ABC | Volume 110, Nº5, May 2018

Original Article Oliveira et al Exercise in acute heart failure Arq Bras Cardiol. 2018; 110(5):467-475 Figure 3 – Correlation between total exercise time and length of hospital stay (days) in exercise groups. 50 40 30 20 10 0 Length of stay (days) 40 60 80 100 120 140 160 180 Total exercise time (min) r = –0.75 p = 0.01 ET+Sham ET+NIV Figure 2 – Dyspnea Borg scale at first day of hospitalization (D1) and at last day of protocol (D10) in Control, Exercise Training (ET) + Sham and ET+non-invasive ventilation (NIV) groups. Notes: * p < 0.05 vs. Control; † p < 0.05 vs. ET+Sham; ‡ p < 0.05 vs. D1. 10 8 6 4 2 0 D1 D10 Dyspnea (Borg scale) Control ET+Sham ET+NIV ‡ ‡ *†‡ It was recently demonstrated that patients with chronic HF has slower oxygen kinetics with increased deoxyhemoglobin kinetics during exercise. 14 On the other hand, Borghi-Silva et al. 16 demonstrated that NIV was able to improve exercise tolerance and reduce the deoxyhemoglobin kinetics in peripheral muscle during exercise in patients with chronic HF. In our study, the ET+NIV group showed better response to aerobic exercise. The mechanism for this response is beyond the scope of our study, however it is likely that NIV influenced muscle blood flow redistribution, from the respiratory muscles to the peripheral muscles, improving oxygen delivery and utilization. Study limitations The present study has some limitations that should be addressed. First, we had a small number of patients. In addition, our patients performed an aerobic exercise 472