Ventilation Modes and Current Trends

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Ventilation Modes and Current Trends

• Denny Gish, BSRT, RRT
• Clinical Specialist, Adult Respiratory Care
• Legacy Emanuel Hospital and Health Center

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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

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Modes of Ventilation

• The Critical Question...
• How do you choose ?

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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

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What Ends the Breath ?

• Preset pressure reached
• Preset volume is delivered
• Preset time has elapsed

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Ventilator Settings

• Mode Volume control, Pressure control,
  Spontaneous, etc (how the breath goes in)
• VtTidal 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 (gt/ 5
  cmH20)
• IP Inspiratory Pressure (ideally lt 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)

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Ventilator Measurements

• Vt tidal volume - ccs or mls
• f frequency, breaths per minute - bpm
• Ve minute ventilation ( Vt f) liters per
  minute
• IE Ratio insp time to exp time (norm is 12)
• 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

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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 pts own Vt f, supported by
  insp boost to augment pts insp efforts. Pt may
  breathe deep or shallow, fast or slow w/o
  intervention from vent.

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Name that Mode of Ventilation

• Evita XL Ventilation Modes
• CMV Continuous Mandatory Ventilation
• AKA- Assist/Control
• MMV Mandatory Minute Ventilation
• AKA-Smart SIMV
• PCVPressure Controlled Ventilation
• used when PIP is gt35
• APRV Airway Pressure Release Ventilation
• Low compliance disorders
• CPAP-Continuous Positive Airway Pressure with
  or without PS

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Draeger V 500

• Ventilation mode
• VC-CMV - Draeger XL has CMV, but it is NOT the
  same!
• VC-ACWorks 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

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NowPuritan Bennet 840
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Viasys Avea
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Servo I buy
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More Advanced Modes

• Volume Support pts 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
  IE ratio. Pt may breathe spontaneously during
  high pressure holds.

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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
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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 acid-base
  balance
• and comfort

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Physiologic Benefits vs Patient-Important
Outcomes

• PaO2 improvement vs Survival Benefit
• For ARDS, inhaled nitric oxide improves PaO2, but
  not mortality
• (Taylor et al, JAMA 20042911603)
• High tidal volumes in patients with ARDS improves
• PaO2, but mortality is lower for small tidal
  volumes
• (ARDSnet, N Engl J Med 2000 3421301)
• For ARDS, prone position improves PaO2, but not
• mortality
• (Gattinoni, N Engl J Med 2001345568)

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ARDS Network Low VT Trial

• Patients with ALI/ARDS of lt 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.
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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!

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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

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PEEP in ARDSHow 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
  end-expiratory 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.
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Optimizing PEEP

• Optimizing PEEP.
• PEEP level is at low lung volume and below
  critical opening pressure.
• PEEP increased to optimize compliance.

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larson
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ARDS Network Low VT Trial

• Allowable combination of FiO2 and PEEP

FiO2 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
PEEP 5 5 8 8 10 10 10
12 14 14 14 16 18 18 20 22 24
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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

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APRV Evidence

• Prospective, randomized intervention study
  (N45) 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
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APRV settings
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If this...
why not this?
- John B. Downs, MD
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High Frequency VentilationHFOVOscillatory
HFJVJETHFPVPercussive
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High Frequency Percussive VentilationHFPV

• -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.

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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

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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 gt 0.60 and/or SpO2 lt 88 on CV with PEEP gt
  15 cm H2O, or
• Plateau pressures (Pplat) gt 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
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High Frequency Percussive VentilationHFPV

• -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.

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Inverse Ratio Ventilation

• 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!

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Other Advanced Interventions

• Require separate or additional machines
• Inhaled Nitric Oxide selective pulmonary artery
  vasodilator. Used for pulm htn, lg saddle PEs,
  to reduce intrapulmonary shunting improve V/Q
  matching. Prohibitively expensive, may cause
  methemoglobin buildup
• High Frequency Ventilation high frequency (gt200
  breathes per min)
• HFOV, HFJV, HFPV
• Extracorporeal Membrane Oxygenation (ECMO)
  similar to bypass pump used in cardiac surgery

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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

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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.