The Extubation Series part 2: The Trials of Weaning Failures

What is weaning failure?

The failure to wean is often considered failing to pass a spontaneous breathing trial. It can also be considered the need for reintubation within 48-72 hours post extubation. Weaning failure is associated with increased morbidity and mortality.   Patients who require more than 7 days of mechanical ventilation after the first attempt of extubation are associated with a significant mortality rate.  

Reasons for failure

Weaning failure is multifactorial.  One of the main factors leading to weaning failure is often the unaligned forces between the respiratory muscles and the respiratory load. Other factors include age, comorbidities, conditions, and in hospital complications.  Also, elevated airway resistance, reduced respiratory system compliance, and impaired gas exchange increase the work of breathing, which contributes to weaning failure.

COPD appears as an independent risk factor for increased duration of weaning and weaning failure.  Vallverdu et al., reports that weaning failure occurred in 61% of the COPD population.  This could be due to the increased resistance of small airways.  Pleural effusions which presents up to 60% of the mechanically ventilated patients, severe left heart dysfunction, alkalosis which causes reduced tissue oxygen delivery with a leftward shift of the oxygen dissociation curve, positive fluid balance, pulmonary hypertension, and delirium also contribute to weaning failure.  

Risks of delayed weaning

• VAP
• VILI
• Increase in sedation
• Deconditioning
• Mental Depression effects
• Increased morbidity and mortality  

Risks of early extubation leading to reintubation within 48 hours. 

• Poor gas exchange

• Aspiration

• Inspiratory muscle fatigue

What can you do?

Re-assess the big picture.  The ABCDE approach could be helpful.   Assess Airway and lung dysfunction, Brain dysfunction, Cardiac dysfunction, Diaphragm dysfunction, and Endocrine dysfunction.  The advantage of this approach is that the clinician will do a systematic review in the most likely causes for failed weaning.  

Re-evaluation by the respiratory therapist of not only the physical assessment of the patient but also the mechanical ventilator can help to facilitate the prevention of the under use or over use of respiratory muscles reducing clinician caused weaning failure.

Weaning failure after extubation

Of course we optimized the patient before extubation.  We reversed the underlying cause for intubation, made sure oxygen requirements were within range, the patient was hemodynamically stable, passed the RSBI and had a positive cuff leak when tested.  We made sure the patient had an intact mental status with ability to protect the airway, minimal secretions with an effective cough, and no known airway obstruction.  However the patient still required reintubation. As we stated, weaning failure is also described when there is a need for reintubation within 48-72 hours following extubation.  Approximately 10-15% of patients intubated will require reintubation.