A system for circuit compliance compensated volume assurance pressure control in a patient respiratory ventilation circuit, having a patient circuit volume estimator for estimating a patient circuit compliance, a patient circuit volume estimator to estimate a circuit volume VOLCKT—EST based on the patient circuit compliance, a patient volume observer, for estimating a patient volume VOLTID—EST based on a measure delivered net volume VOLNET and the patient circuit compliance, a volume assurance controller for generating a circuit compliance volume compensation factor VOLTID—CTL based on a preset assured volume VOLASS—SET and the estimated patient volume VOLTID—EST, and a decelerating inspiratory flow controller, operative to generate a decelerating inspiratory peak flow based on a preset inspiratory time TINSP and the volume compensation factor VOLTID—CTL.