INTRODUCTION
Tracheal intubation over a flexible endoscope is an invaluable technique in airway management, particularly in patients for whom standard laryngoscopy and orotracheal intubation are anticipated to be difficult or impossible. Endoscopic devices may be used for both diagnostic evaluation of the upper airway and tracheal intubation.
INDICATIONS AND CONTRAINDICATIONS
Indications for flexible endoscopic intubation (FEI) in emergency airway management generally are identified during the LEMON evaluation for the difficult airway (see Chapter 2) and include the following:
• Patients who fail the 3-3-2 rule (restricted mouth opening, small mandible, or high larynx) or exhibiting a grade 4 Mallampati score.
• Inadequate oral access, recognized during first assessment of the 3-3-2 rule, is a strong predictor of difficult or impossible orotracheal intubation via conventional means. Examples include wired mandible, trismus, temporomandibular joint disease, tongue and oral floor space-occupying lesions (i.e., angioedema, hematoma, oral infection).
• Distorted upper airway anatomy often precludes visualization by direct or video laryngoscopy and prevents appropriate seating of blind extraglottic airway devices. Examples include pharyngeal abscess, neck or posterior oropharyngeal trauma or hematoma, and base of tongue or laryngeal tumor.
• The patient with laryngeal trauma or suspected tracheal disruption. In these cases, intubation with continuous visualization without neuromuscular blockade is recommended. The endoscope meets this indication.
• The patient for whom strict cervical spine immobility is required, particularly if the airway is predicted to be difficult. Rigid cervical collar and halo brace immobilization are the most common examples. However, severe cervicothoracic kyphosis also poses difficult positioning for most alternative airway interventions.
• The patient with morbid obesity, especially when coupled with additional markers of difficult orotracheal intubation.
• Failed intubation in the “can’t intubate, can oxygenate” scenario, when time permits and immediate patient deterioration or evolving airway disease is not anticipated.
Contraindications to endoscopic intubation are mostly relative and may include the following:
• Excessive blood and secretions in the upper airway have the potential to obscure the indirect view of FEI. Some experienced bronchoscopists transilluminate their way into the trachea, then verify tracheal position via the endoscope, but this is highly operator dependent and requires advanced flexible endoscopic skill.
• Endoscopy in the context of high-grade laryngeal or tracheal obstruction, as with foreign bodies or malignancy, may precipitate total airway obstruction. In patients with high-grade supraglottic airway obstruction and impending complete airway closure, the delays and risks of precipitating laryngospasm or complete airway obstruction may argue against endoscopic intubation in favor of cricothyrotomy.
• Inadequate oxygenation by bag and mask (can’t intubate, can’t oxygenate scenario) does not permit endoscopic intubation because of time constraints of this critical situation.
TECHNIQUE
Overview
Once FEI is recognized as the intended airway technique, the best route must be selected. Outside of disease-related issues, the nasotracheal approach is considered technically easier because the nose maintains the endotracheal tube (ETT) and endoscope in the midline and the nasopharynx provides a panoramic and unobstructed view of the periglottic structures. The time required for topical anesthesia of the nose and use of smaller ETTs are significant drawbacks. The oral route typically accommodates a larger standard sized ETT but requires more technical dexterity. Oral intubating airways are a great asset to maintain midline position and control the tongue. Although either technique can be used with minimal topical anesthesia during an immediate crisis, the oral route is better tolerated when time does not allow for thorough topicalization.
Patient Preparation
Although the emergency difficult or failed airway situation does not usually permit lengthy preparation, a methodical approach aims to provide psychological and pharmacologic patient preparation in a 10- to 20-minute window. Awake FEI generally includes the following patient preparation steps:
• Patient psychological preparation: Good communication with explanation of the procedure improves cooperation with less need for procedural sedation.
• Antisialogogue administration: Glycopyrrolate 0.005 mg per kg IM or IV, at least 10 to 20 minutes in advance of the procedure, reduces secretions to enhance visualization and improve efficacy of topically applied local anesthesia.
• Anesthetize the upper airway: Good anesthesia facilitates endoscopy and manipulation of the upper airway. FEI may be tolerated with limited anesthesia when patient condition mandates immediate intervention (see Chapter 23).
• Procedural sedation: Hypnosis should be used if needed with careful titration to sustain airway patency and spontaneous ventilation. Cooperative patients and those with critical airway compromise may not require or tolerate any sedation for FEI.
Scope Selection
Instrument selection for emergency airway endoscopy is important. Affordable and durable scopes are available from a variety of manufacturers. Flexible endoscopes have several clinical uses including:
• Tracheal intubation, both nasal and oral
• Diagnostic nasopharyngoscopy and laryngoscopy
• Oropharyngeal foreign body identification
• FIGURE 16-1. The Ambu aScope is a single-use, flexible intubating scope.
The scope should be of sufficient caliber and stiffness to guide passage of an ETT through the curves of the airway without kinking and resist being pulled from the trachea. Standard full length (60 cm) adult bronchoscopes are generally recommended for emergency department and critical care use given their availability and breadth of use. These scopes also have the benefit of a working channel for local anesthetic injection, suctioning, and pulmonary lavage. Insufflation of oxygen through the working channel has been recommended to maintain oxygenation and disperse secretions but is now relatively contraindicated following cases of gastric insufflation and perforation. High-risk patients with marginal oxygen saturations may benefit, however, from supplemental oxygenation and may receive 5 L per minute flow through the device. The low flow rate minimizes the risk of injury while supplying oxygen and mitigating the risk of hypoxia.
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