Pediatric Emergency Department
Overcrowding and Impact on Patient Flow
Nathan L. Timm, MD, Mona L. Ho, MS, Joseph W. Luria, MD
Background: Understanding the impact of overcrowding in pediatric emergency departments (PEDs) on
quality of care is a growing concern. Boarding admitted patients in the PED and increasing emergency
department (ED) visits are two potentially significant factors affecting quality of care.
Objectives: The objective was to describe the impact ED boarding time and daily census have on the
timeliness of care in a PED.
Methods: Pediatric ED boarding time and daily census were determined each day from July 2003 to July
2007. Outcome measures included mean length of stay (LOS), time to triage, time to physician, and
patient elopement during a 24-hour period.
Results: For every 50 patients seen above the average daily volume of 250, LOS increased 14.8 minutes,
time to triage increased 6.6 minutes, time to physician increased 18.2 minutes, and number of patient
elopements increased by three. For each increment of 24 hours to total ED boarding time, LOS
increased 7.6 minutes, time to triage increased 0.6 minutes, time to physician increased 3 minutes, and
number of patient elopements increased by 0.6 patients.
Conclusions: ED boarding time and ED daily census show independent associations with increasing
overall LOS, time to triage, time to physician, and number of patient elopements in a PED.
ACADEMIC EMERGENCY MEDICINE 2008; 15:832–837 ª 2008 by the Society for Academic Emergency
Keywords: emergency department, pediatrics, overcrowding, boarding time, census
tals closed; however, the number of ED visits increased
from 90 million to 114 million visits annually.1Despite
the growing crisis, a standard definition or measurement
of overcrowding has yet to be developed, and those rec-
ommendations that do exist have been primarily evalu-
ated in EDs within ‘‘adult’’ academic centers.2–5Little is
known of the best indicators of overcrowding in the
pediatric emergency department (PED).6
In the context of increasing ED visits and long wait
times, EDs still attempt to provide high-quality care. In
2001, the Institute of Medicine described in its report
Crossing the Quality Chasm: ‘‘All health care organiza-
mergency department (ED) overcrowding has
received significant attention over the past few
years. Between 1993 and 2003, nearly 700 hospi-
tions, professional groups, and private and public pur-
chasers should pursue six major aims; specifically,
health care should be safe, effective, patient-centered,
timely, efficient, and equitable.’’7Nevertheless, there is
a growing body of research describing the negative
consequences of ED overcrowding on patient quality
of care in terms of effectiveness of clinical outcomes,
particularly in delays in treatment.8–11These studies
primarily focus on outcomes in ‘‘adult’’ emergency
care. To our knowledge, to date there have been no
studies describing the association between clinical out-
comes and overcrowding in PEDs.
This study focuses on two measures of overcrowding
as described in the input–throughout–output conceptual
model of ED care delivery: ED boarding time and ED
daily census.4Furthermore, given that increased wait-
ing time has been shown to decrease patient satisfac-
tion in the ED, we chose timeliness as our measure of
quality of care for this study, in particular length of stay
(LOS) and time to physician.12–14The goal of this study
was to describe the association of ED daily census and
ED boarding time on patient flow benchmarks in a
PII ISSN 1069-6563583
ª 2008 by the Society for Academic Emergency Medicine
From the Division of Emergency Medicine (NLT, JWL) and the
Division of General and Community Pediatrics (MLH), Cincin-
nati Children’s Hospital Medical Center, Cincinnati, OH.
Received March 20, 2008; revisions received May 28 and June 6,
2008; accepted June 13, 2008.
Address for correspondence and reprints: Nathan Timm, MD;
The study was a retrospective descriptive study over a
4-year period, from July 2003 to July 2007, in the ED
(CCHMC). The study was determined by the CCHMC
Institutional Review Board (IRB) to be exempt from
informed consent and full committee review.
Study Setting and Population
CCHMC is a large, urban, and tertiary care pediatric
teaching hospital, with an ED patient volume of approx-
imately 95,000 visits per year. CCHMC serves the local
pediatric needs of Cincinnati, Ohio, and is the primary
pediatric referral center for southwest Ohio, northern
Kentucky, and eastern Indiana.
Mean daily data for each primary outcome were deter-
mined using the mean value of all patients seen during
the 24-hour period (12:00 AM to 11:59 PM). Time data
began when the ED greeter entered the initial patient
identifiers into our electron patient tracking system,
EMSTAT (Allscripts, LLC, Chicago, IL), upon arrival of
the patient to the ED. The time-to-triage interval was
defined as the time interval from the ED greeter enter-
ing the patient identifiers into EMSTAT to when the tri-
age nurse entered patient information into EMSTAT.
The time to physician evaluation was calculated from
the arrival time to when the physician entered his⁄her
name into EMSTAT as the responsible physician for the
patient. Patient elopement was documented in the med-
ical record if the patient left the ED prior to completion
of medical care, and daily cumulative numbers were
The database contained the specific independent pre-
dictors of interest: daily census and ED boarding time.
