International Journal of Clinical Medicine, 2013, 4, 78-85
http://dx.doi.org/10.4236/ijcm.2013.42015 Published Online February 2013 (http://www.scirp.org/journal/ijcm)
Outcomes in Seriously Head-Injured Patients Undergoing
Pre-Hospital Tracheal Intubation vs. Emergency
Department Tracheal Intubation*
John M. Tallon1#, Gordon Flowerdew2, Ronald D. Stewart3, George Kovacs4
1Departments of Emergency Medicine and Surgery, Capital Health, Dalhousie University, Halifax, Canada; 2Department of Commu-
nity Health and Epidemiology, Dalhousie University, Halifax, Canada; 3Faculties of Medicine and Health Professions, Dalhousie
University, Halifax, Canada; 4Department of Emergency Medicine, Dalhousie University, Halifax, Canada.
Received November 24th, 2012; revised December 24th, 2012; accepted January 3rd, 2013
ABSTRACT
Background: The optimal treatment of major head injuries in the resuscitative phase of care post-injury has yet to be
determined. This study measured the effect on mortality of pre-hospital intubation (PHI) vs. emergency department in-
tubation (EDI) of patients suffering serious head injury. Methods: In the single emergency medical services system for
this Canadian province, we used a population-based trauma database, conventional logistic regression (with and without
the use of a propensity score to control for selection effect bias) to evaluate the effect of PHI vs. EDI on in-hospital
mortality. Inclusion criteria were age ≥ 16 years, serious head injury (Abbreviated Injury Score ≥ 3, non-penetrating
trauma) and resuscitative intubation (PHI or EDI). Results: Over 5 years, 283 patients (2000-2005) met inclusion crite-
ria. Conventional unconditional logistic regression modelled on mortality with “PHI vs. EDI” as the intervention of
interest showed an odds ratio of 2.015 (95% CI 1.062 - 3.825) for improved survival if these patients were intubated in
the emergency department rather than in the pre-hospital phase of care. A propensity score adjustment demonstrated a
similar but more conservative point estimate (OR 1.727, 95% CI: 0.993 - 3.004). Conclusions: This observational study
demonstrated a survival advantage with EDI (versus PHI) in seriously head-injured patients in a mature, province-wide
emergency medical services system.
Keywords: Trauma; Head Injury; Tracheal Intubation; Mortality; Emergency Medical Services; Emergency Medicine
1. Introduction
Injury remains the leading cause of death in Canada for
those under age 45 years and the largest contributor to
potential life years lost of any single disease process in
Canada under the age of 70 years [1]. Within this popu-
lation group, traumatic brain injury (TBI) is the most
common cause of death, and its prevention and treatment
remain distinct challenges for health care providers, pub-
lic health organizations and society as a whole [2,3]. TBI
is the primary contributor to overall injury morbidity and
disability-adjusted life years, as are other central nervous
system injuries, such as spinal cord injury [3], and is the
primary injury in patients discharged to long-term care.
As such, while the prevention of head injuries with vari-
ous engineering, educational and enforcement methods is
of paramount importance, the optimal post-injury care of
patients suffering head injury also has clear implications
for improved outcomes.
Secondary brain injury (after the primary traumatic
insult) can be directly attributable to transient episodes of
hypoxia and/or hypotension, either of which can double
associated post-injury mortality [4]. Relatively simple
pre-hospital interventions, including prevention of hy-
poxia and the use of fluids to prevent hypotension, can
thus potentially ameliorate significant mortality and mor-
bidity in the patient suffering head injury [4-6]. The em-
phasis on empiric and timely intervention with oxygen
and tracheal intubation in the emergency medical ser-
vices (EMS) phase of care has been continually empha-
sized in the literature and published in guidelines for care
of this cohort of patients [7,8]. Tracheal intubation for
seriously ill, head-injured patients has served as a resus-
citative treatment tenet for decades in the pre-hospital
environment [9-14]. However, it is only recently that this
advanced intervention has been comprehensively studied
to determine its true effectiveness in the field.
*There are no conflicts of interest by the authors in relation to this article.
