• respiratory muscles

Some concepts in medicine (as perhaps with other aspects of life) are so appealing that their appeal endures in the absence of data. Inspiratory muscle training (IMT) in COPD is arguably one example.

In 1976, Leith and Bradley showed, in a study undertaken in a handful of healthy subjects,1 that IMT could improve maximum inspiratory mouth pressure (PI_max). The rationale for IMT in patients with COPD was based on the observations that PI_max was reduced in COPD2 and on the data which seemed to show that respiratory muscle fatigue limited exercise in COPD.3 IMT was welcomed by enthusiasts perhaps because it came against a paucity of effective treatments for COPD, and early studies showed that, as with healthy volunteers, IMT could improve performance on tests of inspiratory muscle strength. As elegantly documented in a recent editorial,4 responsible opinion, including the American College of Chest Physicians,5 the American Thoracic Society and European Respiratory Society,6 continued on the one hand to recommend that IMT be included in pulmonary rehabilitation programmes (PRPs) for patients with COPD while on the other hand requesting more studies.

This story, which played over decades, in fact defied data at each stage. First, it was by no means certain that IMT improved inspiratory muscle strength; even Leith and Bradley’s original work1 showed that the type of training undertaken determined which test results improved (ie, …