2010 American Heart Association

S734 Circulation November 2, 2010
position in the trachea. False-positive readings (ie, CO 2 is
detected but the tube is located in the esophagus) have been
observed in animals after ingestion of large amounts of
carbonated liquids before the arrest; however, the waveform
does not continue during subsequent breaths. 96
False-negative readings (defined in this context as failure
to detect CO 2 despite tube placement in the trachea) may be
present during cardiac arrest for several reasons. The most
common is that blood flow and delivery of CO 2 to the lungs
is low. False-negative results also have been reported in
association with pulmonary embolus because pulmonary
blood flow and delivery of CO 2 to the lungs are reduced. If
the detector is contaminated with gastric contents or acidic
drugs (eg, endotracheally administered epinephrine), a colorimetric
device may display a constant color rather than
breath-to-breath color change. In addition, elimination and
detection of CO 2 can be drastically reduced with severe
airway obstruction (eg, status asthmaticus) and pulmonary
edema. 93,97,98 For these reasons, if CO 2 is not detected, we
recommend that a second method be used to confirm endotracheal
tube placement, such as direct visualization or the
esophageal detector device.
Use of CO 2-detecting devices to determine the correct
placement of other advanced airways (eg, Combitube, laryngeal
mask airway) has not been studied; their utility will
depend on airway design. However, effective ventilation
through a supraglottic airway device should result in capnograph
waveform during CPR and after ROSC.
Esophageal Detector Devices. The EDD consists of a bulb
that is compressed and attached to the endotracheal tube. If the
tube is in the esophagus (positive result for an EDD), the suction
created by the EDD will collapse the lumen of the esophagus or
pull the esophageal tissue against the tip of the tube, and the bulb
will not re-expand. The EDD may also consist of a syringe that
is attached to the endotracheal tube; the provider attempts to pull
the barrel of the syringe. If the tube is in the esophagus, it will
not be possible to pull the barrel (aspirate air) with the syringe.
However, studies of the syringe aspiration EDD 79,99 and
the self-inflating bulb EDD 78–80 indicate that the accuracy
of these devices does not exceed that of auscultation and
direct visualization for confirming the tracheal position of
an endotracheal tube in victims of cardiac arrest. Given the
simplicity of the EDD, it can be used as the initial
method for confirming correct tube placement in addition
to clinical assessment in the victim of cardiac arrest when
waveform capnography is not available (Class IIa, LOE
B).
The EDD may yield misleading results in patients with
morbid obesity, late pregnancy, or status asthmaticus, or
when there are copious endotracheal secretions, 100,101 because
the trachea tends to collapse in the presence of these conditions.
There is no evidence that the EDD is accurate for the
continued monitoring of endotracheal tube placement.
Thoracic Impedance. Transthoracic impedance is slightly but
significantly higher during inspiration than during exhalation.
102 Air is a poor electric conductor. Preliminary studies
suggest that changes in thoracic impedance, as measured
through standard defibrillation pads, may distinguish tracheal
from esophageal intubations. 103–105
There are 2 published reports involving 6 patients where
ventilation-induced changes in thoracic impedance disappeared
after esophageal intubation. 106,107 There is little evidence
for the use of thoracic impedance in diagnosing
adequacy of ventilation during CPR. Treatment decisions
should not be based solely on thoracic impedance measurements
until further study has confirmed its utility and accuracy
in this population.
Postintubation Airway Management
After inserting and confirming correct placement of an
endotracheal tube, the provider should record the depth of
the tube as marked at the front teeth or gums and secure it.
There is significant potential for endotracheal tube movement
with head flexion and extension 108–110 and when the
patient is moved from one location to another. 111,112
Continuous monitoring of endotracheal tube placement
with waveform capnography is recommended as discussed
above. The endotracheal tube should be secured with tape
or a commercial device (Class I, LOE C). Devices and tape
should be applied in a manner that avoids compression of
the front and sides of the neck, which may impair venous
return from the brain.
One out-of-hospital study 113 and 2 studies in an intensivecare
setting 114,115 indicate that backboards, commercial devices
for securing the endotracheal tube, and other strategies
provide equivalent methods for preventing inadvertent tube
displacement when compared with traditional methods of
securing the tube (tape). These devices may be considered
during patient transport (Class IIb, LOE C). After tube
confirmation and fixation, obtain a chest x-ray (when feasible)
to confirm that the end of the endotracheal tube is
properly positioned above the carina.
Ventilation After Advanced Airway Placement
Except for respiratory rate, it is unknown whether monitoring
ventilatory parameters (eg, minute ventilation, peak pressure)
during CPR will influence outcome. However, positivepressure
ventilation increases intrathoracic pressure and may
reduce venous return and cardiac output, especially in patients
with hypovolemia or obstructive airway disease. Ventilation
at high respiratory rates (�25 breaths per minute) is
common during resuscitation from cardiac arrest. 116,117 In
animal models, slower ventilation rates (6 to 12 breaths per
minute) are associated with improved hemodynamic parameters
and short-term survival. 116,118–124
Because cardiac output is lower than normal during
cardiac arrest, the need for ventilation is reduced. Following
placement of an advanced airway, the provider delivering
ventilations should perform 1 breath every 6 to 8
seconds (8 to 10 breaths per minute) without pausing in
applying chest compressions (unless ventilation is inadequate
when compressions are not paused) (Class IIb, LOE
C). Monitoring respiratory rate coupled with real-time
feedback during CPR may result in better compliance with
ventilation guidelines. 125
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