- Requirement for positive pressure ventilation
- Surgical procedures requiring muscular paralysis
- Surgical procedures requiring special positioning in which airway management during the case may be challenging, such as prone positioning
- To maintain a patent airway, such as in patients with trauma to the face or neck
- Airway protection from secretions, blood, or gastric contents
- Pulmonary toilet
- Maintenance of adequate oxygenation and/or ventilation
All contraindications to direct laryngoscopy are relative. In the controlled or elective settings the following contraindications should be considered:
- Anticipated difficult intubation due to multiple anatomic features or past history (see below)
- Severe limitation of mouth opening
- Unstable cervical spine or unstable atlanto-occipital joint (e.g., severe rheumatoid arthritis, trauma, Down syndrome)
- Major trauma, abnormal anatomy, or tumor of the mandible, maxilla, larynx, neck, mediastinum, or trachea
- History of extensive radiation therapy of the airway with a fixed larynx
- History of tracheotomy or tracheal stenosis
- Active airway bleeding
The operator should be familiar with use of equipment for mask ventilation
- Face mask and ventilation apparatus with oxygen supply
- Suction apparatus with Yankauer suction tip
- Short and long blade handles with batteries
- Selection of laryngoscope blades (e.g., Miller [straight] sizes 2 and 3; Macintosh [curved] sizes 3 and 4); metal or disposable
- Dental guard
- Foam head support/pillow or blankets
- Endotracheal tube, with or without stylet
- Stethoscope
- Clean 10-mL plastic syringe for cuff inflation
- Capnograph or colorimetric carbon dioxide detector
- Tape or adhesive device to secure the endotracheal tube
- Tape or ophthalmic ointment for eye protection
A focused pre-procedure physical exam of the airway will in many cases provide predictive information regarding the anatomy of the airway visualized on direct inspection. The exam should also include assessment and documentation of dentition, including caps; implants; crowns; and loose, missing, or decaying teeth. Identification and removal of any personal ornamentation, such as tongue-piercing ornaments, should occur before undertaking airway manipulation.
Pharynx
The oropharynx includes the structures of the upper airway from the soft palate to the level of the hyoid bone. The oropharynx opens anteriorly into the mouth, is bounded laterally by the two palatine arches and tonsils, and includes the posterior tongue. The laryngopharynx includes the epiglottis and larynx, which in turn consists of the vocal folds and vocal cords; the thyroid, cricoid, and arytenoid cartilages; and the intrinsic muscle of the larynx. The larynx begins where the upper airway divides to form the laryngeal inlet and the upper esophagus. The epiglottis is a cartilaginous flap attached to the posterior tongue, which forms a protective flap between the trachea and the upper esophagus.
Many major nerves contribute to pharyngeal and laryngeal function. Pharyngeal function is governed by cranial nerves IX, X (pharyngeal plexus), and XI (pharyngeal branch), which control elevation and shortening of the pharynx, alterations in palate position, the size of the pharyngeal lumen, and bolus transport of food in the esophagus. Motor innervation of the larynx is via the external and recurrent laryngeal branches of cranial nerve X. In addition, the facial nerve (cranial nerve VII) and cervical spinal nerves (C1-C3) contribute to motor function of the upper airway via actions of the mylohyoid muscle on the hyoid bone to pull the larynx up and the infrahyoid muscles, which pull the larynx down. Mandibular action during phonation is also controlled by the mandibular branch of the trigeminal nerve. Sensory innervation of the larynx is via the internal laryngeal branch of the vagus nerve (cranial nerve X) above the vocal folds and the recurrent laryngeal branch of the vagus nerve below the vocal folds.
Important internal landmarks involved in laryngoscopy and intubation include the epiglottis, the vallecula, the intrinsic cartilages of the larynx (arytenoids, thyroid, and cricoid), the true and false vocal cords, and the hyoid bone.
External Anatomic Features
Important external landmarks include the mental protuberance of the mandible, thyroid cartilage, hyoid bone, and cricoid cartilage. Anatomic features of direct relevance to laryngoscopy include extent of mouth opening, extent of jaw subluxation, ability to flex and extend the neck, neck circumference, tongue size protrusion, ability to visualize the uvula or soft palate with mouth opened and tongue protruded in the sitting posting without phonation (Mallampati score), mandibular size, mentohyoid distance, thyromental distance, and protuberant dentition. These measures are not sensitive or specific enough to predict whether the view will be limited on direct laryngoscopy. Limitations of movement, low Mallampati score, and short anatomic distances may warrant alternative strategies to endotracheal intubation.
The extent of visualization of the glottal opening under direct laryngoscopy is categorized by standardized grade (Cormack-Lehane scale) and is useful for objective description of the view for future airway management.
With a Macintosh blade, upward (axial) force on the hyoepiglottic ligament raises the epiglottis to reveal the glottal opening. With the straight Miller blade, the upward force under and against the epiglottis pulls the entire structure superiorly. External pressure on the cricoid cartilage (located just inferior to the thyroid cartilage and cricothyroid membrane) may in some cases improve the view of an anteriorly displaced larynx. A related intervention on the larynx, the BURP (backward, upward, rightward pressure) maneuver, has also been reported to improve visualization of the vocal cords in some patients.
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Figure 1
:
Basic equipment for direct laryngoscopy and intubation. On the left is a size 7.0 endotracheal tube with syringe attached to the inflation valve of the cuff. From top to bottom are a tongue depressor, two nasal airways, a tooth guard, oral airway, and two laryngoscopes. The upper laryngoscope handle is attached to a Macintosh (curved style) blade, and the lower laryngoscope handle is attached to a Miller (straight style) blade.
Figure 2
:
Laryngoscope handles and blades (two sizes of laryngoscope blade handles, from top to bottom: Miller 2, Miller 3, Macintosh 4, Macintosh 3 blades).
Figure 3
:
The mouth, oropharynx, posterior pharynx, and larynx, lateral view. From Drake L, Vogl AW, Mitchell AWM, Tibbitts RM, Richardson PE: Gray’s Atlas of Anatomy. Philadelphia, Churchill Livingstone/Elsevier, 2008, p 504.
Figure 4
:
The oropharynx and laryngopharynx, posterior views. From Drake L, Vogl AW, Mitchell AWM, Tibbitts RM, Richardson PE: Gray’s Atlas of Anatomy. Philadelphia, Churchill Livingstone/Elsevier, 2008, p 505.
Figure 5
:
Mallampati score. From right to left, Class I: fully visible uvula, tongue, soft palate; Class II: both hard and soft palate can be seen, along with the upper portion of the tonsils and uvula; Class III: soft and hard palate and the base of the uvula are seen; Class IV: only hard palate can be seen.
Figure 6
:
View of the laryngeal inlet as seen by direct laryngoscopy. From Drake L, Vogl AW, Mitchell AWM, Tibbitts RM, Richardson PE: Gray’s Atlas of Anatomy. Philadelphia, Churchill Livingstone/Elsevier, 2008, p 512.
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