Extubation is the removal of an endotracheal tube (ETT), which is the last step in liberating a patient from the mechanical ventilator. To discuss the actual procedure of extubation, one also needs to understand how to assess readiness for weaning, and management before and after extubation.
Other terms related to extubation are 'weaning' and 'liberation.' Weaning is a gradual transition from full invasive ventilatory support to spontaneous ventilation with minimal support. Liberation, on the other hand, means complete discontinuation of mechanical ventilation. The current trend is to use the term 'liberation' as opposed to 'weaning' in intensive care unit (ICU) ventilator management because the goal is to liberate patients from the ventilator as soon as possible rather than weaning over several days to weeks. Weaning is more common in long-term, acute care settings.
All patients who are on mechanical ventilation for any reason require liberation as soon as possible. Clinicians should take into account the cause of the patient's respiratory failure, prognosis, and expected course of the disease, as well as the absence of any reasons to stay on mechanical ventilation for a longer time.
Providers should start planning extubation as early as day one of intubation.
Any patient who successfully passes the spontaneous breathing trial (SBT) should be extubated unless a change in management plans.
Extubation is contraindicated in patients who are not candidates for initiating ventilator liberation strategy and in those who have failed the spontaneous breathing trial.
Generally, the following groups of patients are not candidates for liberation; however, individual cases vary.
All equipment needed for intubation should be readily available including 2 to 3 different sizes of ETTs, bag-mask with positive end expiratory-pressure (PEEP) valve, airway bougies, tube exchangers, traditional direct laryngoscope, video laryngoscope, flexible bronchoscope, drugs needed for induction, and suction catheters.
Ideally, an airway bag should be available in all ICUs. It should include supraglottic airways, video laryngoscopes, and cricothyrotomy kits.
Equipment for oxygenation post-extubation should be available, either nasal cannula, oxygen mask, venturi mask, high flow oxygen system, or continuous positive airway pressure (CPAP)/bilevel positive airway pressure (BPAP).
For extubation in the ICU, a respiratory therapist and bedside nurse should be present with the intensivist. In the operating room, a clinician skilled in airway management should be available. During extubation of a difficult airway in either location, an anesthesiologist should be available.
The preparation for extubation is a long process, which begins on the day of the patient's intubation and continues through the acute management of the primary problem which caused respiratory failure.
All ventilated ICU patients should be assessed daily for readiness to wean. Physicians should determine the benefits of early weaning versus morbidity and mortality associated with failed extubation. A weaning/liberation protocol should be in place to achieve this goal. It should have the following components:
During the preparation phase of extubation, practitioners should pay attention to:
1) Assessment of Readiness to Wean
The assessment takes into account reviewing all the aforementioned contraindications, including clinical improvement of the cause of respiratory failure, oxygenation and ventilation parameters, mental status, secretions, cardiovascular stability, and specific weaning parameters.
Several weaning parameters have undergone assessment and use in clinical studies, which are helpful when taken into account with the overall clinical picture, but they are not very sensitive or specific when considered individually.
2) Spontaneous Breathing Trial (SBT)
Initiation of the weaning trial commences at the time of the first spontaneous breathing trial. The duration of the SBT can be between 30 minutes to 2 hours. Several techniques can be used to conduct the SBT:
This approach is a well-established method. It involves attaching the end of the ETT to a short piece of tubing that acts as a reservoir, and it provides a connection to humidified fresh gas flow. This method is simple, well tested, and imposes a pulmonary workload that is comparable to that encountered after extubation; this is labor-intensive, and there is no monitoring of flow, pressure, or volume, and there are no alarms. A similar method called "flow by" can also be used when ventilating pressures, rate, and tidal volume is set to zero while the patient is still attached to the ventilator.
Pressure Support Ventilation
It is becoming a more popular technique for conducting the SBT. Despite theoretical concern that the use of pressure support ventilation may not mimic the true post-extubation workload, and difficulty predicting the level of support necessary to completely compensate for resistive load, this does not appear problematic in practice.
Automatic Tube Compensation
In this method, the ventilator compensates for the degree of resistance provided by the ETT. It is available on most of the modern ventilators.
Continuous Positive Airway Pressure (CPAP)
CPAP is said to increase functional residual capacity and maintain small airways. It is also beneficial for left ventricular dysfunction and has very minimal side effects. Despite the potential risk that a patient may pass the SBT but experience cardiac failure on extubation, most clinicians are comfortable with using low levels of CPAP with other techniques mentioned earlier.
Automated weaning aims to reduce the requirement for clinician input in a weaning process and improve outcomes. These automated systems use closed-loop controls to interpret clinical data in real-time, gradually reduce pressure support, and perform the SBT. At least three different clinical trials and one meta-analysis have shown that the weaning time can be reduced with a computer-driven automated weaning protocol.
3) Suitability for Extubation
If the patient has passed the SBT, he/she should undergo reassessment for the suitability of extubation. Many of these assessments may have been done at the start of the weaning trial or as a part of the daily assessment of the patient's readiness to wean.
The most important part of this assessment is assessing the ability of the patient to protect and maintain a patent airway.
The immediate post-extubation phase should be managed as carefully as the ventilated phase because the first 24 hours post-extubation are difficult and tenuous.
The most feared complications of extubation are the failure and immediate need for re-intubation and post-extubation stridor.
