Inclusion and exclusion criteria of the Medical Research Council (MRC) study and Nocturnal Oxygen Treatment Trial (NOTT) [29, 30]

TrialInclusion criteriaExclusion 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.