Download Out-of-Hospital Endotracheal Intubation: Where Are We?

EMERGENCY MEDICAL SERVICES/AIRWAY/SPECIAL CONTRIBUTION
Out-of-Hospital Endotracheal Intubation: Where Are We?
Henry E. Wang, MD, MPH
Donald M. Yealy, MD
From the Department of Emergency Medicine, University of Pittsburgh School of Medicine,
Pittsburgh, PA.
While remaining prominent in paramedic care and beneficial to some patients, out-of-hospital
endotracheal intubation has not clearly improved survival or reduced morbidity from critical illness or
injury when studied more broadly. Recent studies identify equivocal or unfavorable clinical effects,
adverse events and errors, interaction with other important resuscitation interventions, and challenges
in providing and maintaining procedural skill. We provide an overview of current data evaluating the
overall effectiveness, safety, and feasibility of paramedic out-of-hospital endotracheal intubation. These
studies highlight our limited understanding of out-of-hospital endotracheal intubation and the need for
new strategies to improve airway support in the out-of-hospital setting. [Ann Emerg Med. 2006;47:
532-541.]
0196-0644/$-see front matter
Copyright © 2006 by the American College of Emergency Physicians.
doi:10.1016/j.annemergmed.2006.01.016
SEE EDITORIAL, P 542.
INTRODUCTION
Paramedic out-of-hospital endotracheal intubation
originated in the 1970s from efforts to improve outcomes
from cardiac arrest and major trauma.1–5 At that time, the
best available methods for paramedic out-of-hospital airway
management and ventilation were bag-valve-mask ventilation
and the esophageal obturator airway.6 –9 Bag-valve-mask
performance was perceived to be inadequate, and esophageal
obturator airway use resulted in many complications,
including inadequate or delayed ventilation, aspiration,
pharyngeal and esophageal injury, gastric rupture, tracheal
occlusion, and inadvertent tracheal intubation.6,8,10 –15 Outof-hospital endotracheal intubation offered an alternative
method to optimize care, promising superior airway
protection, efficient ventilation, and a route to deliver
endobronchial medications.16 Endotracheal intubation was
also the standard for in-hospital resuscitation, classified as a
“definitely helpful” intervention by then-current Advanced
Cardiac Life Support guidelines.17 Several authors reported
groundbreaking efforts to implement out-of-hospital
endotracheal intubation in Boston, Columbus, San Diego,
and Pittsburgh.1– 4
Despite its accepted role in clinical practice for more than 25
years, a growing body of literature suggests that out-of-hospital
endotracheal intubation is not achieving its intended
overarching goals. In selected cases, the intervention may cause
harm. In this article, we provide an overview of recent data
evaluating the effectiveness, safety, and feasibility of paramedic
out-of-hospital endotracheal intubation.
532 Annals of Emergency Medicine
Is Out-of-Hospital Endotracheal Intubation Effective?
The fundamental test of a medical intervention is whether it
improves the outcome of the targeted patients.18 In this light,
the overarching goal of out-of-hospital endotracheal intubation
is to reduce mortality and morbidity for those in need of airway
support. Several investigators have evaluated survival and
neurologic outcome after out-of-hospital endotracheal
intubation19 –33 (Table). These studies largely involve
retrospective analyses of predominantly injured patients.
Although 2 studies identified increased survival from out-ofhospital endotracheal intubation, the remaining efforts found
either decreased or no effect on survival. No studies have
identified improved neurologic outcome from out-of-hospital
endotracheal intubation.
Of these out-of-hospital endotracheal intubation studies, the
most notable effort is by Gausche et al.22 In this prospective
trial, 830 critically ill pediatric out-of-hospital patients in Los
Angeles County received either bag-valve-mask ventilation or
bag-valve-mask followed by out-of-hospital endotracheal
intubation. The authors found that an airway strategy
incorporating out-of-hospital endotracheal intubation offered
no survival or neurologic benefit over bag-valve-mask
ventilation alone. Although limited by its patient population
(primarily pediatric patients in a large urban location), this
seminal effort represents the largest prospective, controlled
evaluation of out-of-hospital airway management interventions.