Daily census was determined by the total number of
patients arriving in the ED during a 24-hour period
(12:00 AM–11:59 PM). The ED boarding time was defined
by the cumulative number of hours all admitted patients
spent waiting for an inpatient bed. The time began
when the disposition was set in the electronic medical
record for a patient to be admitted and ended when the
patient left the ED. This included patients waiting trans-
fer to the floor under normal operating conditions, as
well as those patients boarded in the ED because of no
available inpatient beds in the hospital.
Two other independent variables were included for
use in the multivariable analysis: daily percentages of
high-acuity patients and activation of alternative ED
beds during high volume days. Acuity levels of patients
were determined by a five-tier triage system developed
and utilized by our ED. The percentage of the highest
acuity levels of 1 and 2 were used in the analysis. Types
of patients included in these categories included trauma
patients and patients requiring emergency medical
attention (i.e., patients with severe asthma, sepsis, or
long bone fractures). Patients with these triage acuity
levels were taken directly to the shock-trauma suite or
to the first available room to facilitate rapid medical
evaluation. Furthermore, alternate rooms within the
hospital, but outside of our ED (clinic space), were
made available for ED patient care during high-volume
days. Availability and use of these rooms was incorpo-
rated into the analysis.
The primary outcomes were mean time to triage, mean
time to physician evaluation, and mean overall LOS.
Mean times to triage and physician evaluation were cal-
culated for all patients. Mean LOS was calculated only
for patients discharged home. In addition, the number
of patients who eloped from the ED (defined as leaving
priorto completion of
documented for each day. A database was created from
EMSTAT, which contained
measures as well as the independent variables for each
day over the 4-year time span.
our primary outcomes
Outcome variables of daily mean LOS, daily mean time
to triage, and daily mean time to physician evaluation
were log-transformed due to the right-skewed distribu-
tion of these variables. General linear models were
used for the analysis of each transformed variable.
Poisson regression models were used to analyze the
elopement count, which followed a Poisson distribution.
Daily census and ED boarding time were predictor vari-
ables of interest. Adjustment covariates of percentage
of high-acuity patients, percentage of admitted patients,
or availability of alternative bed were introduced in a
stepwise fashion and were kept in the model at p < 0.05
or if inclusion of a covariate changed the coefficient for
census or ED boarding time by more than 10%. SAS
statistical software (SAS v.9.1.3, SAS Institute, Inc.,
Cary, NC) was used for all statistical analysis.
The sample size in our study was 1,461 ED days. Because
all data were captured electronically, there were no miss-
ing data. Overall patient flow measures for the study per-
iod are included in Table 1. Models of LOS, time to
triage, time to physician, and elopement are presented in
Table 2. For every census increase of 50 patients, LOS
Daily Means of Variables
VariableDaily Means (Range)
Time to triage (min)
Time to physician (min)
(number of patients)
ED census (number of patients)
ED boarding time (hr)
Percentage of high-acuity
Alternative bed activation*
LOS = length of stay.
*Proportion of days in which alternative bed activation
ACAD EMERG MED•September 2008, Vol. 15, No. 9•www.aemj.org
increased by 9.1% (p < 0.0001; Figure 1); i.e., LOS
increased about 11.4 minutes per 50 patients from a cen-
sus of 100 to 250 and about 14.8 minutes per 50 patients
from a census of 250 to 400. For every ED boarding time
increase of 24 hours, LOS increased by 4.4% (p < 0.0001;
Figure 2); i.e. LOS increased about 6.1 minutes per 24-
hour increment from 0 to 48 hours and about 7.6 min-
utes per 24-hour increment from 48 to 240 hours.
Figure 3 illustrates the relationship between census
and time to triage. For every census increase of 50
patients, time to triage increased by 53.7% (p < 0.0001);
i.e., time to triage increased about 1.8 minutes per
50 patients from a census of 100 to 250 and about
6.6 minutes per 50 patients from 250 to 400. For every
ED boarding time increase of 24 hours, time to triage
increased by 6.7% (p < 0.0001; Figure 4); i.e., time to tri-
age increased about 0.6 minutes per 24-hour increment
from 0 to 240 hours.
For every census increase of 50, time to physician
increased by 27.2% (p < 0.0001; Figure 5); i.e., time to
physician increased about 8.8 minutes per 50 patients
from a census of 100 to 250 and about 18.2 minutes per
50 patients from 250 to 400. For every ED boarding
time increase of 24 hours, time to physician increased
by 5.3% (p < 0.0001; Figure 6); i.e., time to physician
increased about 3 minutes per 24-hour increment from
0 to 240 hours.
Outcome InterceptCensus50ED Boarding Time % Acuity Alternative BedModel Fit Statistics
R2= 0.546, p < 0.001
R2= 0.618, p < 0.001
R2= 0.660, p < 0.001
v2= 1088, d.f. = 4*, p < 0.001
ln(Time to triage)
ln(Time to physician)
d.f. = degrees of freedom; ED = emergency department; LOS = length of stay.
*R2does not apply to Poisson regression.
