FIG. 17:  The scientific rationale behind pulmonary rehabilitation only goes back as far back as 1991.  Before that time, pulmonary rehabilitation was utilized by clinicians who judged from their own experience that it was effective, but there were no randomized controlled trials to demonstrate that it worked.  The first study to demonstrate this was a simple experiment performed by Casaburi and colleagues in Italy, in which 19 patients with moderately advanced COPD performed high-intensity or low-intensity exercise training.^[14] The low-intensity exercise training was associated with a longer period of exercise, so that the total amount of work in both groups was similar.