July - September 2006: 
Volume 19, Issue 3

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High frequency oscillatory ventilation
High frequency oscillatory ventilation is an alternative mode of mechanical ventilation featuring a combination of high respiratory rate and low tidal volume. Compared to conventional mechanical ventilation, it presents essential differences in principles of operation and mechanisms ensuring adequate blood gas exchange. The applied mean airway pressure is constant and produced by adjustable collateral airflow. Ventilation is achieved through an electromechanical oscillating piston, creating a pressure difference (ΔP) superimposed to the mean airway pressure. Thus, there is a constant cyclic volume supply; tidal volume is proportional to the pressure difference (ΔP). HFOV was initially applied only in neonates with acute respiratory distress syndrome. In the last decade, its use has expanded to adults with ARDS. Considering to-date available evidence, the use of HFOV in adults with ARDS has many advantages over conventional mechanical ventilation. Nevertheless, further comparative controlled randomized studies are necessary.