Session SA2.5

The Synchrony between Baroreflex Sequences and Cardio-Respiratory Activity

F Vallais*, D Lucini, M Pagani, G Baselli

Politecnico di Milano
Milano, Italy

The development of multivariate model or modeling approach based on a-priori knowledge, provide quantifiable indexes to estimate the cardiorespiratory interactions; however the relevant transients are not exhaustively described by linear parameters. Consequently, a local pattern analysis in the time-domain is fostered in order to extract further information and the possible relationships and synchronism with baroreflex sequences.This preliminary study focused on the observation of respiratory and diastolic arterial pressure (dap) signal during the appearance of linear relationship between systolic arterial pressure (sap) and rr intervals (rri) considered as an up and down baroreflex. Two groups of patient were studied (a young (n=7) and a middle-aged (n=8) group) during an incremental workload bicycle-ergometer test, including successively a phase of rest (Rest), three epoch of exercise respectively at 10% (Exe1), 20% (Exe2), 30% of the nominal maximal effort, and finally a phase of recovery (Rec). Blood pressure, EKG and respiratory signals were continuously recorded. The number of up and down sequences did not differ significantly in both group. The BRG obtained from the up baroreflex sequences were not significantly different from the BRG of the down baroreflex sequences. The number of sequence decreased dramatically with the intensity of exercise, and with age. Phase-locked between the baroreflex sequences and both the respiratory and the dap signal were observed during each epoch, and in both group. Increasing sequences were present in the expiratory phase with a local minima in the dap signal, whereas decreasing sequences occurred in the inspiratory phase with a local maxima in the dap signal. The behavior of the BRG during this protocol was largely discussed in previous works. The relationship between the respiration and heart rate (respiratory sinus arrhythmia (RSA)) was clearly evidenced with all baroreflex sequences. The phase relationship noticed between the baroreflex sequence, the respiratory and also dap signal might suggest a relationship between the arterial baroreflex and the Bainbridge reflex. These observations might help in the understanding the physiology of cardio-respiratory interactions and possible confounding effects to be accounted for in clinical applications.

(Abstract Control Number: 188)