SLE5000
HFOV
Presented by
SAYU ABRAHAM
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High Frequency Ventilation
• Defined by FDA as a ventilator that delivers more than
150 breaths/min.
• Delivers a small tidal volume, usually less than or equal
to anatomical dead space volume.
• While HFV’s are frequently described by their delivery
method, they are usually classified by their exhalation
mechanism (active or passive).
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Differences between HFOV and CMV
CMV
HFOV
Rates
0 - 150
180 - 900
Tidal Volume
4 - 20 ml/kg
0.1 - 5 ml/kg
Alv Press
0 - > 50 cmH2O
0.1 - 5 cmH2O
End Exp Vol
Low
Normalized
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High Frequency Ventilation
• Types of HFV’s Approved for use in both Neonates and Pediatrics
• SLE5000
HFOV
• SensorMedics 3100A
HFOV
• Bird Volumetric Diffusive
HFPPV
• Types of HFV’s Approved for use in Neonates Only
• Bunnell Life Pulse
HFJV
• Infrasonics Infant Star (discontinued)
HFFI
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SLE5000
• Electrically powered,
electronically controlled
• Conventional and HFOV
ventilator
• Paw of 3 - 35 mbar
• Delta P from 4 – 180 mbar
• Frequency of 3 - 20 Hz
• I:E Ratio 1:1
• Active exhalation
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“HFOV”:
Insp. Line Resistor
SLE 2000
(Trigger sensibility)
Bias flow 5l/min
Peep adjustment
Rotating jet
Exp. Valve Block
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Indications of HFOV
Neonatal
RDS/HMD
Air leak syndromes
MAS
PPHN
CDH
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Ventilator Induced Lung Injury
• Barotrauma
• Volutrauma
• Stretch Injury
• Biochemical Injury
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Pulmonary Injury Sequence
of the neonatal patient:
Absence of Surfactant
Atelactasis
Tidal Breathing
High Distending Pressures
Airway Stretch / Distortion
Cellular Membrane Disruption
Edema / Hyaline Membrane Formation
Higher FIO2 , Volumes, Pressures
Volutrauma, Barotrauma, Biotrauma
PIE, BPD
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Pulmonary Injury Sequence
• If we cannot prevent the injury sequence ,
then the target goal is to interrupt the
sequence of events.
• High Frequency Oscillation does not
reverse injury, but will interrupt the
progression of injury.
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Ventilator Induced Lung Injury
Premature baboon model
Coalson J. Univ Texas San Antonio
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Ventilator Induced Lung Injury
Premature baboon model
Coalson J. Univ Texas San Antonio
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Pulmonary Injury Sequence
• There are two injury zones
during mechanical
ventilation
• Low Lung Volume
Ventilation tears
adhesive surfaces
• High Lung Volume
Ventilation over-distends,
resulting in “Volutrauma”
• The difficulty is finding the
“Sweet Spot”
Froese AB, Crit Care Med 1997;
25:906
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Ventilator Induced Lung Injury
Alveolar Protein
30%
25%
20%
15%
10%
CMV-S
CMV
0%
HFOV-S
5%
HFOV
Percent Debris
• HFOV with Surfactant as
Compared to CMV with
Surfactant in the Premature
Primate
– HFOV resulted in
• Less Radiographic Injury
• Less Oxygenation Injury
• Less Alveolar
Proteinaceous Debris
Mode
Jackson C AJRCCM 1994; 150:534
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HFOV
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Theory of Operation
• Oxygenation is primarily controlled by the
Mean Airway Pressure (Paw) and the FiO2
• Ventilation is primarily determined by the
stroke volume (Delta-P) and the frequency
of the ventilator.
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HFOV effectively decouples:
Oxygenation & Ventilation
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HFOV Principle:
Pressure curves CMV / HFOV
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Principles of the SLE5000
HFOV
“Super-CPAP” system
to maintain lung volume
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Optimized Lung Volume Strategy:
Increase Lung Volume above critical opening
pressure to the Optimum and keep it there in
Inspiration and Expiration.
