WEANING FROM THE

VENTILATOR AND

EXTUBATION IN ICU

R黃心治

Curr Opin Crit Care. 2013 Feb;19(1):57-64.

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Purpose of review

� Both extubation delay and especially the need for reintubation are associated with poor outcomes.

� Review the recent literature on weaning and to clarify the role of certain interventions intending to help in this process.

Recent findings

� Cardiac dysfunction is probably one of the most common causes of weaning failure.

� Several studies have evaluated the ability of B-natriuretic peptides and echocardiographictools to predict weaning outcome due to cardiac origin, attempting to prevent its failure.

� Noninvasive ventilation may have a potential benefit in preventing respiratory failure after extubation of hypercapnic patients, although more studies are needed to define a target population.

1. Failure of planned extubation: 10–20%

2. patients who fail extubation have a high mortality: 25–50%.

� Multicentre trial

� Use of noninvasive ventilation (NIV) to treat post-extubation respiratory distress,

� Mortality was found higher in the group using NIV

� Due to the delay in reintubation: around 2 h in the standard group versus more than 12 h in the NIV group

� THE FIRST STEP: TO BREATHE ON ONE’S OWN WITHOUT THE VENTILATOR

� SECOND STEP: TO BREATHE WITHOUT THE ENDOTRACHEAL TUBE

� UPPER AIRWAY OBSTRUCTION AFTER EXTUBATION

� NONINVASIVE VENTILATION IN THE POSTEXTUBATION PERIOD

FIRST STEP

� Resolution of disease for which the patient was intubated

� Cardiovascular stability with no need or minimal vasopressors

� No continuous sedation

� Adequate oxygenation defined as paO2/FiO2 of at least 150 mmHg with PEEP up to 8cmH2O.

� Earilier study: paO2/FiO2 was above 200 mmHg with PEEP 5 cmH2O or less.

Three group of weaning

� Simple weaning: succeed the first weaning trial and extubated without difficulty

� Difficult weaning: fail the first weaning trial and require up to three trials or 7 days to achieve successful weaning

� Prolonged weaning: includes patients who require more than 7 days of weaning after the first weaning trial

About BNP

� High basal levels or an increase in B-type natriuretic peptides measured at the end of spontaneous breath-ing trial

� Related to weaning failure due to cardiac origin

� Predict postextubation respiratory distress/

extubation failure

About BNP

� A multi-centre study

� Diuretics guided by brain natriuretic peptide (BNP) measurements

� shortening duration of weaning suggesting that negative fluid balance using diuretics could hasten extubation.

� a large randomized controlled trial

� use of a conservative fluid strategy shortened the duration of mechanical ventilation in patients with acute lung injury

About Echocardiographic

indices

� Several studies suggest that patients who have diastolic dysfunction, as indicated by an increase in E/Ea ratio with normal systolic function, could be at a high risk of weaning failure

� Interestingly, a recent innovative study found that the loss of lung aeration measured using pulmonary echography may be more helpful in predicting postextubation respiratory distress than BNP measurement or echo-cardiography.

SECOND STEP

� spontaneous breathing trial (SBT) (T-tube)

� not predict well the consequences of the tube removal in terms of upper airway patency and

lower airway protection, removal of secretions and, ultimately, the ability to sustain spontaneous

breathing.

Factors associated with extubation

failure

age, primary reason for intubation, neurological dysfunction, cough

efficacy and amount of secretions

UPPER AIRWAY OBSTRUCTION

AFTER EXTUBATION

� Postextubation laryngeal oedema is due to the pres-sure exerted by the endotracheal tube and is favoured by the conditions of intubation and the duration of mechanical ventilation

� occurs in about 5–15% of the patients

� more often in women

� low patient’s height /tube diameter ratio

� The presence of detectable leak does not rule out the occurrence of upper airway obstruction

UPPER AIRWAY OBSTRUCTION

AFTER EXTUBATION

� Upper airway obstruction was found to be the cause of extubation failure in 7–20% of the cases

� reached 38% in a large multicentric study focusing on postextubation stridor

� methylprednisolone prior to extubationreduced the incidence of stridor and the rate of reintubation due to laryngeal oedema

UPPER AIRWAY OBSTRUCTION

AFTER EXTUBATION

� reintubation is purely linked to transient laryngeal oedema, it does not seem to be associated with a poor prognosis

NONINVASIVE VENTILATION(NIV)

IN THE POSTEXTUBATION

PERIOD� prophylactic NIV after extubation may be

useful to prevent acute respiratory failure in selected populations

� NIV employed for treating postextubationacute respiratory failure has no proven benefit and can even increase mortality by delaying reintubation

NONINVASIVE VENTILATION(NIV)

IN THE POSTEXTUBATION

PERIOD� NIV was found to be effective in preventing

postextubation respiratory failure in patients having hypercapnia at the end of the SBT

� NIV could reduce the risk of reintubation in postoperative patients after major elective abdominal surgery or lung resection, and could even reduce mortality in this latter group.

Conclusion

� The results of large randomized controlled trials give an overall incidence of extubationfailure relatively‘low’ (10–20%) for the general ICU population.

� However, the individual risk of reintubation can become unacceptably high in some at-risk populations with an extremely high mortality in case of extubation failure.