Definition

• High Frequency Oscillatory Ventilation (HFOV) is a method of mechanical ventilation that uses a constant distending pressure (mean airway pressure [MAP]) with pressure variations oscillating around the MAP at very high rates (up to 900 cycles per minute).
• Tidal volumes are often less than the dead space so HFOV relies on alternative mechanisms of gas exchange.¹
   

Indications for Use

At present HFOV is only indicated as a rescue therapy:

• Failure of conventional ventilation in the term infant (persistent pulmonary hypertension or meconium aspiration.
• Severe respiratory failure unresponsive to conventional ventilation or to reduce barotrauma when conventional ventilator settings are high.
• Air leak syndromes (pneumothorax, pulmonary interstitial emphysema)
  HFOV should be used with caution as it is not yet proven to be of benefit in the elective or rescue treatment of preterm or term infants with respiratory dysfunction.^{2, 3, 4}

^{Potential benefits}

^{Improves and maintains oxygenation}

• ^{A higher mean airway pressure (MAP) can be achieved without subjecting the lungs to very high peak pressures}
• ^{Oxygenation is governed by MAP and FiO2 so maintaining a high MAP improves oxygenation}
   
• ^{The Optimal Lung Volume Strategy recruits alveoli and lung segments and once an optimal lung volume is achieved recruitment, lung volume and oxygenation can be maintained with a lower MAP. See hysteresis curve below.}

^{Improved CO2 Elimination}

• ^{In conventional mechanical ventilation the expiratory phase is passive whereas in HFOV both inspiration and expiration are active and so greater CO2 elimination can be achieved.}

^{Separation of Oxygenation and Ventilation}

• ^{In HFOV ventilation (CO2 elimination) and oxygenation can be managed independently}
• ^{In conventional ventilation oxygenation and ventilation are closely linked and ventilator adjustments to either will affect the other. In HFOV they can be treated separately and optimised independently4}

^{May create less lung injury5, 6}

• ^{Optimal Lung Volume Strategy may minimise injury through atelectotrauma}
• ^{Small tidal volume ventilation may reduce volutrauma}
• ^{Not relying on high peak pressures to achieve an adequate MAP may reduce barotrauma}
• ^{Air-trapping may also be reduced as both the inspiratory and expiratory phases are active.}
   

Parameters

Management

Oxygenation and ventilation are best considered separately as they can be altered independently.

References