Cardiorespiratory interactions during slow (

In this work we used a multi-parametric approach and spectral analysis techniques to investigate cardio-respiratory interactions during spontaneous Periodic Breathing (PB) in 30 chronic heart failure patients and volitional PB in 16 normal subjects. We acquired supine resting recordings of instantaneous lung volume (IL V), heart rate, O₂ saturation at the ear and systolic and diastolic arterial pressure. An instantaneous tidal volume signal was derived from the ILV signal. In both groups we found strong evidence of a generalized cardio-respiratory rhythm at ≈ 0.02 Hz, the frequency of PB, which accounted for most of the variability of all cardiovascular signals. Phase and timing relationships between signals at the frequency of PB were markedly different in the two groups providing important insights into the complex links between respiration and circulation at very low (