IJCS | Volume 32, Nº5, September/October 2019

486 Figure 1 - Flowchart of participants during the trial . Cerqueira et al. NMES after cardiac surgery Int J Cardiovasc Sci. 2019;32(5):483-489 Original Article Moreover, no reports of muscle pain, discomfort, or fatigue that could lead to interruption of NMES therapy, or even a dyspnea complaint, confirmed by the maintenance of the respiratory variables of RR and SpO 2 , were observed. Our findings are in agreement with those of another study that found no significant changes in RR and SpO 2 with the use of NMES in critically-ill patients. 17 Our study had no dropouts. This is in accordance to previous studies that reported low dropout rates of 1.5% in patients in the postoperative period 3 and 11% for patients with heart failure. 18 These data support the use of NMES, because it was well tolerated by the patients during the acute phase, when they are submitted to invasive procedures and subject to pain. 2,19,20 The parameters used in the NMES studies are divergent, ranging from 250 ms–400 ms for pulse duration, 1.75 Hz–100 Hz for frequency, and 2–12 s to 4–24 s for the clicks. 21 Some authors report that high frequencies ≥ 50 Hz improvedmuscle strength, 22 whereas others state that the intensity of NMES response varies based on the patient’s interaction. 16 Differently from the present study, another study has shown that NMES induced energy expenditure and cardiovascular response similar to other types of exercise in other patient profiles, with higher HR increases, but using low-frequency NMES techniques. 23 This same study even suggested that this technique using low frequency would lead to higher physiological