#Corresponding author. Recently a number of studies have questioned the

Outcomes in Seriously Head-Injured Patients Undergoing Pre-Hospital Tracheal Intubation
vs. Emergency Department Tracheal Intubation
79
benefit of pre-hospital tracheal intubation (PHI) and sug-
gested possible harm. Recommendations are now being
formulated for the first time proposing that this proce-
dure be performed only in the more controlled environ-
ment of an emergency department or by critical care pro-
viders. In Canada, only one such study has been per-
formed, and there are no reported urban or rural studies
encompassing an entire state or province, and utilizing
one pre-hospital system [15]. The Canadian province of
Nova Scotia is unique in that it has a single pre-hospital
system with a single province-wide trauma database, as
well as standardized medical treatment protocols within a
single ground and air ambulance system.
The main purpose of this study was to measure the ef-
fects of PHI vs. emergency department intubation (EDI)
on the mortality outcome of seriously head injured pa-
tients in a modern province-wide Canadian pre-hospital
or EMS system.
2. Ethics Approval
This study obtained full ethics approval from the Capital
Health Ethics Review Board.
3. Methods
This was a retrospective cohort study using data from the
Nova Scotia Trauma Program Registry, a province-wide
registry that houses comprehensive data on all severely
injured patients [16]. Over 5600 patients are now in-
cluded in the trauma registry, which has detailed infor-
mation on seriously injured patients in Nova Scotia dat-
ing back to 1994. Data sources for the registry include
the in-hospital patient record, as well as the pre-hospital
patient care record, which includes ground ambulance
and/or air medical transport patient care records and in-
formation from the provincial communication and dis-
patch centre for EMS. The main outcome of interest was
in-hospital mortality. The Canadian province of Nova
Scotia had a population of 913,462 in 2005 and 908,007
in 2001, with minimal variation during the study period;
it is approximately 55,284 km2 in size, with a significant
rural component (53%) [17]. A single tertiary care and
neurosurgical centre for the entire province is located in
the provincial capital of Halifax.
3.1. Study Sample
All subjects ≥ 16 years of age and <80 years of age be-
tween April 1, 2000, and March 31, 2005, were included.
[18,19]. Subjects must have suffered a serious blunt head
injury with an associated Abbreviated Injury Scale (AIS)
of ≥3 for the head (neck excluded), and have been en-
tered into the provincial trauma registry. The AIS scale
number arithmetically defines serious head injury and
has been used in other pre-hospital and trauma head in-
jury research to define serious head injury [20-25]. Fi-
nally, included subjects must have undergone tracheal
intubation either in the field (PHI) or in an emergency
department (EDI). Patients transferred from another fa-
cility by ambulance were included if, during the transfer,
they underwent intubation by EMS providers. If they
were intubated in an emergency department prior to tran-
sport, they were included in the EDI group.
Excluded were those with penetrating injuries to the
head (such as gunshot wounds), those with isolated major
burns or those who were intubated at other phases of care
(i.e. the operating room, intensive care unit, etc.).
Figure 1 shows the conceptual model for the study
and final sample derivation methodology.
The final cohort included 329 eligible patients with
major head injury who underwent PHI or EDI over the
five-year period.
3.2. Data Analysis
All analyses were conducted using SPSS, version 15.0
(SPSS Inc., Chicago, IL). Epi Info version 3.3.2 (Centers
for Disease Control and Prevention, Atlanta, GA) was
used for sample-size calculations.
NS Trauma
Registry
All major trauma
2000-2005
(≥16 years of age)
*
Serious head
injury
AIS ≥3
*
Serious head
injury and TI
(PHI or EDI)
Final sample with full data for
analysis with logistic
regression
N = 283
Outcome:
In-hospital
mor t a l i t y
EDI
(CONTRO L)
N = 181
PHI
(EXPOSURE)
N = 102
N = 329
N = 917
N = 2258
Figure 1. Study sample: 16 - 79 years of age. *Excluding
deaths at scene. AIS: Abbreviated Injury Scale; EDI: emer-
gency department intubation; PH I: pre-hospital intubation;
TI: tracheal intubation.

Outcomes in Seriously Head-Injured Patients Undergoing Pre-Hospital Tracheal Intubation
vs. Emergency Department Tracheal Intubation
80
Descriptive statistics were used to explore the data
prior to detailed analysis; this included means, medians,
standard deviations, histograms and box plots for con-
tinuous data and tabulation and percentages for categori-
cal data. Univariate analysis using the Chi-square test for
categorical variables and the Mann-Whitney U test for
continuous variables was performed, with significance
defined as a p < 0.05. The association between the pri-
mary outcome variable (survival) and the predictor vari-
ables was also evaluated using univariate logistic regres-
sion analysis. This produced a crude odds ratio for the
association between each predictor and the primary out-
come.
