• Rescue following failure of conventional ventilation (e.g. PPHN, MAS)
• To reduce barotrauma when conventional ventilator settings are high 
• Airleak (pneumothorax, PIE)

Oxygenation and CO₂ elimination are independent

Preparation for HFOV

• If significant leakage around ETT, insert a larger one
• Optimise blood pressure and perfusion, complete any necessary volume replacement and start inotropes, if necessary, before starting HFOV
• Invasive blood pressure monitoring if possible
• Correct metabolic acidosis
• Ensure adequate sedation 
• Muscle relaxants not necessary unless already in use

Initial settings on HFOV

MAP

• Optimal (high) volume strategy preferred but consider low volume strategy when air leaks present

Amplitude (delta P on SLE ventilator)

• Gradually increase amplitude until chest seen to wobble well
• Obtain early blood gas (within 20 min) and adjust settings as appropriate
• Change frequency only after discussion with consultant

Making adjustments once HFOV established

* both over and under-inflation can result in hypoxia. If in doubt, perform chest X-ray

• Amplitude maximal when chest ‘wobbling’, minimal when movement imperceptible
• Frequent blood gas monitoring (every 30–60 min) in early stages of treatment as PaO₂ and PaCO₂ can change rapidly 
• If available, transcutaneous TcPCO₂
• CO₂ diffusion coefficient (DCO₂)
  
  • indicator of CO₂ elimination which correlates well with PaCO₂ for an individual baby 
  • calculated as frequency x (tidal volume)²

Chest X-ray

• Within 1 hr to determine baseline lung volume on HFOV (aim for 8 ribs at midclavicular line)
  
  • if condition changes acutely and/or daily to assess expansion/ETT position, repeat chest X-ray

Chest wall movement

• Suction indicated for diminished chest wall movement indicating airway or ETT obstruction 
• Always use an in-line suction device to maintain PEEP
  
  • increase FiO₂ following suctioning procedure
  • MAP can be temporarily increased by 2–3 cm H₂O until oxygenation improves

Falling DCO₂

• Suggests rising PaCO₂ 

Low PaO₂

• Suboptimal lung recruitment
  
  • increase MAP 
  • consider chest X-ray
• Over-inflated lung
  
  • reduce MAP: does oxygenation improve? Check blood pressure
  • consider chest X-ray
• ETT patency
  
  • check head position and exclude kinks in tube
  • check for chest movement and breath sounds
  • check there is no water in ETT/T-piece
• Air leak/pneumothorax
  
  • transillumination (see Transillumination of the chest guideline)
  • urgent chest X-ray

High PaCO₂

• ETT patency and air leaks (as above)
• Increase amplitude, does chest wall movement increase?
• Increased airway resistance (MAS or BPD) or non-homogenous lung disease, is HFOV appropriate?

Persisting acidosis/hypotension

• Over-distension 
  
  • reduce MAP: does oxygenation improve?
• Exclude air leaks; consider chest X-ray

Spontaneous breathing

• Usually not a problem but can indicate suboptimal ventilation (e.g. kinking of ETT, build-up of secretions) or metabolic acidosis

• Reduce FiO₂ to <0.4 before weaning MAP (except when over-inflation evident)

• When chest X-ray shows evidence of over-inflation (>9 ribs), reduce MAP

• Reduce MAP in 1–2 cm decrements to 8–9 cm 1–2 hrly or as tolerated

• If oxygenation lost during weaning, increase MAP by 3–4 cm and begin weaning again more gradually. When MAP is very low, amplitude may need increasing 

• In air leak syndromes (using low volume strategy), reducing MAP takes priority over weaning the FiO₂

• Wean the amplitude in small increments (5–15%) depending upon PCO₂

• When MAP <8 cm H₂O, amplitude 20–25 and blood gases satisfactory, consider switching to conventional ventilation or extubation to CPAP