Transcript Slide 1

Chapter 47
Discontinuing Ventilatory Support
Objectives
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List factors associated with ventilator dependence.
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Explain how to evaluate a patient before attempting
ventilator discontinuation or weaning.
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List acceptable values for specific weaning indices used to
predict a patient’s readiness for discontinuation of
ventilatory support.
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Describe factors that should be optimized before an
attempt is made at ventilator discontinuation or weaning.
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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.
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Contrast the advantages and disadvantages associated
with various weaning methods and techniques.
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Describe how to assess a patient for extubation.
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Explain why some patients cannot be successfully
weaned from ventilatory support.
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Introduction
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Ventilatory support sustains life but is not curative.
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It has many complications and hazards.
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It should be withdrawn expeditiously.
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Balance desire for early extubation with its exposure to the
risks of reintubation.
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Methods of Discontinuing
Ventilation
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Three main methods
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Spontaneous breathing trials (SBT)
SIMV
PSV
Novel modes with no data to support
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MMV = mandatory minute volume, VSV = volume support
ventilation, ATC = automatic tube compensation, PAV =
proportional assist ventilation
**Systematic review: 1 SBT per day has shown best results
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Discontinuing Ventilatory Support
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Success is tied to
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Ventilatory work load versus capacity
Oxygenation status
Cardiovascular status
Psychological factors
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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.
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66 Measurements:
8 Most Consistently Predictive
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Spontaneous rate
6 to 30 beats/min
Spontaneous VT
>5 ml/kg
f/VT (RSBI) – most predictive
<105
Minute ventilation
<10 L/min
MIP
<20 to 30 mm Hg
P0.1
<6 cm H2O
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P0.1/MIP
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CROP (CDyn, f, O2, PImax) >13
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<0.3
* No single index has high predictive power, so it is important to
consider the total picture.
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Preparing the Patient
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Patient should be rested and stable.
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Maximize bronchodilator and antiinflammatory
medications as well as bronchial hygiene.
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Communicate well with patient so as to relieve/minimize
anxiety.
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Optimize nutrition, acid/base status, fluid balance, and
oxygenation.
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Minimize sedation.
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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.
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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
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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 are 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.
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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 a formal wean
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VT
RR
MIP
>5 ml/kg
<30–35 beats/min
<20 cm H2O
Alternate: adequate cough, no vasopressors
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P/F ratio >200
PEEP
5
f/VT
<105
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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
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Weaning With SIMV
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Faster weans claimed but contrary to evidence
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Ease of use is primary reason for use
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Evidence that at 50% of full ventilatory support, patient
WOB approximates that on CPAP
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In addition, demand flow SIMV imposes considerable
WOB.
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Modern ventilators minimize this effect.
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Weaning With SIMV (cont.)
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Support set below required level; patient makes up the
difference.
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Once precipitating event corrects, support is rapidly
reduced.
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Support is typically reduced in increments of 2 breaths per
minute until spontaneous ventilation is achieved.
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PSV Weaning
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Level is set to PSVmax 8 to 10 ml/kg.
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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
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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.
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SpO2 monitor continuously
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Cardiovascular status
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Extubation
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Weaning and extubation separate decisions
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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
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Postextubation Stridor
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Occurs in 2% to 16% of ICU patients
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Can result in complete airway obstruction
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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%
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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 is 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
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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.
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Definition: ventilator dependency remains following 3
months of weaning attempts.
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Special long-term acute care facilities specialize in
weaning these patients.
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Once dependency established, goal is to restore highest
level of independence.
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Terminal Weaning
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Refers to weaning in the face of catastrophic and irreversible
illness
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Weaning occurs despite the likely result of patient death
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Decision is 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
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