A Concept on Dual Control of Mechanical Ventilation Based on the Extension Strategy

Though volume control and pressure control modes are both commonly used in mechanical ventilation, they have their shortcomings that the former may generate high peak pressures and the latter may be prone to unstable gas exchange. Therefore, a dual control mode, which attempts to deliver a constant tidal volume while limiting peak pressure or attempts to limit peak pressure but assures tidal volume delivery, is proposed. However, the dual control requires to control two variables which are nonlinear and uncertain, and if a dynamic time-variant situation is faced, traditional control strategies may not be adequate. We suggest to apply the extension control strategy because of its ability to solve incompatible problems. A fuzzy control strategy is employed when the variables change slowly with time. An extension control strategy will take over the control when the variables change fast and suddenly with time. Analysis demonstrates that a fuzzy-extension controller has the potential to improve on conventional control methods in mechanical ventilation.