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RSPT 2353 – Neonatal/Pediatric Cardiopulmonary Care
High Frequency Ventilation in the Pediatric and Neonatal
Patient
Lecture Notes
I.
High-Frequency Jet Ventiliation (HFJV) –
a. Used in tandem with a conventional ventilator
b. Operate in 4 – 11 Hz; pulses of gas is delivered through adapter at ETT
c. Conventional ventilator
 Allow sighs
 Provides PEEP
 Allows continuous flow of gas available at ETT
d. Limitations
 HFJV allows passive exhalation
 More compliant lungs require lower rates
II.
High Frequency Oscillating Ventilation (HFOV) was designed to perform
the following functions:
a. To serve as a ventilation mode when conventional ventilation has
failed.
b. To provide a mode of ventilation that minimizes barotrauma, or
damage to the delicate tissue in the lungs.
III.
Definition of HFOV: a rapid rate ventilation using low tidal volumes
a. The oscillator uses a diaphragm piston unit to actively move gas in
and out of the lungs and requires a special circuit (rigid or flexible)
b. Differs from conventional ventilation in that it provides rate of 1201200 bpm with volumes of 0.1 – 1.5 cc/kg. Conventional ventilation
provides rates of 1 – 120 bpm and 4 – 20 cc/kg.
IV.
Indications for HFOV – They are not clearly defined, but do include:
a. Air leaks such as pneumothorax and pulmonary interstitial
emphysema (PIE)
b. To reduce barotrauma when conventional ventilator settings are
getting very high
c. When conventional ventilation is failing, particularly in meconium
aspiration syndrome (MAS), pneumonia, persistent pulmonary
hypertension of the newborn (PPHN), and pulmonary hemorrhage.
d. Respiratory Failure – Defined as PaCO2 > 55 torr, PaO2 <50 torr
V.
Effects on lung tissue
a. The lung parenchyma in children is especially delicate and the high
peak pressure used in conventional ventilation can be harmful to the
delicate lung tissue.
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b. Barotrauma occurs when the lung tissue is damaged due to the
excessive pressures.
c. HFOV offer the advantage of improved CO2 removal at lower peak
pressures.
VI.
Effects on cardiopulmonary status
a. HFOV can cause hemodynamic changes
b. This is due to the continuous pressures that are generated by HFOV
which causes increased pressures in the thoracic cavity.
c. The increased thoracic pressure can impede cardiac output.
d. The decreased CO affects the blood pressure and a vicious cycle can
ensue.
e. To avoid this happening, the pt hemodynamic status must be
monitored continuously.
f. Arterial lines are necessary.
VII.
Settings
a. Amplitude – also called ΔP
 HFOV is more dependent on amplitude than on rate.
 Similar to Vt on conventional ventilation
 Proper setting is determined by observing chest
excursion/movement with oscillation.
 This setting should be enough to vibrate or “wiggle” the
thorax from the nipple line to the umbilicus
 Settings are changed by 1-2 cmH2O
 Changes in amplitude require readjustment in the MAP.
b. Frequency
 Similar to rate in conventional ventilation
 Measured in Hertz (Hz)
 Multiply the number of Hz X 60 to obtain the exact rate
 Initial Hz settings
< 1000 gms
15 Hz
2 - 12 kg
10 Hz
13 - 20 kg
8 Hz
21 - 30 kg
7 Hz
> 30 kg
6 Hz
 Setting depends on the size of the pt and the disease process
 Changes in frequency dramatically changes Amplitude and MAP
c. MAP
 Similar to peak airway pressure in conventional ventilation
 For diffuse alveolar disease, the initial MAP should be set
approx 2-4 cmH2O over the value of MAP on the
conventional ventilator
 If compression of the heart is noted on CXR, and decrease in
MAP is necessary.
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 Decrease by 0.5 to 1 cmH2O on the MAP dial.
 A spontaneous pneumothorax is a complication that can
result from increased MAPs
d. FiO2
VIII.
 Initial FiO2 is selected to optimize pulmonary vascular
resistance while the ventilator is opening the lungs.
Monitoring on HFOV
a. Arterial access (UAC in neonates, peripheral in pediatric) is
advantageous.
b. Blood pressure is especially important because of the hemodynamic
changes that can occur during HFOV
 High pressures lead to a decrease in CO – tissues and organ
perfusion are affected
 Also includes monitoring of Urine output, kidney function
c. CXR
 Obtain a CXR 30-60 minutes after initiation of HFOV
 Determines if MAP is compressing the heart
 Chest expansion of 8.5 to 9 ribs indicates proper inflation
 As lungs heal, they are more compliant and can become
hyperinflated leading to pneumothorax.
 Regular chest films should be taken to monitor chest
expansion.
d. Paralytic agents
 May cause fluid retention and should be taken into
consideration
 The pt may be paralyzed initially, but paralytics should not
be used for extended periods of time.
 As soon as tolerated by pt, paralytic agents should be
discontinued.