Baseline demographics of the study population
| Total population (N=1746) | London population (n=1118) | Rouen population (n=628) | P value | |
| Age (years) | 60.5 (±15.9) | 58.8 (±15.7) | 63.6 (±15.8) | <0.001 |
| Gender (male), n (%) | 949 (54) | 613 (55) | 336 (54) | 0.617 |
| PaCO2 at admission for NIV set-up (kPa)* | 7.1 (6.2–8.1) | 7 (6.1–8.0) | 7.5 (6.6–8.8) | <0.001 |
| Spirometry at NIV set-up† | ||||
| FEV1 (L) | 1.1 (0.7–1.6) | 1.1 (0.7–1.7) | 1.0 (0.7–1.4) | 0.078 |
| FVC (L) | 1.7 (1.2–2.4) | 1.7 (1.1–2.4) | 1.9 (1.4–2.4) | <0.001 |
| Underlying respiratory disease | 0.007 | |||
| Neuromuscular diseases, n (%) | 397 (22.7) | 290 (25.9) | 107 (17) | <0.001 |
| Motor neuron disease | 144 (36.3) | 84 (29) | 60 (56.1) | <0.001 |
| Duchenne muscular dystrophy | 49 (12.3) | 37 (12.8) | 12 (11.2) | |
| Postpolio syndrome | 40 (10.1) | 39 (13.4) | 1 (0.9) | |
| Myotonic dystrophy | 27 (6.8) | 19 (6.6) | 8 (7.5) | |
| Spinal cord injury | 24 (6) | 14 (4.8) | 10 (9.3) | |
| Diaphragm palsy | 21 (5.3) | 13 (4.5) | 8 (7.5) | |
| Other neuromuscular conditions‡ | 92 (23.2) | 84 (29) | 8 (7/5) | |
| Obstructive airway diseases, n (%) | 334 (19.1) | 199 (17.8) | 135 (21.5) | 0.001 |
| COPD | 305 (91.3) | 182 (91.5) | 123 (91.1) | 0.733 |
| Bronchiectasis | 14 (4.2) | 8 (4) | 6 (4.4) | |
| Asthma | 10 (3.0) | 5 (2.5) | 5 (3.7) | |
| Other obstructive conditions‡ | 5 (1.5) | 4 (2) | 1 (0.7) | |
| Chest wall diseases, n (%) | 95 (5.4) | 59 (5.3) | 36 (5.7) | 0.714 |
| Kyphoscoliosis | 58 (61.1) | 32 (53.3) | 26 (72.2) | 0.003 |
| Scoliosis | 15 (15.8) | 15 (25.0) | 0 (0) | |
| Post-tuberculosis | 10 (10.5) | 3 (5.0) | 7 (19.4) | |
| Pneumonectomy | 5 (5.3) | 3 (5.0) | 2 (5.6) | |
| Other restrictive conditions‡ | 7 (8.3) | 7 (11.6) | 1 (2.8) | |
| Obesity hypoventilation syndrome with or without obstructive sleep apnoea, n (%) | 515 (29.5) | 319 (28.5) | 196 (31.2) | 0.251 |
| Obstructive sleep apnoea, n (%) | 184 (10.5) | 122 (10.9) | 62 (9.9) | 0.517 |
| Overlap between obstructive airway disease and sleep apnoea, n (%) | 221 (12.7) | 129 (11.5) | 92 (14.6) | 0.072 |
| COPD | 206 (93.2) | 122 (94.6) | 84 (91.3) | 0.588 |
| Asthma | 10 (4.5) | 6 (4.7) | 4 (4.3) | |
| Bronchiectasis | 5 (2.3) | 1 (0.8) | 4 (4.3) | |
Results are expressed in terms of mean and SD or median and IQR for continuous variable and in frequency for categorical values.
*n=1096.
†n=803.
‡Full list of other conditions can be found in online supplementary material.
COPD, Chronic obstructive pulmonary disease; NIV, non-invasive ventilation; PaCO2, Partial pressure of carbon dioxide in arterial blood.