Stiell, Ian G
Research Proposal
A Study to Develop Clinical Decision Rules for the
Hospital Admission of Patients with Acute Dyspnea
1. INTRODUCTION
Shortness of breath or dyspnea is a common presenting complaint in the emergency department
(ED) and is associated with clinical conditions that have high rates of death and morbidity, particularly
in older patients. Patients with dyspnea require the use of substantial diagnostic and therapeutic
resources in the ED prior to a decision being made on whether hospital admission is warranted. There
is, however, little evidence to guide decisions on appropriate patient disposition.
The most common conditions causing respiratory difficulty in older patients are congestive
heart failure, chronic obstructive pulmonary disease, and community acquired pneumonia. Congestive
heart failure (CHF) is a condition in which the heart cannot pump enough blood to the other organs.
This can lead to swelling in the lower extremities and to fluid collecting in the lungs which interferes
with breathing. Chronic obstructive pulmonary disease (COPD) is a respiratory disorder largely
caused by smoking, which is characterized by progressive, partially reversible airflow obstruction,
systemic manifestations, and exacerbations of dyspnea that increase in frequency and severity over
time. Community acquired pneumonia (CAP) is an infection of the lungs caused by one of many
different types of bacteria or viruses in patients who have not recently been hospitalized.
Older patients with CHF, COPD, and CAP are often admitted to hospital for their treatment. A
small but important number of these patients die, require intensive care therapy, or suffer morbidity
such as myocardial infarction. Many other patients are discharged after a brief period of therapy in the
ED and do well at home. Some patients initially discharged from the ED, however, suffer relapse and
must return to receive additional ED treatment or be admitted to the hospital. The issue of hospital
admission decisions is an important question in modern health care. There is a significant shortage of
hospital beds, EDs are overcrowded, and the decision to admit or discharge a patient from the ED is of
considerable importance to the patient and to the health care system. There are, however, no widely
accepted or validated guidelines to aid with the decision to admit or discharge these patients.
Our research group has developed an expertise for developing clinical decision rules such as
the Ottawa Ankle Rules and the Canadian C-Spine Rule. Clinical decision rules are clinical tools
developed from original data for the purpose of assisting with bedside diagnostic and therapeutic
decisions. We believe there is a need to develop new decision rules to assist with the admission
decisions for ED patients with CHF, COPD, and CAP. We have also piloted a standardized assessment
tool for respiratory distress patients being considered for discharge from the ED, the “3-Minute Walk
Test” and we believe this may become a key component of decision rules for admission. This walk test
assessment has patients walk at their own pace for 3 minutes with ongoing measurements of
respiratory rate, heart rate, and oxygen saturation. Our preliminary data suggest that this tool may be
able to identify patients at increased risk of adverse events and who, therefore, are not safe for
discharge. Our research group also has considerable experience in conducting clinical studies on
patients with CHF, COPD, and CAP and in conducting patient safety studies.
The overall goal of this study will be to develop three separate decision rules to guide the
admission decisions of physicians for older ED patients with acute dyspnea secondary to CHF, COPD,
or CAP. In particular, these rules will be highly sensitive for predicting the potential for development
of adverse events amongst such patients. This will improve and standardize admission practices for
these patients, diminishing both unnecessary admissions as well as unsafe discharge decisions.
