General principles

  1. Uses extremely low tidal volumes (1-3 cc/kg) at high respiratory rates (frequencies of 5to 15 Hz)
  2. Effectively ventilates with intrapulmonary pressures and volume changes that are less than with conventional ventilation - prevents barotrauma and volutrauma

Indications

Failure of conventional mechanical ventilation, ARDS/ALI, air leaks (pneumothorax, PIE), persistent pulmonary hypertension, pulmonary hemorrhage, congenital diaphragmatic hernia

Complications

Hypotension secondary to decreased venous return
Pneumothorax as evidenced by sudden hypotension/desaturations, decreased chest wall movement
ETT Obstruction causing or secondary to suboptimal pulmonary toilet and mucus clearance

HFOV settings

MAP (cmH2O): level of pressure held in the lung

  • Supports oxygenation
  • Initial MAP 2-5 cm higher than on CMV, range variable
  • Monitor degree of lung expansion by CXR

Frequency (Hertz): number of breaths per second

  • Infants started on 10, lowered to increase ventilation (lower Hz = increased tidal volume)

Power/Amplitude (cmH2O): Volume of gas generated by each high frequency wave

  • Inversely proportional to PaCO2
  • Initial Power 4-5, adjusted to obtain adequate chest wall vibration

Inspiratory Time (%): set at 33%, 1:2 ratio

    Management principles

    Hypercarbia

    • Suction Pt using inline suction
    • Increase POWER to increase ventilation
    • *A change of 0.3 units in power changes the CO2 by ~3 mm Hg
    • Decrease Frequency to increase tidal volume
    • Take cuff down in ETT
    • Increase Bias Flow to 30-40 L/min
    • Ensure ETT patent

    Hypoxemia

    • Increase MAP or FiO2
    • *Follow CXR closely to avoid hyperinflation!

    Never disconnect to suction unless emergent (de-recruitment occurs quickly)

    Wean slowly when ready (MAP change of 1-2 every 8-12 hours)