Weaning Modes
and Protocol
• Causes of Ventilator Dependence
• Assessment for Discontinuation Trial
• Spontaneous Breathing Trial (SBT)
– Extubation Criteria
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Failure of SBT
Weaning Modes
Weaning Protocols
Role of Tracheostomy
Long-term Facilities
Stages of Mechanical Ventilation
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Causes of Ventilator Dependence
Who is the “ventilator dependent’?
• Mechanical ventilation > 24 h
or
• Failure to respond during discontinuation
attemps
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Causes of Ventilator Dependence
Causes
Description
Neurologic controller
Central drive
Peripheral nerves
Respiratory system
Mechanical loads
Ventilatory muscle properties
Gas exchange properties
Cardiovascular system
Cardiac tolerance of ventilatory muscle work
peripheral oxygen demands
Psychological issues
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Assessment for Discontinuation
Trial
Criteria for discontinuation trial:
• Evidence for some reversal of the
underlying cause for respiratory failure
• Adequate oxygenation and pH
• Hemodynamic stability; and
• The capability to initiate an inspiratory
effort
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Assessment for Discontinuation
Trial
Extubation failure
• 8-fold higher odds ratio for nosocomial
pneumonia
• 6-fold to 12-fold increased mortality risk
• Reported reintubation rates range from 4
to 23% for different ICU populations
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Assessment for Discontinuation
Trial
Criteria Used in Weaning/Discontinuation in different studies
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Assessment for Discontinuation
Trial
Measurements used To Predict the Outcome of a Ventilator
Discontinuation Effort in More Than One Study
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Spontaneous Breathing Trial
• Formal discontinuation assessments
should be performed during spontaneous
breathing
• An initial brief period of spontaneous
breathing can be used to assess the
capability of continuing onto a formal
SBT.
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Spontaneous Breathing Trial
• How to assess patient tolerance?
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the respiratory pattern
the adequacy of gas exchange
hemodynamic stability, and
subjective comfort.
Spontaneous Breathing Trial
Criteria Used in Several Large Trials To Define
Tolerance of an SBT*
*HR heart rate; Spo2 hemoglobin oxygen saturation.
Spontaneous Breathing Trial
• The tolerance of SBTs lasting 30 to 120
min should prompt consideration for
permanent ventilator discontinuation
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Spontaneous Breathing Trial
Frequency of Tolerating an SBT in Selected Patients and Rate
of Permanent Ventilator Discontinuation
Following a Successful SBT*
*Values given as No. (%). Pts patients.
†30-min SBT.
‡120-min SBT.
Do Not Wean To Exhaustion
Weaning to Exhaustion
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RR > 35/min
Spo2 < 90%
HR > 140/min
Sustained 20% increase in HR
SBP > 180 mm Hg, DBP > 90 mm Hg
Anxiety
Diaphoresis
Mechanical Ventilation
Rest 24 hrs
PaO2/FiO2 ≥ 200 mm Hg
PEEP ≤ 5 cm H2O
Intact airway reflexes
No need for continuous infusions of vasopressors or inotrops
> 100
RSBI
<100
Stable Support Strategy
Assisted/PSV
24 hours
Daily SBT
Low level CPAP (5 cm H2O),
Low levels of pressure support (5 to 7 cm H2O)
“T-piece” breathing
30-120 min
Yes
RR > 35/min
Spo2 < 90%
HR > 140/min
Sustained 20% increase in HR
SBP > 180 mm Hg, DBP > 90 mm Hg
Anxiety
Diaphoresis
No
Extubation
Extubation Criteria
Ability to protect upper airway
– Effective cough
– Alertness
Improving clinical condition
Adequate lumen of trachea and larynx
– “Leak test” to identify patients who are at risk for
post-extubation stridor
Extubation
Criteria
Post Extubation Stridor
• The Cuff leak test during MV:
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Set a tidal Volume 10-12 ml/kg
Measure the expired tidal volume
Deflated the cuff
Remeasure expired tidal volume (average of 46 breaths)
– The difference in the tidal volumes with the
cuff inflated and deflated is the leak
• A value of 130ml  85% sensitivity
95% specificity
Extubation
Criteria
Post Extubation Stridor
• Cough / Leak test in spontaneous breathing
– Tracheal cuff is deflated and monitored for the
first 30 seconds for cough.