2. BACKGROUND
2.1 Statement of the Problem
2.1.1 Emergency Department Crowding and Admission Decisions
Overcrowding in hospital EDs is one of the most challenging issues currently facing the
Canadian health care system. It is defined as a situation in which the demand for emergency services
has exceeded the ability to provide care within a reasonable time.1 It is a complex issue which has been
emerging as a health care crisis in the past decade in most large, urban and academic North American
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Research Proposal
EDs.2 In Canada, there is recognition that the cause of ED overcrowding is multifactorial and the
problem is system wide, with no simple solutions.3;4 An ED Overcrowding model has been used to
conceptualize ED processes and to identify strategies for reducing overcrowding.5 This model is based
on engineering principles, queuing theory and compartmental models of patient flow. The role of
admissions in the current overcrowding crisis cannot be ignored. For example, the leading cause of
ED overcrowding cited in a recent Canadian Agency for Drugs and Technologies in Health report was
ED in-patients or access block, whereby patients admitted to the hospital must stay in the ED due to a
lack of ward beds.6 The inability of EDs to decant the admitted patients reflects system wide issues
related to active care bed shortages, lack of chronic care alternatives, inefficiencies within the inpatient setting, and inconsistencies in ED decision making among physicians. The issue of admissions
has become so important in the UK that they have recently established a commission to reduce
admissions on 20 sentinel diagnoses. Importantly, CHF, COPD, and CAP are all on that list.7
2.1.2 Patient Safety Patient safety is a major problem in healthcare.8 Studies from Canada, the US,
and many other countries demonstrate that large numbers of patients experience avoidable harm during
the course of their treatments.9-15 In Canada, an estimated 28,000 patients die from health care error
annually.9 Several types of healthcare errors can lead to ‘avoidable harm’. For example, diagnostic
errors can lead to harm as patients will have delayed or incorrect treatments. Other common errors
include treatment errors and procedural errors. Another class of errors is termed ‘system errors’. These
occur when defects in the health care system are the direct cause of harm. For example, system errors
include cases in which equipment malfunctions lead to harm, or situations where a patient receives
inappropriate attention because of overcrowding. In the ED, one common error includes unsafe
disposition decisions. In these cases, patients with serious conditions such as CHF, COPD, or CAP are
sent home inappropriately and consequently experience worse outcomes than expected. Our
preliminary research suggests that 4-6% of ED patients experience harm related to such errors.16;17
2.1.3 Dyspnea in the ED Setting The appropriate evaluation of dyspnea is key to the practice of
emergency medicine. This symptom is associated with high risk clinical syndromes including
myocardial infarction, pulmonary embolism, asthma, CHF, COPD and CAP. This proposal will focus
on the latter three common ED presentations of dyspnea for which accurate medical decisions on
disposition are critical and for which evidence-based guidelines are lacking.
2.1.4 Congestive Heart Failure CHF is a common and serious condition that affects 200,000 to
300,000 people in Canada.18 In one study, CHF was the second most common reason for
hospitalization in Canada with the average length of stay being 12.9 days and accounting for 1.4
million hospital days.19 Moreover, CHF often co-exists with other chronic diseases (such as diabetes
mellitus, COPD, and coronary artery disease) which further contribute to hospitalization and prolonged
lengths of stay. Importantly, patients who are admitted to hospital for CHF have readmission rates as
high as 30% to 60% within 3 to 6 months after initial discharge.20-22 Randomized controlled trial
evidence for the efficacy of well accepted therapies in the ED setting is lacking.23-26 Until recently,
there were no clinical guidelines for the management of acute CHF. The recent European Society of
Cardiology acute CHF guidelines focused primarily on treatment of the acute heart failure symptoms.27
The decision to admit patients to the hospital from the ED for CHF is largely not evidencebased. Although there are numerous studies that have examined the outcome of patients hospitalized
for heart failure there are surprisingly few published studies on the outcome of patients discharged
from the ED with a primary diagnosis of acute CHF. Relapse after discharge is a particularly
problematic issue.28-32 For example, in a recent study in Edmonton, Alberta, 46% of patients with CHF
were discharged from the ED after their assessment and treatment, 14% relapsed (50% were admitted)
within 30 days, and 7.4% of patients died within 180 days after initial presentation to the ED.33
Patients with CHF exacerbations re-presented with acute myocardial infarction, acute coronary
syndrome, and recurrent CHF. In 2003, Brewer reported that 43% of patients discharged from the ED
with heart failure returned for an unscheduled visit within 30 days and overall 20% of patients required
hospital admission within this period.34 A study by Rame showed that 60% of patients returned to the
ED with another acute episode of CHF within 3 months of the initial visit; more than half of these
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patients required hospitalization.35 Clearly, the ED presentation of CHF is a critical event for patients
with CHF, and better decision making in the ED could reduce resource utilization, improve outcomes
and improve the patient’s quality of life.
