Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. Chapter 47 Discontinuing Ventilatory Support

Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.2 Learning Objectives  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.3 Learning Objectives (cont.)  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.4 Introduction  Ventilatory support sustains life but is not curative  Has many complications and hazards  Should be withdrawn expeditiously  All patients should be evaluated on a daily basis for their ability to wean from ventilatory support  Balance desire for early extubation with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. Ventilatory Capacity 5

Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.6 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 C.It should be withdrawn expeditiously.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.7 Methods of Discontinuing Ventilation  Three main methods 1. Spontaneous breathing trials (SBT) 2. SIMV 3. PSV  Novel modes with no data to support  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. Probability of Successful Weaning 8

Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.9 Discontinuing Ventilatory Support  In general, patients being considered for removal from ventilatory support fall into one of four categories: 1. removal is quick and routine, normally the vast majority of patients 2. need a more systematic approach, about 15 to 20% of ventilated patients 3. require days to weeks to wean, usually less than 5% of patients 4. 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.10 Global Criteria for Discontinuing Ventilatory Support (cont.)  Success is tied to  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.11 Most Important Criteria 1.Reversal of disease state that necessitated ventilatory support 2.Oxygenation status adequate on <0.5 FIO 2 3.Medically and hemodynamically stable 4.Patient can breathe spontaneously  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 Measurements: 8 Most Consistently Predictive  Spontaneous rate 6 to 30 beats/min  Spontaneous V T >5 ml/kg  f/V T (RSBI) – most predictive<105  Minute ventilation<10 L/min  MIP<  20 to 30 mm Hg  P 0.1 <6 cm H 2 O  P 0.1 /MIP<0.3  CROP (C Dyn, f, O 2, PI max )>13 * 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.13 Which of the following predictive value is consistent with a patient weaning successfully? A.Spontaneous rate40 beats/min B.Spontaneous VT4 mL/kg C.f/VT (RSBI)85 D.MIP–18 mm Hg

Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.14 Preparing the Patient  Patient should be rested and stable  Maximize bronchodilator and anti- inflammatory 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.15 Rapid Ventilator Discontinuance  Patients that are likely to wean rapidly  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  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.16 Progressive Weaning of Ventilatory Support  Patients likely to need longer weaning period  Ventilated longer then 72 hours  Marginal: oxygen, ventilatory, cardiovascular, or medical status  Most common methods of weaning:  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.17 Progressive Weaning: SBT  T-tube trial  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.18 Initial Screening SBT  Perform 2–3 minute SBT. If 2 out of 3 of the criteria below are met, start formal wean  V T >5 ml/kg  RR <30–35 beats/min  MIP-a.k.a (NIF)<  20 cm H 2 O  Alternate: adequate cough, no vasopressors  P/F ratio>200  PEEP  5  f/V T <105

Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.19 SBT Termination  Termination occurs if any of these criteria met  Agitation, anxiety, diaphoresis, altered mental state  Respiratory rate > 30 or 35 beats/min  SpO 2 <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.20 Weaning With SIMV  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  Modern ventilators minimize this effect.

Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.21  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 Weaning With SIMV (cont.)

Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.22 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.23 PSV Weaning  Level is set to PSVmax 6 to 10 ml/kg.  On resolution of precipitating event  PSV reduced increments 2 to 4 cm H 2 O, usually 1 to 2 times per day  Rested at nights  2 strategies for discontinuance of PSV: Patient tolerates PSV of 5 – 8 cm H 2 O 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.24 Monitoring During Weaning  PaCO 2 best index of adequacy of ventilation but only tied to clinical data  PaCO 2 40 mm Hg with f/V T of 250 shows impending ventilatory failure.  PaCO 2 40 mm Hg with f/V T of 40 shows ability to breathe spontaneously.  SpO 2 monitor continuously  Cardiovascular status

Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.25 Extubation  Weaning and extubation separate decisions  Extubation requires  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.26 All of the following are required for extubation, except: A.Maximal edema B.Patients ability to protect airway C.Airway patency D.Adequate pulmonary hygiene

Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.27 Postextubation Stridor  Occurs in 2% to 16% of ICU patients  Can result in complete airway obstruction  Management includes  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.28 Failure of Extubation  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.29 Chronically Ventilator-Dependent Patients  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.30 Terminal Weaning  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.  Must meet ethical and legal guidelines  May be due to advanced directives, current patient decision, or very poor prognosis