Methods

Randomised double blinded placebo controlled crossover trial. Study conducted in Toronto, Canada.

Participants

Nine males patients with COPD and an arterial oxygen tension (PaO2) while sitting and breathing room air of less than 60mm Hg (hypoxemia) with clinical and ECG evidence for cor pulmonale were selected. All patients were stable and showed no subjective change or change in exercise tolerance for 3 months prior to the start of the study.

Interventions

All patients were assigned five weeks of liquid oxygen therapy (at 2 L/min providing 19.7+‐2.2% oxygen) or five weeks of liquid air treatment in a double‐blinded randomised crossover order. All patients were taught how to use the portable gas apparatus (Linde walker) prior to start of study. All study measurements were also taught prior to the start of the study. All patients were visited at home once a week for study measurements and at the end of the five week period, all patients came into hospital for complete assessment. Exercise challenge consisted of a bicycle ergometer with progressively increasing workloads starting at 50 kilopond meters/min and increased by 50 kilopond meters every minute until patient stopped. There was a 10 day washout period (when no portable gas apparatus was supplied) after which coded gas apparatus were delivered to the patients home.

Outcomes

All study measurements were done 4‐24 hours after patients stopped use of portable gas apparatus. FVC, MVV, FEV1/FVC, RV, RV/TLC, gas diffusion, heart rate, VE, arterial pH, PaCO2, PaO2, miles walked per day using pedometer, reticulocyte count, hematocrit, hemoglobin.

Notes

Study used codes to conceal treatment allocation.

Jadad score = 4

Risk of bias

Bias

Authors' judgement

Support for judgement

Allocation concealment?

Low risk

A ‐ Adequate

Methods

Randomised double blinded placebo controlled crossover trial. Study conducted in Victoria, Australia.

Participants

Thirty‐six patients entered the study and 10 dropped out for various reasons. Data reported on 26 patients who completed the study. All patients had COPD without resting hypoxemia (PaO2 > 60 mmHg), baseline values were mean (SD): age 73(6), FEV1 0.9(0.4) L, DLco 10.6 (2.4) ml/mim/mm Hg, PCO2 41 (3.3) mm Hg, SaO2 94 (2.1). None of the patients had an exacerbation of their COPD in the preceding 3 months, none had symtomatic cardiac dysfunction, angina pectoris or locomotor disability.

Interventions

All patients were assigned six weeks of portable gas oxygen cylinders (at 4 L/min intranasally) or six weeks of portable air treatment in a double‐blinded randomised crossover fashion. All patients were made familiar with diary cards and with performance of exercise tests. Exercise challenge consisted of step tests (patient stepped in time with a metronome at a previously determined level and until patient voluntarily stopped) and 6 minute walking distance (6MWD). All study measurements were done and taught prior to the start of the study. Study measurements were done at baseline and at the first and second six week periods. There was no mention in the study of a washout period.

Outcomes

All study measurements were done with the patient using both air and oxygen irrespective of whether the patient was using air or oxygen in the preceding 6 weeks, the results were reported separately (only study measurements using air were used in the review as it was same methodology as the other study). Borg score, 6MWD, quality of life using CRDQ, symptom scores, SaO2.

Notes

Study used camouflaged cylinders for treatment delivery.

Jadad score = 4

Risk of bias

Bias

Authors' judgement

Support for judgement

Allocation concealment?

Low risk

A ‐ Adequate