Upper Airway Obstruction
Airway obstruction may be total or partial. Total obstruction
is characterized by the lack of any air movement or breath sounds. Confronted with
ineffective breathing efforts, it is important that inexperienced persons not interpret
any retractive movements of the rib cage and the diaphragmatic tugging motions as
respiration. Actual air movement must be perceived by feeling with the hand or placing
the ear over the mouth. Recognition of obstruction depends on close observation
and a high index of suspicion.
The patient with partial obstruction exhibits diminished tidal
exchange that is associated with retraction of the upper chest and accompanied by
a snoring sound if the obstruction is nasopharyngeal or by inspiratory stridor if
obstruction is near the area of the larynx. If inspiratory efforts are severe, the
upper airway may undergo a dynamic inspiratory compression because of the marked
pressure gradient in the upper airway.
Treatment of upper airway obstruction depends for the most part
on whether it is caused by soft tissue obstruction, tumor, foreign body, or laryngospasm.
Most often, upper airway obstruction is caused by a reduction of the space between
the pharyngeal wall and the base of the tongue by relaxation of the tongue and jaw.
The same obstruction may occur with foreign bodies or even with dentures. In the
absence of a foreign body, airflow may be restored by preventing the mandible from
falling back. Forward motion is applied by placing the forefinger and second finger
behind the angle of the mandible.
The patient's neck can also be slightly extended to provide an optimal airway. The
extension of the neck and anterior displacement of the mandible moves the hyoid bone
anteriorly and lifts the epiglottis to provide clear access to the laryngeal inlet.
If the occiput is elevated toward a sniffing position, less extension is required
to achieve airway patency.[1]
Oropharyngeal obstruction
can also be overcome to some extent by increased oropharyngeal pressure from manual
inflations with a breathing bag. One of the major concerns with such manual inflation
of the lungs without tracheal intubation is the potential for gastric insufflation
with high inflation pressures. The relationship between pressure and gas entry into
the stomach has been examined in unconscious, paralyzed patients.[2]
Gastric inflation rarely occurred when pressures less than 15 to 20 cm H2
O
were used. In general, such pressures were associated with tidal volumes well in
excess of 1 L.
One of the primary skills required of anesthesiologists is the
ability to correct upper airway obstruction in the unconscious or anesthetized patient.
This obstruction is commonly attributed to occlusion of the pharynx by the tongue,
which falls back. Correction of such a problem would be expected by insertion of
devices called oropharyngeal or nasopharyngeal
airways (insertion is described later in the chapter). The nasopharyngeal
airway is a soft rubber tube that is less traumatic and better tolerated in lighter
stages of anesthesia or unconsciousness. The airway itself extends sufficiently
into the pharynx to pass behind the base of the tongue. In situations in which the
nares do not permit passage, bleeding occurs, or obstruction is not perceived, an
oropharyngeal airway may be used. The latter is designed for insertion along the
tongue until teeth or gums prevent further passage. Placement of these devices that
provide an artificial passage behind the tongue does not in many cases provide unobstructed
airflow. This suggests that the tongue is not the principal cause of upper airway
obstruction in the anesthetized patient.
This idea is further borne out by the common experience of the
need to use head tilt and maintain head extension, even in patients with an oral
airway in place. It is difficult to understand how this means of establishing airway
patency produces any forward pull on the tongue. This maneuver elevates the hyoid
and epiglottis in anesthetized patients. Further support of the mandible may be
provided by forward traction or pressing forward at the mandibular angles. When
these simple maneuvers and the use of artificial airways do not provide adequate
relief of upper airway obstruction, the insertion of an endotracheal tube to bypass
the upper airway must be contemplated.
