This is a prospective, quantitative, randomized, crossover study. Were included in this study 10 people in the Intensive Care Unit at University Hospital in Uberlandia, on the first day of the postoperative coronary artery bypass graft (CABG). For data collection was performed randomization on the block (2: 4), to determine the first technique to be used and then a wash-out period of one hour was allowed for the research subject reaches the systemic arterial pressure, heart rate, respiratory rate and oxygen saturation baseline. And after, for cross-over, the second technique was performed. Non-invasive ventilation was performed for 30 minutes each ventilator. All subjects underwent noninvasive ventilation using two models of ventilators, they are conventional (designed for invasive ventilation but is also used in non-invasive ventilation mode) and specific (designed for non-invasive ventilation). Hemodynamic, autonomic and respiratory variables are monitored. We use the hypothesis that non-invasive ventilation performed with two fan models can alter autonomic function and that there is hemodynamic changes related to autonomic function in different ventilators in postoperative coronary artery bypass grafting.

Background: The patients in postoperative coronary artery bypass graft (CABG) have impaired cardiac autonomic function. However, no studies have evaluated the influence of different ventilators during noninvasive ventilation (NIV) in the autonomic modulation associated with hemodynamic changes. Objective: Evaluate the autonomic behavior and hemodynamic changes during the execution of the NIV with two models of mechanical ventilators in subjects after CABG. Material and Methods: This is quantitative randomized, prospective, crossover study. The subjects were selected on first day postoperatively CABG and was performance NIV procedure using two different ventilators: conventional ventilator and specific ventilator for the use of NIV for 30 minutes, each. Block randomization was used to determine the technique that begins to approach then by crossover, perform the sequential technique. The heart rate variability (HRV), heart rate, respiratory rate, oxygen peripheral saturation and arterial pressure were evaluated before procedure, in the instants 5, 10, 15, 20, 25, 30 minutes during NIV each and 15 minutes after the end of the NIV application. HRV was evaluated using the time and frequency domain.

Inclusion criteria

• Age over 18 years .Who were breathing spontaneously with peripheral oxygen saturation (SpO2) ≥ 90% and supplemental oxygen ≤ 3 l / min.
• Indication for use of NIV

Exclusion criteria

• Hemodynamic instability with hypertensive response being considered systolic blood pressure (SBP) greater than 180 mmHg and diastolic blood pressure (DBP) greater than 110 mmHg, or difference in SBP and DBP less than 20 mmHg or framework shock considering SBP <90 mmHg and / or DBP <50 mmHg, since the normal SBP were between 90-130 mmHg and DBP 60-90 mmHg
• Presence of active cardiac pacemaker
• Invasive mechanical ventilation more than 24 hours
• Use of intra aortic balloon
• Postoperatively Myocardial infarction after surgery
• Ineffective cough with bronchial hypersecretion
• Inability to adequately swallowing and/or protect the airway
• Abdominal distension
• Nausea
• Vomiting