3. Background
• High frequency oscillatory ventilation (HFOV) is a type 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). This creates small tidal
volumes, often less than the dead space.
• In conventional ventilation large pressure changes (the
difference between PEEP and PIP) create physiological tidal
volumes.
• HFOV is the only mode of ventilation where both Inspiratory
and Expiratory is ACTIVE. Meaning the ventilator pushes and
pulls air in and out of the lung due to the forward and
backward action of the piston.
4. Indications :-
1
2
3
Failure of conventional ventilation in the term infant
(Persistent Pulmonary Hypertension of the Newborn
[PPHN], Meconium Aspiration Syndrome [MAS]).
NB: The evidence for HFOV in term infants with
severe pulmonary dysfunction is not strong.
Air leak syndromes (pneumothorax, pulmonary
interstitial emphysema [PIE])
Failure of conventional ventilation in the preterm
infant (severe RDS, PIE, pulmonary hypoplasia) or to
reduce barotrauma when conventional ventilator
settings are high.
6. • Early Intervention :
A term used to describe the application of HFOV to
an infant within the first FOUR hours of life, or one
that has not been conventionally ventilated.
Proactive
7. • Proactive
Is a term applied to the Infant on Conventional
Ventilation that reaches a specific thresholds and is
then transferred to the Oscillator prior to the onset of
barotrauma or airleak.
8. • Rescue :
Is a term used to describe the Infant that has failed all
Mechanical Ventilation strategies, and gas exchange
continues to deteriorate; or develops airleak and is
then transitioned to the oscillator.
9. Indications :HFOV is not as yet proven to be of benefit in the elective or
rescue treatment of preterm infants with respiratory
dysfunction and may be associated with an increase in
intraventricular haemorrhage.8Furthermore, caution is needed
when HFOV is used as high airway pressures may result in
impaired cardiac output causing hypotension requiring
inotropic support or volume expansion. Some infants poorly
tolerate the extra handling involved in switching ventilators or
may not respond to HFOV. If there is no improvement with
HFOV, consider reverting to conventional ventilation.
10. Terminology
Frequency
•High frequency ventilation rate (Hz = cycles per
second, i.e. 10Hz = 10 cycles/sec = 600 cycles/min)
MAP
Amplitude
Oxygenation
•Mean airway pressure (cmH2O)
•delta P or power is the variation around the MAP
•Oxygenation is dependent on MAP and FiO2. MAP
provides a constant distending pressure equivalent to
CPAP. This inflates the lung to a constant and optimal
lung volume maximising the area for gas exchange
and preventing alveolar collapse in the expiratory
phase.
•In HFOV oxygenation can be separated from
ventilation as they are not dependent on each other
as is the case with conventional ventilation.
Ventilation or CO2 elimination is dependent on
amplitude and to a lesser degree frequency.
Ventilation
12. Initial settings on HFOV
Optimal lung
volume
strategy
(aim to
maximise
recruitment of
alveoli).
Low volume
strategy
(aim to
minimise lung
trauma)
•Set MAP 2-3 cmH2O above the MAP on
conventional ventilation
• MAP in 1-2 cmH2O steps until oxygenation
improves
•Set frequency to 10 Hz
Consider recruitment manoeuvres after discussion
with consultant
•Set MAP equal to the MAP on conventional
ventilation
•Set frequency to 10 Hz
•Adjust amplitude to get an adequate chest wall
vibration.
13. What after ……………… ?
• Obtain an early blood gas and adjust settings as
appropriate.
• Obtain chest radiograph to assess inflation
15. Primary control of CO2 is by the stroke volume produced by
the Power Setting
16. Making adjustments once established on HFOV
Poor
Oxygenation
Over
Oxygenation
Increase FiO2
Decrease FiO2
Increase MAP*
(1-2cmH2O)
Decrease MAP
(1-2cmH2O)
Under
Ventilation
Increase
Amplitude
Decrease
Frequency**
(1-2Hz)
if Amplitude
Maximal
Over
Ventilation
Decrease
Amplitude
Increase
Frequency**
(1-2Hz)
if Amplitude
Minimal
17. Chest Radiograph
• Initial chest radiograph at 1-2 hrs. to determine the
baseline lung volume on HFOV (aim for 8 ribs).
• A follow-up chest radiograph in 4-6 hours is recommended
to assess the expansion.
• Thereafter repeat chest radiography with acute changes in
patient condition.
18. Weaning
•Reduce FiO2 to <40% before weaning MAP (except when
over-inflation is evident).
•Reduce MAP when chest radiograph shows evidence of overinflation (>9 ribs).
•Reduce MAP in 1-2cm H2O increments to 8-10 cm H2O.
•In air leak syndromes (low volume strategy), reducing MAP
takes priority over weaning the FiO2.
•Wean the amplitude in 2-4cm H2O increments.
•Do not wean the frequency
•Discontinue weaning when MAP 8-10 cm H2O and Amplitude
20-25
•If infant is stable, oxygenating well and blood gases are
satisfactory then infant could be extubated to CPAP or
switched to conventional ventilation. Discuss with consultant.
