High frequency oscillatory ventilation.

Abstract

Forty years have elapsed since investigators first appreciated that tidal volumes measuring less than the physiologic dead space can produce reliable ventilation when delivered at high frequencies. Of all high frequency ventilation techniques, high frequency oscillatory ventilation (HFOV) is the most well studied and is the most commonly utilized in clinical practice today. In HFOV, small volume oscillatory vibrations are superimposed on continuous distending pressure in a manner that allows efficient CO2 elimination during continuous alveolar recruitment. By preserving end-expiratory lung volume, minimizing cyclic stretch, and avoiding alveolar overdistension at end-inspiration, HFOV is uniquely capable of providing the ultimate “open lung” strategy of ventilation. Over the past decade, a growing evidence base implicating phasic alveolar stretch in the pathogenesis of acute and chronic lung injury in patients with respiratory failure has driven the iterative refinement of HFOV management protocols for infants, children, and adults. The next step toward applying HFOV in a manner that takes into account the heterogeneity of parenchymal involvement in diseases such as the acute respiratory distress syndrome will require the development of non-invasive bedside technologies capable of identifying regional changes in lung volume and lung mechanics. Electrical impedance tomography (EIT) is a promising technique that could play a supporting role in the conduct of future clinical trials seeking to identify HFOV strategies that are maximally lung protective.