TABLE 1

Demographics of children with cystic fibrosis (CF) and healthy children for all visits with two or more acceptable multiple-breath washout (MBW) trials, visits with three or more acceptable MBW trials and visits with only two acceptable MBW trials obtained within a single testing session

All visits (two or more acceptable trials)Three or more acceptable trialsTwo acceptable trials
CFHealthyCFHealthyCFHealthy
Subjects714749362211
Test occasions1046166423819
Age years5.1±1.04.8±1.15.0±1.04.8±1.15.1±1.05.0±0.8
Male31 (44)22 (54)27 (43)19 (53)15 (39)6 (55)
Height cm109.9±8.8108.8±8.2109.7±8.8108.8±8.2108.4±8.9111.1±7.1
Weight kg19.4±3.719.2±3.919.7±3.819.2±3.918.9±3.521.0±5.1
Height z-score−0.08±1.00.17±1.00.04±1.10.09±1.1−0.27±0.950.34±0.95
Weight z-score0.32±0.890.51±1.20.44±0.930.34±1.00.12±0.780.84±1.5
Multiple-breath washout test
 Functional residual capacity L0.88±0.230.85±0.180.87±0.250.87±0.170.89±0.210.94±0.17
 Lung clearance index8.13±1.547.10±0.60***8.19±1.506.84±0.63***8.05±1.666.69±0.48***
 First moment ratio1.78±0.311.65±0.12***1.81±0.311.58±0.14***1.75±0.321.52±0.10**
 Second moment ratio6.91±2.795.54±0.87***7.11±2.835.07±0.97***6.63±2.824.62±0.59**
Respiratory infection
 Any infection47/97 (48)24/60 (40)23/37 (62)*
 Infection with a pro-inflammatory pathogen32/97 (33)17/60 (28)15/38 (39)
Inflammation      
 Total cell count ×106 mL−18.13±14.0 8.93±17.2 6.32±5.16 
 Macrophages %75.1±23.4 76.2±23.1 79.8±18.3 
 Neutrophils %23.3±23.0 23.0±23.1 19.3±18.8 
 Neutrophil elastase present32/92 (35) 18/55 (33) 14/37 (38) 
 Neutrophil elastase ng·mL−1874.4±2155.0 904.7±2067.6 1231.1±3127.9 
 Interleukin-8 pg·mL−13227.34±7826.1 4228.2±9674.7 1454.7±2118.0 
Structural lung disease      
 Bronchiectasis present46/65 (71) 33/49 (67) 13/16 (81) 
 Bronchiectasis extent %1.25±2.89 1.11±2.51 1.67±4.09 
 Air trapping present52/65 (80) 35/49 (71) 13/16 (81) 
 Air trapping extent %5.10±10.1 4.65±8.04 6.14±15.5 
 Structural lung disease extent %4.04±3.56 3.96±2.69 3.91±5.68 

Data are presented as n, mean±sd, n (%) or n/N (%). z-scores for height and weight were calculated using World Health Organization Child Growth Standards [16, 17]. Demographics and MBW outcomes were compared between children with CF and healthy children; MBW outcomes, demographics and clinical data were compared between visits with three or more acceptable trials and visits with only two acceptable trials. *: p<0.05; **: p<0.01; ***: p<0.001.