Two large multicenter randomized controlled trials have been conducted that compared HFOV with conventional lung-protective ventilation: the OSCILLATE (Oscillation for Acute Respiratory Distress Syndrome Treated Early) ( 2) and OSCAR (Oscillation in ARDS) ( 3) trials. Arterial oxygenation during HFOV can be regulated by adjusting the F i O 2 and/or by increasing mean airway pressure. The frequency and magnitude of the oscillations can be varied to generate different tidal volume and minute ventilation frequency is typically set between 5 and 10 oscillations per second. The adult ventilator is essentially a high-flow continuous positive airway pressure system with the superimposed generation of oscillations through large membrane diaphragms, like a magnet audio loudspeaker cone. High-frequency oscillatory ventilation (HFOV) is conceptually an appealing method of mechanical ventilation for patients with ARDS, maintaining gas exchange with a small tidal volume, increased intrathoracic pressure, and reduced alveolar collapse. In patients receiving mechanical ventilation, attempts are therefore made to minimize VILI by reducing alveolar overdistension (stress and strain) using application of a sufficient level of positive end-expiratory pressure to prevent atelectrauma. VILI has been attributed primarily to excessive tidal volumes increased alveolar collapse (atelectrauma) may also contribute. It is well established that mechanical ventilation can aggravate the lesions of ARDS, in a process called ventilator-induced lung injury (VILI). It is characterized by acute onset of diffuse inflammatory lung injury, which causes increased pulmonary vascular permeability, leading to increased lung weight, loss of aerated lung tissue, decreased lung compliance, and increased physiological dead space the end result is severe hypoxemia. Acute respiratory distress syndrome (ARDS) is still associated with considerable morbidity and mortality ( 1).
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