Bringing back the old: time to reevaluate the high-frequency ventilation strategy

Objective: To examine the role of frequency in high-frequency ventilation (HFV) on carbon-dioxide (CO 2 ) elimination and lung injury, independent of its effect on tidal volume. Study Design: An anatomically representative lung model was attached to a mechanical ventilator capable of providing HFV with a constant volume. CO 2 was infused directly into the lung, and a commercially available end-tidal CO 2 detector was used to determine CO 2 elimination. CO 2 elimination and amplitude of pressure transmissions were evaluated using frequencies ranging from 5 to 15 Hz. The pressure–volume index (PVI) was described as the product of the volume and pressures delivered to the lung, a surrogate for lung injury. Result: The use of increasing frequencies directly correlated with improved CO 2 clearance when keeping the tidal volume fixed, expressed as percent CO 2 remaining in the lung at 25 s (66.5 (±1.1)%, 50.5 (±0.1)% and 37.8 (±0.3)% at 5, 10 and 15 Hz, respectively, P