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Chapter 47
Discontinuing Ventilatory Support
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
Learning Objectives
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Discuss the relationship between ventilatory
demand and ventilatory capacity in the context
of ventilator discontinuance.
List factors associated with ventilator
dependence.
Explain how to evaluate a patient before
attempting ventilator discontinuation or weaning.
List acceptable values for specific weaning
indices used to predict a patient’s readiness for
discontinuation of ventilatory support.
Describe factors that should be optimized before
an attempt is made at ventilator discontinuation
or weaning.
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Learning Objectives (cont.)
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Describe techniques used in ventilator weaning,
including daily spontaneous breathing trials,
synchronized intermittent mandatory ventilation,
pressure support ventilation, and other newer
methods.
Contrast the advantages and disadvantages
associated with various weaning methods and
techniques.
Describe how to assess a patient for extubation.
List the primary reasons why patients fail a
ventilator discontinuance trial.
Explain why some patients cannot be
successfully weaned from ventilatory support.
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Introduction
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Ventilatory support sustains life but is not
curative
Has many complications and hazards
Should be withdrawn expeditiously
All patients should be evaluated on a daily
basis for their ability to wean from ventilatory
support
Balance desire for early extubation with its
exposure to the risks of reintubation.
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Ventilatory Capacity
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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All of the following are TRUE about mechanical
ventilation, except:
A. Ventilatory support sustains life but is not
curative.
B. It has few complications and hazards.
C. It should be withdrawn expeditiously.
D. All patients should be evaluated on a daily basis
for their ability to wean from ventilatory support
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Methods of Discontinuing Ventilation
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Three main methods
1.
2.
3.
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Spontaneous breathing trials (SBT)
SIMV
PSV
Novel modes with no data to support
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VSV = volume support ventilation, MMV= mandatory
minute volume ventilation, ATC = automatic tube
compensation, PAV = proportional assist ventilation
**Systematic review: 1 SBT per day has shown best results
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Probability of Successful Weaning
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Discontinuing Ventilatory Support
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In general, patients being considered for
removal from ventilatory support fall into one
of four categories:
1.
2.
3.
4.
removal is quick and routine, normally the vast
majority of patients
need a more systematic approach, about 15 to
20% of ventilated patients
require days to weeks to wean, usually less than
5% of patients
ventilator-dependent or “unweanable” patients,
less than 1% of patients
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Global Criteria for Discontinuing
Ventilatory Support
(cont.)
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Success is tied to
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Ventilatory work load versus capacity
 Oxygenation status
 Cardiovascular status
 Psychological factors
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Most Important Criteria
1. Reversal of disease state that necessitated
ventilatory support
2. Oxygenation status adequate on <0.5 FIO2
3. Medically and hemodynamically stable
4. Patient can breathe spontaneously
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If the above are all true, then perform a
formal evaluation for extubation.
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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66 Measurements:
8 Most Consistently Predictive
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Spontaneous rate
Spontaneous VT
f/VT (RSBI) – most predictive
Minute ventilation
MIP
P0.1
6 to 30 beats/min
>5 ml/kg
<105
<10 L/min
<20 to 30 mm Hg
<6 cm H2O
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P0.1/MIP
<0.3
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CROP (CDyn, f, O2, PImax)
>13
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* No single index has high predictive power, so it is
important to consider the total picture.
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Which of the following predictive value is
consistent with a patient weaning successfully?
A.
B.
C.
D.
Spontaneous rate
Spontaneous VT
f/VT (RSBI)
MIP
40 beats/min
4 mL/kg
85
–18 mm Hg
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Preparing the Patient
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Patient should be rested and stable
Maximize bronchodilator and antiinflammatory medications as well as
bronchial hygiene
Communicate well with patient so as to
relieve/minimize anxiety
Optimize nutrition, acid/base status, fluid
balance, and oxygenation
Minimize sedation
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Rapid Ventilator Discontinuance
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Patients that are likely to wean rapidly
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Presenting problem corrected in 72 hours
Good weaning parameters
Good results in SBT of 30 to 120 minutes
If the above criteria are met, most patients
can be removed from ventilatory support
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If the patient can protect his or her airway, then
extubate at this time
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Progressive Weaning of
Ventilatory Support
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Patients likely to need longer weaning period
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Ventilated longer then 72 hours
Marginal: oxygen, ventilatory, cardiovascular, or
medical status
Most common methods of weaning:
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SBT alternating with rest periods on
• A/C, SIMV, or significant levels of PSV
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Progressive Weaning: SBT
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T-tube trial
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5 to 30 minutes SBT
1 to 4 hours of rest on A/C, SIMV, or high PSV
Gradually, SBT times increase while rest periods
diminish
Patients rested at night
Alternate method is 1 SBT/day and then rest.