Unconditional logistic regression by backwards like-
lihood ratio-based stepwise methodology was used to de-
termine the effect of PHI (vs. EDI) on outcome, control-
ling for identified confounding variables [26,27]. Con-
founders included in the initial model evaluation were:
age, injury severity score, presence of pre-hospital shock,
Glasgow Coma Score (GCS) at the scene of injury as as-
sessed by EMS, surgical intervention in the operating
room, presence of co-morbidities and total time to final
emergency department arrival from EMS arrival at the
injury scene. Odds ratios for survival were generated
with 95% confidence intervals.
A propensity score was then derived by generating in-
dividual predicted probabilities of PHI for each subject in
the original non-parsimonious logistic regression mod- el
[28], with all potential cofounders included. The mod- el
selected by stepwise regression was then rerun, with the
propensity score added as a predictor.
4. Results
Between April 1, 2000, and March 31, 2005, 2258 pa-
tients with major injuries entered into the Nova Scotia
Trauma Registry. Of these patients, 917 (40.6%) suffered
major head injury as defined by an AIS of ≥ 3.
Of those suffering a major head injury, 329 (35.9% of
major head injuries) underwent either PHI (n = 116,
35.3% of intubations) or EDI (n = 213, 64.7% of intuba-
tions). This represents a rate of 65.8 patients with major
head injury intubated per year during the study period.
Of the 329 patients with major head injury undergoing
tracheal intubation, 283 subjects had complete data for
use in the logistic regression analysis (see Figure 1).
Table 1 summarizes the characteristics of the two
study populations. Overall, the PHI group had a signifi-
cantly higher unadjusted mortality, higher injury severity
score (ISS), lower GCS (at scene), a shorter length of
stay and a higher prevalence of hypotension (shock)
overall, indicating a different and more severely injured
cohort. Unadjusted mortality in the EDI cohort was
24.9%, and in the PHI cohort was 50%. These numbers
are quite similar to those found by Wang [25], who
demonstrated an overall unadjusted mortality of 37.1%,
with higher mortality in the PHI cohort (48.5%) vs. his
EDI cohort (28.2%).
The mechanisms of injury for the final head injury
cohort were characterized by a preponderance of motor
vehicle collisions (52.6%), as would be expected, fol-
lowed by falls (25.8 %) (Table 2). Overall crude mortal-
ity in intubated patients was 33.8%, demonstrating that-
this was a seriously injured population.
Table 1. Characteristics of study cohort (n = 329).
Characteristic PHI (n = 116) EDI (n = 213) p value
Mortality, % (n) 50 (58) 24.9 (53) p < 0.001*
ISS median (mean) 29 (32.3) 26 (27.7) p = 0.003†
GCS at scene median (mean) 4 (5.9) 8 (8.3) p < 0.001†
ED SBP, mmHg median (mean) 130 (118.5) 138 (137.7) p = 0.009†
Age median (mean) 34.5 (39.2) 38 (40.2) NS†
Sex, % male (n) 75.9 (88) 72.3 (154) NS*
LOS, days, median (mean) 6 (22) 12 (28.9) p = 0.003†
Total time to final ED, min, median (mean) 105 (155) 161.5 (205.2) NS†
Comorbidities present, % (n) 26.7 (31) 31.0 (66) NS*
Number of intermediate hospitals, % p = 0.001*
0 59 (68) 39 (83)
1 39.3 (46) 53.5 (114)
2 1.7 (2) 7.5 (16)
Presence of shock,‡ % (n) 17.0 (20) 4.9 (10) p = 0.001*
OR intervention, % (n) 47.4 (55) 54.9 (117) NS*
Data are median (mean) unless otherwise specified; *Chi-square test; †Mann-Whitney U Test; ‡Systolic blood pressure < 90 mm Hg; ED, emergency depart-
ment; EDI, emergency department intubation; ED SBP, emergency department systolic blood pressure; GCS, Glasgow Coma Score; ISS, injury severity score;
OS, length of stay; NS, not significant; OR, operating room; PHI, pre-hospital intubation. L

Outcomes in Seriously Head-Injured Patients Undergoing Pre-Hospital Tracheal Intubation
vs. Emergency Department Tracheal Intubation
81
4.1. Univariate Analysis
Table 3 shows the characteristics of the study population
based upon the primary outcome measure (mortality).
