High frequency oscillatory ventilation (HFOV) as therapy for acute lung injury and ARDS

Mechanical ventilation is the mainstay of therapy for acute lung injury, a disease with remainingly high morbidity and mortality. As a result of an improved understanding that mechanical ventilation itself can contribute to and aggravate the disease process, The term ventilator-associated lung injury (VALI) has been introduced. Main risk factor for VALI are (1) alveolar overdistention caused by excessivly high tidal volumes and/or inspiratory pressures (volu-/barotrauma), as well as (2) cyclic alveolar collapse promoted by insufficient endexpiratory pressure. So called "lung-protective ventilatory strategies" aim at minimizing these risk factors by the use of small tidal volumes and high PEEP levels. High frequency oscillatory ventilation (HFOV) can be regarded as an ultimate form of this approach, combining minimal pressure changes with a high continuous distending pressure (CDP). That CPD is generated using high fresh gas flows ("Super-CPAP"), while a piston pump incorporated into the system creates an oscillatory flow at frequencies ranging from 3-7 Hz. An initial lung volume recruitment manoeuvre is mandatory for the optimal use of HFOV. Whereas for many years HFOV is a well established therapy for the infant respiratory distress syndrome, experience in adults is still rare. First results, however, look promising, and HFOV might as well turn out as a valuable treatment modality for ARDS.