High-Frequency Oscillatory Ventilation in Adults
High frequency oscillatory ventilation (HFOV) is an alternative method of ventilation that theoretically achieves the goals of lung protective ventilation. During HFOV, gas exchange occurs through the application of a constant mean airway pressure (mPaw) that is usually higher than that applied during conventional ventilation (CV). Theoretically, HFOV may lead to improved alveolar recruitment while avoiding both the cyclic closing and opening of alveolar units and the high peak airway pressures that occur with CV. The potential adverse effects of HFOV include cardiovascular compromise or barotrauma from the higher airway pressures.
The theoretical benefits of HFOV over CV are supported by the results of animal studies. In primates and surfactant-deficient rabbits, the use of HFOV leads to improved gas exchange, more uniform lung inflation, and reduced histopathologic evidence of ventilator-induced lung injury. The potential importance of reduced alveolar cycling and lung distention is supported by other animal studies, in which the use of HFOV was associated with reduced levels of inflammatory mediators when compared to CV, despite the use of similar mPaw levels. In the neonatal and pediatric population, HFOV, utilizing an aggressive volume recruitment strategy, results in improvements in oxygenation compared with CVA Despite the use of higher mPaw levels in these trials, HFOV appears to be associated with a lower incidence of ventilator-associated lung injury, as indicated by a lower incidence of barotrauma and a decreased requirement for supplemental oxygen at 30 days. Importantly, this physiologic benefit may lead to improved patient outcomes, as demonstrated by a trial showing a reduction in ventilator days and mortality with the use of HFOV in very low-birth-weight infants.