Cardiovascular diseases, especially acute myocardial infarction (AMI), represent the major cause of mortality and morbidity in the world. The myocardial ischemia is often the precipitating cause of pulmonary edema and noninvasive ventilation (NIV) with positive pressure has been used as a therapeutic modality.

Objective: to evaluate the effects of NIV on heart rate variability (HRV) and on ventilatory and hemodynamic variables in patients with myocardial infarction.

Materials and methods: ten patients with acute myocardial infarction, with Killip I classification, will use continuous positive airway pressure (CPAP) and Bilevel ventilation during 30 minutes, according randomization. Then ventilatory and hemodynamic variables will be registered and electrocardiogram signals will be recorded for posterior analyses of HRV. Data will be collected before, during and after positive pressure ventilation.

Statistical Analysis: Data will be compared using One Way Anova Repeated Measures, followed by Tukey test.

The patients will be recruited in Bonsucesso Federal Hospital with diagnosis of myocardial infarction, confirmed by electrocardiogram and cardiac enzymes, between 24 and 72 hours after the event.

Participation in the study protocol will be done according to eligibility criteria:

The study will be a randomized and crossover clinical trial for evaluation and comparison of heart rate variability and ventilatory and hemodynamics variables during ventilation with CPAP and Bilevel.

CPAP will be applied via a facial mask, with expiratory positive airway pressure of 10 cmH2O. Bilevel will be applied via facial mask, with inspiratory positive pressure (IPAP) of 20 cmH2O and expiratory positive airway pressure (EPAP) of 10 cmH2O.

Inclusion Criteria:

• acute myocardial infarction with Killip I classification, hemodynamic stability, between 24 and 72 hours post event;
• agreement to participate in the study, according written informed consent;
• 45 to 80 years old age.

Exclusion Criteria:

• unstable angina;
• systolic blood pressure < 80 mmHg;
• patients who presented ST elevation > 2 mm or with second-degree atrioventricular block;
• presence of pacemaker.