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) | |||||
| Female | 24 (51%) | 26 (62%) | ||||
| Age years | 16.05 (5.9–63.7) | 24.32 (5.7–56.1) | ||||
| Height cm, Z-score | 154.6±52.2, −0.07±1.1 | 158.4±17.9, −0.79±1.1 | ||||
| Weight kg, Z-score | 52.2±18, 0.60±1.1 | 59.7±20.6, −0.27±1.2 | ||||
| FEV1 % pred, Z-score | 72.9±16.8, −2.29±1.43 | Not done | ||||
| SF6Inn | N2ExD | Difference p-value | SF6Inn | N2ExD | Difference p-value | |
| LCI2.5 | 9.5±2.3 (8.82 to 10.19) | 14.0±3.7 (12.88 to 15.14) | −4.5 (−5.2 to −3.8), p=<0.0001 | 6.3±0.5 (6.12–6.5) | 7.3±0.72 (7.03–7.48) | −0.9 (−1.1 to −0.7), p<0.0001 |
| LCI5 | 6.8±1.4 (6.38 to 7.23) | 7.9±1.7 (7.31 to 8.32) | −1.01 (−1.2 to −0.8), p<0.0001 | 5.1±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 L | 1.9±0.6 (1.73 to 2.09) | 2.5±0.9 (2.23 to 2.78) | −0.6 (−0.7 to −0.5), p<0.0001 | 2.3±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 L | 18.4±7.7 (16.1–20.8) | 38.5±18.7 (33.9–44.2) | −20.1 (−23.9 to −16.3), p<0.0001 | 14.5±5.6 (12.8–16.2) | 19.8±7.9 (17.4–22.3) | −5.3 (−6.4 to −4.2), p<0.0001 |
| SF6Inn | Mean LCI difference 3.2±0.4 (2.5 to 3.9) p<0.0001 | |||||
| N2ExD | Mean 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.