The San Diego Rapid Sequence Intubation Trial tested the
large-scale implementation of rapid sequence intubation
performed by ground-based paramedic units.20 In this outcomes
analysis, 209 traumatic brain injury patients receiving out-ofhospital rapid sequence intubation (neuromuscular blockade–
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Out-of-Hospital Endotracheal Intubation
Table. Studies evaluating survival or neurologic outcome after out-of-hospital endotracheal intubation.*
Study
Bochicchio et al,
200329
Bulger et al, 200519
Christensen and
Hoyer, 200330
Cooper et al,
200131
Davis et al, 200320
Davis et al, 200521
DiRusso et al,
200532
Gausche et al,
200022
Lockey et al,
200123
Murray et al,
200024
Sloane et al,
200025
Stockinger et al,
200426
Suominen et al,
200033
Wang et al, 200427
Primary Comparison
(Group Sizes)
Design
Primary Population
Prospective observational;
single trauma center
(Baltimore); univariable/
stratified
Retrospective; single trauma
center (Seattle);
multivariable adjusted
Severe TBI; ETI in field
or ED
OOH-ETI (78) vs ED-ETI (113)
Higher mortality (OR 2.1; 95%
CI 0.9–5.0)†‡ in OOH-ETI
group
Severe TBI; RSI or ETI
in field
OOH-RSI (775) vs OOH-ETI
(302)
Retrospective; single mobile
emergency unit with
anesthetist (Denmark)
Retrospective; National
Pediatric Trauma Registry;
univariable
Prospective interventional
series, historical controls;
countywide (San Diego);
multivariable adjusted
Retrospective; countywide
trauma registry (San
Diego) multivariable
adjusted
Retrospective; National
Pediatric Trauma Registry;
multivariable adjusted
All trauma; ETI in field
with and without
drugs
Severe pediatric TBI
OOH-ETI with (62) vs without
(12) drugs
Higher mortality (OR 1.6; 95%
CI 1.0–2.4) and poorer
neurologic outcome (1.7;
1.2–2.6) in OOH-ETI group
Higher mortality (OR 15.2; 95%
CI 1.9–673.2)† for OOH-ETI
without drugs
No difference in mortality (OR
1.0; 95% CI 0.6-1.6)†
Severe TBI; RSI in
field vs non-ETI
historical controls
OOH-RSI (209) vs non-OOH-ETI
(627)
Severe TBI; ETI in field
or ED
OOH-ETI (2,665) vs ED-ETI
(2,220)
All pediatric trauma
OOH-ETI (1,928) vs non–trauma
center ETI (1,647), trauma
center ETI (1,874) and nonETI (44,739)
Prospective controlled
(pseudorandomized)
interventional trial;
countywide (Los Angeles)
Retrospective; single air
medical service (Great
Britain); descriptive
Retrospective; countywide
trauma registry (Los
Angeles); multivariable
matched/adjusted
Retrospective; single trauma
center (San Diego);
univariable
Pediatrics; ETI or BVM
in field
OOH-ETI/BVM (420) vs OOHBVM (410)
All trauma; ETI in field
without drugs
Mortality of OOH-ETI without
drugs (486)
Severe TBI
OOH-ETI (57) vs non-OOH-ETI
(57)
Higher mortality (OR 4.2; 95%
CI 2.1–8.9) in OOH-ETI group
Severe TBI; RSI in
field or ED
OOH-RSI (47) vs ED-RSI (267)
Retrospective; single trauma
center (New Orleans);
univariable/stratified
Retrospective; single trauma
center (Finland);
univariable
All trauma; ETI or BVM
in field
OOH-ETI (316) vs OOH-BVM
(217)
Severe pediatric TBI
OOH-ETI (24) vs non–trauma
center ETI (13) vs trauma
center ETI (22)
Retrospective; statewide
trauma registry
(Pennsylvania);
multivariable and
propensity-score adjusted
Severe TBI; ETI in field
or ED
OOH-ETI (1,797) vs ED-ETI
(2,301)
No difference in mortality (OR
0.6; 95% CI 0.1–2.6)† or
neurologic outcome (1.1;
0.3–3.8)†
Higher mortality (OR 18.0; 95%
CI 11.2–29.1)† in OOH-ETI
group
Lower mortality for OOH-ETI vs
non–trauma center ETI (OR
0.1; 95% CI 0.002–1.1)†‡;
no difference vs trauma
center ETI (3.7; 0.9–15.8)†
Higher mortality (OR 4.0, 95%
CI 3.2–4.9), poorer
neurologic outcome (1.6;
1.2–2.3), and poorer
functional outcome (severe
impairment 1.9; 1.3–2.5) in
OOH-ETI group
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Primary Finding
OOH-ETI (479) vs OOH-BVM
(99)
Higher mortality (OR 1.6; 95%
CI 1.1–2.2) and poorer
neurologic outcome (1.6;
1.2–2.3) in OOH-RSI group
