Michael F. Murphy
Richard D Zane
The Clinical Challenge
Anatomically, the term upper airway refers to that portion of the anatomy that extends from the lips and nares to the first tracheal ring. Thus, the first portion of the upper airway is redundant: a nasal pathway and an oral pathway. However, at the level of the oropharynx, the two pathways merge and redundancy is lost. The most common, life-threatening causes of acute upper airway distortion and obstruction occur in the region of this common channel and are typically laryngeal. In addition, disorders of the base of the tongue and the pharynx can cause obstruction (Box 30-1). This chapter deals with problems that distort or obstruct the upper airway. Foreign bodies in the upper airway are dealt with in Chapter 36.
Approach to the Airway
The signs of upper airway distortion and obstruction may be occult or subtle. Deadly deterioration may occur suddenly and unexpectedly. Seemingly innocuous interventions, such as small doses of sedative hypnotic agents to alleviate anxiety or the use of topical local anesthetic agents, may precipitate sudden and total airway obstruction. Rescue devices may not be successful and may even be contraindicated in some circumstances. The goal in these patients is to proceed rapidly in a sensible, controlled manner to manage the airway before complete airway obstruction occurs.
When should an Intervention be Performed?
Chapter 1 deals with the important question of when to intubate. If airway obstruction is severe, progressive, or potentially imminent, then immediate action (often cricothyrotomy) is required without further consideration of moving the patient to another venue (e.g., the operating room, another hospital). Failing such an indication for an immediate cricothyrotomy, the question becomes more difficult: What is the expected clinical course?
BOX 30-1 Causes of Upper Airway Obstruction
A. Infectious
a. Viral and bacterial laryngotracheobronchitis (e.g., croup)
b. Parapharyngeal and retropharyngeal abscesses
c. Lingual tonsillitis (a lingual tonsil is a rare but real congenital anomaly and a well-recognized cause of failed intubation)
d. Infections, hematomas, or abscesses of the tongue or floor of the mouth (e.g., Ludwig's angina)
e. Epiglottitis (also known as supraglottitis)
B. Neoplastic
a. Laryngeal carcinomas
b. Hypopharyngeal and lingual (tongue) carcinomas
C. Physical and chemical agents
a. Foreign bodies
b. Thermal injuries (heat and cold)
c. Caustic injuries (acids and alkalis)
d. Inhaled toxins
D. Allergic/idiopathic: including angiotensin-converting enzyme inhibitor–induced angioedema
E. Traumatic: blunt and penetrating neck and upper airway trauma
Penetrating wounds to the neck and airway are notoriously unpredictable (see Chapter 27). Some advocate securing the airway regardless of warning signs, whereas others advocate expectant observation. There are substantial problems with the second strategy. The first is that the patient often remains relatively asymptomatic until they suddenly and unexpectedly totally obstruct, resulting in an airway (and patient) that cannot be rescued. The second is that unless fiberoptic scopes are used, the observer is only able to see the anterior portion of the airway and not the posterior and inferior parts where the obstruction will likely occur. In other words, when not using fiberoptics, one can see only “the tip of the iceberg.”
Thus, for any condition where the obstruction may be progressive, silent, and unobservable externally (e.g., angioedema, vascular injuries in the neck, epiglottitis), acting earlier to secure the airway rather than later is the most prudent course.
There are three cardinal signs of acute upper airway obstruction:
· “Hot potato” voice: the muffled voice one often hears in patients with mononucleosis and very large tonsils
· Difficulty in swallowing secretions, either because of pain or obstruction; the patient is typically sitting up, leaning forward, and spitting or drooling secretions
· Stridor
The first two signs do not necessarily suggest that total upper airway obstruction is imminent; however, stridor does. The patient presenting with stridor has already lost at least 50% of the airway caliber and requires immediate intervention. In the case of children younger than 8 to 10 years with croup, medical therapy may suffice. In older children and adults, the presence of stridor typically mandates a surgical airway or, at the least, a double setup. This technique uses an awake attempt (e.g., using ketamine sedation) from above with the capability, prepared in advance, to move to a surgical airway if needed. Positive pressure by bag and mask or other noninvasive ventilatory devices has been described as one method to help open an obstructed airway and may buy some time; however, this technique should not be relied on as more than a temporizing maneuver.
What Options Exist if the Airway Deteriorates or Obstructs?
