Robert J. Vissers
INITIAL APPROACH
Control of the airway is the single most important task for emergency resuscitation.
The initial approach to airway management is simultaneous assessment and management of the adequacy of airway patency (the A of the ABCs), and oxygenation and ventilation (the B of the ABCs).
PATHOPHYSIOLOLGY
The upper anatomic airway includes the oral and nasal cavities down to the larynx. The lower airway includes the trachea, bronchi, and lungs.
Potentially difficult intubations can be predicted by the following:
1. External features suggestive of difficulty, such as a beard or obesity, short neck, receding chin, or tracheotomy scars.
2. Inability to open the mouth three fingerbreadths, or a thyromental distance less than three finger-breadths.
3. A relatively large tongue for the oral cavity as estimated by the inability to visualize more than the base of the uvula in a cooperative patient opening the mouth in a sniffing position (Fig. 3-1).
4. Evidence of upper airway obstruction.
5. Lack of neck mobility. This should be assessed only in patients without potential C-spine injury.
FIG. 3-1. Classification of tongue size relative to the size of the oral cavity as described by Mallampati and colleagues. Class I: Faucial pillars, soft palate, and uvula can be visualized. Class II: Faucial pillars and soft palate can be visualized, but the uvula is masked by the base of the tongue. Class III: Only the base of the uvula can be visualized. Class IV: None of the three structures can be visualized.
EMERGENCY CARE AND DISPOSITION
Assess patient’s color and respiratory rate; respiratory or cardiac arrest may be an indication for immediate intubation.
Open the airway with head tilt-chin lift maneuver (use jaw thrust if C-spine injury is suspected). If needed, bag the patient with the bag-valve-mask device that includes an O2 reservoir. A good seal depends on proper mask size. This technique may require an oral or nasal airway or two rescuers (one to seal the mask with 2 hands and the other to bag the patient).
Provide continuous monitoring of vital signs, oxygen saturation, and end-tidal CO2 (if possible).
Determine the need for invasive airway management techniques. Do not wait for arterial blood gas analyses if the initial assessment indicates the need for invasive airway management. If the patient does not require immediate airway or ventilation control, administer oxygen by facemask to ensure an O2 saturation of 95%. Do not remove oxygen to draw an arterial blood gas analysis unless deemed safe from the initial assessment.
Preoxygenate all patients prior to intubation regardless of saturation. Assess airway difficulty before initiation of advanced airway techniques (see later in the chapter).
OROTRACHEAL INTUBATION
The most common means used to ensure a patent airway, prevent aspiration, and provide oxygenation and ventilation is orotracheal intubation.
Rapid sequence intubation (RSI) should be used unless the patient’s condition makes it unnecessary (ie, cardiac arrest) or it is contraindicated because of an anticipated difficult airway.
EMERGENCY DEPARTMENT CARE AND DISPOSITION
Prepare equipment, personnel, and drugs before attempting intubation. Assess airway difficulty and anticipate required airway rescue.
Ensure adequate ventilation and oxygenation and monitoring while preparing equipment. Preoxygenate with a nonrebreather oxygen mask or with a bag-valve-mask if the patient is not ventilating adequately.
Select blade type and size (usually a no. 3 or 4 curved blade or a no. 2 or 3 straight blade); test the blade light. Select the tube size (usually 7.5–5.8 mm in women, 8.0–0.8 mm in men) and test the balloon cuff. The use of a flexible stylet is recommended.
Patient positioning is critical to successful intubation. Position the patient with the head extended and neck flexed, possibly with a rolled towel under the occiput to align the oropharyngolaryngeal axes. If C-spine injury is suspected, maintain the head and neck in a neutral position with an assistant performing inline stabilization.
Once the vocal cords are visualized, gently pass the tube between the cords. Remove the laryngoscope, check for tube placement by ventilating and listening for bilateral breath sounds and absence of epigastric sounds. Inflate the cuff.
If the cords are not visualized, manipulate the thyroid cartilage using backward, upward, and rightward pressure (the “burp” maneuver) to help bring the cords into view. If unsuccessful, reoxygenation may need to be performed with bag-valve-mask device. Consider changing the blade, the tube size, or the position of the patient before further attempts. Consider using an intubating stylet (bougie). Three unsuccessful attempts define a failed airway, and other rescue techniques must be considered.
Confirm placement objectively with an end-tidal CO2 detector, capnography, or in cardiac arrest, with an esophageal detection device. Check tube length; the usual distance (marked on the tube) from corner of the mouth to 2 cm above the carina is 23 cm in men and 21 cm in women.