2.1.5 Chronic Obstructive Pulmonary Disease Chronic obstructive pulmonary disease (COPD) is a
respiratory disorder largely caused by smoking, which is characterized by progressive, incompletely
reversible airflow obstruction, systemic manifestations, and increasing frequency and severity of
exacerbations.36 COPD is a major cause of morbidity and mortality in North America. Estimates of
Canadian health-professional-diagnosed COPD prevalence rates, derived from the 1994-95 National
Health Survey, indicate a COPD prevalence rate of 4.7% in persons aged 55-64, 5.4% in those 65-74
and 8.3% in persons aged greater than 75.37 Recent trends suggest that disease prevalence and hospital
discharge rate in Canada is stable in men, but increasing among women, reflecting a 40 year societal
trend towards increased smoking among females.38 As outlined below, these estimates likely
underestimate the true prevalence of COPD in Canada. In Canada, deaths from COPD increased from
4,438 in 1980 to 9,398 in 1998, establishing COPD as the fourth leading cause of death in men and the
seventh in Canadian women.39 Studies suggest that patients who experience frequent exacerbations of
COPD (more than two per year) are at higher risk for death, and that these patients experience greater
declines in health-related quality of life compared to those who have fewer exacerbations.40 Canadian
data show that hospitalizations for COPD peak in mid-winter and are linked to hospitalizations for
respiratory tract infections among men and women over age 50.39 Economic analyses suggest that
hospitalization alone consumes up to 70% of all medical expenses for patients with COPD.38
Data from the US National Hospital Ambulatory Medical Care Survey showed that there were
an estimated 1,549,000 annual ED visits for COPD in the US in 2000.41 This rate has been increasing
over time.36 Roughly one half of COPD patients who present to the ED are hospitalized and 2000 data
from the US National Hospital Discharge Survey showed that 726,000 hospitalizations from COPD.42
A clinical trial done by our group showed that relapse, defined as an unscheduled visit to a physician’s
office or return to the ED within 30 days because of worsening respiratory symptoms, occurred in 35%
of COPD patients who were discharged from 10 Canadian academic EDs.43
2.1.6 Community Acquired Pneumonia CAP is commonly defined as an acute infection of the
pulmonary parenchyma that is associated with at least some symptoms of acute infection, accompanied
by the presence of an acute infiltrate on a chest radiograph consistent with pneumonia in a patient not
hospitalized or residing in a long-term-care facility for >14 days before onset of symptoms. Symptoms
of acute lower respiratory infection may include several (in most studies, at least 2) of the following:
fever or hypothermia, rigors, sweats, new cough with or without sputum production or change in color
of respiratory secretions in a patient with chronic cough, chest discomfort, or the onset of dyspnea.44
CAP is a common ED presentation and assessments are an important component of
management. In the United States, the incidence of pneumonia has been estimated at 12 per 1000, and
annual admissions to hospital are in the range of 1 million per year.44;45 Further, it is estimated that
75% of the decisions to admit patients are made in the ED. There have been many guidelines
developed to guide treatment, admission varies based on factors such as age, gender, co-morbidities,
severity of illness, and outcomes can range to the extreme of respiratory failure and death.
Admission to hospital is a complex issue fraught with medical misjudgment. For example, in
the past many patients with excellent outcomes were admitted, consuming valuable in-patient
resources. Conversely, those who needed to be admitted often were not, and suffered adverse
consequences such as relapse, prolonged morbidity, and even death. Admission rules were first
developed and validated by the Patient Outcomes Research Team (PORT), and suggested that patients
could be categorized into 5 classes from low risk (Class I; mortality < 1%) to high risk (Class V;
mortality ~ 30%).46-48 The PORT Pneumonia Severity Index (PSI) is composed of demographic,
clinical, laboratory and radiographic findings at presentation (Appendix 1-2a). Emergency physicians
find these guidelines to be cumbersome and difficult to use, to be lacking other issues (e.g.,
intravenous drug abuse, homelessness, support systems), and to be lacking any functional
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assessment.49 In summary, despite some advancement in the past decade, the decision to admit CAP
patients remains complex and often not evidence-based.50;51
Relapse after ED discharge for CAP patients does occur but less frequently than for COPD
and CHF patients.52 In a recent study in North American EDs, approximately 12% of patients with
CAP who were discharged from the ED after their assessment and treatment returned with a relapse.53
Patients with CAP relapses can also present with co-morbidities such as CHF, exacerbations of COPD
and other chronic conditions, as well as complications of treatment. Clearly, the ED presentation of
CAP is a critical event for patients, especially the elderly. Improved decision making in the ED could
reduce resource utilization, improve outcomes and improve the patient’s quality of life.
