A Novel Quantification Method of Cardiopulmonary Coupling Based on Cross-Frequency Coupling

Dynamic heart rate is a reflection of the functionality of the autonomic nervous system (ANS) and is closely related to vital signs. Combining it with respiratory signals for the analysis of cardiopulmonary coupling (CPC) can provide a more precise depiction of physiological states. However, traditional CPC algorithms emphasize the correlation within the identical frequency band of respiration and heart rate variability (HRV), which may not effectively reveal the intrinsic relationship between them. A novel method of quantifying CPC bidirectionally and across multiple frequency bands is proposed in this study by employing the Hilbert-Huang transform (HHT) and phase-amplitude coupling (PAC) techniques, applying it to analyze respiratory signals and Electrocardiograms (ECG) from groups of different ages to assess the performance of their autonomic nervous system. We observed a superiority of CPC value in healthy infants, indicating a decline in the function of ANS as one ages.