Limitations of the study
We must first identify two key study limitations. One refers to the absence of randomized study group allocation, due to the absence of patient registration in the hospital where the study was performed. The second limitation other relates to the fact that COPD patients do not commonly consult a physician until the symptoms become extremely disturbing, or they delay the diagnosis because they think that their symptoms relate to their smoking habit. This reporting once symptoms progress increases the probability of companion disease and, with advancing age, the appearance of other conditions. Given the possible influence of concomitant disease on the management of COPD, we did not accept such participants for the study. On the other hand, the small number of participants who satisfied these eligibility conditions created an important limitation to the study.