The effect of exercise training on exercise oscillatory ventilation in heart failure

To the Editor,

We have read with great interest the article by Panagopoulou et al. ¹ published as an essential contribution on the value of exercise training in patients with heart failure presenting exercise oscillatory ventilation (EOV). The principal finding of this study is that high intensity aerobic interval training (HIAIT) with or without strength training (S) diminishes EOV in patients with heart failure.

The authors refer to randomization of patients into HIAIT or HIAIT+S but describe instead a (retrospective) cohort study of afore-acquired data by the same research group. It is unclear how the total study population (N = 38) was selected out of a bigger dataset. The EOV+ patients conducted two different training modalities (n = 12 HIAIT, n = 8 HIAIT + S) but it is uncertain which training the EOV– group completed. The results stated no differences between the two training groups either in EOV characteristics or in cardiopulmonary exercise test derived parameters. Notwithstanding this, the authors provided a pathophysiologic explanation for EOV based on the effect of HIAIT + S. In our opinion, it is not possible to make such statements solely based on these results since no significant differences were found between EOV+ and EOV–. In fact, the only significant difference was the decline of EOV duration. On top of that, two other EOV characteristics, amplitude and average length, were not different. The authors concluded that the percentage of EOV presence was decreased after exercise. However, it was not evaluated in how many patients EOV remained present after training. This depends largely on the applied definition of EOV. The authors adopted the definition made by Corrà et al.; ² a feasible choice but only evaluating total duration and size of amplitude during exercise in comparison with rest. Since no gold standard is available, it was shown that also other definitions, that is, that of Leite et al., ³ in which amplitude (≥5 l/min, three consecutive cycles) is an important characteristic, could be relevant. When using this definition it would be doubtful that the same number of patients would present EOV. Certainly, since the average amplitude reported was only 5.2 ± 2.0 and the total cycles observed in each patient is uncertain, the strongest statement that could be made based on this study is that EOV duration was significantly decreased, but it is questionable what the clinical importance of this finding might be. We strongly support the authors’ suggestion to computerize the assessment of EOV so that defining and assessing EOV can be more standardized. In fact, this has already been stated, investigated and developed by our research group. ⁴

Over the last year, it was illustrated in a large cohort and meta-analysis that HIAIT does not have the superior effect to which the authors refer.^5,6 It is questionable whether training at 50% peak work rate, as applied in this study, could be considered as high intensity.

Meanwhile, the authors should be congratulated for their interesting and extensive work.