1. Chapter 47 Discontinuing Ventilatory Support

2. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 2 Objectives  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.

3. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 3 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.  Explain why some patients cannot be successfully weaned from ventilatory support.

4. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 4 Introduction  Ventilatory support sustains life but is not curative.  It has many complications and hazards.  It should be withdrawn expeditiously.  Balance desire for early extubation with its exposure to the risks of reintubation.

5. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 5 Methods of Discontinuing Ventilation  Three main methods  Spontaneous breathing trials (SBT)  SIMV  PSV  Novel modes with no data to support  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

6. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 6 Discontinuing Ventilatory Support  Success is tied to  Ventilatory work load versus capacity  Oxygenation status  Cardiovascular status  Psychological factors

7. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 7 Most Important Criteria 1. Reversal of disease state that necessitated ventilatory support 2. Oxygenation status adequate on <0.5 F IO 2 3. Medically and hemodynamically stable 4. Patient can breathe spontaneously  If the above are all true, then perform a formal evaluation for extubation.

8. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 8 66 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.

9. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 9 Preparing the Patient  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.

10. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 10 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.

11. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 11 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 A/C, SIMV, or significant levels of PSV

12. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 12 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 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.

13. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 13 Initial Screening SBT  Perform 2–3 minute SBT. If 2 out of 3 of the criteria below are met, start a formal wean  V T >5 ml/kg  RR <30–35 beats/min  MIP <  20 cm H 2 O  Alternate: adequate cough, no vasopressors  P/F ratio>200  PEEP  5  f/V T <105

14. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 14 SBT Termination  Termination occurs if any of these criteria met  Agitation, anxiety, diaphoresis, altered mental state  Respiratory rate > 30 or 35 beats/min  Sp O 2 <90%  20% change in HR or HR > 120 to 140 beats/min  Systolic BP > 180 mm Hg or 180 mm Hg or < 90 mm Hg

15. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 15 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.

16. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 16  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.)

17. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 17 PSV Weaning  Level is set to PSVmax 8 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 PSV of 5 – 8 cm H 2 O with no distress Patient tolerates CPAP with no PSV without distress Patient tolerates CPAP with no PSV without distress

18. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 18 Monitoring During Weaning  Pa CO 2 best index of adequacy of ventilation but only tied to clinical data  Pa CO 2 40 mm Hg with f/V T of 250 shows impending ventilatory failure.  Pa CO 2 40 mm Hg with f/V T of 40 shows ability to breathe spontaneously.  Sp O 2 monitor continuously  Cardiovascular status

19. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 19 Extubation  Weaning and extubation separate decisions  Extubation requires  Ability to protect airway Gag Gag Effective cough Effective cough  Airway patency Minimal edema Minimal edema Positive “cuff-leak” > 12% volume loss Positive “cuff-leak” > 12% volume loss  Adequate pulmonary hygiene

20. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 20 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%

21. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 21 Failure of Extubation  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

22. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 22 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.

23. Mosby items and derived items © 2009 by Mosby, Inc., an affiliate of Elsevier Inc. 23 Terminal Weaning  Refers to weaning in the face of catastrophic and irreversible illness  Weaning occurs despite the likely result of patient death  Decision is 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