) p<0.0001
N2ExDMean LCI difference 6.8±0.6 (3.6 to 7.9) p<0.0001

Results show mean±sd or median (range) with 95% confidence intervals for LCI2.6 and functional residual capacity (FRC). FEV1: forced expiratory volume in 1 s; HC: healthy control; LCI: lung clearance index; LCI2.5: lung clearance index calculated from washout to 1/40th of the tracer gas starting concentration; LCI5: lung clearance index calculated from washout to 1/20th of the tracer gas starting concentration; FRC: Functional Residual Capacity; CEV: Cumulative Expiratory Volume; MBW: multiple-breath washout; N2ExD: Exhalyzer D nitrogen device; SF6Inn: modified Innocor sulfur hexafluoride device.