Esophageal
Detection Device (EDD)
White
Paper(1)
Tools for Confirmation of Endotracheal
Tube Placement in the Prehospital Setting
|
By
Kevin High, RN, MPH, EMT
|
July 2000, MERGINET -
Being able to secure a patient's airway is probably the most important skill a
prehospital provider performs. For ALS providers, endotracheal intubation
remains the standard of care for securing a patient's airway. Successfully
intubating the patient is just part of the battle. Confirming and maintaining
proper placement during treatment and transport is of paramount importance.
Inadvertent esophageal intubation can be at the very least detrimental, and
oftentimes catastrophic.
Esophageal intubation of
critically ill patients occurs in 8 percent of attempts, 1 thus highlighting the
need for proper confirmation of endotracheal tube position. Confirming
successful endotracheal tube placement can be difficult in the acutely ill or
injured patient — and confirming proper placement in the prehospital setting
can be unbelievably challenging. Ambient noise, poor lighting, and space
limitations are just some of the obstacles, but confirming endotracheal tube
placement is a skill that must nonetheless be mastered.
An
EMS
provider's clinical exam of
the patient is one method of confirming ET placement, but this can be
unreliable, especially when used as the sole method of determining confirmation.
Using methods other than clinical exam boosts the chances of determining proper
endotracheal tube placement. Much of the data compiled on confirmation of
endotracheal tube placement has been gathered from patients that have been
intubated in the OR under much more ideal conditions than are often found in the
field. Given this, we need to arm ourselves with tools to carefully and
accurately determine endotracheal tube placement.
Methods
There
are three common methods of endotracheal tube confirmation in the prehospital
setting: physical assessment, capnographic determination of ETCO 2 via a
colorimetric device, and the esophageal detector device.
- Physical
assessment
For many years, physical exam of the patient was the "gold
standard" for determining endotracheal tube placement outside the
hospital setting. The technique of direct visualization and auscultation,
etc. has been taught to prehospital providers as the standard of care, and
in some circles remains so. White and Slovis referred to these techniques as
the "fool's gold standard" because of their notorious
unreliability. This is not to say it should not be done. Proper physical
assessment to determine endotracheal tube placement should consist of
visualization of the endotracheal tube passing between the vocal cords,
auscultation over the epigastrium, auscultation just below the right and
left axilla, observation of chest rise and fall, and the presence of
condensation in the endotracheal tube. However, all of these methods can
fail, and/or are notoriously unreliable. In fact, study after study shows
that physical assessment, on its own, is faulty for determining endotracheal
tube placement. 2
·
One reason is
because direct visualization of the vocal cords is not always possible, and
after the endotracheal tube has been placed, it can easily become dislodged.
Direct visualization is often hindered by vomitus, blood, or anatomic distortion
secondary to trauma. The presence or absence of breath sounds, or the rise and
fall of the chest, even to an experienced examiner, may or may not determine
correct endotracheal tube placement. 1 Also,
Anderson
, et al, cite that the
presence of condensation in the tube was found in >50 percent of patients
that they had intentionally intubated into the esophagus. 3 Auscultation, even
by experienced providers, has its pitfalls, and can fail in up to 15 percent of
patients. 1,3 For one, ambient noise often precludes obtaining a good
assessment.
- End
Tidal CO 2 (ETCO 2 ) Detector
Anesthesiologists and anesthetists have required endotracheal tube
confirmation with ETCO 2 for years. The ETCO 2 detector is rapidly becoming,
if not already established as, a standard of care in the air medical
industry and in many facets of emergency medicine. The end tidal CO 2 (ETCO
2 ) detector most used in the prehospital setting is a colorimetric
qualitative device that changes color in the presence of ETCO 2 . Some
devices are inserted between the Ambu-bag and the endotracheal tube, and
have a small window through which one can observe the colormetric paper.
Other devices have the colormetric paper included as part of the in-line
assembly of the Ambu-bag. One of the limitations of the ETCO 2 detector is
the potential for secretions to come in contact with the colormetric paper,
thus rendering it unrecognizable.
·
Using the ETCO
2 detector on patients in cardiac arrest presents by far the biggest limitation.
