New insights on the origin of the VLF cardiorespiratory rhythm in chronic heart failure patients

In this study the authors investigated in a group of 14 chronic heart failure (CHF) patients showing a periodic breathing (PB) pattern: 1) the phase relationship between ventilation and arterial O/sub 2/ saturation to verify the respiratory control instability hypothesis of PB; 2) the relationship between these signals and heart period (HP) variability. A clear very low frequency (VLF) oscillation around 0.02 Hz, associated with PB, was observed in the instantaneous lung volume (ILV), instantaneous minute ventilation (IMV), O/sub 2/ saturation at the ear (SpO/sub 2/) and HP signals. The coherence between signals was on average >=0.8, thus confirming that during PB a more general cardiorespiratory rhythm takes place. The median phase lag between IMV and SpO/sub 2/ was -206/spl deg/ (IMV leads); between ILV and HP was -202/spl deg/ (ILV leads). SpO/sub 2/ and HP were almost synchronous. The authors´ findings are consistent with and clearly support the instability hypothesis for PB. As concerns the link between respiratory and HP oscillations the authors´ results point out that, besides central coupling and lung stretch receptors feedback, an important role in the linkage between respiratory and cardiovascular regulation might be played by arterial chemoreceptors.