Since the introduction of mechanical ventilation, modes of mechanical ventilation have evolved from volume or pressure-targeted, time cycled modes to patient cycled modes. There has been a trend over the years toward the use of ventilatory modes in which some degree of spontaneous respiratory activity is preserved, known as partial ventilator assist. Conventional ventilator modes use drop changes in pressure or flow to trigger or terminate a supporting breath. Patient triggered modes have a number of distinct advantages over control modes. These modes have been shown to reduce the adverse effects of prolong sedation, ventilation-perfusion mismatch, hemodynamic instability, neuropathy associated with use of neuromuscular blocking agent and ventilator induced diaphragmatic dysfunction, while also improving gas exchange, but even in the most common partial ventilatory assist mode (pressure support) asynchrony could be seen.