High-Frequency Ventilation- Basics and Practical Applications

Management of HFV
6 Management of HFV
6.1 Transition from conventional ventilation
Before you begin with high-frequency ventilation remember to
read the mean airway pressure. Then switch over to oscillatory
ventilation, which requires only the push of a button in case of the
Babylog 8000.
Having reduced the IMV rate to about 3 bpm, or having switched to
CPAP, immediately readjust MAP to optimally open up the lung. The
Babylog 8000 PEEP/CPAP rotary knob controls mean airway pressure
under HFV. Three different strategies have been de scribed and
found suitable for clinical application:
1. Set MAP 2 to 5 mbar above the MAP of the preceding conventional
ventilation. Then increase MAP step by step until
oxygenation improves and the lung is optimally inflated.
2. Within the initial 3 to 5 minutes of HFV set MAP 6 to 8 mbar higher
than the MAP of the conventional ventilation. Then reduce MAP
again to a level of 0 to 2 mbar above the MAPof the conventional
ventilation. Thereafter vary MAP so as to maintain oxygenation.
3. Keep the MAP on the level of the conventional ventilation. Maintain
lung expansion through initial and intermittent sustained inflations.
(cf. chapter 5).
In our hospital we prefer the first strategy. Experienced users may also
combine them.
Keep the IMV pressure 2 to 5 mbar below the PIP of the conventional
ventilation. An oscillatory frequency of < 10 Hz is a good
value to start with. Set the amplitude as high as possible to have the
patient’s thorax visibly vibrating. Strive to obtain oscillatory volumes of
at least 2 ml/kg. After 30 to 60 minutes the inflation of the lung
should be assessed with a chest x-ray. Optimal lung inflation correlates
with obtaining an 8 – 9 posterior rib level ex pansion and decreased
lung opacification. [4, 11, 22, 23, 29, 67, 95, 97, 103, 109].
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