Is high-frequency ventilation more beneficial than low-tidal volume conventional ventilation?

The ventilator goals of the ICU clinician faced with caring for a critically ill child who has ALI/ARDS remain relatively simple: provide adequate ventilation and oxygenation without overdistending alveoli or furthering lung injury. How one obtains these goals is much less simple. The current use of CV calls for the use of relatively low V(T)s and limiting peak inspiratory pressure and plateau pressure while accepting a certain degree of respiratory acidosis. The ICU team can also often achieve these same goals with HFOV. How, then, does one use evidenced-based medicine to pick the best mode of mechanical ventilation for a particular patient? The answer is controversial, to say the least. Does one start with a gentle, open-lung mode of CV then switch to HFOV if the child deteriorates? Or does one use HFOV from the very early stages of ALI? Animal data appear to point to advantages of HFOV when used early in the course of ALI. Most of these studies report a beneficial effect of HFOV when applied on expanded lungs in the early stages of the disease process. These beneficial effects encompass improved gas exchange, oxygenation, lung tissue morphology and pulmonary mechanics. The studies by Arnold and colleagues in the pediatric population also help to answer our questions. In their work, the early initiation of HFOV was associated with improved gas exchange and a trend toward a lower mortality. In adults, Derdak and colleagues demonstrated the superiority of HFOV in terms of gas exchange and oxygenation; however, no statistical significant difference was found for mortality. So, where is the clinician left after a review of these data? It would appear that (1) low-V(T) CV remains a cornerstone of therapy for the pediatric patient who has ALI/ARDS; (2) HFOV is a safe and well-tolerated mode of mechanical ventilation; (3) early use of HFOV (as opposed to the rescue use of this mode) may be of benefit based on animal and human data; and (4) like so many areas of pediatric critical care, clinicians must await new data and trials that will help them continue to improve the care they provide.