Extubation failure and need to be re-intubated within 72 hours, is noted in 12 to 14% of planned extubations. Risk factors for reintubation include a weak cough and frequent suctioning. Additional features that may predict reintubation include a rapid shallow breathing index over 58 breaths per minute per liter, a positive fluid balance during the 24 hours preceding extubation, and pneumonia as the reason for the initial intubation. Patients age 65 and older with severe chronic cardiac or respiratory disease appear to be at particularly high risk for extubation failure. Extubation failure carries a higher risk of ICU mortality..
In recent times, the use of non-invasive ventilation (NIV), mostly in the form of BPAP, has gained prominence. Current evidence favors prophylactic use of NIV immediately after extubation to prevent reintubation in only selected high-risk patients, like chronic obstructive pulmonary disease (COPD) and hypercapnia. Otherwise, NIV use for post-extubation respiratory failure has not shown to reduce reintubation rate or ICU mortality.
In addition to the use of NIV, high flow oxygen systems have gained popularity over the last few years in selected patients with hypoxemic respiratory failure, and studies have shown to reduce the re-intubation rate.
Weaning failure means that the patient is not able to tolerate the SBT, which is different from extubation failure where the patient can pass the spontaneous breathing trial leading to successful extubation which later fails. An international consensus conference proposed a classification of patients based on the difficulty and length of the weaning process. Accordingly, patients are categorized into three groups of simple, difficult, and prolonged weaning. The simple weaning group (30 to 58% of patients) are easy to wean and able to be extubated after the first SBT. The difficult weaning group (26 to 40% of patients) require up to 3 SBTs or up to 7 days to achieve successful weaning. Both of these groups have relatively lower mortality of 0 to 13%. The prolonged weaning group (6 to 30% of patients) require more than 3 SBTs or more than 7 days to achieve successful weaning. The third group has higher mortality of 13 to 22%. Any weaning failure should prompt physicians to comprehensively assess the patient for all potential problems which can cause weaning failure. Subsequent SBT should only take place when these presumed predisposing factors have been addressed.
Post-extubation stridor is uncommon and seen only in less than 10% of unselected critically ill patients and correlates with increased rates of reintubation, prolonged duration of mechanical ventilation, and longer length of ICU stay. Stridor is the result of laryngeal edema.
Several identified risk factors include:
The cuff-leak test is used to predict the occurrence of post-extubation stridor. It should be performed if any of the risks mentioned above are identified. Some providers do the cuff-leak test regularly, but there is insufficient evidence to suggest its regular use.
The two methods of performing the cuff-leak test are:
Management of Post-extubation Stridor
For patients who have no cuff-leak when tested before extubation, a short course of steroids (methylprednisolone 20 mg every 4 hours for four doses) may be helpful. This course has support from a few studies and meta-analyses.
For patients who develop post-extubation stridor, nebulized epinephrine, intravenous methylprednisolone, high flow O2, and CPAP is an option if clinically stable. Otherwise, prompt reintubation is warranted if significant airway obstruction is suspected. Following reintubation, a short course of steroids is the recommendation with re-assessment of cuff-leak. If a leak is present, extubation is generally safe. If cuff-leak is reduced or absent, extubation over an airway exchange catheter should be considered, usually in consultation with bedside anesthesiology or ENT consultant.
Intubation and extubation are both critical aspects of the hospital management course for any critically ill patient and require documentation in electronic medical records with dates and times along with the complications and difficulties encountered.
The process of ventilator liberation is long and involves many factors that require the attention of multiple members of the patient care team. Coordination between different providers is essential.
The SBT cannot be conducted without first conducting a spontaneous awakening trial. This trial requires very close coordination between the bedside nurse and bedside respiratory therapist. As a part of the daily morning assessments, "sedation vacation" should be included to the point that the patient is alert, awake, and able to follow commands. While the nurse is doing daily sedation vacations or spontaneous awakening trials, the respiratory therapist is assessing readiness to wean and initiating the spontaneous breathing trial.
Communication between all members of the team is crucial so that everyone knows their role and responsibilities. A team-centered, interprofessional approach to care during extubation that includes physicians, nursing, respiratory therapists, and pharmacists is the best approach to achieve a positive patient outcome, irrespective of the course of events during extubation.
Several studies have demonstrated a significant reduction in the ICU length of stay and ventilatory days if the team follows certain protocols and policies, although other studies have argued against using protocolized weaning. In practical terms, protocols save a significant amount of time in decision making and facilitate quicker liberation. All patients need to have a respiratory therapy driven liberation pathway in place which needs to be followed for all patients except when ordered by the physician-in-charge not to follow.
The American Thoracic Society and the American College of Chest Physicians Clinical Practice Guidelines for Liberation from Mechanical Ventilation in Critically Ill Adults
The summary of these clinical practice guidelines applicable to acutely hospitalized adults on mechanical ventilators for more than 24 hours is as follows:
Although the recommendations suggested by the American Thoracic Society and the American College of Chest Physicians, published in 2017, are conditional and not strong, they certainly will benefit healthcare professionals in decision making in the ICU setting. The chapter on the approach to extubation from mechanical ventilation by Alistair Nichol and colleagues in the book entitled "Evidence-Based Practice of Critical Care" is an important reference for healthcare professionals involved in the management of critically ill patients.
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