Analysis of variability of cardiac frequency during constant load exercise with application of binível in COPD-HF patients

Abstract

Chronic Obstructive Pulmonary Disease (COPD) and Heart Failure (HF), besides changes in respiratory and cardiovascular functions, lead to multisystemic alterations. Among these changes, it has been described that cardiac autonomic control is impaired both in rest and physical exercise in COPD and in HF only. On the other hand, non-invasive ventilation (NIV) during exercise may be effective in reducing symptoms, ventilatory changes and has a possible modulating role in heart rate variability (HRV). However, it is not yet known if NIV can have a positive impact on HRV during the constant load exercise test (CCT) in patients with COPD + HF coexistence. Objective: To assess the effect of NIV on HRV during CCT in patients with COPD-HF. Hypothesis: We believe that NIV may improve cardiac autonomic modulation during CCT in these patients. Study design: Controlled, randomized, double blind clinical trial. Subjects: There will be 14 patients evaluated with COPD-HF, diagnosed in 2 outpatient clinics of medical specialties (Pulmonology and Cardiology) of São Carlos. Methods: Patients with COPD-HF will be randomized to determine the order of pressure (bilevel or sham) blindly by the 1: 1 method with opaque envelopes. Participants will be submitted to the following tests: (I) Cardiopulmonary exercise test (CPET), with a cycle ergometer ramp protocol; (II) 7 days after CPET, patients will be submitted to 2 constant load tests (CCT) (Binivel and Sham) up to the limit of tolerance, using 80% of the peak load of the CPET during CCT; (III) the R-R (iR-R) intervals will be continuously collected. HRV will be calculated by linear models in time and frequency domain, as well as nonlinear indices, at rest, during CCT as well as post-exercise recovery. Expected results: We hope that the NIV can modulate the HRV indexes during the ECT, contributing to a better sympatovagal balance during exercise.