Mechanical ventilation weaning

Defined as the process of abruptly or gradually withdrawing ventilatory support.

Mechanical ventilation can be discontinued abruptly in approximately 75% of mechanically ventilated patients provided that the underlying cause of respiratory insufficiency has either improved or been resolved.

Most patients need to be liberated, rather than gradually withdrawn from mechanical ventilation.

Premature or failed attempts at extubation, typically requires re-intubation and is associated with increased rates of ventilator associated pneumonia and mortality.

A delay in extubation increases patient’s risk of being oversedated and developing delirium or ventilator associated events.

Managing patients with the invasive ventilation involves daily screenings to identify those who are ready to undergo a spontaneous breathing trial and to ascertain those ready for separation from ventilator support.

To extubate a patient, the patient needs to be awake, able to cough and protect their airway.

Extubation failure risk factors include: weak cough, heavy secretions, and depressed level of consciousness.

The risk of reason to patient in the ICU is approximately 10%, but it may exceed 20% among patients who have a higher risk of excavation failure.

If it is not possible to wean a patient to extubation, and the patient cannot protect his/her airway, it is best to perform tracheotomy

It may be difficult to wean a patient if ongoing inflammatory processes persist in the lungs: consolidation, fibrosis, and diffusion defects.

There most effective method of weaning to discontinuation is spontaneous breathing trials (SBT), and they should not be performed more than once daily.

A spontaneous breathing trial is a standard test performed to assess the patient for excavation readiness by establishing a condition that minimizes the physiologic condition after extubation.

In a spontaneous breathing trial patients have to show clinical improvement in the initial reason for ventilation and satisfy several safety criteria, and they would be provided with minimal or no ventilatory assistance and their ability to tolerate and maintain spontaneous breathing is assessed.

Spontaneous breathing trials can be performed with a T-piece after the patient is disconnected from the ventilator or with the use of a low level pressure support ventilation.

Among patients who had a high risk of excavation failure, spontaneous breathing trials performed with pressure support and ventilation did not result in significantly more ventilating three days at 28 days then spontaneous breathing trials performed with a T-piece (Thille AW).

Using the spontaneous breathing trial 55-75% of patients have successful extubation within 24 hours of their first sucessful spontaneous breathing trial and are deemed easy to wean, and patients who require up to one additional week of ventilators support are difficult to wean and those needing more than one additional week require prolonged weaning.

Among patients requiring mechanical ventilation in whom a spontaneous breathing trial had failed, early extubation to noninvasive ventilation did not short in time to liberation from any ventilation.

Ventilation duration is influenced by weaning methods.

Extubation as soon as possible is pref2242ed.

Traditionally elective extubations occur during the day, when hospital staffing is optimal.

Overnight extubation is associated with worse outcomes for critically ill patients (Gershongorn HB).

Approximately 20% of patients in ICUs on mechanical ventilation undergogo overnight extubation, which is associated with higher rates of ICU and hospital mortality than patients undergoing extubation during the daytime.

A reintubation rate of 10% is acceptable goal in weaning.

Approximately 10-20% of patients require re-intubation despite having passed a spontaneous breathing trial, and no simple way to identify those at prohibitively high risk of re-intubation.

Failure to achieve success with extubation, required re-intubation can be catastrophic and is associated with an absolute risk of death up to 50%.

Immediate extubation expedites weaning and reduces the duration of mechanical ventilation as compared with a more gradual discontinuation of ventilatory support.

The ability to breathe spontaneously can be tested by performing a trial with either T-tube or pressure support of 7 cmH2O lasting either 30 or 120 min.

When such trials are unsuccessful, gradual withdrawal from mechanical ventilation can be attempted while factors responsible for the ventilatory dependence are corrected.

Randomized studies found that, in difficult-to-wean patients, synchronized intermittent mandatory ventilation (SIMV) is the most effective method of weaning.

Among patients on mechanical ventilation, a spontaneous breathing trial consisting of 30 minutes of pressure support ventilation, compared with two hours of T-peace ventilation, lead to significantly higher rates of successful extubation supporting the use of shorter, less demanding ventilation strategy for spontaneous breathing trials.

Weaning from mechanical ventilation requires discontinuation of mechanical ventilation and removal of any artificial airway.

In mechanically ventilated patients at high risk of extubation failure, the use of high flow nasal oxygen with non-invasive ventilation immediately after excavation significantly decreases the risk of re-intubation compared with high flow nasal oxygen alone.

A direct method of assessing readiness to maintain spontaneous breathing is the initiation of a trial of unassisted breathing.

If a patient is able to sustain spontaneous breathing, a judgement must be made regarding whether the artificial airway can be removed based on the patient’s mental status, airway protective mechanisms, ability to cough and character of secretions present.

In a randomized study of tracheotomized patients requiring mechanical ventilation, unassisted breathing via a tracheostomy, compared to pressure support resulted in a shorter median time to weaning (jubran A et al).

In the above study the mode of weaning did not effect survival at 6 and12months.

Oxygenation impairment after extubation is frequent and frequently be corrected by conventional oxygen therapy delivery by nasal prongs, or Venturi masks, with fraction of inspired oxygen and flow targeted to the degree of hypoxia.