Ventilator Weaning

Weaning Considerations

  • Optimize Nutritional Status
    • To optimize respiratory muscle function
  • Optimize Treatment of Airway Obstruction
    • Use bronchodilators/steroids (as required)
  • Optimize Mental Status
    • Avoid sedatives
  • Optimize Neuromuscular Function
    • Avoid paralytics (if possible) or discontinue as soon as possible
  • Optimize Acid-Base Status
    • Correct metabolic acidosis to avoid excessive work of breathing post-extubation
    • Correct metabolic alkalosis to avoid decreased respiratory drive post-extubation
  • Optimize Secretion Management
    • Assure that secretions will be manageable post-extubation
  • Optimize Oxygen Demands
    • Treat fever, etc to decrease metabolic demand/oxygen consumption
  • Optimize Cardiac Status
    • Optimize treatment of underlying coronary artery disease/ischemia (if present)
  • Optimize Fluid Status
    • Extubation (removal of ETT + mechanical ventilation) results in an effective increase in right-sided venous return (which may exacerbate congetsive heart failure, if present)
    • Treat fluid overload (if present)

Diaphragmatic Disuse Atrophy

  • Studies have demonstrated that the combination of 18-69 hrs of complete diaphragmatic inactivity and mechanical ventilation results in marked atrophy of human diaphragmatic fibers, and that there is increased diaphragmatic proteolysis during inactivity
  • Compared with diaphragm-biopsy specimens from control subjects, specimens from case subjects showed decreased cross-sectional areas of slow-twitch and fast-twitch fibers, decreased glutathione concentration, and increased activity of proteolytic enzymes

Weaning Modalities

  • Studies Supporting the Performance of Daily Spontaneous Breathing Trials (SBT’s)
    • Daily spontaneous breathing trials decrease the duration of mechanical ventilation, decrease cost of intensive care, and decrease complication rates [MEDLINE]
    • Awakening and Breathing Controlled (ABC) Trial (2008): paired daily sedation vacation + spontaneous breathing trial decreases duration of mechanical ventilation, decreases ICU/hospital length of stay, and decreases mortality rate [MEDLINE]

WEANING WORK


Weaning Criteria

  • Spontaneous Breathing Trial for 30-120 min (on T-Piece or CPAP/Low-Level PS): best predictor of successful extubation

    • No difference between 2 hr trial on T-piece vs 2 hr trial on PS-7 -> 81% of pts were successfully extubated in both groups
    • Assess: breathing pattern, gas exchange, hemodynamics, etc.
    • Assess: ability to cough and clear secretions (note: alertness is not a prerequisite for successful extubation)
    • Reintubation rates can be a good measure of whether extubation practices are under/over aggressive
  • Index of Rapid Shallow Breathing <105 (on T-Piece or CPAP/Low-Level PS): although trial with 1 min of T-piece breathing has a 92% sensitivity for predicting weaning failure, it is inferior to spontaneous breathing trial in predicting successful weaning

    • Specificity is much lower (due to presence of non-pulmonary factors (CHF, glottic edema, etc) which can affect the success of weaning
  • Other Indices (CROP index, etc.): inferior to spontaneous breathing trial in predicting successful weaning

  • NIF (PImax): does not predict successful weaning
  • FVC: does not predict successful weaning
  • Early Application of NIPPV: when used for pts who failed a T-piece trial, NIPPV resulted in a shorter duration of weaning time, decreased ICU length of stay, and decreased incidence of nosocomial pneumonia

Weaning Protocols

  • Rationale
    • Use of weaning protocols with a team approach (nurse, MD, and RT) decreases the duration of mechanical ventilation and cost of intensive care better than individual physician-driven weaning without a protocol
    • This benefit occurs regardless of the mode of weaning employed
    • In studies, no particular weaning mode has been shown to be superior to any other
  • Clinical Efficacy
    • Effect of Daily Sedation Vacation and Spontaneous Breathing Trials (NEJM, 1996) [MEDLINE]: daily spontaneous breathing trials decrease the duration of mechanical ventilation, decrease the cost of intensive care, and decrease complication rates
    • Awakening and Breathing Controlled (ABC) Trial (Lancet, 2008) [MEDLINE]: paired daily sedation vacation and spontaneous breathing trial decreases duration of mechanical ventilation, decreases ICU/hospital length of stay, and decreases mortality rate
    • Study of Standardized Weaning Protocols from Mechanical Ventilation (Cochrane Database Syst Rev, 2014) [MEDLINE]: standardized weaning protocols decrease duration of mechanical ventilation, weaning duration, and ICU length of stay

Extubation Failure

Epidemiology

  • Extubation Failure Increases Mortality Rate: extubation failure is associated with 43% mortality rate, vs that of 12% in those who were successfully extubated [MEDLINE]

Etiology

Ventilatory Failure

  • Mechanism: high work of breathing

Inability to Protect Airway

  • Mechanism: decreased ability to maintain neuromuscular upper airway patency
  • Presence of gag reflex and alertness are not absolute requirements for extubation

Inability to Clear Secretions

  • Mechanism: impaired secretion clearance from upper airway
  • Required frequency of suctioning is surrogate for “excessive secretions”
  • Peak cough flows of >160 L/min predict successful extubation or decannulation in neuromuscular or spinal cord injured pts