Higher mortality (OR 2.1; 95%
CI 1.8–2.5)† in OOH-ETI
group
Higher mortality for OOH-ETI vs
non–trauma center ETI (OR
3.2; 95% CI 2.7–3.7)†§; vs
trauma center ETI (4.1; 3.5–
4.8)†§; vs non-ETI (142.0;
119.6–168.5)†§ Poorer
neurologic outcome for OOHETI vs non–trauma center or
trauma center ETI储
No difference in mortality (OR
0.8; 95% CI 0.6–1.1) or
neurologic outcome (0.9;
0.6–1.2)
Low (0.2%) survival
Annals of Emergency Medicine 533
Out-of-Hospital Endotracheal Intubation
Wang & Yealy
Table. Continued
Study
Winchell and Hoyt,
199728
Design
Retrospective; countywide
trauma registry (San
Diego);
univariable/stratified
Primary Population
Blunt trauma, GCS
score ⱕ8
Primary Comparison
(Group Sizes)
OOH-ETI (527) vs non–OOH-ETI
(565)
Primary Finding
Lower mortality (OR 0.6; 95%
CI 0.5–0.8)† in OOH-ETI
group; no difference in
neurologic outcome (1.4;
1.0–1.9)†
BVM, Bag-valve-mask ventilation; ETI, endotracheal intubation; GCS, Glasgow Coma Scale; OOH, out-of-hospital; RSI, rapid sequence intubation; TBI, traumatic brain
injury.
*Only the primary findings (survival and neurologic outcome) are summarized; results of other outcomes and subgroup analyses are not presented.
†
Odds ratio calculated from published results.
‡
Author stated significant at P⬍.05.
§
Calculated univariable odds ratios; multivariable adjusted figures not published.
储
Odds ratios could not be calculated from published results.
assisted endotracheal intubation) were matched to 627 historical
nonintubated controls, facilitating a comparison of out-ofhospital rapid sequence intubation with the alternative of no
out-of-hospital endotracheal intubation at all. The authors
observed higher mortality in patients receiving out-of-hospital
rapid sequence intubation (odds ratio 1.6; 95% confidence
interval [CI] 1.1 to 2.2). This study is notable because of its
large-scale evaluation of one of the most advanced airway
management techniques.
In the evaluation of this series of studies (listed in the Table
and discussed above), several important observations arise about
their methods, designs, and limitations. Most of these efforts
used retrospective designs involving a single-center or
countywide trauma registry and included primarily injured or
head-injured patients.19 –21,23–33 The Gausche study is the only
effort using a prospective, controlled design in medical
(nontrauma) cases.22 The studies noted in the Table evaluated
survival to hospital discharge only; they did not study long-term
outcomes and often inferred neurologic outcome from discharge
destination (ie, discharge to home, rehabilitation center,
psychiatric facility, or jail ⫽ “good neurologic outcome”;
discharge to nursing home or other extended care facility ⫽
“poor” neurologic outcome). None used formal neurologic or
functional measures such as the Glasgow Outcome Scale or the
Functional Independence Measure.34,35
Risk adjustment is important in retrospective analyses
because many confounding factors can lead to adverse
outcome, not just the manner of airway management.36
However, only some authors used multivariable adjustment
to account for these variations.19 –21,24,27,32 Several studies
using univariable analysis (including the 2 efforts identifying
a survival benefit for out-of-hospital endotracheal intubation)
may not have adequately accounted for confounders.28,33 For
example, Winchell and Hoyt28 analyzed 1,098 head-injured
patients and found that out-of-hospital endotracheal
intubation increased survival by 21%, but this effort did not
adjust for severity of injury or illness. Suominen et al33
evaluated 59 pediatric traumatic brain injury patients and
534 Annals of Emergency Medicine
found that out-of-hospital endotracheal intubation resulted
in a 34% increase in survival over patients intubated in the
emergency department (ED) of a referring hospital; however,
this small effort similarly did not adjust for severity of injury
or illness.
