Ventilation Modes
and Current Trends
Denny Gish, BSRT, RRT
Clinical Specialist, Adult Respiratory Care
Legacy Emanuel Hospital and Health Center
Objectives
• Review current ventilator modes
– Mode descriptions
• Review trends in Respiratory Care
– ARDS Network recommendations
– Best PEEP
– Recruitment Maneuvers
• Identify various methods of High Frequency
Ventilation
Modes of Ventilation
The Critical Question...
How do you choose ?
What Starts the Breath ?
• Controlled or timed breaths
• Controller is really an interval timer
• Assisted breaths are triggered by patient
inspiratory effort in addition to Controlled
breaths
• Spontaneous breaths allowed in some modes
What Ends the Breath ?
• Preset pressure reached
• Preset volume is delivered
• Preset time has elapsed
Ventilator Settings
• Mode: Volume control, Pressure control, Spontaneous, etc
(how the breath goes in)
• Vt:Tidal Volume (size of breath 8-10 cc/kg, 4-6cc/kg for ARDS)
• “Volutrauma” can be as damaging as “Barotrauma”
• f : Frequency (rate # breaths per minute 10-15 bpm)
• PEEP: Positive End Expiratory Pressure (>/= 5 cmH20)
• IP: Inspiratory Pressure (ideally < 30 cmH20)
• FIO2: Fraction of Inspired Oxygen
All ordered by MD or by unit protocol
• Ti or V: Inspiratory time or Flowrate (how long it takes the breath
to go in - generally per RT discretion based on pt comfort & condition)
Ventilator Measurements
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Vt = tidal volume - cc’s or ml’s
f = frequency, # breaths per minute - bpm
Ve = minute ventilation ( Vt * f) liters per minute
I:E Ratio= insp time to exp time (norm is 1:2)
PIP (or PAP) = Peak Inspiratory Pressure – cmH20
MAP = Mean Airway Pressure – cmH20
PEEP = Positive End Expiratory Pressure – cmH20
Pplat = Plateau or Static Pressure (true lung inflation
pressure (eliminates airway & tubing resistance) – cmH20
• Cstatic = Static Compliance (normal 40-60 ml/cmH2O)
Learn to read measurements off vent screen
Some Basic Modes
• Volume Control: set Vt & f, pt may assist
• Pressure Control: set IP & f, pt may assist
• Synchronized Intermittent Mandatory Ventilation:
set Vt & f, pt may take unassisted spontaneous breaths as well
– Mandatory Minute Volume Ventilation – MMV: mandatory breaths
are only provided if spontaneous breathing is not sufficient and below
the prescribed minimum ventilation.
• Pressure Support: pt’s own Vt & f, supported by insp
boost to augment pt’s insp efforts. Pt may breathe deep or
shallow, fast or slow w/o intervention from vent.
Name that Mode of Ventilation
Evita XL – Ventilation Modes
• CMV– Continuous Mandatory Ventilation
*AKA- Assist/Control
• MMV– Mandatory Minute Ventilation
*AKA-Smart SIMV
• PCV–Pressure Controlled Ventilation
*used when PIP is >35
• APRV– Airway Pressure Release Ventilation
*Low compliance disorders
• CPAP-Continuous Positive Airway Pressure – with
or without PS
Draeger V 500
Ventilation mode
VC-CMV - Draeger XL has CMV, but it is
NOT the same!
VC-AC–Works like CMV on the Draeger XL
VC-MMV-Draeger XL has MMV and it
performs exactly like the VC-MMV on the
V500
PC-AC – Draeger XL has PCV
PC-APRV with AutoRelease - Draeger XL
does not have an autorelease function
SPN-CPAP/PS/VS-Draeger XL has
CPAP mode that has Pressure Support
capabilities, but no Volume Support
Now…Puritan Bennet 840
Viasys Avea
Servo I buy
More Advanced Modes
• Volume Support: pt’s own f w/PS for goal Vt. Vent
guarantees Vt by adjusting the PS based on lung compliance
and/or resistance to ensure a preset tidal volume.