Benefits:
- homogenous gas distribution
- reduced regional atelectasis
- maximized gas exchange area and
pulmonary blood flow
- better matching of ventilation/perfusion
- reduction of intrapulmonary shunting
- reduced Oxygen exposure
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Optimized Lung Volume Strategy:
Decrease Tidal Volumes to less or equal to
dead space and increase frequency.
Benefits:
- enhanced gas exchange due to combined
gas transport mechanisms
- no excessive volume swings
- reduced regional over-inflation and
stretching
- reduced Volutrauma
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Oxygenation
• The Paw is used to
inflate the lung and
optimize the
alveolar surface
area for gas
exchange.
• Paw = Lung Volume
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CT 1
CT 2
CT 3
Paw = CDP
Continuous
Distending
Pressure
CDP =
Lung Volume
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“Open up the lung
up
and keep it open!”
Burkhard Lachmann, 1992
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Primary control of CO2 is by the stroke volume
produced by the Delta P Setting.
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Regulation of stroke volume
• The stroke volume will increase if
– The amplitude increases (higher delta P)
Stroke
volume
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Secondary control of PaCO2 is the stroke volume
produced by the set Frequency.
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Regulation of stroke volume
• The stroke volume will increase if
– The amplitude increases (higher delta P)
– The frequency decreases (longer cycle time)
Stroke
volume
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HFOV Principle:
I
+
+
+
+
+
Amplitude
Delta P =
Tv =
Ventilation
CDP=FRC=
Oxygenation
E
-
-
-
-
HFOV = CPAP with a wiggle !
-
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Pressure transmission
Gerstmann D.
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Airway Pressure Transmission HFOV :
Pressure
Amlitude
Delta P =
TV =
Ventilation
I
+
+
+
+
_
_
_
+
+
_
+
_
_
+
+
_
+ CDP / MAP
_ = Lungvolume
= Oxygenation
_
E
ET Tube
Trachea
Alveolus
Transmission
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HFOV Mechanisms of Gas Transport
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Mechanisms of HFOV Gas Exchange
• There are six mechanisms
of gas exchange during
HFOV
– Convective Ventilation
– Asymmetrical Velocity
Profiles
– Taylor Dispersion
– Pendeluft
– Molecular Diffusion
– Cardiogenic Mixing
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Practical preparation
• Avoid leak around the E.T tube
• Tc PO2,CO2,Pulse oxymeter and invasive blood
pressure monitoring
• Baseline CXR
• Optimize blood pressure and perfusion(volume
replacement and inotropes)
• Muscle relaxant/sedation
• Reusable low compliance circuits must be used
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NURSING CARE
• Perform through suction before connecting to the oscillator.
• Assess patient upon commencement of HFOV.Monitor vital
signs, chest wiggle must be evaluated upon initiation and
followed closely thereafter. If chest wiggle diminishes it
may be ETtube moved or obstructed. Chest wiggle on one
side indicates patient developed pneumothorax,thus chest
wiggle assessment should be performed after
repositioning.
• Auscultation the chest by putting in standby mode.
• A closed suction should be used. It is not necessary to
disconnect the patient to suction as this will potentially
derecruit lung volumes.
• The point at which the ET tube is cut and secured at lips
should be initially noted this measurement is reference.
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Continued………
•
•
•
•
•
Evaluation of lung expansion on CXR
Check capillary refill, skin color and temperature
Comparing central and peripheral pulses
Monitoring of ECG Tracing
Frequent CXR’s blood gases in initial stabilization
period
• Optimal lung volume for oxygenation is 8-9 rib
inflation
• Blood pressure and perfusion should be
optimized prior to HFOV,any volume replacement
should be completed and inotropes commenced
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if necessary
Continued………
• Muscle relaxants are not indicated since
spontaneous respiratory effort will be a
clinical indicator of adequacy of ventilation
• Sedation with opiates is often indicated
THANKYOU
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