Newer modes of ventilation
Dr P K Dash
Trivandrum
Transition
Older ventilators
Newer ventilators
History of ventilation
Introduction of modes
Goals of ventilation
Best mode selection
Why new modes
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More safely assist patient
Less likelihood of ventilator associated lung injury.
Less hemodynamic compromise
More effectively ventilate/oxygenate
Improve patient - ventilator synchrony
More rapid weaning
Evolution
• Volume control
• Pressure control
• Pressure support
• Dual control
• Algorithm based
• Knowledge based
Basic modes
Settings
Newer modes
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Dual control modes
Proportional Assist Ventilation (PAV)
Closed loop PSV
Automatic tube compensation
Adaptive Support Ventilation (ASV)
Dual control modes
First generation dual modes
VAPS and PA
Bird 8400Sti
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Bear 1000
Tbird
Combines volume ventilation & pressure support
Uses TV, peak flow, and pressure support
Targets PS level with at least set peak flow
Continues until flow decreases to set peak flow, then:
– If TV not delivered, peak flow maintained until vol. limit
– If TV or more delivered, breath ends
First generation dual modes
PRVC and Volume support
Maquet Servo-i
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Servo 300
Combines volume ventilation & pressure control
Set TV is “targeted”
Ventilator estimates vol./press. relationship each breath
Ventilator adjusts level of pressure control breath by breath
PRVC
(1) Test breath (5 cm H2O);
(2) Pressure is increased to deliver
set volume;
(3) Maximum available pressure;
(4) Breath delivered at preset E, at
preset f, and during preset TI;
(5)When VT corresponds to set value,
pressure remains constant;
(6) If preset volume increases, pressure
decreases; the ventilator continually
monitors and adapts to the patient’s
needs
Volume support
(1) VS test breath (5 cm H2O);
(2) Pressure is increased slowly until
target volume is achieved;
(3) Maximum available pressure is 5 cm
H2O below upper pressure limit;
(4) VT higher than set VT delivered results
in lower pressure;
(5) Patient can trigger breath;
(6) If apnea alarm is detected, ventilator
switches to PRVC
Summary
Ventilator settings
– Minimum respiratory rate
– Target tidal volume
– Upper pressure limit
– FIO2
– Inspiratory time or I:E ratio
– Rise time
– PEEP
Advantages and disadvantages
• Decelerating inspiratory flow pattern
• Pressure automatically adjusted for changes in
compliance and resistance within a set range
– Tidal volume guaranteed
– Limits volutrauma
– Prevents hypoventilation
• Pressure delivered is dependent on tidal volume achieved
on last breath
– Intermittent patient effort  variable VT
• Less suitable for patients with asthma or COPD
Second generation of dual modes
Auto flow
Evita 4,
Adaptive support ventilation
Hamilton Galileo
Autoflow
• First breath uses set TV & I-time
– Pplateau measured
• Pplateau then used
• V/P measured each breath
• Press. changed if needed (+/- 3)
• Then similar to PRVC
• Adds high TV alarm & limit
• Can be used in CMV, SIMV and MMV
Adaptive support ventilation
Adaptive support ventilation
Bi-level ventilation methods
Allow spontaneous breaths at two airway pressures
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Reduction of shunt due to the alveolar recruitment
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Better venous return
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Reduced Risk of Pulmonary Muscle Atrophy
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Weaning is enhanced
Advantages of spontaneous ventilation
– BiPAP (Drager E-4 & E-2 dura)
– BiLevel (NPB 840)
– APRV (NPB 840, Drager E-4 & E-2 dura)
BiPAP
(Drager E-4 & E-2 dura)
Spontaneous
Breathing
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Reduction of the
invasivness of Ventilation
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Reduction of Sedation
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One Ventilation Mode from
Intubation to Weaning
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More comfortable for the
Patient
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Fewer Alarms (easier
handling)
BIPAP
PCV
Other newer modes
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Proportional assist ventilation
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Smart care
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Automatic tube compensation
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Neural adjusted ventilator assist
Proportional assist ventilation
• Supports according to the patient's effort, based on the respiratory
flow signal and by adjusting inspiratory airway pressure in proportion
to the patient's effort;
• PAV requires accurate, instantaneous measurement of compliance
and resistance
• Only provides assisted ventilation
• Improves patient – ventilator synchrony
• Does not improve ventilation/oxygenation – no control of ventilatory
pattern!
