The effects of time-varying breathing on human neurophysiological and cardiovascular mechanisms

We varied the timing of respiration as a means to modulate and better understand otherwise hidden human central neural and cardiovascular mechanisms. Time-frequency methods (wavelet transform, wavelet phase coherence, and directional coupling) were applied to analyze these time-varying signals. We found that respiration causally modulates both sympathetic (weakly) and vagal motoneuron (strongly) oscillations over a wide frequency range - one that extends well below the frequency of actual breaths. Breathing frequency does not affect phase coherence between diastolic pressure and muscle sympathetic oscillations, but it augments phase coherence between systolic pressure and R-R interval oscillations over a limited portion of the usual breathing frequency range.