Table 3– Main gas washout parameters and intra-visit reproducibility

	Baseline	1 week	1 month	6 months	CV %	ICC^#
Healthy adults n	40	40	40	38
LCI	6.94±0.61	7.09±0.64	7.12±0.74	7.05±0.66	4.4±3.0	0.71
FRC_MBW L	3.21±0.81	3.03±0.76	2.97±0.73	2.92±0.71	7.7±6.6	0.82
S_cond L⁻¹	0.028±0.026	0.026±0.020	0.021±0.017	0.028±0.029	72.9±41.8	0.44
S_cond×V_T	0.029±0.029	0.027±0.024	0.023±0.019	0.028±0.030	73.1±41.9	0.62
S_acin L⁻¹	0.058±0.028	0.058±0.029	0.057±0.039	0.055±0.041	48.7±78.2	0.42
S_acin×V_T	0.060±0.034	0.065±0.036	0.058±0.037	0.058±0.041	44.4±34.4	0.52
dN₂ % N₂ per L	0.99±0.42	1.03±0.43	1.23±0.68	1.10±0.46	16.4±16.5	0.80
dN₂×VC % N₂	3.82±1.36	3.81±1.27	4.26±1.73	4.04±1.31	14.1±11.9	0.84
SIII_DTG g·mol⁻¹·L⁻¹	−0.206±0.108	−0.195±0.089	−0.205±0.109	−0.216±0.121	22.2±31.4	0.80
SIII_DTG×V_T g·mol⁻¹	−0.204±0.091	−0.199±0.089	−0.201±0.096	−0.212±0.110	20.7±30.5	0.82
AUC g·%·mol⁻¹	16.40±5.38	16.87±5.37	17.18±5.88	17.17±6.27	17.5±52.5	0.93
COPD patients n	20	19	17	15
LCI	12.23±2.67	12.40±3.48	12.07±2.88	12.42±2.62	5.3±5.4	0.89
FRC_MBW L	4.19±1.27	4.30±1.00	4.13±1.23	4.20±1.66	5.9±5.8	0.87
S_cond L⁻¹	0.045±0.034	0.042±0.031	0.050±0.035	0.047±0.032	45.1±32.0	0.67
S_cond×V_T	0.046±0.034	0.045±0.031	0.048±0.033	0.043±0.029	29.8±22.4	0.66
S_acin L⁻¹	0.343±0.139	0.330±0.143	0.348±0.153	0.384±0.156	16.3±15.8	0.86
S_acin×V_T	0.355±0.150	0.354±0.160	0.367±0.167	0.354±0.162	8.8±8.5	0.87
dN₂ % N₂ per L	7.43±5.38	7.40±4.01	7.44±4.00	7.17±3.41	7.8±5.7	0.81
dN₂×VC % N₂	20.60±6.84	22.01±7.92	22.18±7.49	21.46±6.80	7.1±5.1	0.83
SIII_DTG g·mol⁻¹·L⁻¹	−0.653±0.428	−0.635±0.419	−0.721±0.447	−0.820±0.459	10.1±9.0	0.95
SIII_DTG×V_T g·mol⁻¹	−0.630±0.344	−0.601±0.325	−0.664±0.305	−0.726±0.353	9.6±9.8	0.96
AUC g·%·mol⁻¹	33.07±18.59	32.32±18.36	24.50±18.46	25.43±20.18	7.9±14.1	0.97

Data are presented as mean±sd unless otherwise stated. Intra-visit reproducibility was assessed as distribution (mean±sd) of the intraindividual coefficient of variation (CV) of three single measurements of all subjects and all test occasions. ICC: intraclass correlation coefficient; LCI: lung clearance index; FRC_MBW: functional residual capacity measured by nitrogen multiple-breath washout; S_cond: index of conductive ventilation inhomogeneity; V_T: tidal volume; S_acin: index of acinar ventilation inhomogeneity; dN₂: phase III slope of nitrogen single-breath washout; VC: vital capacity; SIII_DTG: phase III slope of double tracer gas single-breath washout; AUC: area under the curve (double tracer gas single-breath washout). ^#: calculated from three individual trials on the same day.