– Only cough associated with respiratory gurgling
(heard without a stethoscope and related to
secretions) is taken into account.
– The tube is then obstructed with a finger while
the patient continues to breath.
– The ability to breathe around the tube is
assessed by the auscultation of a respiratory
flow.
Extubation Criteria
• The risk of postextubation upper airway
obstruction increases with
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the duration of mechanical ventilation
female gender
trauma, and
Repeated or traumatic intubation
Failure of SBT
• Correct reversible causes for failure
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adequacy of pain control
the appropriateness of sedation
fluid status
bronchodilator needs
the control of myocardial ischemia, and
the presence of other disease processes
• Subsequent SBTs should be performed
every 24 h
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Failure of SBT
Respiratory
Increased resistance
Decreased compliance
Increased WOB and exhaustion
Auto-PEEP
Cardiovascular
Backward failure: LV dysfunction
Forward heart failure
Metablic/Electrolytes
Poor nutritional status
Overfeeding
Decreased Mg and PO4 levels
Metabolic and respiratory alkalosis
Infection/fever
Major organ failure
Stridor
Failure of SBT
• Left Heart Failure:
– Increased metabolic demands
– Increases in venous return and pulmonary
edema
• Appropriate management of
cardiovascular status is necessary before
weaning will be successful
Failure of SBT
Factors affecting ventilator demands
Failure of SBT
Therapeutic measures to enhance weaning progress
Weaning Modes
• Patients receiving mechanical ventilation
for respiratory failure who fail an SBT
should receive a stable, nonfatiguing,
comfortable form of ventilatory support
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Weaning Modes
Modes of Partial Ventilator Support
*SIMV synchronized intermittent mandatory ventilation; PSV pressure support ventilation; VS
volume support; VAPS(PA) volume assured pressure support (pressure augmentation); MMV
mandatory minute ventilation; APRV airway pressure release ventilation.
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Weaning Modes
PSV: Pressure Support
• Gradual decrease in the level of PSV on
regular basis (hours or days) to minimum
level of 5-8 cm H2O
• PSV that prevents activation of accessory
muscles
• Once the patient is capable of maintaining
the target ventilatory pattern and gas
exchange at this level, MV is discontinued
Weaning Modes
SIMV: synchronized intermittent
mandatory ventilation
• Gradual decrease in mandatory breaths
• It may be applied with PSV
• Has the worst weaning outcomes in
clinical trials
• Its use is not recommended
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Weaning Modes
New Modes
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VS, Volume support
Automode
MMV, mandatory minute ventilation
ATC, automatic tube compensation
ASV, adaptive support ventilation
Weaning Protocols
• With the assisted modes, to achieve
patient comfort and minimize imposed
loads, we should consider:
– sensitive/responsive ventilator-triggering
systems
– applied PEEP in the presence of a triggering
threshold load from auto-PEEP
– flow patterns matched to patient demand, and
– appropriate ventilator cycling to avoid air
trapping are all important to
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Weaning Protocols
• Weaning protocols
– Developed by multidisciplinary team
– Implemented by respiratory therapists and
nurses to make clinical decisions
– Results in shorter weaning times and shorter
length of mechanical ventilation than
physician-directed weaning
• Sedation protocols should be developed
and implemented
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Role of Tracheotomy
• Candidates for early tracheotomy:
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High levels of sedation
Marginal respiratory mechanics
Psychological benefit
Mobility may assist physical therapy efforts.
Role of Tracheotomy
• The benefits of tracheotomy include:
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improved patient comfort
more effective airway suctioning
decreased airway resistance
enhanced patient mobility
increased opportunities for articulated speech
ability to eat orally, and
more secure airway
Role of Tracheotomy
• Concerns:
– Risk associated with the procedure
– Long term airway injury
– Costs
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Long-term Facilities
• Unless there is evidence for clearly
irreversible disease (e.g., high spinal cord
injury or advanced amyotrophic lateral
sclerosis), a patient requiring prolonged
mechanical ventilatory (PMV) support for
respiratory failure should not be
considered permanently ventilatordependent until 3 months of weaning
attempts have failed.