2.2 Methodological Standards
2.2.1 Clinical Decision Rules
Clinical decision (or prediction) rules attempt to reduce the
uncertainty of medical decision making by standardizing the collection and interpretation of clinical
data.21;54-57 A decision rule is derived from original research and may be defined as a decision making
tool that incorporates three or more variables from the history, physical examination, or simple tests.
These decision rules help clinicians with diagnostic or therapeutic decisions at the bedside. There has
been considerable interest in the methodological standards for their development and validation and
these may be summarized as follows.58-60 a) The outcome or diagnosis to be predicted must be clearly
defined and assessment should be made in a blinded fashion. b) The clinical findings to be used as
predictors must be clearly defined and standardized and their assessment must be done without
knowledge of the outcome. c) The reliability or reproducibility of the predictor findings must be
demonstrated. d) The subjects in the study should be selected without bias and should represent a wide
spectrum of characteristics to increase generalizability. e) The mathematical techniques for deriving
the rules must be identified. f) Decision rules should be clinically sensible: have a clear purpose, be
relevant, demonstrate content validity, be concise, and be easy to use in the intended clinical
application. g) The accuracy of the decision rule in classifying patients with (sensitivity) and without
(specificity) the targeted outcome should be demonstrated. h) Prospective validation on a new set of
patients is an essential test of a new decision rule. This validation process is very important because
many statistically derived rules or guidelines fail to perform well when tested in a new population.61-63
The reason for this poor performance may be statistical, i.e., overfitting or instability of the original
derived model,64 or may be due to differences in prevalence of disease or differences in how the
decision rule is applied.65;66 The methodological standards for a validation study are similar to those
described above. i) Implementation to demonstrate the true effect on patient care is the ultimate test of
a decision rule; transportability can be tested at this stage.67
2.2.2 Patient Safety Studies evaluating patient safety commonly use ‘adverse events’ and
‘preventable adverse events’ as outcomes. 9-15 In this literature, an adverse event is a poor health
outcome that is caused by medical care as opposed to the patient’s underlying disease. For example, an
allergic reaction to penicillin would be considered an adverse event. Adverse events are preventable if
they were avoidable. For example, if a patient was prescribed penicillin despite having a previous
reaction to it, then the adverse event should not have occurred (i.e. it was preventable). On the other
hand, if the patient had never been exposed to penicillin, the event would not be avoidable.
Rating cases as adverse events is not based on explicit criteria because there are large numbers
of treatments in healthcare and even larger number of possible adverse events. It would be almost
impossible to achieve consensus on explicit criteria for all such complications. Therefore, in order to
determine whether an outcome was due to medical care and whether it was preventable, physicians
review the case and perform judgments based on their own implicit criteria. To classify cases as
adverse events, patient safety investigators require that ratings from two physicians must agree.9-15
2.3 Previous Studies to Develop Admission Criteria for Respiratory Distress
2.3.1 Congestive Heart Failure In the past, virtually all patients with acute CHF were
hospitalized.68 Today, many of these patients are seen in the ED and subsequently discharged to the
community for follow up with their personal physicians. Although numerous studies have examined
the outcome of patients hospitalized for heart failure, there are surprisingly little published data on the
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outcome of patients discharged from the ED with a primary diagnosis of acute CHF.28-32 This suggests
that the decision to hospitalize or discharge a patient with acute CHF from the ED is largely based on a
lack of high-quality evidence and/or administrative factors.
The few studies to develop admission guidelines for CHF have important limitations. In
particular, these studies use large administrative databases rather that prospective and specific ED data
collection. Hence, they were unable to evaluate the status of patients after a period of ED management
and they did not incorporate any form of walk test. None of these guidelines have been prospectively
validated nor been implemented into practice. Auble developed a rule based upon a retrospective
review of two proprietary Pennsylvania databases and used only patients who were admitted.28 This
rule has not been prospectively validated. Fonarow developed a decision guideline from a large U.S.
in-hospital registry of heart failure patients and stratified risk based upon 3 variables: systolic blood
pressure, blood urea nitrogen, and serum creatinine.69 This model also does not incorporate variables
later in the ED course and has not been prospectively validated to evaluate safety and effectiveness.
Lee developed a complex scoring model to predict mortality for CHF patients already admitted to
Canadian hospitals.70 Again, this study is limited by not including patients discharged from the ED, by
not including ED status after treatment, and not being prospectively validated.
