Exploring Cardiopulmonary Interactions: A Novel Phase-Amplitude Coupling Method

The cardiopulmonary coupling (CPC) involves complex interactions between the autonomic nervous system and respiratory control, affecting heart and respiratory rates. This study introduces a novel phase-amplitude coupling (PAC) method using the direct modulation index (dMI) for analyzing the bidirectional interactions between the heart rate variability and respiration of participants listening to classical music. The Empirical Mode Decomposition (EMD) was employed to decompose the RR intervals and the respiration signals, and the dMI-based PAC is then applied to the decomposed IMFs. The results demonstrate a notable enhancement in RESP-RR interactions during music exposure, indicating a stronger influence of respiratory patterns on heart rate during this relaxed state. Additionally, a pronounced cardiopulmonary coupling was observed in the low-frequency bands under conditions of listening to music. These findings highlight the complex, bidirectional interactions between breathing and heart rate. The dMI method emerges as a robust, noise-resistant analytical tool with promising implications for cardiovascular research and potential clinical applications.