Direct Laryngoscopy

James Snyder

Steve Orebaugh

CONCEPT

When face mask ventilation is inadequate to provide necessary airway support, or when long-term positive pressure ventilation is required, an endotracheal tube (ETT) should be placed. In most circumstances, direct laryngoscopy (DL) is the simplest and most readily applied means of placing the ETT. Indications for DL and endotracheal intubation are summarized below (Table 5-1).

Table 5-1 Indications for Tracheal Intubation

Indication	Example
Airway patency	Unconscious patient
Airway protection	Patient at risk for aspiration
Oxygenation failure	Pneumonia with hypoxemia
Ventilation failure	Severe asthma with respiratory failure
Management of secretions	Copious sputum from pneumonitis
Provision of hyperventilation	Increased intracranial pressure
Drug administration	Inability to secure intravenous access
Muscle paralysis for surgery	Intra-abdominal and intrathoracic surgery

When difficulty is unlikely and when conditions are optimized prior to the attempt at intubation (for instance, during elective cases in the operating room), the standard sniffing position is an efficient starting position for experienced practitioners to intubate unassisted.

EVIDENCE

On the other hand, various factors weigh toward optimizing conditions to ensure “first pass success.” Preparation for successful intubation on the first attempt is indicated by urgency, anatomic predictors of difficulty (see Chapter 9), cardiopulmonary instability, a likely full stomach, possible gastric insufflation by first responders in codes, overly large body habitus, and (especially) limited operator experience.

KEYS TO “FIRST PASS SUCCESS”

The case for first pass success has been well summarized by Levitan.¹ In emergent or unplanned situations requiring intubation, maneuvers to cope with unpredicted difficulty are planned into the approach rather than added sequentially as might occur in a conventional approach. Once familiar with the maneuvers that maximize first pass success, the operator may choose a simpler approach. Keys to first pass success include (1) manipulation of the axial anatomy (ie, head, neck, torso positioning) to achieve optimal rather than adequate glottal exposure, (2) retention of fine motor control, through the use of assistants or physical supports for optimal position of the upper torso and head/neck, (3) effective navigation to find and control the epiglottis, and (4) early use of bimanual laryngoscopy. Each key requires practice until it is automated. Integrated performance to complete intubation within 30 seconds, as recommended for unstable patients, requires more practice.

PREPARATION FOR LARYNGOSCOPY

Careful preparation for intubation requires a mental checklist. Of many helpful pneumonic devices, the authors prefer “STOP MAID,” to remember the following (Fig. 5-1):

S:	Suction
T:	Tools for intubation (laryngoscope blades, handle) and for difficulty with ventilation and/or intubation (laryngeal mask airway [LMA], intubating LMA, lightwand, optical stylet, etc.)
O:	Oxygen source for preoxygenation and ongoing ventilation
P:	Positioning—shoulder roll and head elevation as high as it does not interfere with blade insertion; PLAN B: Effective airway management requires careful planning so that back up plans can be executed when the primary technique (plan A) fails.²
M:	Monitors, including EKG, pulse oxymetry, blood pressure, end-tidal CO₂, or esophageal detectors
A:	Assistant, ambu bag with face mask, airway devices (tubes, syringe, stylets)
I:	Intravenous access
D:	Drugs including hypnotic, muscle relaxant and desired adjuncts

FIGURE 5-1 Intubation equipment.

Effective airway management requires careful planning so that back up plans can be executed when the primary technique fails

POSITIONING

Positioning can facilitate both blade insertion and glottic exposure. The sniffing position, most clearly defined by Horton et al³ is atlanto-occipital extension, and elevation of the head to achieve “lower neck flexion [of] 35°,” which in normal volunteers required head support of 31 to 71 mm. Further head elevation may facilitate DL and may be essential for intubation in difficult cases.²,³,⁴,⁵,⁶,⁷ Clinical and geometric observations show flexing the thoracic spine to elevate the head may facilitate DL more than flexion of the cervical spine (Figs. 5-2, 5-3, 5-4).

Axial Positioning During Blade Insertion

Experienced operators typically can expose the glottis with no or minimal elevation of the patient’s head and torso from the sniffing position and usually require no assistance to improve glottic view even when complex manipulations are necessary. For less experienced operators and when patient instability demands first pass success, head lift by an assistant from the initiation of DL requires less left hand force, improves sensitivity and control, and frees the right hand for external manipulation. As described by Murphy: “… the sniffing position is a starting position only … make it dynamic. Use your right hand behind the head to lift it, flex and extend the head on the neck, rotate it left and right as needed to bring the target into view. Once the best view is obtained, have an assistant hold the head in this position.”⁷

Opening the Mouth

The mouth is opened widely by supporting the index, long, and/or ring fingers of the right hand against the upper teeth, and crossing the thumb down against the lower teeth (Fig. 5-5). Atlanto-occipital extension, provided by placing the right hand against the occiput of the unconscious patient, can help to open the mouth as well. Mouth opening and/or blade insertion may be compromised by retrognathism, prominent upper teeth, obesity, large breasts, short thick neck, or neck flexion. Elevation of the upper thorax as by a shoulder roll, or creation of a “ramp,” can facilitate mouth opening and blade insertion by improving submandibular compliance and increasing physical separation of the chin from the chest (Figs. 5-2, 5-3 and 5-4 and Fig. 5-6). Simply rotating the blade for insertion, then turning it into the correct plane, may be helpful, with care that rotation not result in torque pressure against the teeth. A short-handled laryngoscope may also be useful in these settings.

FIGURE 5-2 When a normal heavy-set individual opens his mouth the submandibular and anterior cervical spaces impinge (despite, in this example, head elevation of 5 cm). As a result, submandibular compliance is decreased (compare A and B). C. Impingement is made worse when head elevation is achieved by cervical flexion, especially in patients with a short neck or who are heavy-set. D. Flexion of the thoracic spine enables a higher head elevation relative to the chest while decreasing impingement. (Table level is the same in all photos.)

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