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410 PART 4: Pulmonary Disorders

patients also have urticaria. The evaluation of these patients is beyond the patient with UAO while the relevant airway personnel and equip-
the scope of this review. ment are assembled. This approach may serve to “buy time” while a con-
Angioedema due to Angiotensin-Converting Enzyme Inhibitors Angioedema occurs in a sensus is reached among the medical team—anesthesia, otolaryngology,
small fraction (0.1%-0.5%) of patients receiving angiotensin-converting and the critical care service—as to the best approach to monitoring and
enzyme (ACE) inhibitors. Still, because of the widespread use of these potentially securing the airway.
inhibitors. Attacks typically occur shortly after initiation of therapy, but ■ SECURING THE AIRWAY
agents, a significant percentage of all cases of UAO are caused by ACE
may occur years later. The angioedema seems to respond poorly if at The unconscious patient with UAO who is unable to be ventilated
all to treatment with corticosteroids, antihistamines, and epinephrine; should first undergo a head-tilt or jaw thrust maneuver to advance the
although studies demonstrating the efficacy of these agents are lack- mandible and relieve any obstruction from the tongue base in the hypo-
ing, they are frequently administered anyway. The pathophysiology is pharynx. In patients with suspected cervical spine injury, the jaw thrust
unclear; although accumulation of bradykinin has been implicated as may be performed without the head-tilt maneuver. Placement of an oral
the cause, the occurrence of angioedema in some patients who have been airway also facilitates ventilation when the UAO is proximal. If these
switched from ACE inhibitors to angiotensin receptor antagonists, which measures are unsuccessful, the obstruction is likely to be more distal.
do not inhibit the catabolism of bradykinin, raises questions about the The manner in which the airway is secured depends not only upon
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mechanisms by which each agent causes angioedema. Based on limited the tempo of illness and the location of the UAO but upon the experi-
evidence, it appears that for patients with a risk of angioedema attributed ence and preferences of the airway operator. As a general rule, awake
to an ACE inhibitor that the risk of subsequent angioedema while taking fiberoptic intubation by an experienced operator is the procedure of
an angiotensin receptor blocker is between 2% and 17%. We therefore choice when the UAO is known to be severe and progressive and when
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believe that angiotensin receptor antagonists should be used in patients time permits. A variety of devices and techniques are available for this
who have had a prior episode of angioedema attributed to ACEI therapy procedure, including simple video laryngoscopy and devices that com-
only when there is no other reasonable alternative. bine both video and rigid laryngoscopic approaches. In situations in
which the glottis cannot be well visualized, a variety of supralaryngeal
TREATMENT OF UPPER AIRWAY OBSTRUCTION airways are available for placement (see Chap. 45). These devices should
not be used when there is known hypopharyngeal or esophageal pathol-
The most important aspect of managing a patient with suspected UAO ogy, or when time permits an attempt to secure the airway by an expe-
is to immediately summon to the bedside a clinician experienced in rienced otolaryngologist or anesthesiologist. Depending on the level
the management of such patients. Once a significant UAO has been of obstruction, ventilation may still not be possible despite successful
diagnosed, early involvement of anesthesia and otolaryngology services insertion of such devices, a situation that may be rapidly lethal.
is crucial. The approach to management varies considerably depending If the airway cannot be effectively secured with an endotracheal tube,
on the site, severity, and tempo of UAO; while patients with slowly pro- a surgical airway is indicated. Emergency cricothyrotomy is performed
gressive or easily treatable causes of UAO may be managed expectantly, by first making a 1-cm horizontal incision just above the superior border
signs of impending respiratory arrest dictate that the airway be secured of the cricoid, which can be found 2 to 3 cm below the thyroid notch.
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immediately. The presence of an experienced clinician is also important The cricothyroid membrane is then slit in the midline with the blade
in ensuring that inappropriately aggressive interventions do not take directed inferiorly so as to avoid damaging the vocal cords. If the blade is
place, such as attempts at intubation by an inexperienced operator with passed too deeply, entry into the esophagus is possible. The hole is then
inadequate equipment and backup. In such cases, attempts to secure widened with a blunt instrument to allow passage of a small tube or can-
the airway may in fact precipitate a catastrophe. Because each patient nula for ventilation. Complications include vocal cord injury, esophageal
requires an individual approach to management, making explicit recom- perforation, and later, subglottic stenosis. While jet ventilation via nee-
mendations is difficult. Following is a discussion of available techniques dle cricothyrotomy utilizing a 14-gauge angiocath may allow adequate
for treating patients with UAO. ventilation of the patient pending definitive therapy, the frequency of
■ GENERAL STABILIZING MEASURES complications is high and operator experience with this technique is
typically limited.
If the patient has normal mentation and is able to speak, attempts can be It cannot be overemphasized that, time permitting, the optimal
made at stabilizing a severe UAO with noninvasive means pending defin- approach to securing an obstructed upper airway is best determined
itive treatment. Because the pressure required to drive airflow across the through a multidisciplinary approach involving the critical care team,
upper airway depends in part on the density of the gas, the inhalation of a anesthesia, and otolaryngology. Available techniques for securing the
low-density inert gas such as helium in combination with oxygen has the airway are discussed in greater detail in Chap. 45.
have been shown to decrease the transdiaphragmatic pressure swings and ■ THE DECISION TO EXTUBATE
effect of reducing the work of breathing. In fact, helium-oxygen mixtures
the pressure-time index of the diaphragm, as well as improve comfort, Deciding when to extubate a patient with an UAO is often difficult. The
in a group of patients with postextubation stridor. The proportion of presence of the endotracheal tube makes an assessment of upper airway
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inhaled gas that can be administered as helium is obviously limited by patency difficult. Sometimes improvement in the UAO is suggested by
the need to maintain an adequate arterial saturation. On the other hand, the overall clinical course; for example, if a patient was intubated for a
mixtures comprising less than 70% helium are of little to no benefit. borderline indication in the setting of a soft tissue infection, a signifi-
The value of noninvasive positive pressure ventilation in patients with cant reduction in facial and neck swelling may indicate that the UAO
UAO is uncertain. This therapy may help maintain airway patency and has improved to the point where extubation is safe. Similarly, complete
airflow by serving as a pneumatic “splint,” stabilizing ventilation resolution of lip, tongue, and hypopharyngeal swelling from angioedema
and averting a potentially hazardous intubation. On the other hand, is often accompanied by resolution of laryngeal edema. However, care
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the decision to defer intubation in favor of noninvasive ventilation may must be taken in such circumstances. It is frequently useful to perform
allow the UAO an opportunity to progress to a point at which intubation a “cuff leak” test. After scrupulous oral and endotracheal suction, the
becomes more difficult, if not impossible. Similarly, the use of noninva- endotracheal tube cuff is deflated. If a patient is unable to pass air
sive ventilation is inadvisable when the UAO is critical and expected to around the tube, its removal may not be tolerated, particularly if the
progress (eg, in the case of a rapidly progressive upper airway infection tube is small (ie, 6.0 or 6.5 mm). When the patency of the airway is in
or tumor awaiting definitive therapy, such as surgery or radiation). question, it is useful to pass a tube changer through the endotracheal
Perhaps the best use of noninvasive ventilation is in the stabilization of tube prior to its removal. The tube changer is usually well tolerated by

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