Difficulty weaning from mechanical ventilation

OVERVIEW

Difficulty weaning is an important ICU challenge

• 20% to 30% of patients are difficult to wean from invasive mechanical ventilation

The general approach to ventilator weaning and extubation is covered here:

• Weaning from mechanical ventilation
• Extubation assessment in ICU

DEFINITIONS

Classification of weaning by duration

• “Simple” — ventilator discontinued after the first assessment
• “Difficult” — ventilator discontinued from 2–7d after initial assessment
• “Prolonged” — ventilator discontinued in >7d after initial assessment

Weaning failure

• Weaning failure is defined as the failure to pass a spontaneous-breathing trial or the need for reintubation within 48 hours following extubation
• predicting success is important to reduce rates of reintubation
• reintubation is associated with a 7-11x increase in hospital mortality
• reintubation rates of 10 to 15% are typical for most well-run ICUs (a target of 0% is unrealistic and would lead to prolonged ventilation)

RISKS OF DELAYED WEANING

• infection e.g. VAP
• ventilator-associated lung injury (VALI)
• need for sedation and associated complications
• airway trauma from prolonged intubation
• deconditioning
• costs
• psychological effects

REASONS FOR VENTILATOR DEPENDENCY

Two types of factors:

• Disease-imposed factors
  — e.g. mechanical and/or gas exchange issues that continue to require PPV
• Clinician-imposed factors
  — e.g. clinician delay in recognizing the ability of a patient to have mechanical ventilation discontinued
  — e.g. inappropriate ventilator settings that overload (or underload) respiratory muscles, preventing recovery

APPROACH TO DIFFICULTY WEANING AND THE PROLONGED MECHANICAL VENTILATION PATIENT

Aggressively seek and treat reversible causes of ventilator dependence (e.g. “WHEANS NOT”) and optimise factors discussed in Weaning from mechanical ventilation.

• wheeze (especially COPD and asthma)
• heart disease and fluid overload
• electrolytes and metabolic derangement
• anxiety
• neuromuscular disease and wekaness
• sepsis
• nutrition insufficiency
• opiates and other sedatives
• thyroid disease

If patient failed SBT but passed ‘wean screen’:

• consider an extubation attempt to ensure that the irritant and loading effects (e.g. demand-valve insensitivity/unresponsiveness) of the artificial airway are not the cause of the SBT failure
• careful reevaluation of the need(s) for ongoing ventilatory support should be coupled with a daily reassessment for the appropriateness of repeat SBTs
• Ventilatory support between SBTs should be comfortable interactive support that does not necessarily have to be “weaned”
• do not perform SBTs more often than daily (i.e. q24h) to avoid fatigue

Multidisciplinary rehabilitation interventions aimed at optimizing all of the factors that contribute to ventilator dependence, such as:

• nutrition
• physiotherapy
• psychosocial support

A strategy of slow-paced gradual reduction in ventilation support is used by most experts for patients with prolonged mechanical ventilation

• wean patients to about 50% of their maximal support levels (ie, 50% of their initial inspiratory pressure settings) without using daily SBTs
• When that has been achieved, gradually lengthening daily SBTs should be re-instituted

Consider tracheostomy if likely to remain intubated for >7-14 days in patients:

• requiring high levels of sedation to tolerate translaryngeal tubes
• with marginal respiratory mechanics and reduced airway resistance from tracheostomy may reduce risk of muscle overload
• that may psychological benefit from ability to eat orally, to communicate by speaking, and enhanced mobility
• in whom enhanced mobility may assist physiotherapy

Unless there is evidence for clearly irreversible disease (eg, high spinal cord injury, amyotrophic lateral sclerosis), a patient requiring prolonged ventilatory support should not be considered permanently ventilator-dependent until 3 months of weaning attempts have been made.

References and Links

LITFL

• CCC — Weaning from mechanical ventilation (Hot Case)

Journal articles and textbooks

• El-Khatib MF, Bou-Khalil P. Clinical review: liberation from mechanical ventilation. Crit Care. 2008;12(4):221. PMC2575571.
• Macintyre NR. Evidence-based assessments in the ventilator discontinuation process. Respir Care. 2012 Oct;57(10):1611-8. PMID: 23013898. [free full text]
• MacIntyre NR, Epstein SK, Carson S. Management of patients requiring prolonged mechanical ventilation: report of a NAMDRC consensus conference. Chest. 128(6):3937-54. 2005. [pubmed] [free full text]
• MacIntyre N. Discontinuing mechanical ventilatory support. Chest. 2007 Sep;132(3):1049-56. PMID: 17873200. [free full text]
• O’Callaghan DJ, Wyncoll D. What size tube doctor? Bigger may be better – at least for weaning. Crit Care. 2013 Mar 27;17(2):422. PMID: 23535005. [free full text]