Synchronization-Dissipation in the Cardiorespiratory System

Dissipative coupling is known to induce synchronization. Conversely it may be hypothesized that oscillators driven to synchronize may reduce power dissipation in their coupling. The latter scenario is realized in the human cardiorespiratory system where cardiac and respiratory rhythms are controlled by the central nervous system while interacting viscoelastically through the pulmonary vasculature. Here we examine the functional significance of this coupling which is observed in respiratory sinus arrhythmia (RSA). By modelling electrical and viscoelastic interactions within the cardiorespiratory system, we identify the conditions leading to synchronization. We demonstrate that, when present, synchronization reduces cardiac power losses by $10\%$ in humans and up to 55% in other species. The predicted gain in cardiac output is compared to the gain observed in vivo by pacing the heart with a device restoring RSA. It is therefore surmised that RSA may improve cardiac pumping efficiency by reducing dynamic stress and power dissipation in the pulmonary vasculature.