The comparison (exposure) groups in these studies differ,
each posing a different scientific question. For example, the
Davis et al,20 Murray et al,24 and Winchell and Hoyt28 studies
used controls that did not receive out-of-hospital endotracheal
intubation; we do not know whether these individuals later
received ED endotracheal intubation or no endotracheal
intubation at all. In our analysis of intubated traumatic brain
injury patients in Pennsylvania, we excluded patients not
receiving endotracheal intubation in either the out-of-hospital
or ED setting, hence facilitating a comparison of endotracheal
intubation during the acute out-of-hospital or ED phases
only.27 In contrast, the Bulger et al19 study compared out-ofhospital conventional and rapid sequence endotracheal
intubation techniques, excluding patients not intubated in the
out-of-hospital setting. This latter study compares different outof-hospital endotracheal intubation techniques, not out-ofhospital endotracheal intubation versus non-out-of-hospital
endotracheal intubation.
In summary, few studies have demonstrated benefit from
out-of-hospital endotracheal intubation.28,33 Most showed
an adverse or no effect on outcome.20 –22,24,26,27,29,31,32
These observations contradict the assumption that aggressive
airway intervention is associated with improved resuscitation
outcomes. Larger studies with prospective designs may be
instrumental in revealing an undetected benefit. However, an
important alternate reaction is to recognize that multiple
studies arrived at similar conclusions and identified
substantial effect sizes, despite their differing populations,
disease groups, designs, and limitations. If not directly
causative, out-of-hospital endotracheal intubation may have
close parallel relationships with factors leading to adverse
outcome. A logical direction is to better identify the
underlying relationships.
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Is Out-of-Hospital Endotracheal Intubation Safe?
Therapeutic “safety” refers to freedom from accidental injury
during the course of medical care.37 Adverse events and errors
may contribute to the poor outcomes associated with out-ofhospital endotracheal intubation. This relationship is plausible,
given that out-of-hospital endotracheal intubation is a complex
procedure with many potential pitfalls, including key errors (eg,
unrecognized esophageal tube placement) that can result in
morbidity or death. Errors may be more likely in the
uncontrolled out-of-hospital environment than in other
settings.38 Several recent efforts highlight the underrecognition
of out-of-hospital endotracheal intubation errors.
Katz and Falk39 evaluated 108 paramedic endotracheal
intubation patients arriving at a regional trauma center in
Florida. The authors used a systematic physician approach to
confirm proper tube placement on ED arrival, including the
selected use of direct revisualization. The authors found that
more than 25% of the endotracheal tubes were misplaced, two
thirds of these in the esophagus. The authors partially attributed
the results to noncompliance with out-of-hospital protocols
requiring placement confirmation using carbon dioxide
detection. Jemmett et al40 conducted a similar study of 109
paramedic endotracheal intubation patients in Maine (an
emergency medical services [EMS] system with no carbon
dioxide detection protocol) and found a similar tube
misplacement rate of 12%. Jones et al41 reported a lower (5.8%)
tube misplacement rate for 208 paramedic endotracheal
intubation in Indianapolis, but this study occurred in a region
serviced primarily by a single EMS agency with close medical
oversight.
Dunford et al42 examined a subset from the San Diego
Rapid Sequence Intubation Trial, finding that accidental oxygen
desaturation (SaO2 ⬍90%) occurred in 31 of 54 (57%) patients
and marked bradycardia (pulse rate ⬍50 beats/min) in 6 of 54
(19%) patients. Moreover, in 84% of these adverse events, the
paramedic described the intubation effort as “easy.” Ehrlich et
al43 compared field (out-of-hospital), referring hospital and
trauma center endotracheal intubation of pediatric trauma
patients. Complications (esophageal intubation, mainstem
intubation, aspiration, barotrauma, incorrect tube size, tube
dislodgment) occurred in two thirds of the 59 out-of-hospital
endotracheal intubations.
