Features of phase synchronization of cardiovascular and respiratory oscillations in humans

Phase interactions between cardiovascular and respiratory systems were analyzed at rest in volunteers. 22 healthy normotensive non-smoking subjects aged from 21 to 45 years participated in the study. The following physiological signals were recorded simultaneously: respiratory rate, heart rate variability (HRV), forearm and foot skin blood flow, tissue blood volume from hand and foot finger pads. The degree of synchronization between phases of analyzed signals was estimated with the value of wavelet phase coherence function. It was found high phase synchronization between respiration and tissue blood volume oscillations of both fingers and low synchronization between respiration and skin blood flow oscillations of both skin sites under study. It was also obtained high phase synchronization between HRV and tissue blood volume oscillations of both fingers as well as low synchronization between HRV and skin blood flow oscillations of both skin sites at the respiration frequency (~ 0.3 Hz). There are similarities of phase interactions of both analyzed signals (blood flow and blood volume) with HRV in the low frequency range from 0.0095 to 0.1 Hz. These results were independent of extremities under study. We assume the results obtained can be used for development of new diagnostic approaches for assessment of state of peripheral vessels in pathologies.