editorial: variable ventilation stochastic or physiologic

Variability of tidal volume and respiratory rate in normally breathing man has long been demonstrated [1]. however because of lack of knowledge and technology primary ventilators could only deliver a fixed tidal volume in a fixed rate the so called volume controlled ventilation (vcv). vcv was volume preset time triggered and cycled and there was no synchronization with patient’s breaths. at that time ventiltory management was associated with serious lung damage caused by ventilator [2-3]. today that is referred as ventilator induced lung injury. frequent complications of ventilatory support forced physicians and engineers to develop newer modes of mechanical ventilation. advances in control mechanisms, servo valves, flow and pressure sensors led to introduction of synchronized modes of ventilation like synchronized intermittent mandatory ventilation (simv) and pressure support ventilation (psv).