The invention comprises a ventilation apparatus with a ventilator controlled by a computing system employing a method in which:- a duration ratio factor (D1, D2) is set in the computing system；- a minute volume (Mv) is determined；- a functional dead space volume (Vd) is determined；- a time constant (R∗C) is determined；- a respiration frequency (f) is computed, based on a previously defined lung model (LM), depending on said determined minute volume (Mv), said determined functional dead space (Vd), said determined time constant (R∗C) and said set duration ratio factor (D1,D2), where said computed respiration frequency (f) is optimized on at least one minimum of a delivered parameter (G_tot)；- the computed respiration frequency (f) is further optimized based on a percentage of spontaneous breaths of the patient (%Support) using said computing system；- an inspiratory time (Ti) and an expiratory time (Te) are determined；- a tidal volume (Vt) and said determined minute volume (Mv) is computed； and- a delivered respiratory parameter is closed loop controlled.
