The Optimization of Breathing Signals and Ventilatory Control with Nonlinear Respiratory Mechanics under Hypercapnia and Eucapnia

In this study, the optimal human respiratory control model proposed earlier was modified to include the nonlinear respiratory mechanics by replacing the resistance with a lumped viscous resistance of the flow through total respiratory system, and a resistance of flow which is proportional to the power of flow rate. To evaluate the effect of the nonlinear respiratory mechanics in the optimal respiratory control, the model was simulated under hypercapnia and eucapnia with CO2 inhalation and exercise input. The optimized breathing signals, including neuromuscular drive, airflow, and lung volume profiles, were demonstrated and the ventilatory responses with the optimized breathing patterns were examined. In comparison with the simulation result of linear respiratory mechanics, the nonlinear model was found to optimize the neuromuscular drive and airflow with ramplike and triangular waveform, respectively.