Page 573 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

CHAPTER 45: Airway Management 393

pressure (PEEP). The most common indications for changing ETTs in venous return and cardiac output. Mechanical ventilation is also
include failure of the cuff to retain volume and pressure, occlusion of the frequently associated with a resolution of hypoxia, hypercapnia, and
tube by inspissated secretions and clots, and the requirement for a differ- dyspnea, and a proportionate decline in circulating catecholamines. In
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ent tube than the one originally inserted (eg, one of a larger diameter, or addition, patients with obstructive lung disease can develop high levels
a different type such as a single- rather than a double-lumen tube). Tube of auto-PEEP very quickly during vigorous ventilation with an Ambu
changes motivated by complete occlusion or cuff rupture in the face of bag, which can be associated with hypotension. 44,45 Finally, high levels of
high PEEP may be dire emergencies; most other ETT changes are not. PEEP can increase the pulmonary vascular resistance, with an associated
Practitioners called on to change an ETT have the advantage that the shift of the interventricular septum into the left ventricle and decreased
patient already has an artificial airway, and hence the ease or difficulty stroke volumes 46,47 (see Table 45-5).
of obtaining an airway has been discovered at least once for the patient.
If laryngoscopy was easily accomplished before, and the patient’s airway COMPLICATIONS
anatomy has not changed appreciably (eg, as a result of edema), many
practitioners elect to perform ETT changes with direct laryngoscopy Airway manipulation in critically ill patients is a necessarily hazardous
under deep sedation and paralysis. This practice is safe when the old undertaking (Table 45-8). Death, circulatory collapse, arrhythmias,
tube is withdrawn simultaneously with the introduction of the new tube hypoxia, airway trauma, aspiration, and failed intubation can all occur,
into the trachea. Many operators prefer to perform ETT changes with even when the airway is managed flawlessly.
the patient breathing spontaneously, reasoning that attempts at ventila- Right mainstem intubation is a common consequence of intubation
tion by the patient will delay the onset of hypoxia and hypercarbia in the in the ICU. It can be avoided in many cases by taping tubes at 23 cm at
event of difficulty in inserting the new airway. Withdrawing the old the lip in males and 21 cm at the lip in females of average stature (using
tube prior to attempting laryngoscopy, or when the view is difficult, can
produce a cannot-intubate, cannot-ventilate situation, which can quickly
become a crisis.
A variety of semirigid catheters are available for use as tube chang- TABLE 45-8 Complications of Intubation
ers. Although they can be helpful in difficult circumstances, they can Immediate
become dislodged from the trachea, and in some cases it is impossible
to thread the new tube over them. Tube changers may be best used in Right mainstem intubation
combination with direct laryngoscopy when the anatomy is challeng- Esophageal intubation
ing. Tube changers with a central lumen may be used to attempt to jet Gastric aspiration
ventilate patients in the event that a more permanent airway cannot be
established immediately. In patients with substantial facial and neck Dental injury, tooth aspiration
edema or burns, several assistants will be required for successful tube Mucosal laceration or tear
changes. Fiberoptic-guided exchange of tracheal tubes requires both Hypertension/tachycardia
excellent preparation of the airway (including treatment with drying Myocardial ischemia
agents such as glycopyrrolate and aggressive suctioning), and a high
degree of skill by the operator, but can produce success where most or Elevated intracranial pressure
all other approaches would yield failure. 39 Hypotension
In addition to their use for tube exchanges, tube changers can also Arrhythmias
play an important role when extubating the patient with a known or
suspected difficult airway. If a patient is extubated over a tube changer, it Ventricular premature beats
can be left in place and used either to facilitate reintubation or to provide Ventricular tachycardia
jet ventilation to the lungs until a more satisfactory means of providing Ventricular fibrillation
oxygenation can be established. 40
Atrial fibrillation
Bradycardia (in young patients)
PHYSIOLOGIC CHANGES ASSOCIATED WITH Bronchospasm
INTUBATION AND MECHANICAL VENTILATION
Vocal cord trauma
Tracheal intubation has a range of important physiologic consequences. Dislocation of arytenoid cartilage
These are not complications of the procedure per se, but are consequences
of the presence of an artificial airway and mechanical ventilation. Pain
Tracheal intubation and the institution of PPV can cause a variety of Chronic
changes in circulatory physiology. Laryngoscopy and tracheal intubation Serous or purulent otitis
are frequently accompanied by hypertension and tachycardia.
ETTs may cause an increase in airway resistance. An 8.0-mm ETT Sinusitis
causes a 20% increase in airway resistance in the normal airway, all of it in Mucosal ulceration
the central airways and nonresponsive to therapy with inhaled broncho- Necrosis of lip or nose
dilators. Smaller tubes have exponentially higher resistances. A 7.0-mm
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ETT has twice the resistance of an 8.0-mm tube, whereas a 9.0-mm tube Granulomas
has one-third the resistance of an 8.0-mm tube. The airways resistance Dental damage from biting
associated with a particular tube increases as inspissated secretions accu- Tracheal mucosal injury
mulate in the tube, decreasing its diameter and increasing the turbulence of
flow. Tracheal intubation can also precipitate bronchospasm in susceptible Tracheoesophageal fistula, tracheo-innominate fistula
individuals, which can further increase airways resistance. Laryngeal stricture
Hypotension frequently follows successful tracheal intubation and Vocal cord synechiae/paralysis
mechanical ventilation, and has many contributing factors. First, Tracheomalacia, cricoarytenoid edema, subluxation and fracture
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these usually entail a change in mean intrathoracic pressures from large
negative pressures to large positive pressures, with a corresponding fall Tracheal stenosis

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