Patients in cardiac arrest, even with on-going cardiopulmonary resuscitation,
are in a low cardiac output state, which leads to low expired CO 2
concentrations. This renders the ETCO 2 detector somewhat unreliable. 4 However,
in patients whose cardiac output is not low, the ETCO 2 detector is extremely
reliable. It offers an easy and continuous method to determine proper ET tube
placement. A quick glance at the device gives the examiner a nice sense of
security.
·
The ETCO 2
detector is especially useful in environments where physical exam, especially
auscultation, is limited. However, sufficient light must be available to see the
color change, and the colorimetric paper must not be soiled. For example, air
medical transport is a noisy, sometimes dark environment with space limitations.
This seriously impedes physical exams, so other methods must be employed to
accurately determine endotracheal tube placement.
- Esophageal
Detector Device (EDD)
The esophageal detector device is inexpensive, portable, and very easy to
use. It is available as either a self-inflating bulb or a syringe device,
and is gaining popularity in
EMS
circles. It has been extensively tested, and
has been shown to work well in both the prehospital arena and in the
hospital setting. The EDD relies on the anatomic differences between the
trachea and the esophagus. Application of negative pressure, either through
aspiration of the syringe plunger or the bulb, leads to the collapse of the
esophagus around the end of the endotracheal tube. This is due to the
fibromuscular structure of the esophagus, whereas the trachea is very rigid
and remains open due to its cartilaginous rings. In an improperly placed
endotracheal tube, the bulb will be unable to fully inflate, or the syringe
plunger will not be able to completely (or nearly completely) pull back from
the body of the syringe. Not only is the EDD inexpensive, it's portable,
easy to use, and not dependent on patient condition or environmental
conditions (such as good lighting, low ambient noise, etc). Unlike the ETCO
2 detector, the EDD works just as well and is just as accurate if the
patient is in cardiac arrest. 5
Conclusion
The
EDD is more accurate than other methods (physical exam and ETCO 2 ) in the
overall emergency patient population because of its greater accuracy in cardiac
arrest patients. 4 However, the ETCO 2 detector is well suited in patients with
spontaneous circulation. 1 Using both devices can potentially exclude esophageal
intubation virtually 100 percent of the time.
Even with its many
limitations, physical exam must never be totally replaced by any machine, mode,
or gadget. That said, its limitations should be recognized, and adjunct devices
employed. Ideally, the optimal way to determine endotracheal tube placement
seems to point to the use of all of these methods while recognizing the
limitations of each.
Footnotes
- Knapp, S., Kofler, J., Stoiser, B., Thalhammer, F.,
Burgmann, H., Posch, M., Hofbauer, R., Stanzel, M., and Frass, M. "The
Assessment of Four Different Methods to Verify Tracheal Tube Placement in
the Critical Care Setting," Anesthesia Analg. , 1999: 766-770.
- White, S., and Slovis, C. "Inadvertent Esophageal
Intubation in the Field: Reliance on a Fool's 'Gold Standard,'"
Academy
of
Emergency Medicine
,
1997 89-91.
- Andersen, K., and Hald, A. "Assessing the
position of the endotracheal tube: The reliability of different
methods," Anaesthesia ,
1989, 44: 984-985.
-
Bozeman
, W.P., Hexter, D., Liang,
H.K., and Kelen, G.D., "Esophageal Detector Device versus detection of
end-tidal CO 2 level in emergency intubations," Annals
of Emergency Medicine , 1996: 595-599.
- Schaller, R.J., Huff, J.S., and Zahn, A.,
"Comparison of a colorimetric end-tidal CO 2 detector and an esophageal
aspiration device for verifying endotracheal tube placement in the
prehospital setting," Prehospital
Disaster Medicine , 1997 Jan-March: 57-63.
Kevin High, RN, MPH, EMT, is a flight nurse with Vanderbilt
LifeFlight in Nashville, TN. He has 14 years of prehospital experience and
has had other articles in Air Med , Journal of Emergency Nursing , Air Medical
Journal , and Emergency Medicine . He actively lectures on local, state, and
occasionally national levels. He lives in rural Middle
Tennessee
and is happily married to
a local hospital executive.
B-PRA-EDD White Paper(1).doc(
01-10-05
)