Recently there has been much discussion of the role of the serum marker, B-type Natriuretic
Peptide (BNP), for the diagnosis and prognosis of patients with CHF.71-74 BNP is a cardiac
neurohormone released by the ventricles during systolic dysfunction or ventricular wall stress. There is
a correlation between elevated BNP levels and the presence and severity of CHF. Higher BNP levels
are associated with increased mortality and morbidity for outpatients with CHF, an effect that is
independent of other cardiac markers, including troponin. Despite enthusiasm for BNP in the literature
and in U.S. EDs, its value for improving care in the ED is unclear and its use is not common in
Canada.75;76 We believe that our study offers a unique opportunity to evaluate the usefulness of BNP
levels in predicting adverse events for CHF patients being considered for discharge.
2.3.2 Chronic Obstructive Pulmonary Disease A recently published prospective cohort study of
140 COPD patients discharged from 29 North American EDs revealed that by day 14, 21% had
relapsed and re-presented for urgent clinic or ED visits.77 This study developed a multivariate model
for relapse but is limited by very small sample size, not including response to therapy or a walk test.
No prospective validation has been reported. An ED study of 83 COPD patients showed that a
spirometry FEV1 value of less than 40% of predicted, identified patients who required hospital
admission or who suffered a relapse after being discharged from hospital with a sensitivity of 0.96,
specificity of 0.58, and overall accuracy of 0.78.78 Combining clinical assessment with spirometry led
to an improvement in specificity to 0.73. The authors concluded that patients with an FEV1 of > 40%
of predicted or no clinical evidence of respiratory distress after treatment may be safely discharged
from the ED. This very small study has not been validated but does provide useful information. Other
ED studies have shown that physician estimation of FEV1 in the ED is poor, that peak expiratory flow
rates in the ED do not acceptably agree with the actual FEV1 measurement, and that there is not good
correlation between the arterial pO2 and the FEV1 in the ED.79-81
2.3.3 Community Acquired Pneumonia Early work in the development of decision rules for CAP
has focused on the decision to hospitalize53.82;83 Subsequently, models focused on mortality, based on
the argument that the identification of patients at low risk for mortality or complication would result in
these patients being safely treated as outpatients. Researchers have developed and validated prognostic
rules for the elderly;84 for patients admitted to the general ward,85-88 and to the intensive care unit .89-92
The most frequently quoted rule is the Patient Outcomes Research Team (PORT) Pneumonia
Severity Index (PSI) developed for pneumonia.46 In this rule, a variety of historical, physiological,
physical examination and laboratory factors are combined to determine a cumulative PORT PSI score.
Scores that are low represent groups of patients (Class I and II) with low mortality risk (< 1%) and
these patients are generally safe for discharge if they have appropriate antibiotic treatment and followup. Patients with higher scores (Classes IV, V) have higher mortality (~10 and 30%, respectively) and
should be admitted to hospital. Class III patients may need short hospitalizations or observation
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following assessment. The PORT PSI score has been validated and its use has been widely encouraged
in North American guidelines.46-48;51 Unfortunately, the rule is cumbersome, difficult to remember, and
many emergency physicians feel that it does not reflect some of the important issues relevant to their
setting (e.g., social situation, homelessness, compliance, poverty, drug abuse, etc). In addition, the rule
does not incorporate response to ED therapy nor any form of walk test. The 2006 edition of "Rosen's
Emergency Medicine" says this about the PORT PSI: "Although this method of assessing the likelihood
of successful outpatient management is helpful, it can be cumbersome to use, has not been modeled to
predict acute life threatening events, does not take into account dynamic evaluations over time, and
has many important exceptions (e.g. an otherwise low-risk patient with hypoxia would be discharged
by strict interpretation of this rule)…Additional discharge criteria could include improving vital signs
over a several-hour observation period, ability to take oral medications, an ambulatory pulse oximetry
greater than 90%, home support, and ability to follow up.”49
2.3.4 Functional Walk Tests Patients with chronic cardiac and respiratory disease often have walk
tests administered as a means of evaluating functional status, treatment effectiveness, and establishing
prognosis.93 These are done in the office or clinic setting under controlled conditions. A variety of
walk tests exist, including time-based tests (e.g. 2-min walk test, 6-min walk test, 2 and 12-min walk
test); fixed-distance tests (e.g. 100 m, half-mile, and 2-km walk tests; velocity-determined walk tests
(e.g. self-paced walk test); and controlled-pacing incremental tests (e.g. incremental shuttle walk
test).94-100 These functional walk tests are exercise tests that measure functional status or capacity,
mainly the ability to undertake activities of daily living. Walk tests require no technical expertise,
making them inexpensive and easy to administer and therefore ideal for the ED setting. More
importantly, they employ an activity that individuals perform on a daily basis (i.e. walking).