Self-reporting methods are often used to identify medical
errors in the in-hospital setting.37 In the Gausche et al22 study,
of 186 initially successful endotracheal intubations, paramedics
reported unrecognized esophageal intubation in 2%, tube
dislodgment in 14%, and mainstem intubation in 18%. In a
prospective multicenter effort involving 45 EMS services, we
demonstrated the feasibility of using anonymous, structured,
closed-form, self-reporting forms to identify out-of-hospital
endotracheal intubation errors.44 Of 1,953 endotracheal
intubations, tube misplacement (esophageal, delayed
recognition or unrecognized, or dislodgment) was reported in
61 (3.1%) intubations, multiple endotracheal intubation
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attempts (4 or more laryngoscopies) occurred in 62 (3.2%)
intubations, and endotracheal intubation efforts failed in 359
(18.5%) intubations. More than 22% of patients experienced 1
or more of these errors or complications. Although these data
are limited by self-reporting biases and a moderate return rate
(68%), they still identify worrisome “best case” error rate
estimates; that is, true error rates are likely to be higher, not
lower, than reported with this design.
These data highlight our incomplete awareness of and
limited ability to identify out-of-hospital endotracheal
intubation errors. For example, the Katz and Falk study
highlighted that out-of-hospital endotracheal intubation is
prone to detection bias; errors go undetected unless
systematically identified.39 Cases series describing tracheal and
pulmonary injury from out-of-hospital endotracheal intubation
indicate that many errors are identified only through invasive
tests or autopsy.45,46 Dunford et al42 showed that during the
course of routine care, rescuers are often unaware of adverse
events, even when equipped with the most advanced monitoring
techniques. Although none of these efforts formally linked outof-hospital endotracheal intubation errors to outcome, these
events have plausible connections with patient outcome. These
studies highlight our underrecognition and incomplete
understanding of the range of errors occurring during out-ofhospital endotracheal intubation.
Does Out-of-Hospital Endotracheal Intubation Affect Other
Aspects of Care?
Current paramedic textbooks portray endotracheal
intubation as a procedure to be completed independent of other
patient care tasks.47 However, other interventions often occur
concurrently with endotracheal intubation; for example, chest
compressions, electrical therapy, intravenous access, or the
administration of drugs. An important recent realization is that
out-of-hospital endotracheal intubation may influence patient
outcome by interacting with or affecting the execution of these
simultaneous therapies. These observations have occurred in
several disease groups. For example, after successful out-ofhospital endotracheal intubation, rescuers commonly perform
ventilation manually (without the assistance of portable
ventilators) using tactile feedback only. Consequently, out-ofhospital endotracheal intubation may result in unintended
hyperventilation, which may be deleterious in certain
conditions. In porcine models of hemorrhagic shock, Pepe et
al 48,49 found that increased respiratory rates (20 and 30
breaths/min) resulted in decreased systolic blood pressure and
cardiac output, respectively. Davis et al50 showed that
hyperventilation occurs frequently after out-of-hospital rapidsequence intubation for traumatic brain injury, a condition in
which hyperventilation can reduce cerebral perfusion. The
investigators noted an association between hyperventilation and
increased mortality.51
Aufderheide and Lurie52 and Aufderheide et al53 identified
the same hyperventilation phenomenon in intubated cardiac
arrest patients. Using physician responders to monitor out-ofAnnals of Emergency Medicine 535
Out-of-Hospital Endotracheal Intubation
hospital cardiac arrest victims, the authors also found that
accidental hyperventilation raised intrathoracic pressure during
chest compressions, thereby impeding coronary perfusion
pressure, an important element for successful resuscitation.54
They observed that these episodes occurred despite the specific
training of the paramedics in this study.
Experts believe that control of intracranial pressure is
important in the treatment of traumatic brain injury.50,55–57
Physicians often use rapid sequence intubation to attenuate
intracranial pressure response to the stress of endotracheal
intubation.56 The aim to control intracranial pressure led to the
proposal to replace nasotracheal intubation with rapid sequence
intubation in these patients. However, the San Diego Rapid
Sequence Intubation Trial found that adverse events such as
inadvertent hyperventilation, oxygen desaturation, bradycardia,
and increased mortality occurred with rapid sequence
intubation approaches.20,42,51 Thus, efforts to precisely control
one aspect of physiology during airway management disturbed
other body systems.
