Intubation
In addition to failed intubation, a most feared complication of
intubation is esophageal intubation, although this occurs most frequently in the
setting of inexperience. Unfortunately, except for direct visualization of the tube
passing through the cords, fiberoptic confirmation of placement, and presence and
persistence of appropriate levels of end-tidal carbon dioxide levels, the usual clinical
means for determining endotracheal placement of the tube may not always be reliable.
These include presence of bilateral breath sounds, chest movement, exhaled tidal
volumes, tube condensation, epigastric auscultation, reservoir bag filling and compliance,
and chest radiography.[51]
Routine monitoring of
end-tidal carbon dioxide is helpful in the definitive determination of tube placement
when visualization is impossible and fiberoptic equipment is not available. A colorimetric,
single-use carbon dioxide detector (FEF end-tidal carbon dioxide detector, Fenem,
New York, NY) may be employed when capnometry is unavailable.[52]
The esophageal detector device employs a self-inflating bulb that is connected to
the endotracheal tube and can be carried in a mobile airway case when capnography
is not available. The principle of its use is that the esophagus collapses when
subatmospheric pressure is applied, and the bulb therefore should stay collapsed
if esophageal intubation has occurred. This contrasts with the more rigid trachea
that allows for free aspiration of gas and reinflation of the bulb. The esophageal
detector device was initially reported to be quite effective, but subsequent studies
have noted problems in the obese and in the parturient.[53]
[54]
This device may have a place in intubations
when capnography is not available but independent confirmation is encouraged. The
same limitations apply to the practice of forceful sternal compression to expel tracheal
air through the tube.
The endotracheal tube or stylet may also cause mechanical damage
to the pharynx, esophagus, larynx, and trachea. This may involve blunt injury, dissection,
or perforation. The delicate structures of the larynx (e.g., vocal cords, arytenoids)
are especially susceptible. Infections or barotrauma may follow these types of injuries.
Acute injury to the trachea is associated with the use of a stiff protruding stylet
and previous pathology such as trauma. Gentle, careful manipulation of the airway
and proper use of a stylet that is removed after the glottis is entered should help
avoid most of these types of injury.
Endobronchial intubation is most common when there is the least
distance for the tube tip to be placed properly above the carina but below the vocal
cords, as in small children. Guidelines for placement distance have been discussed
(see Table 42-5
). In patients
older than 1 year, right-sided endobronchial intubation is far more common. Hypoxemia,
bronchospasm, atelectasis, and coughing may result. Auscultation and observation
of the chest may suggest the diagnosis, but the tube may have to be pulled back a
small distance to finalize it. Fiberoptic bronchoscopy is the optimal diagnostic
tool. The clinician
must be extremely careful when withdrawing the tube in awkward positions or in the
difficult airway. Properly placed tubes also may change their position during head
movement, abdominal insufflation, or repositioning of the patient.[26]
Inadvertent extubation may occur during repositioning and surgical manipulation
and may even result from head movement and coughing in small children, such that
continued vigilance is essential.
In addition to bronchospasm, the endotracheal tube has several
other effects on pulmonary mechanics. The tube acts as a fixed resistor that substitutes
for the normal upper airway resistance. The cross-sectional area of an 8.0-mm ID
tube (50 mm2
) is not remarkably less than the mean cross-sectional area
of the glottis (i.e., narrowest part of the adult airway) during quiet breathing.
The use of 8.0-mm tubes in men or 7.0-mm tubes in women whose glottic aperture is
smaller does not impose an undue increase in resistance. However, anatomic dead
space is reduced by intubation. In adults, functional residual capacity is not altered
by the presence of an endotracheal tube.[49]
Several complications are peculiar to nasal intubation. Epistaxis
may occur even when vasoconstriction, a lubricated tube, and careful manipulation
are employed. The inflated cuff may tamponade the hemorrhage if correctly positioned.
Patients with pharmacologic or spontaneous coagulopathies judged to be significant
by the clinician should not be intubated nasally. Severe hemorrhage may result and
require simple tamponade with devices that include the balloons of Foley catheters
and require expert consultation with otolaryngologists. The stream of blood pouring
down the pharynx may also make subsequent oral intubation extremely difficult.
The nasal or nasopharyngeal mucosa may be damaged and false passages
created. Tracheal or esophageal trauma can lead to the serious complications of
pneumothorax and infection, respectively. Adenoids, polyps, and foreign bodies may
be displaced, causing bleeding and even airway obstruction. Nasal instrumentation
in these situations should be done under direct vision if possible. The problems
of bacteremia and basilar skull fracture have been mentioned previously. Endocarditis
prophylaxis is indicated for bacteremia.[54]
In
cases of basilar skull fracture, intubation is contraindicated for fear of entering
the cranium or introducing central nervous system infection. Nasal necrosis is more
likely a complication of chronic intubation but may occur perioperatively, especially
with the use of nasal RAE tubes. Ulceration of the inferior turbinate may also occur.
Sinusitis and otitis are two more common sequelae of longer-term nasotracheal intubation.
[55]
