A ventilator and method of ventilator control. The ventilator includes a pneumatic system for providing and receiving breathing gas, and a controller operatively coupled with the pneumatic system. The controller employs closed-loop control to provide positive breathing assistance to a patient. Supplemental feed-forward compensatory assistance is also provided, in addition to and independently of that commanded by the closed-loop control. The supplemental assistance may be determined, set or selected based on a ventilator parameter and/or an operator parameter, and/or as an automatic ongoing compensatory mechanism responding to varying patient respiratory demand.