[Is helium beneficial in a pulmonary rehabilitation program for severe COPD?]

Helium is known to reduce airflow limitation. Our hypothesis was that severe COPD patients undertaking exercise would show greater improvement in endurance under a heliox mixture (80/20%) than under air alone. This hypothesis was tested in a double-blinded, randomized study.

Out of the 53 patients included, 45 were randomly assigned to two groups : Heliox (n= 23) and Air (n= 22). Patients were assessed with spirometry under air and heliox, incremental exercise test, constant workload (80% Wmax) exercise test and weekly 6-minute walk test. The two groups went through fifteen 30-minute retraining sessions in the overall framework of an identical pulmonary rehabilitation program.

There was no significant difference in endurance improvement (Heliox : +52.5 sec, Air:+114sec, median value). FEV1 improvement under heliox exceeding 10% identified a group of 20 patients as "helium responders", who improved their endurance time by a median of 135sec compared to 50sec for the "non-responders" (non-significant difference).

In patients with severe COPD, use of Heliox in exercise retraining did not produce significantly improved endurance. On the other hand, "helium responders" showed more FEV1 improvement than non-responders. Improved FEV1 under heliox should therefore be used in future studies as an inclusion criterion.