I read with interest the paper of Machado et al. regarding the effects of a community-based pulmonary rehabilitation program (PR) during acute exacerbations of Chronic Obstructive Pulmonary Disease (COPD).1 Pulmonary rehabilitation is a multicomponent regime known to improve exercise capacity, functional capacity and quality of life and reduce symptom burden and hospitalizations among COPD patients.2 Current ERS/ATS statement recommends the implementation of a home-based PR program for exacerbated COPD patients who present at hospital; however the level of recommendation is moderate, since published data is currently limited.3 Moreover, the optimal time point of initiation and the PR program that could provide the most benefit is still to be identified. The study of Machado et al.1 offers further interesting information in this context. The severity of obstruction and its potential impact on the outcomes of the PR program would be an interesting addition to the study results. Although the study sample is rather small, so subject categorization according to the severity of the disease is probably not possible, it would be interesting to know whether the effect of this community-based PR program was similar among COPD patients with moderate, severe and very severe obstruction. Similarly, this data would be useful for exploring characteristics of drop-outs, since published data in PR studies indicate that those patients who drop out have more severe disease overall, than the ones who complete the intervention.4

The lack of characterization of the severity of COPD acute exacerbation (AECOPD) can be reported as a limitation of Machado et al. study.1 According to Global Obstructive Lung Disease (GOLD), AECOPD is classified as mild when treated with extra short-acting bronchodilators, as moderate when treated with short-acting bronchodilators plus antibiotics and/or oral corticosteroids, while in severe AECOPD patient requires hospitalization or visits the emergency room.5 Since participants in both groups (experimental and control) were identified by pulmonologists at hospital, one would expect that they suffered from severe or moderate-to-severe exacerbation. However, the data from the medication usage is rather contradictory; no extra bronchodilation was given to any of the patients, while the use of antibiotics and/or oral corticosteroids tend to differ between the groups. It is unlikely that the results of this study would have been different if medication usage was similar between the groups. Nevertheless, accurate characterization of the severity of AECOPD would offer valuable information as to who can receive a community-based PR program during exacerbation and who would benefit the most.

The authors have to be commended for offering a multidimensional program including psychoeducational and nutritional support, respiratory training, muscle strengthening and aerobic training, which they describe in detail. However, the exact point in time for starting PR has to be accurately defined. Published data indicate that PR outcomes differ when it is initiated early or late after AECOPD onset,6 so this is an issue that has to be further addressed in detail.

In conclusion, a community-based multidimensional PR program seems to be safe and effective for COPD patients during acute exacerbation. More prospective, randomized trials are needed in order to define the optimal outpatient PR regimen and when it should be initiated, according both to the severity of COPD and the severity of acute exacerbation.