| The dynamic interactions among the peripheral inputs that originate from the chemoreflexes, baroreflexes and pulmonary stretch receptors, together with central autonomic coupling between respiratory and cardiovascular efferents, play important roles in determining the physiological effects that accompany sleep apnea such as Obstructive Sleep Apnea. However, previous modeling studies have focused primarily on specific regions of interest. The purpose of this study is to integrate the key features of existing cardiovascular and respiratory models into a comprehensive model that is capable of simulating the dynamics of cardiorespiratory control during wakefulness and sleep. The model allows the simulation of important cardiorespiratory interactions that occur during obstructive sleep apnea, such as the differential effects of apnea and arousal on heart rate and blood pressure. For instance, the model is capable of simulating the hypoxia-induced bradycardia that is unmasked by the absence of vagal feedback from the lung stretch receptors during apnea. As well, the model incorporates a realistic simulation of the wake-sleep cycle and allows changes in sleep-wake state to interact with the respiratory and cardiovascular subsystems. The comprehensive cardiorespiratory model is implemented using SIMULINK ® (The Mathworks, Natick, MA), a graphical environment that allows the user to easily convert control block diagrams into networks of blocks of mathematical functions. The advantages of this form of implementation lie in: (1) the modularity of its various components; (2) the flexibility with which changes can be made to selected portions of the program; and (3) transportability of the model across different computer platforms and operating systems. |