The answer to this question needs to incorporate the following when considering alternatives to cricothyrotomy:
· Will rescue bag-mask ventilation (BMV) be possible? Will a mask seal be possible to achieve, or is the lower face disrupted? Has a penetrating neck wound entered the airway rendering it incompetent to high airway pressures? As discussed in Chapter 5, the bag and mask devices most commonly used in resuscitation settings are capable of generating 50 to 100 cm of water pressure in the upper airway, provided that they do not have positive-pressure relief valves and that an adequate mask seal can be obtained. Pediatric and neonatal devices often incorporate positive-pressure relief valves that easily can be defeated if needed. This degree of positive pressure is often sufficient to overcome the moderate degree of upper airway obstruction caused by redundant tissue (e.g., the obese), edematous tissue (e.g., angioedema, croup, epiglottitis), or laryngospasm. Lesions that are hard and fixed, such as hematomas, abscesses, cancers, and foreign bodies, produce an obstruction that cannot be reliably overcome with bag-mask ventilation, even with high upper airway pressures.
· Where is the airway problem? If the lesion is at the level of the face or oral and nasal pharynx and orotracheal intubation is judged to be impossible (for whatever reason), but there is oral access, then supralaryngeal rescue devices such as laryngeal mask airways (LMAs), King LTs, and Combitubes may be considered and ought to be immediately at hand to attempt rescue of the airway.
What are the Advantages and Risks of an Awake Look?
In most instances, unless the patient is in crisis or deteriorating rapidly, an awake direct laryngoscopy is possible. If the tip of the epiglottis is visible without paralysis (grade 3 view) and is in the midline, orotracheal intubation employing rapid sequence intubation (RSI) is probably possible, especially when using a bougie, unless the working diagnosis is a primary laryngeal disorder. However, it has been shown that this maneuver is not failsafe in that the airway rarely may be more difficult to visualize in some patients after induction and paralysis. If a primary laryngeal disorder is suspected, complete visualization of the larynx is mandatory (e.g., fiber-optic visualization). Attempting direct laryngoscopy in an awake, uncooperative patient with a laryngeal disorder is potentially dangerous and ill advised.
Is RSI Reasonable?
If one is confident that orotracheal intubation is possible and highly confident that the patient can be successfully ventilated using BMV or some other device, then it is reasonable to proceed with RSI (e.g., early in the course of a penetrating neck injury). A double setup with readiness for a surgical airway is still advised. Even then, in patients with occult upper airway obstruction, some would say that RSI is not considered advisable, and a controlled, urgent surgical or fiber-optic airway is appropriate, especially if patient cooperation and time are limited. One's degree of confidence in being able to secure an airway is multifactorial and depends highly on experience, the clinical practice environment and armamentarium of airway devices. These airway problems underscore the importance of securing alternative airway devices, such as the fiberoptic bronchoscope or video laryngoscope, in addition to a conventional laryngoscope and bougie. Practicing alone off-hours with only a direct laryngoscope is obviously very different than having access to these advanced devices and consultative backup.
Tips and Pearls
· Be reluctant to transfer patients with suspected acute upper airway obstruction and unsecured airways, even short distances. Always secure the airways of patients with significant acute penetrating neck wounds or blunt laryngeal trauma before transport.
· Angioedema involving the upper airway is a dangerous and unpredictable condition. The external examination of the lips, tongue, and pharynx tell you little of what is going on at the level of the airway. Intervention earlier rather than later is the most prudent course of action. Often, flexible fiberoptic nasopharyngoscopy will provide the additional information that is needed.
· The patient with acute upper airway obstruction, a disrupted airway, or a distorted airway who can protect and maintain the airway and can maintain oxygenation and ventilation should always be considered a difficult airway, and the difficult airway algorithm should be used.
· The patient with upper airway obstruction, a disrupted airway, or a distorted airway who cannot maintain oxygenation or ventilation should be considered a failed airway, and the failed airway algorithm should be used.
· Blind techniques (e.g., blind nasotracheal intubation) of airway management in these situations are contraindicated and should not be attempted.
· Bag-mask ventilation alone cannot be relied on to rescue the airway, particularly if the obstruction is caused by a fixed lesion.
· RSI is usually contraindicated unless the awake look proves otherwise or the RSI is done early after onset of the disease or injury.
· Contemplate a cricothyrotomy early and prepare for it before the awake look.
· Titrate ketamine rather than sedative/hypnotic drugs (e.g., midazolam, propofol, thiopental, etomidate) to get an adequate awake look. Topical anesthesia of the airway will not be particularly successful and will not be adequate unless accompanied by sedation.
· If the awake look indicates that orotracheal intubation is not possible or is equivocal, proceed directly to a cricothyrotomy or fiberoptic intubation.
· If the patient suddenly crashes and the lesion is above the level of the larynx, do two-handed BMV and try an extraglottic airway device while setting up for a cricothyrotomy. If the lesion is at the larynx, do two-handed bag-mask ventilation and proceed immediately to a cricothyrotomy.