A recent review documented the use of these walk tests in the outpatient setting but we are
aware of no previous work validating this approach for acutely ill patients in the ED setting.93
Nevertheless, many emergency physicians use some variation of a walk test as part of their assessment
of the suitability to discharge older patients, particularly those with shortness of breath.49 We believe
there is a great need to standardize the walk test for ED use and to validate its usefulness in predicting
short-term outcomes for these patients.
2.4 Preparatory Work by Applicants
3-Minute Walk Test Pilot Study The applicants recently conducted a pilot study to evaluate the
feasibility and predictive value of a “3-Minute Walk Test” specifically designed for older ED patients
with shortness of breath.101 Details are provided in the draft manuscript (Appendix 1-3a). We enrolled
Ottawa Hospital ED patients aged 50 years or older with CHF, COPD, or stable chest pain and who
were being considered for discharge by the attending emergency physician. Patients were supervised
by a respiratory therapist and medical student research assistant and were asked to ambulate within the
ED at their own pace either on room air or baseline home oxygen level. At each minute for 3 minutes,
one minute post-walk, and at baseline, the values four measurements were recorded: dyspnea on the
modified Borg scale, oxygen saturation, heart rate, and respiratory rate. The outcome measures
included admission to hospital, need for BiPAP, need for intubation, relapse within 14 days, and death.
Overall, 40 patients were enrolled into the study (16 CHF, 9 COPD, 15 stable chest pain) and
12 patients (30%) had adverse outcomes (Table 1). Completion of the walk test was the best predictor
of outcome, with 96% of those with good outcomes completing the test compared to only 58% of those
with adverse outcomes (p<0.01) (Table 2). A repeated measures general linear model compared
minute-by-minute measurements and showed good discrimination between the good and adverse
outcome groups, with p-values <0.10 for dyspnea, respiratory rate, heart rate, and oxygen saturation
measurements (Figure). We believe that the additional effort of measuring respiratory rate manually is
not a useful component. We concluded that this standardized 3-Minute Walk Test was simple to
perform in the ED and provided valuable prognostic information and should be further evaluated.
Review of Cases at Study Sites To prepare for the current application, we conducted a health
records review of all patients seen in the ED with CHF and COPD at one Ottawa Hospital campus
over a 3-month period in 2005.102 After excluding patients who were obviously too ill to be discharged
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(HR > 110, Oxygen saturation < 90%, chest pain), we reviewed clinical and outcome characteristics
(Table 3). Among 77 CHF patients, 38% were admitted from the ED, 29% suffered an adverse event,
and 19% of all patients relapsed within 14 days. Among 40 COPD patients, 30% were admitted from
the ED, 20% suffered an adverse event, and 15% relapsed within 14 days. We also found that 12
specific clinical and laboratory findings were significantly associated with adverse outcome.
For CAP patients, we reviewed data from a cohort seen in the University of Alberta Hospital.52
Among 364 CAP patients seen in the ED and aged 50 years or more, 75% were admitted to hospital,
7.5% died, and 8% relapsed back to the ED within 7 days.
Clinical Decision Rule Research
Over the past 15 years our group has conducted a unique series
of studies to develop clinical decision rules for diagnostic imaging in the ED. We hold a CIHR Group
Grant for Decision Support Tools for Clinicians and Patients and have also published several
methodology papers.59;60;103;104 a) Ottawa Ankle Rules Project. From 1991-95, we conducted a series
of studies involving 17,000 patients to derive, validate, and implement decision rules for radiography
in acute ankle injuries.105-108 A cost-effectiveness study showed that widespread use could lead to large
health care savings.109 Two large surveys showed that the Rules are used by virtually all Canadian
emergency physicians and by most in the U.S., U.K., France, and Spain.110;111 b) Ottawa Knee Rule
Project. We also completed studies to develop a decision rule for radiography in knee injuries.112-114
We demonstrated the potential cost-effectiveness of this rule as well as the fact that it is being widely
adopted by physicians.115 c) Canadian C-Spine Rule Project. We have conducted a series of CIHR
funded studies to derive, validate and implement the Canadian C-Spine Rule in multicentre studies
with more than 27,000 patients.116-118 d) Canadian CT Head Rule Project. We have also conducted
another series of CIHR funded studies to derive, validate and implement the Canadian CT Head Rule
in multicentre studies with more than 10,000 patients.119;120
Patient Safety Research Our group has performed patient safety studies in a number of settings
demonstrating that errors occur across the continuum of healthcare, including hospitals, family doctors
offices, nursing homes, and EDs. In the ED, one common error includes unsafe disposition decisions.
