A method of augmented spontaneous ventilation that is flow, pressure or time cycled pressure limited and patient triggered. A form of spontaneous ventilation where flow is delivered to the airway up to a clinician pre- set pressure limit and continued until the machine senses either a drop in inspiratory flow beyond a preset threshold, excessive inspiratory pressure or prolonged inspiratory time. In PSV the patient determines the inspiratory rate, time, volume and flow. PSV can be employed as a mode of mechanical ventilation or in the SIMV mode.