· Heliox may buy time. Helium is less dense than nitrogen, reducing turbulent flow and resistance through tight orifices, as is the case with some causes of upper airway obstruction. The commercial preparations are usually 80% helium and 20% oxygen, and provided lung function is adequate, this mix will produce acceptable oxygen saturations. Other concentrations may be prepared.
· Crush injuries to the larynx and laryngeal fractures are best managed with tracheostomy rather than cricothyrotomy. Gently performed RSI or fiberoptic intubation may be advisable if circumstances permit.
· In the event of a tracheal separation (e.g., clothesline-type injury to the neck) when one is performing a surgical airway, grasp the distal stump with an instrument before opening the pretracheal fascia.
· The patient with a bulky pharyngeal or laryngeal tumor may be intubated using a fiberoptic technique. Although this technique typically requires more time to perform, it is preferable to surgically invading an airway that may hemorrhage or be subject to subsequent operative resection.
Evidence
1. Is there much in the way of evidence relating to the emergency management of patients with acute upper airway obstruction? The evidence with respect to the emergency management of the patient with an airway that is potentially or actually disrupted, distorted, or obstructed is essentially anecdotal. Most of the information dealing with the topic comes either from the surgical or anesthesia literature: primarily small series or case reports. There are no controlled studies comparing intervention with expectant observation. In the surgical literature, cricothyrotomy, as might be expected, is typically overrecommended. In the anesthesia literature, intubation under deep inhalation anesthesia and spontaneous ventilation has been the standard and, as might be expected, cricothyrotomy is underrecommended. Despite the lack of scientifically sound studies, the following additional reading is recommended (1,2,3,4,5).
2. How commonly does angiotensin-converting enzyme inhibitor (ACEI)–induced angioedema require intubation? The clinical course of ACEI-induced angioedema is extremely unpredictable, and life-threatening presentations requiring airway interventions are reported in up to 20% of these patients (6,7,8,9,10). According to the literature, 0% to 22.2% of patients with angioedema will require intubation (11). It is extremely difficult to predict which patients who present with a stable airway will progress to a requirement for airway intervention. Researchers from Boston (11) retrospectively analyzed cases of ACEI-related angioedema and determined that increasing age and oral cavity/oropharyngeal involvement predicted the need for airway intervention. These predictors had a sensitivity of 65.2% and specificity of 83.7%. The clinical course of angioedema, especially ACEI induced, is unpredictable. It is recommended that these patients be admitted for close monitoring for at least 24 hours.
3. Do adult patients who present with stridor secondary to epiglottitis require immediate airway management? Since the advent of the Haemophilus influenzae vaccine, epiglottitis has now become a largely adult disease. Most cases of adult epiglottitis are secondary to other infectious etiologies (12), and many patients have an underlying anatomical abnormality such as cancer or surgery. Even though most adult patients with epiglottitis can be managed conservatively, the presence of stridor is ominous and is a predictor of the need for airway management (13).
References
1. Crosby E, Reid D. Acute epiglottitis in the adult: is intubation mandatory? Can J Anaesth 1991;38:914–918.
2. Donald PJ. Emergency management of the patient with upper airway obstruction. Clin Rev Allergy 1985;3:25–36.
3. Halvorson DJ, Merritt RM, Mann C, et al. Management of subglottic foreign bodies. Ann Otol Rhinol Laryngol 1996;105:541–544.
4. Jacobson S. Upper airway obstruction. Emerg Med Clin North Am 1989;7:205–217.
5. Tong MC, Chu MC, Leighton SE, et al. Adult croup. Chest 1996;109:1659–1662.
6. Kaplan AP, Greaves MW. Angioedema. J Am Acad Dermatol 2005;23:373–388.
7. Kostis JB, Kim HJ, Rasnak J, et al. Incidence and characteristics of angioedema associated with enalapril. Arch Intern Med 2005;165:1637–1642.
8. Reid M. Angioedema. April 26, 2006. Available at: http://www.emedicine. com/med/topic135.htm.
9. Roberts JR, Wuerz RC. Clinical characteristics of angiotensin-converting enzyme inhibitor-induced angioedema. Ann Emerg Med 1991;20:555–558.
10. Thompson T, Frable MA. Drug-induced, life-threatening angioedema revisited. Laryngoscope 1993;103:10–12.
11. Zirkle M, Bhattacharyya N. Predictors of airway intervention in angioedema of the head and neck. Otolaryngol Head Neck Surg 2000;123:240–245.
12. Roscoe DL. Microbiologic investigations for head and neck infections. Infect Dis Clin North Am 2007;21(2):283–304.
13. Frantz TD. Acute epiglottitis in adults: analysis of 129 cases. JAMA 1994;272(17):1358–1360.