Patients who survived had a statistically lower ISS,
higher GCS, lower age, longer length of stay, longer time
to final emergency department arrival, less shock and
more frequent operating room surgical interventions.
Further univariate analysis, using simple logistic re-
gression to elaborate the crude relationship between
mortality and the study intervention (PHI vs. EDI)
showed significant odds of survival if intubation was
performed in the emergency department environment
(OR 3.019, 95% CI 1.871 - 4.871). A similar survival
relationship was demonstrated when analyzing outcomes
of air ambulance intubation vs. ground ambulance intu-
bation (OR 6.316, 95% CI 2.718 - 14.672), although the
wide confidence interval was reflective of the small air
medical sample size (n = 45). No statistical difference
was shown between air ambulance and emergency de-
partment intubation outcomes in univariate simple logis-
tic regression analysis (OR 1.018, 95% CI 0.482 - 2.148).
4.2. Multivariate Analysis
Prediction of mortality predicated upon conventional lo-
gistic regression was performed by the inclusion of co-
variates felt to be potential confounders previously de-
scribed in the literature and available within the provin-
cial database. These final chosen covariates (as well as
the “treatment/intervention” variable) included GCS, shock,
ISS, age, operating room surgical intervention, comor-
bidities and total time to final emergency department. We
then performed conventional unconditional logistic re-
gression using a backwards stepwise likelihood ratio se-
lection process.
The total number of patients in the database available
for this analysis (and subsequent propensity analysis and
adjustment) was 283 (or 86% of all subjects); the re-
maining subjects (46/14%) were unavailable for analysis
due to missing data elements. This final analysis cohort
Table 2. Mechanism of injury in study cohort.
Frequency %
Motor vehicle accident 173 52.6
Fall 85 25.8
Assault 26 7.9
Pedestrian vs. vehicle 23 7.0
Other 22 6.7
Total 329 100.0
Table 3. Characteristics of survivors and non-survivors (n = 329).
Survivors (n = 218) Non-survivors (n = 111) p value
ISS median (mean) 26.0 (27.4) 29.0 (33) p = 0.001†
GCS scene (n = 301) median (mean) 8.0 (8.3) 3.0 (5.8) p < 0.001†
ED SBP, mmHg (n = 314) median (mean) 136 (135.4) 130 (121.5) p = 0.179
Age, y (n = 329) median (mean) 32 (36) 48 (48.2) p < 0.001†
Sex, male (n = 242); % (n) 74 (161) 73 (81) p = 0.864*
LOS, d (n = 327) mean (median) 23 (36.4) 1.0 (6.6) p < 0.001†
Total time to final ED, min (n = 307)
Mean (median) 160.5 (200.1) 72.0 (162) p = 0.028†
Comorbidities present, % (n); (n = 97) 17.3 (57) 12.2 (40) p = 0.063*
# intermediate hospitals, %, (n) p = 0.056*
0 70 (153) 54.6 (61)
1 24.5 (53) 40 (44)
2 5.5 (12) 5.4 (6)
Presence of shock,‡ % (n), (n = 29) 1.9 (6) 7.3 (23) p < 0.001*
OR intervention, % (n) (n = 172) 41.6 (137) 10.6 (35) p < 0.001*
Data are median (mean) unless otherwise specified; *Chi-square test; †Mann-Whitney U Test; ‡Systolic blood pressure <90 mm Hg; ED, emergency depart-
ment; EDI, emergency department intubation; ED SBP, emergency department systolic blood pressure; GCS, Glasgow Coma Score; ISS, injury severity score;
OS, length of stay; NS, not significant; OR, operating room; PHI, pre-hospital intubation. L

Outcomes in Seriously Head-Injured Patients Undergoing Pre-Hospital Tracheal Intubation
vs. Emergency Department Tracheal Intubation
82
was comprised of n = 102 PHI subjects and n = 181 EDI
subjects (see Figure 1).
The results of the multivariate analysis showed that
EDI was associated with an odds ratio of 2.015 (95% CI
1.062 - 3.825), indicative of an improved probability of
survival vs. PHI in seriously head-injured patients within
the parameters of this model.
The outcome and intervention model was re-run with
the incorporation of a propensity score comprised of all
confounders originally included in the non-parsimonious
model. Propensity scoring adjustment has been well es-
tablished for use in observational clinical studies to assist
in reducing bias associated with the intervention of in-
terest. The propensity score will most often render a
more conservative outcome than traditional logistic re-
gression modelling. In this study, the use of a propensity
score resulted in an odds ratio demonstrating a more
conservative (but still positive) point estimate (OR 1.727,
95% CI 0.993 - 3.004), but with a confidence interval not
clearly favouring improved survival for EDI.