Although meriting additional study, these findings in
different disease states suggest that unanticipated physiologic
effects may offset the potential benefits of proper endotracheal
intubation. These observations underscore our poor
understanding of how current field airway management,
oxygenation, ventilation, and other physiologic processes
interact during the resuscitation of different disease states.
How Do Paramedics Learn and Maintain Intubation Skills?
Because the manner of intubation may affect patient
outcome, a logical area of concern involves paramedic
acquisition and maintenance of out-of-hospital endotracheal
intubation skill. For example, in the Gausche et al22 study,
paramedics did not perform pediatric out-of-hospital
endotracheal intubation before the trial. In the San Diego Rapid
Sequence Intubation Trial, paramedics received a 7-hour
didactic session without supplemental live training.58 These
factors may have reduced the potential benefit of out-of-hospital
endotracheal intubation.
Endotracheal intubation is a complex procedure, arguably
more difficult when attempted in the uncontrolled out-ofhospital setting. Unlike physicians working in protected, stable,
and well-illuminated settings (such as the operating room and
ED), paramedics often attempt endotracheal intubation in
awkward situations; for example, on the floor, in cramped
rooms, or in the twisted metal of a motor vehicle.59,60 Out-ofhospital patients are critically ill and often severely injured, and
most would be considered “difficult” or high-risk intubations by
in-hospital anesthesia standards.61 Given these challenges, one
would expect paramedics to acquire and maintain endotracheal
intubation skills well above minimum levels. However,
paramedic endotracheal intubation training and clinical
experience are relatively limited.
For example, there is significant disparity between consensus
procedural standards for paramedic students and other
endotracheal intubation providers. The national paramedic
536 Annals of Emergency Medicine
Wang & Yealy
curriculum requires students to perform 5 successful
endotracheal intubations to graduate.62 In contrast, emergency
medicine residents, anesthesiology residents, and nurse
anesthetist trainees are expected to perform between 35 and 200
endotracheal intubations before graduating from their respective
training programs.63– 68
Using data on 7,635 endotracheal intubations attempted by
802 paramedic trainees from 60 training programs, we found
that across all clinical settings (operating room, field, ED, other
in-hospital), paramedic students attempted a median of 7
endotracheal intubation (interquartile range 4-12).69 Using
multivariable modeling, we predicted that paramedic students
in this cohort required 15 to 20 endotracheal intubation
encounters to attain baseline “proficiency” (predicted
endotracheal intubation success threshold of 90%). Similar
modeling efforts using cohorts of medical students, paramedic
students, and anesthesia residents have identified even higher
thresholds for attaining proficiency.63,66,70,71 These observations
suggest that the ideal level of baseline endotracheal intubation
experience is much higher than the current national standard of
5 endotracheal intubations.62
Endotracheal intubation training in the controlled operating
room setting is ideal, but according to these figures, the number
of operating room cases needed to train paramedic students is
formidable, approximately 80,000 operating room cases
nationally each year (approximately 200 accredited paramedic
training programs times approximately 20 graduating students/
program/year times 20 endotracheal
intubations/student/year⫽80,000 intubations/year).69 This
estimate does not include students in nonaccredited paramedic
programs or paramedics already in clinical practice.
Furthermore, although increasing opportunities for operating
room endotracheal intubation training is desired, paramedic
training programs nationally have observed a general reduction
in these opportunities, a phenomenon attributed to competition
with other students, the widespread use of nonintubation
techniques (such as the laryngeal mask airway), and
anesthesiologists’ medicolegal concerns.72
Mannequins and human simulators provide opportunities
for paramedic endotracheal intubation training, but only 1
study has evaluated how these platforms translate to clinical
skill. In an effort occurring more than 20 years ago, Stewart et
al2 assigned paramedics to different training strategies, including
combinations of mannequin, animal, and operating room
endotracheal intubation. Although the authors indicated no
difference in clinical endotracheal intubation success rates
between the groups on limited multivariable analysis, the
unadjusted data suggested higher initial and ongoing
endotracheal intubation success in the operating room–trained
groups. A more recent effort by Hall et al73 compared
paramedic operating room training with human simulator
training. Although the authors stated equivalence between the 2
modalities, the evaluated outcome was operating room
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endotracheal intubation performance, not clinical out-ofhospital endotracheal intubation performance.
