Inclusion and exclusion criteria of the Medical Research Council (MRC) study and Nocturnal Oxygen Treatment Trial (NOTT) [29, 30]
| Trial | Inclusion criteria | Exclusion criteria |
| MRC [29] | Stable individuals with chronic bronchitis or emphysema with FEV1 <1.2 L, aged <70 years PaO2 40–60 mmHg (5.3–8.0 kPa) when breathing room air, repeated after 3 weeks One or more episodes of ankle oedema | Restrictive disorders, pulmonary embolism, systemic hypertension, coronary artery disease |
| NOTT [30] | Stable participants PaO2 <55 mmHg (7.3 kPa) (at least two occasions) PaO2 <59 mmHg (7.9 kPa) (at least two occasions) plus one of the following: oedema, haematocrit >55%, or P pulmonale on ECG Lung function: FEV1/FVC <70% after bronchodilator TLC >80% pred Age >35 years | Previous LTOT Other diseases that may be expected to influence mortality |
FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; LTOT: long-term oxygen therapy; PaO2: arterial oxygen tension; TLC: total lung capacity.