5. Discussion
Controversy surrounds the issue of optimal airway man-
agement in the resuscitative and transport phase of pa-
tients suffering severe head injury. Whether a patient
should undergo tracheal intubation in the field (by EMS
personnel) or rapid transfer and intubation in an emer-
gency department is of considerable importance consid-
ering the impact on head-injury outcomes of timely and
optimal oxygenation and ventilation clearly have on head
injury outcomes.
Tracheal intubation for patients with severe head inju-
ries has served as a basic treatment paradigm in the pre-
hospital phase of care for decades in North America [29-
31] as well as Europe, Australia and New Zealand. Pre-
venting hypoxia, optimizing gas exchange and protecting
against aspiration with tracheal intubation constitute the
foundation of resuscitative interventions in this critically
ill group. However only recently has tracheal intubation
been intensively studied to determine efficacy and effec-
tiveness and to define indications for the procedure.
There are now several studies that have questioned the
assumed benefit of pre-hospital tracheal intubation, some
even suggesting possible harm unless it is performed in
the receiving emergency department or in very special-
ized pre-hospital environments, such as air medical trans-
port [15,32-34].
Initial studies of PHI (primarily observational, single
site, case series) were positive in their evaluations and
outcomes analyses [35-39]. Christensen et al. in a Danish
observational study, found an 8% survival improvement
with PHI, but only if done by field anaesthesiologists as
per the EMS care model in Denmark [35]. Ochs et al. [37]
in a 2002 prospective case series, and then Davis et al.
[36] following up on Ochs’ work, demonstrated success
with PHI in a severely head injured population per-
formed by paramedics, but in these studies, “success”
was defined procedurally; patient-oriented outcomes were
not measured. An observational study (Sloane et al.) of
patients undergoing PHI by aeromedical crews vs. major
trauma patients brought to the emergency department for
intubation found no difference in 30 day mortality be-
tween the two groups, but used only univariate analysis,
and the two patient populations were significantly dif-
ferent [38]. Winchell and Hoyt [39] found that out-of-
hospital endotracheal intubation was associated with a
positive effect on traumatic brain injury survival and no
effect on discharge destination, but again, their analysis
used only univariate techniques without controlling for
severity of injury or clinical confounders.
In the last few years, methodologically sophisticated
and larger studies of PHI began, and more recent papers
have produced results and conclusions that question the
basic paradigm of pre-hospital resuscitation [15,20,21,24,
25,33,40-43]. For example, Murray et al. [24] using mul-
tivariate analysis and matching in an urban study using
retrospective data from a trauma registry, found a sig-
nificantly higher relative risk of mortality for the PHI
group. Similarly, Bochicchio et al. [20] described a 1.85
times greater risk of death if intubation occurred in the
field vs. the emergency department; it should be noted,
however, that in this study the patients in the pre-hospital
group suffered more severe injuries.
Two of the more recent and well-designed studies used
mortality [21] and mortality/neurological function [25] as
outcome measures in head-injured populations. In these
seminal papers, outcome measures were statistically sig-
nificantly better in the EDI groups than in the PHI groups.
Davis et al. [21] used a prospective cohort design with
historical controls, whereas Wang et al. [25] used a large
urban retrospective trauma database and employed a pro-
pensity score adjustment to account for potential effects
of pre-existing conditions, in-hospital complications and
social factors. Although these two papers are methodol-
ogically quite different, their results were similar: Davis
et al. concluded that PHI was associated with increased
mortality and a decrease in good functional outcomes,
while Wang et al. reported an increased adjusted odds of
death and poor neurological outcome with PHI vs. EDI
[21,25]. In a follow-up study using different methodol-
ogy from their earlier paper, Davis et al. studied the as-
sociation between PHI and EDI in severe head injury
using a county-wide (San Diego) trauma registry and
multivariate adjustment, and found a higher mortality
(OR 2.1, 95% CI 1.8 - 2.5) in the PHI group, confirming

Outcomes in Seriously Head-Injured Patients Undergoing Pre-Hospital Tracheal Intubation
vs. Emergency Department Tracheal Intubation
83
the findings of Wang et al. [23].