Figure 1. Emergency department (ED) census and length of
stay (LOS). For all figures, the solid line is the predicted line of
the relation between the predictor and the outcome. The
long-short dashed line is the lower 95% confidence limit of the
predicted line, while the short dashed line is the upper 95%
confidence limit of the predicted line.
Figure 2. Boarding time and length of stay (LOS).
Figure 3. Emergency department (ED) census and time to
Figure 4. Boarding time and time to triage.
Timm et al.•PED OVERCROWDING AND PATIENT FLOW
For every census increase of 50, elopement count
increased by 67.3% (p < 0.0001; Figure 7); i.e., elope-
ment count increased about 0.7 per 50 patients at a
census of 100 to 250 and about 3 per 50 patients from
250 to 400. For every ED boarding time increase of
24 hours,elopement count
(p < 0.0001; Figure 8); i.e., elopement count increased
about 0.6 per 24-hour increment from 0 to 240 hours.
To the best of our knowledge, this is the first study that
examines the relationship between ED crowding mea-
sures and timeliness of care in a PED. We defined over-
crowding in our ED by daily volume and cumulative
daily ED boarding time. We examined one aspect of the
quality of care as defined by the Institute of Medicine,
timeliness, by focusing on time to triage, time to physi-
cian evaluation, and LOS. Additionally, we evaluated
the relationship between these ED crowding measures
on the numbers of patients who left prior to completion
of medical care.
In our study, ED boarding time was most strongly
associated with increased overall LOS. Although there
was an association with increasing time to physician
evaluation as ED boarding time increased, this was not
as strong as the association with increased daily cen-
sus. There was a minimal association with increased
time to triage, which is related more strongly to the
number of triage staff and the ED census. Reducing
capacity, independent of increasing demand, resulted in
longer wait times overall for patients. This is consistent
with previous reports. Falvo et al.15showed that ED
boarding time limited optimal utilization of ED treat-
ment capacity. In our particular case, 240 hours of ED
boarding time results in a reduction of 10 ED beds
available over a 24-hour period. In our ED of 48 beds,
this is a 21% reduction in our bed capacity.
Daily census was also more strongly associated with
the number of patients who left without being seen,
compared with ED boarding time. Previous studies in
both pediatric and adult EDs support this relationship
between overcrowding and elopement rates.16–18In
particular, the annual number of pediatric patients leav-
ing PEDs without being seen is about 2.5% of all PED
visits.19Our study provides additional evidence that
these rates increase with increasing daily volumes and
ED boarding times.
Furthermore, ED daily volume showed dramatic asso-
ciation toour outcomes,
increased above our average daily census of 250 visits.
Although the notion that high volume leads to longer
wait times is intuitive, these data provide a model of the
actual impact of increasing patient volume on the
Figure 5. Emergency department (ED) census and time to
Figure 8. Boarding time and elopement.
Figure 6. Boarding time and time to physician.
Figure 7. Emergency department (ED) census and elopement.
ACAD EMERG MED•September 2008, Vol. 15, No. 9•www.aemj.org
timeliness of care provided in our ED. Asaro et al.20
found that the LOS for discharged patients increased
38 minutes between the 20th and 80th percentile in ED
arrivals. Although we did not define 20th and 80th per-
centiles for our ED arrivals, from a daily census of 150
visits to 350 visits, LOS increased by approximately
This study was limited to data collection from one insti-
tution. This was a pediatric ED, so generalizability to
‘‘adult’’ EDs might be difficult due to the scope of
patients seen in our ED. In addition, at our particular
hospital, during times of high hospital bed capacity,
inpatient ward physicians and nurses care for patients
‘‘admitted’’ in the ED, rather than ED physicians and
nurses. This system may lessen the effect of boarding
patients in regard to quality of care, compared to other
hospitals that require the busy ED staff to care for the
Furthermore, the data were collected electronically at
the time of entry of data by greeter, triage nurse, or
physician. Data are not always entered precisely at the
time of an ‘‘event,’’ but we believe that the bias of a
delayed data entry would likely be small, given that we
used daily average data across the ED population and
the large sample size used in the analysis. It would be
difficult to determine if delays in reporting were associ-
ated by overcrowding factors, given the retrospective
nature of the study.
The ED boarding time was distributed over a 24-
hour period and did not specifically determine impact
during busy or slow times of the day. Patients arriv-
ing to the ED during slower times of the day when
there was ED bed availability may not have the same
delays associated with longer wait times due to lack
of bed availability.
We focused only on the timeliness of care as a mea-
sure of quality of care. As previously discussed, there
are a number of other aspects of quality of care, includ-
ing safety, which were not evaluated in this study. Eval-
uating the other facets of quality care in the context of
ED overcrowding represents important areas of focus
for future study.
Increased ED daily census is strongly associated with
delays in time to triage and time to physician evalua-
tion, increased elopement rates, and increased overall
LOS in a PED. Increased ED boarding time had weaker
associations with all outcomes, but was strongly associ-
ated with increased overall LOS. This study supports
the need for process improvement programs to help
expedite the disposition of admitted patients from the
ED to improve the timeliness of care in the pediatric
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Timm et al.•PED OVERCROWDING AND PATIENT FLOW