Cadavers (ie, recently dead patients) have also been used for
paramedic endotracheal intubation training, but only 1 study
has evaluated the connection with clinical performance. Stratton
et al74 compared mannequin with mannequin⫹cadaver training
and found no difference in clinical endotracheal intubation
performance between these groups. However, this inference was
based on 60 paramedics, each performing a mean of only 3
endotracheal intubations. There are no direct comparisons of
cadaver and operating room– based training. Cadavers were
once widely used for teaching paramedic endotracheal
intubation, but recent ethical concerns have curtailed learning
opportunities on the recently dead.75,76
Beyond baseline proficiency, regular clinical experience is
likely an important element for maintaining endotracheal
intubation skill. Studies of complex medical procedures (such as
cardiac catheterization and bypass) suggest that centers and
practitioners who perform these interventions frequently have
improved survival and lower complication rates.77– 80 In Maine,
Burton et al81 found that only 40% of paramedics attempted
out-of-hospital endotracheal intubation annually, and only 1%
to 2% of all paramedics performed 5 or more out-of-hospital
endotracheal intubations annually. Separate from that study, we
used 2003 statewide data from Pennsylvania, tallying the
number of out-of-hospital endotracheal intubations performed
by certified advanced life support rescuers (paramedics, out-ofhospital nurses, EMS physicians).82 We found that rescuers
performed a median of only 1 out-of-hospital endotracheal
intubation (interquartile range 0 to 3) during the study period;
39% performed no out-of-hospital endotracheal intubations,
and 67% performed fewer than 2 out-of-hospital endotracheal
intubations. Thus, contrary to common assumptions, most
individual paramedics performed the procedure infrequently.
Although the exact numbers needed to maintain out-of-hospital
endotracheal intubation skill are unknown, these procedural
frequency figures seem relatively low.
The original models of out-of-hospital endotracheal
intubations in Boston, Columbus, San Diego, and Pittsburgh
were designed for small, closely supervised, highly skilled cadres
of paramedics working in busy urban EMS systems and
supported by intensive training.1– 4 Today, although many
individual paramedics demonstrate exceptional endotracheal
intubation skill, one must reconsider whether all paramedics
nationally can attain the same level of excellence, given current
limits in endotracheal intubation training and clinical
experience.
Can We Improve Out-of-Hospital Endotracheal Intubation?
The current literature draws attention to many problematic
aspects of out-of-hospital endotracheal intubation while offering
few affirmations of current practice. Proposed solutions address
only isolated aspects of the procedure, and none provide perfect
or complete answers. For example, some have proposed that
systematic use of waveform capnography could eliminate
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Out-of-Hospital Endotracheal Intubation
endotracheal tube misplacements in the out-of-hospital
setting.39,83,84 Silvestri et al83 recently reviewed 213 out-ofhospital endotracheal intubations arriving at a Florida Level I
trauma center. The authors found that the tube misplacement
rate was zero percent when waveform capnography was used
and 23.3% when waveform capnography was not used.
However, only limited formal data describe the accuracy of
these devices on cardiac arrests, which comprise most of the
endotracheal intubations in the out-of-hospital setting.83,85– 87
Some directors have expanded the use of sedative or
neuromuscular blocking agents to improve the out-of-hospital
endotracheal intubation success of nonarrest patients.88
However, as discussed previously, the San Diego RapidSequence Intubation Trial showed that important complications
may result when these advanced techniques are introduced on a
large-scale basis.20,42 Because of its profound sedative effects and
stable hemodynamic profile, some EMS systems have used
etomidate alone (without neuromuscular blockade) to facilitate
out-of-hospital endotracheal intubation of nonarrest
patients.89,90 However, a recent randomized controlled trial
comparing etomidate-only with midazolam-only facilitated cases
found no difference in out-of-hospital endotracheal intubation
success rates.91 The observed etomidate endotracheal intubation
success rate in this trial was 76% (95% CI 65% to 87%), which
may be below desired success thresholds. Furthermore, the
authors performed only a limited outcomes analysis.
