Assisted Ventilation Control Based on Phase and Frequency Estimation of Respiratory Drift

Mechanical ventilation control has gained increasing attention in the last few decades, especially within Intensive Care Units, for the treatment of patient with respiratory issues or in the post-operative phase. In this work, we review a simple model of physiological ventilation and define a ventilation control problem for the case of assisted ventilation, where an individual exhibits an own respiratory drift which is, anyway, insufficient to guarantee safe breathing conditions. Frequency and phase of the patient's respiratory signal are assumed to be unknown by the ventilator and are estimated by means of a frequency estimator algorithm (based on a two-stage autocorrelation approach) and with a Phase Locked Loop (PLL), respectively. The control algorithm, at each iteration, varies the amplitude of the pressure wave at the mouth, while the waveform phase and frequency are chosen based on the current estimates of the corresponding quantities in the spontaneous breathing. In some preliminary numerical simulations, a reference tidal volume is correctly tracked, showing the potential of the approach taken.