In these cases, patients with serious conditions such as CHF, COPD, or CAP are sent home
inappropriately and consequently experience worse outcomes than expected. Our preliminary research
suggests that 4-6% of ED patients experience harm related to such errors.16;17
2.5 Rationale for the Study
Patients older than 50 years of age frequently present to the ED with shortness of breath due to
CHF, COPD, and CAP. These patients are often admitted to hospital and not uncommonly suffer
adverse events. At the same time, Canadian hospitals suffer from a shortage of in-patient beds and
severe overcrowding in the ED. There are no widely accepted guidelines to assist physicians with their
decision to admit or discharge these patients with shortness of breath. Our research group has
considerable experience with the management of CHF, COPD, and CAP, with the development of
clinical decision rules, and with patient safety research. We have also conducted pilot research into the
standardization of the 3-Minute Walk Test which we believe will have an important role in ED
admission guidelines. We believe that there is a strong need to develop validated decision rules to
allow rational and safe admission decisions for patients with these conditions. This will ultimately
improve and standardize admission practices for these patients, diminishing both unnecessary
admissions as well as unsafe discharge decisions.
3. SPECIFIC OBJECTIVES
The overall goal of this study will be to develop three separate clinical decision rules to guide
the admission decisions of physicians for older ED patients with acute dyspnea secondary to CHF,
COPD, or CAP. In particular, these rules will be highly sensitive for predicting the potential for
development of adverse events amongst patients aged 50 or more with these three conditions. Clinical
decision rules will improve and standardize admission practices for these patients, diminishing both
unnecessary admissions as well as unsafe discharge decisions.
Specific objectives with regards to older COPD, CHF, and CAP ED patients are to:
1. Prospectively evaluate patients for standardized clinical and laboratory assessments;
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2. Evaluate patients for the 3-Minute Walk Test;
3. Evaluate patients for the development of adverse events within 14 days;
4. Determine the association between the clinical findings, laboratory findings, and the 3-Minute Walk
Test with adverse events;
5. Use multivariate techniques to derive 3 highly sensitive clinical decision rules;
6. Assess the classification performance and potential impact of the derived decision rules; and
7. Determine if the adverse events should be considered “preventable”.
4. METHODS
4.1 Study Design
We will conduct a prospective observational cohort study in four Canadian EDs and will
evaluate older patients with dyspnea for predictor variables prior to assessment of adverse events.
4.2 Setting
The study setting will be four Canadian teaching hospitals with a combined annual ED volume
of approximately 240,000 patient visits (Ottawa Hospital Civic and General Campuses, Kingston
General Hospital, University of Alberta Hospital, Edmonton). These sites have had considerable
success in recruiting many ED patients for clinical studies conducted by the applicants. We are
confident that these sites will enrol large numbers of patients with a wide spectrum of disease severity.
4.3 Study Population
4.3.1 Inclusion Criteria Included will be all stable adults > 50 years, who present with shortness of
breath or dyspnea due to CHF, COPD, or CAP and are well enough to be considered for discharge by
the attending ED physician. Some patients will have more than one diagnosis from amongst CHF,
COPD, and CAP.