• May prevent lung injury, Not shown to improve weaning!
Automatic tube compensation
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Designed to Maintain Tracheal Pressure at Baseline
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Does not require ongoing assessment of resistance!
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Pressure Applied Based Upon Resistive Properties of the Airway and
Patients Inspiratory Flow
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Positive Pressure During Inspiration
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Negative Pressure During Exhalation
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Effectively unloads resistive effort imposed by ETT
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Improves patient – ventilator synchrony
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Reduces risk of lung injury
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Does not improve ventilation/oxygenation –
• No control over ventilatory pattern
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No demonstrated improvement in weaning!
Indications of ATC
Smart care
• It is a knowledge based automated weaning system.
• It contains an automated clinical weaning guideline
• Based on recognised medical expertise and research.
Smart care working principles
• Step 1: Stabilizing within a
respiratory comfort zone
• Step 2: Reducing invasiveness
• Step 3: Testing readiness for
extubation
Respiratory Comfort Zone
Level of PS is automatically adjusted in steps of 2-4 mbar
to keep parameters within following ranges
Spontaneous
breathing rate
>15 bpm
<30 bpm (<34 bpm for patients with
respiratory failure due to neurological
disorders)
Expired tidal
volume
>250 ml (ideal body weight <55 kg)
>300 ml (ideal body weight >55 kg)
End tidal CO2
<55 mmHg (<65 mmHg for patients with
COPD
Contraindications to smart care
Neuro-Ventilatory Coupling
Neural adjusted ventilator assist
NAVA
Ideal
Central Nervous System
Technology
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Phrenic Nerve
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New
Diaphragm Excitation
Technology
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Diaphragm Contraction
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Chest Wall and Lung Expansion
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Current
Airway Pressure, Flow and
Technology
Volume
Ventilator
Unit
Conventional triggering
Conventional ventilator technology uses a
pressure drop or flow reversal to provide
assistance to the patient.
This is the last step of the signal chain leading to
inhalation.
This last step is subject to disturbances such as
intrinsic PEEP, hyperinflation and leakage.
NAVA triggering
• The earliest signal that can be registered with a low
degree of invasivity is the excitation of the diaphragm.
• The excitation of the diaphragm is independent of
pneumatic influence and insensitive to the problems with
pneumatic triggering technologies.
• By following diaphragm excitation and adjusting the
support level in synchrony with the rise and fall of the
electrical discharge, the ventilator and the diaphragm will
work with the same signal input.
• In effect, this allows the ventilator to function as an extra
muscle, unloading extra respiratory work induced by the
disease process.
Availability
Components
Diaphragm need to work or else
Catheters
Signal capture
• All muscles (including the diaphragm and
other respiratory muscles) generate
electrical activity to excite muscle
contraction.
• The electrical activity of the diaphragm is
captured by an esophageal catheter with
an attached electrode array. The signal is
filtered in several steps and provide the
input for control of the respiratory assist
delivered by the ventilator.
Catheter verification
P and QRS waves are present on the top
leads and the P-waves disappear on the
lower leads and with a decrease of the
QRS-amplitude on the lower leads.
When an Edi waveform is present, observe
which leads are highlighted in blue. If the
leads highlighted in blue are in the center
(i.e. second and third leads), secure the
Edi Catheter in this position.
To finally verify correct positioning of the
Edi Catheter press the Exp. Hold and keep
the button depressed until a breathing
effort is registered. A negative deflection in
the pressure curve with a simultaneous
positive inflection in the Edi curve verifies
correct position of the Edi Catheter.
Setting the NAVA level
NAVA preview is a help tool to set the
NAVA level to reach an estimated NAVA
On the uppermost waveform (the pressure
curve), there are two curves presented
simultaneously. The gray curve shows the
estimated pressure, Pest, based on the
Edi signal and the set NAVA level.
NAVA preview is available in all invasive
modes of ventilation except NAVA.
Setting of the ventilator
Setting the ventilator
Post extubation monitoring
Monitoring of the ventilatory pattern of
the patient is superior with NAVA as
the control signal of the respiratory
center is known.
This can of course be done in any
mode of ventilation and is an
invaluable tool in determining
adaptation to the ventilator strategy.
However, patients breathing
spontaneously can also be monitored,
which is a very helpful tool if patients
are developing wheezing after
extubation or during a T-piece trial.
Benefits of NAVA
Closed loop ventilation
New horizon
Thank you