• Pressure Regulated Volume Support: set f and goal Vt, pt
may assist. Ventilator automatically adjusts pressure up or
down, from breath to breath, as patient's airway resistance and
lung compliance changes, in order to deliver the goal tidal
volume.
• Volume Control Plus: same as PRVC
• Airway Pressure Release Ventilation: High and low
pressures set w/minimal timed releases to facilitate gas
exchange, high MAP w/very Inverse I:E ratio. Pt may breathe
spontaneously during high pressure holds.
ARDS Current Definition
The 1994 North American-European Consensus Conference
(NAECC) Criteria:
• Onset - Acute and persistent
• Radiographic - Bilateral pulmonary
infiltrates
• Oxygenation - regardless of the PEEP, with a
Pao2/Fio2 ratio  300 for ALI and  200 for
ARDS
• Exclusion criteria - Clinical evidence of Left
Atrial Hypertension or a PAOP of  18 mm
Hg.
Bernard GR et al., Am J Respir Crit Care Med 1994
Tidal Volume Strategies in ARDS
Traditional Approach
High priority to traditional
goals of acid-base balance
and patient comfort
Lower priority to lung
protection
Low Stretch Approach
High priority to lung
protection
Lower priority to
traditional goals of acidbase balance
and comfort
Physiologic Benefits vs PatientImportant Outcomes
PaO2 improvement vs Survival Benefit
• For ARDS, inhaled nitric oxide improves PaO2, but not
mortality
(Taylor et al, JAMA 2004;291:1603)
• High tidal volumes in patients with ARDS improves
PaO2, but mortality is lower for small tidal volumes
(ARDSnet, N Engl J Med 2000; 342:1301)
• For ARDS, prone position improves PaO2, but not
mortality
(Gattinoni, N Engl J Med 2001;345:568)
ARDS Network Low VT Trial
Patients with ALI/ARDS of < 36 hours
Ventilator procedures
• Volume-assist-control mode
• 6 vs. 12 ml/kg of predicted body weight Vt
(PBW/Measured body weight = 0.83)
• Plateau pressure  30 vs.  50 cmH2O
• Ventilator rate 6-35 to achieve a pH goal
of 7.3 to 7.45
• Oxygenation goal: PaO2 55 - 80 mmHg,
SpO2 88 - 95%
)
ARDS Network. N Engl J Med. 2000.
Lung Recruitment
First and foremost performed to provide an arterial
oxygen saturation of 90% or greater at an FiO2 of
less than 60%
Recruitment of nonaerated lung units (open-lung
concept) but risk of regional lung overinflation :
a highly controversial issue!
Recruitment Maneuvers (RMs)
Effective in improving arterial oxygenation at low
PEEP and small tidal volumes.
Recruitment maneuvers may be poorly effective or
deleterious, inducing overinflation of the most
compliant regions, hemodynamic instability, and an
increase in pulmonary shunt resulting from the
redistribution of pulmonary blood flow toward
nonaerated lung regions.
The effect of recruitment may not be sustained unless
adequate PEEP is applied to prevent derecruitment.
Many questions still need to be answered
PEEP in ARDS:
How much is enough ?
PEEP, by avoiding repetitive opening and collapse of
atelectatic lung units, could be protective against
VILI
PEEP, has been shown to prevent surfactant loss in
the airways and avoid surface film collapse.
The lung is kept open by using PEEP to avoid endexpiratory collapse.
High PEEP should make the mechanical ventilation
less dangerous than low PEEP.
Levy MM. N Engl J Med. 2004.
Rouby JJ, et al. Am J Respir Crit Care Med. 2002.
Gattinoni L, et al. Curr Opin Crit Care. 2005.
Optimizing PEEP
• Optimizing PEEP.
– PEEP level is at low
lung volume and
below critical
opening pressure.