19. Suctioning
•Suction is indicated for diminished chest wall movement (chest
wobble), elevated CO2 and/or worsening oxygenation suggesting
airway or ET tube obstruction, or if there are visible/audible
secretions in the airway.
•Avoid in the first 24 hours of HFOV, unless clinically indicated.
•In-line suctioning must be used (see Suction Protocol for full
procedure)
•Press the STOP button briefly while quickly inserting and
withdrawing suction catheter (PEEP is maintained)
20. Nursing Management – Monitoring and Assessment
and Documentation
Step
Action
V
I
B
R
T
I
O
n
Visibly assess the chest vibration and note changes. Unlike conventional mechanical
ventilation (CMV), you cannot assess a rise and fall of the chest. You need to assess the
amount of vibration being produced. Vibration mainly in the neck could indicate a
dislodged ET tube and asymmetry vibration could indicate pneumothorax. The vibration
produced depends on the amount of amplitude and lung compliance.
Use a visual assessment of the depth of bounce ranging from the umbilicus to the
clavicle.
A
B
G
An ABG needs to be done 10-15 minutes after going onto oscillation. In that first hour
another 2-3 ABG’s will probably be required as oscillation can produce significant changes
in oxygenation and ventilation (CO2). After the 1st hour ABG;s should be done after any
change in oscillation settings, or any clinical reason that deems an ABG to be done (e.g.
falling saturations, increased saturations).
Otherwise 6 hourly if stable and minimal changes occurring with the oscillator
settings.Frequent blood gas monitoring is required at first to assess effectiveness of
HFOV.
CXR
DOCUMENTATI
ON
Ensure CXR taken within ½ hour after commencement of oscillation, to assess the degree
of lung distension, to ensure adequate alveolar expansion and to check that hyperinflation
has not occurred. This will determine MAP setting.
NOTE: X-rays may be performed through mattress.
Amplitude, Hz, FiO2 and MAP settings must be clearly documented by NS-ANP/Medical
staff on the level 3 chart.
21. Nursing Management – Monitoring and Assessment
and Documentation
HR
CNS
BP
Monitoring of infant’s heart rate may be problematic via ECG electrodes.
Heart rate can be monitored as a ‘pulse’ through the UAC .
Evaluation for heart murmurs may require a temporary pause in HFOV
therapy.
Assess infant’s neurological and behavioural state on HFOV. Analgesia
and sedation may be required for comfort and avoidance of ET tube
dislodgment.
Blood Pressure. Be prepared for a potential blood pressure drop; this is
due to the increased intra-thoracic pressure that oscillation can cause,
resulting in decreased venous return. Have volume and / or an inotrope
(usually dopamine) ready.
Auscultation:
AUSCUL Listening to breath sounds in infants ventilated on HFOV may be helpful,
TATION as the sounds (friction sounds) become reduced in the affected side
when the endotracheal tube is low and ventilates only 1 lung or when a
pneumothorax is present. These changes may occur before the infant
becomes symptomatic. Thus auscultation should be performed at the
time of routine assessment or if there is clinical deterioration.
22. Nursing Management of the Baby Requiring HFOV
Step
1
Action
•PositioningThe brakes on the oscillator and incubator / heat table must always
be on.
•Position the oscillator and incubator/heat table diagonally across the bed space.
•Careful positioning of the oscillator is required to avoid pulling on ET tube. Know
and check hourly your ETT landmark.
•Ensure the incubator or heat table is slightly higher than the oscillator to
promote circuit drainage of rainout from the humidification.
•Position the infant's body in alignment with the oscillator so that only the head is
being moved when it is time for a position change.
2
•RepositioningShould be individually assessed on condition of skin integrity and
infant physiological status. You will need a minimum of two people.
•Gel mattress must always be used.
•Do not disconnect tubing during repositioning.
3
•DisconnectionDisconnection is discouraged as it can cause alveolar collapse
and loss of lung volume.
•Use of Neopuff is discouraged unless mechanical failure or severe deterioration
of infant's condition.
23. Nursing Management of the Baby Requiring HFOV
4
•Suction In-line suction must be used.
•Press Stop button briefly on SensorMedics while briefly inserting and
withdrawing catheter. PAW is maintained throughout.
• Rationale for pausing – The oscillator causes a pressure pulse in
the airways. When suctioning if the sensormedics isn’t turned
off the secretions get pushed back down because of this pulse
pressure. So you are having ineffective clearance of secretions.
There is also the potential of air trapping with active piston
movement.
5
•WeighingInfants should not be weighed on HFOV routinely.
•Only weigh an infant if specifically ordered and discussed on ward
round.
•Always use a warm weigh scale.
6
•X-ray SensorMedics onlyTurn oscillations off at start/stop knob briefly
while X-ray is taken
•Remember if MAP is lost, the reset button will need to be held down to
restore MAP and then you can press start again.