Only one Canadian study has been published evaluat-
ing the effects and outcomes of PHI in head-injured pa-
tients [34]. The Ontario Pre-hospital Advanced Life Sup-
port Study (OPALS III) studied the effect of advanced
EMS life support interventions (including PHI) in 2867
major trauma patients (not only head injury) in a pro-
spective before-and-after study. This study showed that
system-wide implementation of full advanced life-sup-
port programs for EMS did not decrease mortality or
morbidity [34]. The Wang study [25,37] also showed
poor functional neurological outcomes in the PHI cohort,
an outcome that could not be measured with the available
data in the current study. No other study has encompassed
an entire state or province or included rural and urban
locations in one emergency medical services system.
In crude analysis for the current observational study, a
distinctly unfavourable outcome (increased mortality)
was statistically associated with PHI in a cohort contain-
ing more seriously injured than the EDI cohort, and this
result was noted even after adjustment for injury severity,
comorbidities and other prognostic variables. In this way,
PHI demonstrated a worrisome poorer outcome, although
a more conservative point estimate was obtained when a
propensity score was utilized. These overall results of
deleterious outcomes with PHI echo those of several
other recent studies [20,22,34]. Unadjusted mortality in
other studies ranged from 23% to 33% for PHI cohorts
[20,21]; Wang et al. found a 48.5% unadjusted mortality
in the PHI group, vs. 28.2% in the EDI group [25], rates
that compare closely to those of the current study (PHI
50% mortality and EDI 24.9% mortality). Clearly, this
cohort of patients (AIS ≥ 3) contains patients with severe
injuries and in need of advanced and timely interventions;
the ongoing questions continue to be which intervention,
and when and where?
The reasons for compromised outcomes with PHI in
major head injury remain elusive but probably include
issues involving paramedic training, the challenges of
airway management skills maintenance, post-intubation
ventilation often characterized by hyper- or hypoventila-
tion, and prolonged intubation attempts with unrecog-
nized hypoxia. It is assumed that these contributory fac-
tors are obviated by intubation in the more controlled
environment of the emergency department (EDI).
Our findings of poor mortality outcomes with PHI are
in the context of a large (province-wide) geographic area
with all the challenges of urban and rural geography,
time and distance [21,25]. The fact that we showed simi-
lar results in a more diverse EMS environment further
informs the argument against PHI unless performed by
advanced airway practitioners in a air medical or critical
care settings.
Limitations and Strengths
Because this was a retrospective database analysis, it can
demonstrate only association; to truly demonstrate causa-
tion, a prospective randomized trial of PHI vs. EDI
would be required. As well, our study contains fewer
patients than that reported in other studies [25], although
sample-size calculations implied robust power to perform
analysis and generate sound results. Although clear mar-
kers of neurological outcome would have been a signifi-
cant addition to this study, limitations of the available
database and lack of access to original charts and long-
term follow-up meant that we were unable to determine
meaningful clinical outcomes (such as neurological-func-
tion) other than mortality.
Another limitation is that the propensity score adjusts
for confounding only by factors used in the model to
generate propensity scores. There may be unobserved
confounders that were missed. As well, propensity scores
work better with larger sample sizes [28,44]. The fact
that up to 14% of the overall cohort had some missing
(and non-retrievable) data elements is also a concern if
“missingness” is related to both the predictor of interest
and the outcome.
Despite these limitations, the unique structure of the
EMS system in Nova Scotia—one neurosurgical site for
serious head injury as part of a single tertiary care centre
for the entire province, plus the population-based man-
date of the Nova Scotia trauma registry—means that this
study possesses strengths of design not present in other
published papers, which were primarily urban in nature
and not state- or province-wide.
6. Conclusion
This study demonstrates a survival advantage for serious
traumatic brain injury if intubation is performed in the
emergency department rather than in the EMS environ-
ment when modelled with logistic regression (OR 2.015,
95% CI 1.062 - 3.825); this result was tempered by a
more conservative point estimate when a propensity
score adjustment was utilized (OR 1.727, 95% CI 0.993 -
3.004). The limitations of a non-randomized design must
be acknowledged, even when a propensity score is used.
However, it seems unlikely that unobserved confounders
would be responsible for all of the apparent association.
This study provides evidence of association that contrib-
utes to the important ongoing debate concerning pre-
hospital intubation in the injured patient.
7. Acknowledgements
The authors would like to acknowledge Ms. Corinne
DeMone for her assistance with the manuscript.

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vs. Emergency Department Tracheal Intubation
84
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