Comparing supplementary oxygen benefits from a portable oxygen concentrator and a liquid oxygen portable device during a walk test in COPD patients on long-term oxygen therapy

Respir Med. 2008 Jul;102(7):1021-5. doi: 10.1016/j.rmed.2008.02.005. Epub 2008 Mar 21.


Background: Differences in oxygen delivery between portable oxygen concentrators (POC) and liquid oxygen (LO) portable units, pose a question if POCs are equally effective as LOs in reducing exercise-induced hypoxaemia.

Design: Randomized, single-blind clinical trial.

Patients: Thirteen COPD patients (means: age 66+/-11 year, FEV(1) 35.2+/-13.7% predicted) and respiratory failure (means: PaO2 52+/-5mmHg, PaCO2 51.3+/-7.5mmHg).

Methods: All patients underwent a series of 6-min walk tests (6MWT) carried out in random order among one of the three devices: POC, LO cylinder and cylinder with compressed air (CA). Oxygen supplementation was 3lpm for LO and an equivalent to 3lpm in a pulse flow system for POC.

Results: The mean SpO2 was equally improved at rest: 92.9+/-2.8% with POC and 91.7+/-2.0% with LO compared to CA-87.8+/-2.7% (POC and LO vs. CA p<0.05). POC and LO significantly improved oxygenation during 6MWT (mean SpO(2) was 84.3+/-5% and 83.8+/-4.2%, respectively) compared to breathing CA-77.6+/-7.4%, p<0.05. Mean 6MWT distance increased with LO (350+/-83m) and POC (342+/-96m) when compared to CA (317+/-84m), however, these differences were not statistically significant. Dyspnoea score assessed at the end of the exercise (Borg scale) was significantly lower when breathing oxygen (4.2+/-1.2 with POC and 4.1+/-1.7 with LO vs. 5.4+/-1.9 with CA, p<0.05).

Conclusions: Effectiveness of oxygen supplementation from a POC did not differ from the LO source during 6MWT in COPD patients with respiratory failure. Oxygen at 3lpm flow was not sufficient to prevent hypoxaemia during strenuous exercise.

Publication types

  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Aged
  • Ambulatory Care
  • Exercise Test
  • Exercise Tolerance
  • Female
  • Humans
  • Hypoxia / prevention & control*
  • Male
  • Oxygen / administration & dosage*
  • Oxygen Inhalation Therapy / instrumentation
  • Oxygen Inhalation Therapy / methods*
  • Pulmonary Disease, Chronic Obstructive / therapy*
  • Treatment Outcome
  • Walking / physiology*


  • Oxygen