– PEEP increased to
optimize compliance.
larson
ARDS Network Low VT Trial
Allowable combination of FiO2 and PEEP:
FiO2
PEEP
0.3 0.4 0.4 0.5 0.5 0.6 0.7 0.7 0.7 0.8 0.9 0.9 0.9 1.0 1.0 1.0 1.0
5
5
8
8
10 10 10 12 14 14 14 16 18 18 20 22 24
APRV Mode
• First described 1987
• Baseline airway pressure is the upper CPAP
level, and the pressure is intermittently
“released” to a lower level, thus eliminating
waste gas
• Time spent at low pressure (short expiratory
time): prevents complete exhalation;
maintains alveolar distension
APRV Evidence
• Prospective, randomized
intervention study (N=45);
PC/PS vs. APRV; patients
with ALI
• Oxygenation was
significantly better in
APRV group
• Sedation use and
hemodynamics were
similar
Puntsen, Am J Respir Crit Care Med,2001
APRV settings
Thigh
Tlow
Phigh
Paw
Plow
insp
Flow
exp
“If this...
why not this?”
- John B. Downs, MD
High Frequency Ventilation
HFOV
Oscillatory
HFJV
JET
HFPV
Percussive
High Frequency Percussive Ventilation
HFPV
• -High Frequency Percussive Ventilation (HFPV) is a
hybrid form of high frequency ventilation.
• -This concept of pneumatic diffusive / convective
protocols is not related to high frequency vibration, jet
insufflation or electronically controlled crank or
magnetically servoed dynamic oscillators.
Rationale for HFV-Based Lung
Protective Strategies
• HFV uses very small tidal volumes
– Avoids excessive end-inspiratory lung volumes
– Allows for higher end-expiratory lung volumes
to achieve better recruitment
• HFV uses much higher respiratory rates
– Allows for maintenance of normal PaCO2 even
with very small tidal volumes
High-frequency Ventilation
• HFOV may improve oxygenation when used as a rescue
modality in adult patients with severe ARDS failing CV.
HFOV may be considered for patients with severe ARDS:
• FiO2 > 0.60 and/or SpO2 < 88% on CV with PEEP > 15 cm H2O,
or
• Plateau pressures (Pplat) > 30 cmH2O, or
• Mean airway pressure  24 cm H2O, or
• Airway pressure release ventilation Phigh  35 cm H2O
HFOV for adults with ARDS is still in its infancy and requires
further evaluations.
Higgins J et al., Crit Care Med 2005
High Frequency Percussive Ventilation
HFPV
• -High Frequency Percussive Ventilation (HFPV) is
a hybrid form of high frequency ventilation.
• It is a combination of convective style ventilation
and percussive high frequency linked together.
Inverse Ratio Ventilation
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Technique used prior to latest generation of vents
Used in refractory hypoxemia
Another way to increase FRC
Expiratory time is longer than inspiratory time.
Heavy sedation/paralytics required
Fluids, pressors usually needed as well due to
decrease in venous return to thorax
Sometimes occurs inadvertently by erroneous vent changes
or pt agitation & high RR. Must be corrected!
Other Advanced Interventions
Require separate or additional machines
• Inhaled Nitric Oxide selective pulmonary artery
vasodilator. Used for pulm htn, lg saddle PE’s, to reduce
intrapulmonary shunting & improve V/Q matching.
Prohibitively expensive, may cause methemoglobin buildup
• High Frequency Ventilation high frequency (>200
breathes per min)
– HFOV, HFJV, HFPV
• Extracorporeal Membrane Oxygenation (ECMO)
similar to bypass pump used in cardiac surgery
Adjuncts
• Recruitment Maneuver
– PEEP - does not recruit alveoli, but can help
maintain alveolar stability
• Prone positioning – has not changed
morbidity or mortality outcomes in ARDS,
but has been shown to help improve
oxygenation
A man suffered from insomnia
and dyslexia. He was also an
agnostic. What did he do?
He stayed up all night wondering
if there was a DOG.