Summary of the demographic characteristics of the available data for each lung volume index
| Participants | Age years | Female | |
| FRC | |||
| He | 683 | 22.3–87.0 | 399 (58.4) |
| N2 | 489 | 3.2–50.0 | 263 (53.8) |
| Plethysmography | 6018 | 6.0–91.0 | 3434 (57.1) |
| Combined techniques | 7190 | 3.2–91.0 | 4096 (57.0) |
| TLC | |||
| He | 681 | 22.3–87.0 | 398 (58.4) |
| N2 | 229 | 4.0–12.9 | 113 (49.3) |
| Plethysmography | 5905 | 6.0–91.0 | 3367 (57.0) |
| Combined techniques | 6815 | 4.0–91.0 | 3878 (56.9) |
| RV | |||
| Combined techniques | 5660 | 4.9–91.0 | 3296 (58.2) |
| ERV | |||
| Combined techniques | 4741 | 7.1–91.0 | 2768 (58.4) |
| IC | |||
| Combined techniques | 5461 | 4.0–91.0 | 3167 (58.0) |
| VC | |||
| Combined techniques | 5654 | 4.9–91.0 | 3300 (58.4) |
Data are presented as n, range or n (%). Demographics of submitted data are presented in relation to the method used to collect data (either helium (He) or nitrogen (N2) multiple-breath washout or plethysmography). FRC: functional residual capacity; TLC: total lung capacity; RV: residual volume; ERV: expiratory reserve volume; IC: inspiratory capacity; VC: vital capacity. RV was calculated as TLC − VC if VC was available and as FRC − ERV if ERV was available.