Baseline characteristics of subjects
| Continuous variables | Mean (SD) |
| Age (years) | 73.2 (6.1) |
| BMI (kg/m2) | 26.3 (6.3) |
| Pack years of smoking | 50.2 (25.0) |
| Baseline arterial blood gas* | |
| pH | 7.41 (0.024) |
| Pao2 (mm Hg) | 61.8 (8.6) |
| Paco2 (mm Hg) | 47.8 (5.5) |
| Bicarbonate (mmol/l) | 29.4 (3.0) |
| Oxygen saturation (%) | 92.7 (2.7) |
| FEV1 (litres) | 0.71 (0.27) |
| FEV1 (% of predicted) | 27.3 (10.3) |
| Categorical variables | N/N (%) |
| Male | 13/18 (72.2) |
| Current smoker | 2/18 (11.1) |
| Ex-smoker | 16/18 (88.9) |
| Use of long-term oxygen | 12/18 (66.7) |
| Home nebuliser | 5/18 (27.8) |
| Long-term oral steroids | 7/18 (38.9) |
| Long-acting ß agonist | 13/18 (72.2) |
| Long-acting antimuscarinic | 9/18 (50.0) |
| Previous hospital admission | 14/18 (77.8) |
↵* Two subjects had arterial blood gas measurements while receiving supplementary oxygen in accordance with the protocol.
BMI, body mass index; FEV1, forced expiratory volume in 1 s; Paco2, arterial carbon dioxide tension; Pao2, arterial oxygen tension.