Extubation and Tube Exchange

Marilyn Menezes

Matteo Parotto

INTRODUCTION

Extubation is a common procedure in critical care medicine. Despite being a vital component of airway management, it appears to receive significantly less attention than endotracheal intubation. However, complications at extubation represent a significant proportion of major airway-related adverse events (28%), as evidenced by published audits such as The Fourth National Audit Project,¹ and closed claims analyses.²^,³ Frequently, reviews of adverse events in this setting highlight how complications could have been prevented with anticipation of potential clinical challenges and adequate preparation.

It is fundamental to note that intentional extubation is always an elective process,⁴ and guidelines from several scientific societies⁵^,⁶ focus on the role of a comprehensive, planned, and safe approach to extubation to mitigate risks for the patient. The recognition of high-risk extubations, creation of an extubation strategy, and the execution of a safe extubation are all important elements with which critical care physicians should be familiar.

The same meticulous planning and communication involved with endotracheal intubation should also be practiced with removal of the endotracheal tube (ETT). Like intubation, recognition of the potentially high-risk extubation is instrumental in the planning process. Despite these important factors, the body of literature on extubation is significantly less comprehensive than intubation. In addition, while not the primary focus of this chapter, accidental extubation is fraught with high risk of adverse patient outcomes and is considered an area of preventable patient harm.⁷ Similarly, adequate planning and assessment are needed for ETT exchange, which represent another essential component of airway management in the ICU.⁸ This chapter will explore approaches to extubation and ETT exchange, and will discuss the utilization of airway exchange catheters (AECs) in this context and as aids in high-risk extubations.

EXTUBATION FAILURE

Failure of extubation, resulting in the need for reintubation or the requirement for unplanned noninvasive positive pressure ventilation (NIPPV), can be challenging to manage and can result in major morbidity and mortality.¹ It is usually due to one of two issues, or both: (1) upper airway obstruction or (2) respiratory failure. Upper airway obstruction, including laryngospasm, is associated with immediate respiratory distress and hypoxia. On the other hand, respiratory failure, or a gradual decline in the ability of the patient to breathe on their own without support, is a much more common issue in the ICU. In this chapter, we will not cover the topic of weaning from mechanical ventilation, a fundamental area of the specialty with which critical care providers will be familiar.

PLANNING FOR EXTUBATION

CASE 1

A 52-year-old female was admitted to the ICU 4 days ago after elective mitral valve replacement. Previous medical history included a right neck dissection and neck radiation for cancer. Initial airway management in the operating room was reported to be difficult, requiring three attempts, with the successful attempt being performed using a hyperangulated video laryngoscope and a styletted size 7.5 ETT. The postoperative course was complicated by cardiac tamponade on day 1, multiple transfusions, hemodynamic instability, and fluid overload. She has subsequently progressed well and is now awake, alert, and oriented, with stable
hemodynamics without pharmacologic support (an echocardiogram shows normal biventricular function, well-seated mitral prosthesis, and no other valvular abnormalities). On the ventilator, she is tolerating pressure support ventilation at an FiO₂ 30%, PEEP 5 cm H₂O, and pressure support 5 cm H₂O, with normal arterial blood gas and rapid shallow breathing index (the ratio of respiratory rate to tidal volume) of 50. Minimal secretions on suctioning the ETT, and strong spontaneous cough. The multidisciplinary team reviewed the patient and thinks she is now ready for extubation.

How would you proceed?

Extubation Criteria

There are defined general principles to follow when considering a patient for extubation. Unlike intubation, intentional extubation is always an elective procedure, and therefore should only be pursued if and when the physiologic, pharmacologic, and contextual conditions are optimized.⁴^,⁵^,⁶ In a busy critical care environment, there are always the pressures of time and bedspace, in addition to a wide spectrum of patient pathologies and clinical presentations. Considering these factors, risks associated with extubation could be assessed, managed, and communicated within a multidisciplinary approach. Using a written “checklist approach” has potential to allow bedside nurses and other health care workers to assess a patient’s readiness for extubation prior to physician attendance for the final decision making. Some institutions have implemented evidence-based checklists and have reduced the incidence of extubation failure.⁹ Table 31.1 highlights the minimal recommendations to consider when evaluating a patient for extubation. Most safety problems are multipronged and multifactorial, and when considering the risk of extubation failure in a critical care setting, factors such as patient population, monitoring, staff ratio, and education, as well as awareness about the problem must be emphasized. Having a consistent, proactive, and predictable approach should be the overall goal of the airway provider and care system.