Some EMS services have improved procedural experience
and proficiency by using fewer targeted-response
paramedics.5,92,93 In the original implementation effort by
DeLeo, the investigator purposely constrained the number of
paramedic units to maximize out-of-hospital endotracheal
intubation procedural exposure.3 Although feasible in dense
urban settings, these strategies may not be possible in remote
rural areas where ambulances already cover large geographic
distances. These approaches are also at odds with the efforts of
communities seeking to increase the number of paramedics in
their regions.94
In the spirit of seeking system-level improvements, one cannot
ignore the question, Should we intubate at all? For apneic or nearapneic patients, alternate airways such as the Combitube
(esophageal-tracheal twin-lumen airway device; Kendall, Inc.,
Mansfield, MA) and laryngeal mask airway (LMA North America,
San Diego, CA) have appealing characteristics and are supported by
some data.95–98 These devices are conceptually simpler than
endotracheal intubation, easier to insert than endotracheal tubes,
require less training, and are less subject to skill decay.71,96,99 –101
These devices have been extensively used as primary and secondary
airway management devices.102–104 There is wide experience with
the use of these devices by nonphysicians and even basic-level
rescuers.97,101,105–112 Combitubes and laryngeal mask airways offer
ventilation and oxygenation comparable with endotracheal
intubation in controlled and field settings.96,100,113–115 Current
advanced cardiac life support guidelines recommend the use of
Annals of Emergency Medicine 537
Out-of-Hospital Endotracheal Intubation
these devices when rescuers have only limited endotracheal
intubation experience.116
Combitubes and laryngeal mask airways have important
adverse effects, limitations, and concerns, including many
similar to those of endotracheal intubation.45,117–122 Most
important, their links to patient outcome have not been
defined. Before Combitubes and laryngeal mask airways can
formally replace endotracheal intubation, we must perform
careful systematic evaluations to verify their safety and
effectiveness.
CONCLUSION
The current literature highlights shortcomings associated
with out-of-hospital endotracheal intubation. Few studies affirm
current practice. Few studies have demonstrated improved
outcome from out-of-hospital endotracheal intubation in any
disease group, and several studies describe worsened outcomes.
In many studies, adverse events and errors associated with outof-hospital endotracheal intubation are frequent. Out-ofhospital endotracheal intubation may inadvertently interact
with other physiologic processes key to optimizing resuscitation.
Significant system-level barriers limit opportunities for
endotracheal intubation training and clinical experience.
Scientists, medical directors, and clinicians must strive to better
understand and ultimately improve this key intervention.
Supervising editor: Robert K. Knopp, MD
Funding and support: Dr. Wang is supported by Clinical
Scientist Development Award K08-HS013628 from the Agency
for Healthcare Research and Quality, Rockville, MD.
Publication dates: Received for publication October 27, 2005.
Revision received January 9, 2006. Accepted for publication
January 11, 2006. Available online February 28, 2006.
Reprints not available from the authors.
Address for correspondence: Henry E. Wang, MD, MPH,
University of Pittsburgh School of Medicine, Department of
Emergency Medicine, 230 McKee Place, Suite 400,
Pittsburgh, PA, 15213; 412-647-4925, fax 412-647-6999;
E-mail [email protected].
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associated with the use of the esophageal-tracheal Combitube.
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with use of the laryngeal mask airway during cardiopulmonary
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2006
Undersea and Hyperbaric Medicine
Subspecialty Examination
The American Board of Emergency Medicine (ABEM) and the American Board of Preventive Medicine (ABPM) will administer
the certifying examination in Undersea and Hyperbaric Medicine on October 2– 6 and October 9 –13, 2006.
Physicians must submit an application to the board through which they are certified. Physicians certified by an American Board
of Medical Specialties member board other than ABEM and ABPM and who fulfill the eligibility criteria must apply to ABPM.
Upon successful completion of the examination, certification is awarded by the board through which the physician submitted
the application.
The eligibility criteria are available from the ABEM office or at www.abem.org.
Application materials are now available for ABEM diplomates and will be accepted with postmark dates through July 1, 2006.
ABPM diplomates should contact ABPM for application cycle information.
AMERICAN BOARD OF EMERGENCY
MEDICINE
3000 Coolidge Road
East Lansing, MI 48823
Telephone: 517.332.4800
Facsimile: 517.332.4853
Volume , .  : June 
AMERICAN BOARD OF PREVENTIVE MEDICINE
330 South Wells Street
Suite 1018
Chicago, IL 60606-7106
Telephone: 312.939.2276
Facsimilie: 312.939.2218
Annals of Emergency Medicine 541