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Long-term Facilities
• Critical-care practitioners should
familiarize themselves with specialized
facilities in managing patients who require
prolonged mechanical ventilation
• Patients who failed ventilator
discontinuation attempts in the ICU
should be transferred to those facilities
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Long-term Facilities
• Weaning strategies in the PMV patient
should be slow-paced and should include
gradually lengthening SBTs
• Psychological support and careful
avoidance of unnecessary muscle
overload is important for these types of
patients
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Thank You
Introduction
• 75% of mechanically ventilated patients are
easy to be weaned off the ventilator with
simple process
• 10-15% of patients require a use of a
weaning protocol over a 24-72 hours
• 5-10% require a gradual weaning over longer
time
• 1% of patients become chronically dependent
on MV
Readiness To Wean
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Improvement of respiratory failure
Absence of major organ system failure
Appropriate level of oxygenation
Adequate ventilatory status
Intact airway protective mechanism (needed
for extubation)
Oxygenation Status
• PaO2 ≥ 60 mm Hg
• FiO2 ≤ 0.40
• PEEP ≤ 5 cm H2O
Ventilation Status
• Intact ventilatory drive: ability to control their
own level of ventilation
• Respiratory rate < 30
• Minute ventilation of < 12 L to maintain PaCO2
in normal range
• Functional respiratory muscles
Intact Airway Protective
Mechanism
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Appropriate level of consciousness
Cooperation
Intact cough reflex
Intact gag reflex
Functional respiratory muscles with ability to
support a strong and effective cough
Function of Other Organ Systems
• Optimized cardiovascular function
– Arrhythmias
– Fluid overload
– Myocardial contractility
• Body temperature
– 1◦ degree increases CO2 production and O2 consumption
by 5%
• Normal electrolytes
– Potassium, magnesium, phosphate and calcium
• Adequate nutritional status
– Under- or over-feeding
• Optimized renal, Acid-base, liver and GI functions
Predictors of Weaning Outcome
Predictor
Value
Evaluation of ventilatory drive:
 P 0.1
 < 6 cm H2O
Ventilatory muscle capability:
 Vital capacity
 Maximum inspiratory pressure
 > 10 mL/kg
 < -30 cm H2O
Ventilatory performance
 Minute ventilation
 Maximum voluntary ventilation
 Rapid shallow breathing index
 Respiratory rate
 < 10 L/min
 > 3 times VE
 < 105
 < 30 /min
Maximal Inspiratory Pressure
• Pmax: Excellent negative predictive value if
less than –20 (in one study 100% failure to
wean at this value)
An acceptable Pmax however has a poor
positive predictive value (40% failure to wean
in this study with a Pmax more than –20)
Frequency/Volume Ratio
• Index of rapid and shallow breathing RR/Vt
• Single study results:
– RR/Vt>105 95% wean attempts unsuccessful
– RR/Vt<105 80% successful
• One of the most predictive bedside
parameters.
Measurements Performed Either While Patient Was Receiving
Ventilatory Support or During a Brief
Period of Spontaneous Breathing That Have Been Shown to Have
Statistically Significant LRs To Predict the
Outcome of a Ventilator Discontinuation Effort in More Than One
Study*
Weaning to Exhaustion
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RR > 35/min
Spo2 < 90%
HR > 140/min
Sustained 20% increase in HR
SBP > 180 mm Hg, DBP > 90 mm Hg
Anxiety
Diaphoresis
Work-of-Breathing
• Pressure= Volume/compliance+ flow X resistance
• High airway resistance
• Low compliance
• Aerosolized bronchodilators, bronchial
hygiene and normalized fluid balance assist
in normalizing compliance, resistance and
work-of-breathing
Auto-PEEP
• Increases the pressure gradient needed to
inspire
• Use of CPAP is needed to balance alveolar
pressure with the ventilator circuit pressure
• Start at 5 cm H2O, adjust to decrease patient
stress
• Inspiratory changes in esophageal pressure
can be used to titrate CPAP
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Gradient
-5
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Gradient
Auto PEEP +10
-5
-15
PEEP
10
Gradient
Auto PEEP +10
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-5
Preparation: Factors Affecting
Ventilatory Demand
Integrative Indices Predicting Success
Measured Indices Must Be Combined
With Clinical Observations
Three Methods for Gradually
Withdrawing Ventilator Support
Although the majority of patients do not require gradual withdrawal of ventilation,
those that do tend to do better with graded pressure supported weaning than
with abrupt transitions from Assist/Control to CPAP or with SIMV used with only
minimal pressure support.
Thank You