TABLE 31.1 Extubation Criteria

Reversal of underlying process	No further need for mechanical ventilation identified No expected need in immediate hospital course
Level of consciousness	Alert patient Sedation medications discontinued
Ability to oxygenate	Spontaneous breathing Tidal volume >5-7 mL/kg SpO₂ >92 with FIO₂ 30
Ability to ventilate	Positive end-expiratory pressure <8 mm Hg Peak voluntary negative pressure >20 cm H₂O
Predictors of impending airway loss	Protecting own airway Reversal of neuromuscular blockade (train of four >90) Peak expiratory flow >60 L/min (cough assessment) Difficult intubation? Difficult bag-mask ventilation?
Pulmonary secretions	Oropharyngeal secretions minimal Risk of aspiration minimal

Risk Stratification

Once the decision to extubate has been made, focus shifts to the identification of which airways may be at increased risk. The Difficult Airway Society recommends risk-stratifying patients into low risk versus high risk of extubation failure (see Tables 31.2 and 31.3).⁶ Patients who fall within the “high-risk” population include those for whom:

TABLE 31.2 Difficult Airway Society Extubation Risk Stratification

Low risk	Fasted? Uncomplicated airway No general risk factors
High risk	Ability to oxygenate uncertain Reintubation potentially difficult General risk factors (Table 31.3)
From Difficult Airway Society Extubation Guidelines Group; Popat M, Mitchell V, Dravid R, Patel A, Swampillai C, Higgs A. Difficult Airway Society Guidelines for the management of tracheal extubation. Anaesthesia. 2012;67(3):318-340.

TABLE 31.3 General Risk Factors for Extubation Failure

Patient-related risk factors

Laryngospasm
Obesity
Obstructive sleep apnea
Chronic obstructive pulmonary disease (COPD)
Neuromuscular diseases
Head and neck radiation history
Parkinson disease
Rheumatoid arthritis
Paradoxical vocal fold motion
Female sex
Advanced age (>70 y)
Anatomically difficult airway. It is important to note that an easy intubation accomplished under controlled elective conditions does not necessarily equate to optimal conditions should an emergent reintubation be required
Physiologic difficulty. Physiologic abnormalities such as hypoxemia, hypercapnia, acidosis, and cardiovascular instability at the time of emergent reintubation may render patients less tolerant of delays and persistent or prolonged intubation attempts

Situational/procedural/contextual risk factors

Head and neck surgical procedures.¹^,³ In the NAP4 registry, adverse events at the time of extubation in patients with head and neck pathologies accounted for 34.2% of all events during emergence or recovery. Examples of head and neck surgical procedures at high risk of extubation failure and complications:
- Upper airway endoscopy
- Thyroidectomy
- Debulking of large oral cancers
- Oral and neck reconstructions requiring surgical flaps
- Carotid endarterectomy
- Anterior cervical spine repairs especially with a bleeding diathesis
- Maxillomandibular fixation
- Forced cervical flexion by a “guardian stitch” between the chin and sternum in tracheal resection surgeries
Neurologic injuries affecting vocal cord motion, dynamic airway collapse, or airway compression above, below, or at the level of the larynx
Restricted airway access, e.g., Halo fixation, cervical collar, jaws wired shut
Prolonged duration of mechanical ventilation (>4 d)
Airway edema due to positioning, airway trauma during initial airway management or fluid overload

Airway risk factors exist and/or
- The ability to oxygenate may be uncertain and/or
- Reintubation may be difficult/impossible
General risk factors exist

