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HFOV

Theory

  • Utilizes supraphysiologic ventilatory frequencies (>60 cycles/min) and low tidal volumes (generally less than dead space)
  • Rather than bulk axial flow, gas flow is theorized to occur due to axial dispersion, collateral flow through pores of Kohn, Pendelluft phenomenon, Taylor dispersion, asymmetric gas profiles, and gas mixing due to the pressure-diameter relationship of the bronchi (if you don't understand what those are, I would venture to say neither do 99% of intensivists)
  • Delivers a constant mean airway pressure (thus promoting oxygenation) without the high peak pressures of conventional mechanical ventilation

Figure 1: HFOV Machine

General Guidelines




Evidence

  • HFOV: Early work in pediatrics demonstrated improved outcomes with HFOV in ARDS vs. conventional ventilation. Further trials, including MOATOSCILLATE, and OSCAR, all in adult patients, have failed to show any significant difference in outcomes between HFOV and conventional ventilation. In fact, OSCILLATE was stopped early after it showed increased mortality (47 vs 35%, p=0.005) in the HFOV group vs. the control group at interim analysis. Gupta et al, in a retrospective (propensity matched) analysis, showed worse outcomes for pediatric patients who received HFOV vs. CMV. Similarly, Bateman et al reported in AJRCCM increased duration of ventilation with HFOV compared to CMV using propensity analysis.

References

1) J.H. Arnold, J.H. Hanson, L.O. Togo-Figuero:Prospective, randomized comparison of high-frequency oscillatory ventilation and conventional mechanical ventilation in pediatric respiratory failure. Crit Care Med.22:1530-1539 19947924362


2) Ferguson ND, Cook DJ, Guyatt GH, Mehta S, Hand L, Austin P, Zhou Q, Matte A,Walter SD, Lamontagne F, Granton JT, Arabi YM, Arroliga AC, Stewart TE, SlutskyAS, Meade MO; OSCILLATE Trial Investigators; Canadian Critical Care Trials Group.High-frequency oscillation in early acute respiratory distress syndrome. N Engl JMed. 2013 Feb 28;368(9):795-805. doi: 10.1056/NEJMoa1215554. Epub 2013 Jan 22.PubMed PMID: 23339639.


3) Young D, Lamb SE, Shah S, MacKenzie I, Tunnicliffe W, Lall R, Rowan K, Cuthbertson BH; OSCAR Study Group. High-frequency oscillation for acuterespiratory distress syndrome. N Engl J Med. 2013 Feb 28;368(9):806-13. doi:10.1056/NEJMoa1215716. Epub 2013 Jan 22. PubMed PMID: 23339638.