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 im proved understanding that mechanical ventilation itself can contribute to a nd aggravate the disease process, The term ventilator-associated lung injur y (VALI) has been introduced. Main risk factor for VALI are (1) alveolar ov erdistention caused by excessivly high tidal volumes and/or inspiratory pre ssures (volu-/barotrauma), as well as (2) cyclic alveolar collapse promoted by insufficient endexpiratory pressure. So called "lung-protective ventila tory strategies" aim at minimizing these risk factors by the use of small t idal volumes and high PEEP levels. High frequency oscillatory ventilation (HFOV) can be regarded as an ultimat e form of this approach, combining minimal pressure changes with a high con tinuous distending pressure (CDP). That CPD is generated using high fresh g as flows ("Super-CPAP"), while a piston pump incorporated into the system c reates an oscillatory flow at frequencies ranging from 3-7 Hz. An initial l ung volume recruitment manoeuvre is mandatory for the optimal use of HFOV. Whereas for many years HFOV is a well established therapy for the infant re spiratory distress syndrome, experience in adults is still rare. First resu lts, however, look promising, and HFOV might as well turn out as a valuable treatment modality for ARDS.