Post-Extubation Upper Airway Obstruction

  • Risk Factors for Post-Extubation Airway Obstruction
    • Increased Duration of Ventilation
    • Female Gender
    • Trauma
    • Repeated or Traumatic Intubation
  • Mechanism: upper airway edema
  • Cuff Leak Test: to assess upper airway patency
    • In a study of medical patients, leak <110 mL (average of 3 values on 6 consecutive breaths) measured during AC ventilation within 24 hrs of extubation predicted post-extubation upper airway obstruction (however, sensitivity/specificity of this test has been challenged in many other studies)
    • False-Positive Leak Test: can occur in cases with late post-extubation upper airway edema
    • False-Negative Leak Test: can occur with large ETT with crusted secretions
  • Treatment
    • Many patients with post-extubation stridor can be treated with steroids, HELIOX (see xxxx, [[HELIOX]]), and/or racemic epinephrine nebulizer treatmenrs and may not necessarily need to be reintubated

References

General

  • A prospective study of indexes predicting the outcome of trials of weaning from mechanical ventilation. N Engl J Med 1991; 324:1445-1450
  • Patient and ventilator work of breathing and ventilatory muscle loads at different levels of pressure support ventilation. Chest 1991; 100:531-533
  • Reduction of duration and cost of mechanical ventilation in an intensive care unit by use of a ventilator management team. Crit Care Med 1991; 19:1278-1284
  • Comparison of three methods of gradual withdrawal from ventilatory support during weaning from mechanical ventilation. Am J Respir Crit Care Med 1994; 150:896-903
  • A comparison of four methods of weaning patients from mechanical ventilation. N Engl J Med 1995; 332:345-350
  • Effect on the duration of mechanical ventilation of identifying patients capable of breathing spontaneously. N Engl J Med 1996; 335:1864-1869 [MEDLINE]
  • Extubation outcome after spontaneous breathing trials with T-tube or pressure support ventilation. Am J Respir Crit Care Med 1997; 156:459- 465
  • A randomized, controlled trial of protocol-directed versus physician-directed weaning from mechanical ventilation. Crit Care Med 1997; 25:567-574
  • Effect of failed extubation on the outcome of mechanical ventilation. Chest. 1997;112(1):186 [MEDLINE]
  • Liberation from mechanical ventilation: a decade of progress. Chest 1998; 114:886-901
  • Noninvasive mechanical ventilation in the weaning of patients with respiratory failure due to chronic obstructive pulmonary disease: a randomized, controlled trial. Ann Intern Med 1998; 128:721-728
  • Introduction to systematic reviews of weaning from mechanical ventilation. Chest 2001; 120(suppl):396S-399S
  • Evidence-based guidelines for weaning and discontinuing ventilatory support: a collective task force facilitated by the American College of Chest Physicians; the American Association for Respiratory Care; and the American College of Critical Care Medicine. Chest 2001; 120(suppl):375S-396S
  • Trials of corticosteroids to prevent post-extubation airway complications. Chest 2001; 120(suppl):464S-468S
  • Trials of miscellaneous interventions to wean from mechanical ventilation. Chest 2001; 120(suppl):438S-444S
  • Trials comparing alternative weaning modes and discontinuation assessments. Chest 2001; 120(suppl):425S-437S
  • Systematic reviews of the evidence base for ventilator weaning. Chest 2001; 120(suppl):396S-482S
  • Efficacy and safety of a paired sedation and ventilator weaning protocol for mechanically ventilated patients in intensive care (Awakening and Breathing Controlled trial): a randomised controlled trial. Lancet. 2008 Jan 12;371(9607):126-34 [MEDLINE]

Diaphragmatic Disuse Atrophy

  • Altered diaphragm contractile properties with controlled mechanical ventilation. J Appl Physiol 2002; 92:2585-2595.
  • Rapid disuse atrophy of diaphragm fibers in mechanically ventilated humans. N Engl J Med 2008; 358(13):1327-1335
  • Estimation of inspiratory muscle pressure in critically ill patients. Intensive Care Med 2010; 36(4):648-655
  • Ventilator-induced diaphragmatic dysfunction. Curr Opin Crit Care 2010; 16(1):19-25

Weaning

  • Effect on the duration of mechanical ventilation of identifying patients capable of breathing spontaneously. N Engl J Med 1996; 335:1864-1869 [MEDLINE]
  • Efficacy and safety of a paired sedation and ventilator weaning protocol for mechanically ventilated patients in intensive care (Awakening and Breathing Controlled trial): a randomised controlled trial. Lancet. 2008 Jan 12;371(9607):126-34 [MEDLINE]
  • Weaning patients from the ventilator. N Engl J Med. 2012 Dec 6;367(23):2233-9. doi: 10.1056/NEJMra1203367 [MEDLINE]
  • Protocolized versus non-protocolized weaning for reducing the duration of mechanical ventilation in critically ill adult patients. Cochrane Database Syst Rev. 2014 Nov 6;11:CD006904. doi: 10.1002/14651858.CD006904.pub3 [MEDLINE]