A novel adaptive control system for noisy pressure-controlled ventilation: a numerical simulation and bench test study

Purpose There is growing interest in the use of both variable and pressure-controlled ventilation (PCV). The combination of these approaches as “noisy PCV” requires adaptation of the mechanical ventilator to the respiratory system mechanics. Thus, we developed and evaluated a new control system based on the least-mean-squares adaptive approach, which automatically and continuously adjusts the driving pressure during PCV to achieve the desired variability pattern of tidal volume ( V T ). Methods The controller was tested during numerical simulations and with a physical model reproducing the mechanical properties of the respiratory system. We applied step changes in respiratory system mechanics and mechanical ventilation settings. The time needed to converge to the desired V T variability pattern after each change ( t c ) and the difference in minute ventilation between the measured and target pattern of V T (ΔMV) were determined. Results During numerical simulations, the control system for noisy PCV achieved the desired variable V T pattern in less than 30 respiratory cycles, with limited influence of the dynamic elastance ( E *) on t c , except when E * was underestimated by >25%. We also found that, during tests in the physical model, the control system converged in <60 respiratory cycles and was not influenced by airways resistance. In all measurements, the absolute value of ΔMV was <25%. Conclusion The new control system for noisy PCV can prove useful for controlled mechanical ventilation in the intensive care unit.