Interferences between baroreflex and respiration. Evaluation by symbolic analysis and conditional entropy

BACKGROUND: The baroreflex is one of the most important short-term cardiovascular autonomic control mechanisms. Its interactions with other reflexes, mainly cardiopulmonary reflexes, are of paramount importance in controlling heart rate. OBJECTIVES: This study assesses the coupling between baroreflex and respiration during a progressive bicycle mild dynamical exercise. METHODS: The coupling was assessed by symbolic analysis and conditional entropy. RESULTS: Findings suggested the close relationship between the baroreflex sequences and the phase of respiratory signal and, thus, the interference between baroreflex and cardiopulmonary reflexes. CONCLUSIONS: Indexes describing baroreflex based on spontaneous variability are strongly affected by cardiopulmonary influence