Narrowing the focus to the high-risk group allows identifying patients who require additional planning. Despite this, care must be taken with tracheal extubation even with patients identified as low risk.⁴ Some of the general risk factors that are highlighted in the high-risk group for extubation are well described in the literature.¹⁰^,¹¹^,¹²^,¹³^,¹⁴^,¹⁵

Special attention should be placed on the airway risk factors section because this can be difficult to identify prior to extubation. The presence of laryngeal edema prior to intubation should be communicated and documented, as well as edema resulting from a traumatic intubation should be suspected. Interventions since intubation, such as extensive fluid resuscitation, may have resulted in further airway edema and could predispose the airway to extubation failure because of obstruction. Anticipated course of disease also plays a role; patients with burns or infection to the face or neck may be more difficult to reintubate than initially recorded.

Additional Testing

If a patient is identified as having a high-risk airway, the critical care team must first decide whether extubation should even be attempted. Importantly, it should be noted that in some circumstances, it may be unsafe to proceed to extubation even if this is postponed to a later time, and an elective tracheostomy should be pursued. A few examples of such situations include surgeries involving extensive intraoral flaps or resulting in significant swelling (either currently present or predictable in the next few hours as a result of surgical interventions) or bleeding in or around the airway.⁴

If extubation remains part of the plan after taking into consideration the patient’s high-risk features, intubation history, and availability of difficult airway tools and specialty support, then additional testing may be needed in order to determine whether conditions are safe enough to extubate. A thorough airway evaluation is necessary as the current airway manager may not have been present during the initial intubation.

Tools to assess the upper airway for possibility of obstruction after extubation are listed in the sections that follow.

Cuff Leak Test

A cuff leak test can be performed in a spontaneously ventilating patient after the oropharynx is suctioned, with the cuff slowly deflated.¹⁵ The ETT is occluded and the patient inhales and exhales slowly. It can also be performed during controlled ventilation. The presence of a cuff leak is used along with other criteria to assess appropriateness for extubation. The presence of a cuff leak on its own does not act as a predictor of a successful extubation, with its original use being a predictor for postextubation stridor in children intubated for croup. The use of the terms “positive” and “negative” cuff leak may create confusion, and stating whether a cuff leak is present or not may provide clearer communication. The lack, however, of a cuff leak, should provide an alert that there might be laryngeal edema and the potential for postextubation stridor, and therefore, a risk for airway obstruction.

A suggested strategy includes assessment of risk factors for postintubation laryngeal edema (traumatic intubation, intubation longer than 6 days, large-sized ETT, female sex, and reintubation after unplanned extubation). The cuff leak test is typically reserved for high-risk patients, and if no leak is present, the recommendations are to delay extubation for the administration of steroids and then to proceed with extubation at least 4 to 6 hours later.¹⁶ A repeat cuff leak test is not required after a course of steroids.¹⁶

Table 31.4 provides details on the cuff leak test.

TABLE 31.4 Cuff Leak Test

*What is the cuff leak test?*	The cuff leak test is used to predict the population that may be at increased risk for postextubation stridor. It is a measurement of the cuff leak volume, which is equal to the difference between the inspiratory tidal volume and the average expiratory tidal volume while the cuff around the endotracheal tube is deflated.
*How is it performed?*	Variable methodologies are described in the literature. The most common is to set the assist control mode with the fixed tidal volumes of 10-12 mL/kg. The inspiratory tidal volume with the cuff inflated is then measured. The cuff is then deflated, and a brief period of coughing usually proceeds. Following the resolution of coughing, four to six breaths are given, and the average value of the three lowest expiratory tidal volumes is computed. The difference between the inspiratory tidal volume with the cuff inflated and the average expiratory tidal volume with the cuff deflated is used to calculate the cuff leak volume.
*Practical application*	The cuff leak volume of <130 mL is generally accepted as indicating a cuff leak is absent (positive test) and places the patient at risk for postextubation stridor and extubation failure. The absence of a cuff leak should therefore alert the airway manager to the potential for a postextubation complication, and a plan should be devised accordingly.