title: Bringing back the old: time to reevaluate the high-frequency ventilation strategy.
abstract: OBJECTIVE
  To examine the role of frequency in high-frequency ventilation (HFV) on carbon-dioxide (CO2) elimination and lung injury, independent of its effect on tidal volume.
  
  
  METHODS
  An anatomically representative lung model was attached to a mechanical ventilator capable of providing HFV with a constant volume. CO2 was infused directly into the lung, and a commercially available end-tidal CO2 detector was used to determine CO2 elimination. CO2 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.
  
  
  RESULTS
  The use of increasing frequencies directly correlated with improved CO2 clearance when keeping the tidal volume fixed, expressed as percent CO2 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<0.05). With a fixed tidal volume, there was a decrease in pressure amplitudes transmitted to the lung with a decline in the PVI (53.9 (±2.7) mmHg ml(-1), 41.1 (±0.9) mmHg ml(-1) and 23.4 (±3.6) mmHg ml(-1), at 5, 10 and 15 Hz, respectively, P<0.05).
  
  
  CONCLUSIONS
  Frequency has a direct relationship with CO2 elimination when tidal volume is fixed. Using low delivered tidal volumes and high frequencies may allow for improved ventilation efficacy, while minimizing lung injury.
authors.affiliation: Division of Neonatology, Department of Pediatrics, Hospital for Sick Children, University of Toronto, Toronto, ON, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Mukerji
authors.affiliation: Division of Neonatology, Department of Pediatrics, Hospital for Sick Children, University of Toronto, Toronto, ON, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Belik
authors.affiliation: Division of Neonatology, Instituto de Investigación Sanitaria Gregorio Marañón, Hospital General Universitario "Gregorio Marañón", University Complutense of Madrid, Madrid, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Sanchez-Luna
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D006612:High-Frequency Ventilation / Q000009:adverse effects / Q000379:methods*; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D055370:Lung Injury / Q000517:prevention & control*; D008953:Models, Anatomic; D011175:Positive-Pressure Respiration; D011312:Pressure; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial / Q000379:methods; D013990:Tidal Volume
chemical_list: D002245:Carbon Dioxide