Secure the tube and verify placement with a portable radiograph.
Immediate complications include unrecognized esophageal intubation or mainstem bronchus intubation. Failure to confirm the position immediately can result in hypoxia and neurologic injury. Endobronchial intubation is usually on the right side and is corrected by withdrawing the tube 2 cm and listening for equal breath sounds.
RAPID-SEQUENCE INTUBATION INDUCTION
Rapid-sequence intubation is the simultaneous administration of an induction and a neuromuscular blocking agent to facilitate orotracheal intubation. This technique couples sedation with muscular paralysis. Anticipated difficulty in mask ventilation or intubation is a relative contraindication to rapid-sequence intubation.
If difficulty is anticipated, consider other methods of airway management such as videolaryngoscopy, awake intubation, cricothyrotomy, or an alternative airway device.
The steps for rapid-sequence intubation are listed in Table 3-1.
Induction agents are described in Table 3-2.
Paralytic agents are described in Table 3-3.
TABLE 3-1 Rapid-Sequence Intubation
TABLE 3-2 Induction Agents
TABLE 3-3 Neuromuscular Paralytic Agents
ALTERNATIVE AIRWAY DEVICES
A number of rescue devices are available for management of the difficult airway.
Intubating stylets (or gum elastic bougies) are semirigid stylets with a coude tip, which can be placed by feel, during laryngoscopy, into the trachea, and then guided over the intubating stylet into the trachea. This device is useful for anterior cords that cannot be directly visualized.
The laryngeal mask airway (LMA) is an airway device that is placed blindly into the supraglottic space. A distal ringed balloon is inflated to seal the glottis above the larynx and allow for ventilation. Aspiration and air leaks may occur. The intubating LMA allows for the placement of a cuffed endotra-cheal tube through the device.
Videolaryngoscopy is an excellent option for airway rescue or as a primary intubation technique. These devices can be advantageous in patients with restricted oral opening or cervical spine mobility.
Crichothyrotomy is performed when intubation, ventilation, and airway rescue have failed. Insert a number-4 cuffed tracheostomy tube (or the largest tube that will fit). Alternatively, use a small cuffed endotracheal tube (No. 6 or the largest tube that will fit). Inflate the cuff. Crichothyrotomy is contraindicated in children younger than 10 to 12 years in whom trans-tracheal jet ventilation is the preferred subglottic technique.
Formal tracheostomy is not recommended as an emergency surgical airway technique due to increased technical difficulty and time required
NONINVASIVE POSITIVE PRESSURE VENTILATION
Noninvasive positive pressure ventilation (NPPV) provides positive pressure airway support using preset volume/pressure of inspiratory air through a face or nasal mask. Noninvasive positive pressure ventilation has been used as an alternative to endotracheal intubation in patients with ventilatory failure due to chronic obstructive pulmonary disease (COPD), and cardiogenic pulmonary edema. Patients need to be cooperative and without cardiac ischemia, hypotension, or dysrhythmia. Table 3-4 lists the advantages and disadvantages of noninvasive positive pressure ventilation.
Continuous positive airway pressure (CPAP) provides constant positive pressure throughout the respiratory cycle. Continuous positive airway pressures are usually between 5 and 15 cm H2O and are adjusted to the patients’ response to therapy.
Bilevel positive airway pressure (BiPAP) uses different levels of pressure during inspiration and expiration. Initial settings of 8 to 10 cm H2O during inspiration and 3 to 4 cm H2O during expiration are reasonable and can be titrated up based on clinical response.
TABLE 3-4 Advantages and Adverse Effects of Noninvasive Positive Pressure Ventilation
Alternative drugs for rapid-sequence induction are listed in Chapter 30 of Emergency Medicine: A Comprehensive Study Guide, 7th ed. Airway management alternatives to the methods described earlier include blind nasotracheal intubation, digital intubation, transillumination, extraglottic devices, flexible and rigid fiberoptics, retrograde tracheal intubation, and transla-ryngeal ventilation, These techniques are described in Chapters 28, 30, and 31 of Emergency Medicine: A Comprehensive Study Guide, 7th ed.
For further reading in Emergency Medicine: A Comprehensive Study Guide, 7th ed., see Chapter 28, “Noninvasive Airway Management,” by A. Michael Roman; Chapter 30, “Tracheal Intubation and Mechanical Ventilation,” by Robert J. Vissers and Daniel F. Danzl; and Chapter 31, “Surgical Airway Management,” by Michael D. Smith.