A method and device determine a level of mechanical ventilatory assist to be delivered to a patient. A patients neural respiratory drive is measured and multiplied by an existing amplification factor to obtain an existing predicted ventilatory pressure. A mechanical ventilator is controlled accordingly. An existing resulting pressure is measured. The patients neural respiratory drive is multiplied by a modified amplification factor to obtain a new predicted pressure. The existing and new predicted pressures are compared to determine an anticipated change in pressure. The mechanical ventilator is now controlled according to the new predicted pressure. A new resulting pressure is measured. The existing and new resulting pressures are compared to determine an actual change in pressure. The anticipated and actual changes in pressure are compared. The amplification factor is increased, maintained or decreased in response to the comparison between the anticipated and actual changes in pressure.
