High frequency oscillation ventilation

Background

• High Frequency Oscillation Ventilation (HFOV) is an alternative method for mechanical ventilation in difficult to oxygenate in critically ill ARDS patients.
• Studied in patients with PaO2/FiO2 < 200
• Goal is to maintain alveolar recruitment for adequate gas exchange and decrease lung injury/atelectrauma
  • Low tidal volumes based around mean airway pressures to keep alveoli open
  • Delivered at high frequency
• See Oscillate trial

Procedure

Ventilator protocol from the Oscillate trial

• Set FiO2 at 100%
• Recruitment maneuver of 40 cmH2O PEEP for 40 seconds
• I:E time of 1:2
• Initiate high frequency ventilation -> 3-15Hz
• VT minimized to keep pH >7.25
  • Goal of 1-4 ml/Kg
• Maitain mean airway pressure of 30 cmH2O with pressure adjusted to maintain a PaO2 of 55-80 mmHg
• Reversion to standard ventilation of mean airway pressure was ≤24 cmH2O for 12 hours or anytime when ≤20 cmH2O
• Re-initiation of HFOV if FIO2 >0.4 or PEEP >14 cmH2O for >1 hour in the subsequent 48 hours

Targets

• pH>7.25
• SpO2 >88% or PaO2 >55mmHg

Oxygenationaltered by:

• FiO2
• Mean airway pressures

Ventilation altered by:

• Frequency
• Inspiratory time
• Amplitude of oscillations

Pros and Cons

• Pros
  • Limits VILI
  • May improve oxygenation when ECMO not available

• Cons
  • No difference or likely to cause harm in adult ARDS patients
  • requires heavy sedation