This can also be done on the ventilator in CPAP
mode with PSV or ATC.
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Initial Screening SBT
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Perform 2–3 minute SBT. If 2 out of 3 of the
criteria below are met, start formal wean
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VT
 RR
 MIP-a.k.a (NIF)
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>5 ml/kg
<30–35 beats/min
<20 cm H2O
Alternate: adequate cough, no vasopressors
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P/F ratio
PEEP
f/VT
>200
5
<105
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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SBT Termination
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Termination occurs if any of these criteria met
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Agitation, anxiety, diaphoresis, altered mental
state
 Respiratory rate > 30 or 35 beats/min
 SpO2 <90%
 20% change in HR or HR > 120 to 140 beats/min
 Systolic BP > 180 mm Hg or < 90 mm Hg
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Weaning With SIMV
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Faster weans claimed but contrary to
evidence
Ease of use is primary reason for use
Evidence that at 50% of full ventilatory
support, patient WOB approximates that on
CPAP
In addition, demand flow SIMV imposes
considerable WOB
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Modern ventilators minimize this effect.
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Weaning With SIMV (cont.)
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Support set below required level; patient
makes up the difference.
Once precipitating event corrects, support is
rapidly reduced.
Support is typically reduced in increments of
2 breaths per minute until spontaneous
ventilation is achieved
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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All of the following are TRUE about SIMV weaning
except:
A. Faster weans claims are supported by evidence
B. Ease of use is primary reason for use
C. Evidence that at 50% of full ventilatory support,
patient WOB approximates that on CPAP
D. Demand flow SIMV imposes considerable WOB
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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PSV Weaning
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Level is set to PSVmax 6 to 10 ml/kg.
On resolution of precipitating event
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PSV reduced increments 2 to 4 cm H2O, usually 1
to 2 times per day
Rested at nights
2 strategies for discontinuance of PSV:
• Patient tolerates PSV of 5 – 8 cm H2O with no distress
• Patient tolerates CPAP with no PSV without distress
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Monitoring During Weaning
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PaCO2 best index of adequacy of ventilation but
only tied to clinical data
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PaCO2 40 mm Hg with f/VT of 250 shows impending
ventilatory failure.
PaCO2 40 mm Hg with f/VT of 40 shows ability to
breathe spontaneously.
SpO2 monitor continuously
Cardiovascular status
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Extubation
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Weaning and extubation separate decisions
Extubation requires
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Ability to protect airway
• Gag
• Effective cough
 Airway patency
• Minimal edema
• Positive “cuff-leak” > 12% volume loss
 Adequate pulmonary hygiene
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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All of the following are required for extubation,
except:
A.
B.
C.
D.
Maximal edema
Patients ability to protect airway
Airway patency
Adequate pulmonary hygiene
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Postextubation Stridor
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Occurs in 2% to 16% of ICU patients
Can result in complete airway obstruction
Management includes
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Cool aerosol mist with oxygen via mask
Nebulized racemic epinephrine (0.5 ml 2.25%)
Nebulized 1 mg in 4 ml NS dexamethasone
HeliOx 60%/40%
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Failure of Extubation
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Up to 25% of patients require MV again
Half of patients with distress following MV
discontinuance develop marked hypercapnia
Myocardial ischemia associated with failed
weaning attempts
Failed weans may be undiagnosed NMD or
psychological dependence
Most common reason: inadequate ventilatory
capability which cannot meet ventilatory
demand
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Chronically Ventilator-Dependent
Patients
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Prolonged MV occurs in 3% to 7% of
ventilated patients, while <1% become
dependent
Definition: ventilator dependency remains
following 3 months of weaning attempts
Special long-term acute care facilities
specialize in weaning these patients
Once dependency established, goal is to
restore highest level of independence
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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Terminal Weaning
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Refers to weaning in the face of catastrophic
and irreversible illness
Weaning occurs despite likely result of patient
death
Decision made by patient and/or family in
consultation with physician.
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Must meet ethical and legal guidelines
May be due to advanced directives, current
patient decision, or very poor prognosis
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
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