Synchronization and modulation in the human cardiorespiratory system

We analyse phase and frequency synchronization in the human cardio-respirat ory system. The method for analysis of noisy nonstationary bivariate data i s applied to simultaneously measured cardiac and respiratory activity. Shor t epochs of phase and/or frequency locking between respiratory and cardiac rhythms are detected in healthy relaxed subjects (non-athletes). We reveal that the strength of phase synchronization is inversely related to the exte nt of respiratory modulation of the heart rate. (C) 2000 Published by Elsev ier Science B.V. All rights reserved.