Types of interventions
Inclusion:
The intervention for the actively-treated group was oxygen therapy,provided through wall oxygen units (in a hospital or clinic),portable oxygen cylinders or liquid oxygen canisters. Intervention for the control group was either placebo (compressed air provided by a wall unit or cylinders) or no intervention (room air). All interventions were given during exercise training which was greater than or equal to three weeks in duration and included a minimum of two sessions a week. Formal (in hospital or a clinic) exercise training as a part of rehabilitation was accepted.
Exclusion:
Long-term (at home for activities of daily living) or short-term(single assessment) studies assessing the efficacy of ambulatory oxygen therapy and studies assessing the efficacy of LTOT without training or rehabilitation were excluded.