a) CHF refers to patients with acute shortness of breath secondary to an exacerbation of
chronic CHF or new onset CHF. There is no gold standard for the diagnosis of heart failure and there
has been much variation in the diagnostic criteria used in previous studies. We will use the criteria
recommended by the working group on heart failure of the European Society of Cardiology.29;121;122
Patients must have appropriate symptoms (shortness of breath or fatigue) with clinical signs of fluid
retention (pulmonary or peripheral) in the presence of an underlying abnormality of cardiac structure
or function. If an element of doubt remains, a beneficial response to treatment for heart failure (for
example, a brisk diuresis accompanied by substantial improvement in breathlessness) will also be
considered. Where the diagnosis is unclear from the case records, a panel of three investigators,
blinded to the outcome and treating physician’s diagnosis, will review the cases. We will not base
diagnosis on BNP as this test is not considered to be specific for CHF.
b) COPD refers to patients with exacerbation of COPD, defined as the presence of an increase
in at least two of the following three clinical criteria: breathlessness, sputum volume, or sputum
purulence.43 Patients either have previously received a diagnosis of COPD or have a one-year history
of chronic dyspnea or cough with sputum production. Additional inclusion criteria necessary are a
history of 15 pack-years or more of cigarette smoking, and evidence of at least moderate airflow
obstruction (as defined by GOLD guidelines) in the emergency department.123 Moderate airflow
obstruction is defined as a ratio of forced expiratory volume in 1 second (FEV1) to forced vital
capacity of 0.70 or less, and a post-bronchodilator FEV1 less than 80 percent of the predicted value.
c) CAP refers to patients who present with a new episode of CAP defined as: 1) presence of a
new radiographic pulmonary infiltrate, and 2) the acute onset of at least one confirmatory clinical
finding suggestive of pneumonia, including cough, dyspnea, pleuritic chest pain, sputum production,
fever, and altered mental status.83 Patients must not have been hospitalized or residing in a long-termcare facility for 14 or more days before onset of symptoms.44
4.3.2 Exclusion Criteria We will exclude patients with any of the following critieria (i.e. patients
who appear to be too ill to be considered for discharge after several (4-8) hours of ED management or
who do not fit with the accepted definitions of CHF, COPD, or CAP):
1. Resting oxygen saturation < 90% on room air or on baseline oxygen levels (after 4-8 hours in ED);
2. Heart rate greater than or equal to 110 bpm (after 4-8 hours in ED);
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3. Systolic blood pressure < 90 mm Hg (after 4-8 hours in ED);
4. Confusion or disorientation;
5. Inability to walk;
6. Ischemic chest pain requiring treatment;
7. Acute ischemic ST-T ECG changes;
8. Terminal status – death expected within weeks from chronic illness;
9. Immunocompromised, neutropenia, HIV infection, transplant patients, immunosuppressive drugs
(CAP patients);
10. Unusual pneumonias such as those due to an obstructing tumour or tuberculosis (CAP patients);
11. Hospital admission within 14 days; pneumonia within 6 weeks (CAP patients);
12. From nursing home or chronic care facility.
4.3.3 Patient Selection Consecutive eligible patients will be entered into the study if they meet the
inclusion and exclusion criteria and if study personnel are available to perform the 3-Minute Walk
Test. This will occur 24 hours per day, seven days per week. The initial decision to select patients will
be made by the attending emergency physicians based upon their diagnosis of CHF, COPD, or CAP.
Final determination of eligibility will be made by a panel of investigators, who will be blinded to the
outcomes of the patients. Basic demographic and clinical data will also be collected for eligible
patients who are not enrolled into the study.
4.3.4 Ethical Considerations The research ethics boards of the participating hospitals have
determined that written informed consent need not be obtained for this observational study. As in
previous similar studies conducted by our group, normal patient management will not be altered.
Patients are not being subjected to new therapy, invasive procedures, undue risk or discomfort, or
investigations beyond that which would normally be required in the course of patient care. The 3Minute Walk Test is merely a standardized form of the clinical assessment which is part of routine care
for these patients. We do not expect to approach patients after discharge from the ED. Patient
confidentiality will be maintained throughout the study and patient identifiers will be removed.
4.4 Management Protocols
We will encourage each of the four sites to standardize the ED management of patients with the
three sentinel study conditions, CHF, COPD, and CAP. Towards that end, we have reviewed local care
plans and guidelines for these conditions from Kingston and Edmonton (Appendix 1-2b). We will
encourage all sites to adopt variations on these care plans for their ED staff.
4.4 Standardized Patient Assessment
4.4.1 Patient Assessment Patient assessments will be made by Registered Respiratory Therapists or
Registered Nurses. These research assistants will be trained by means of lectures and practical
demonstrations to assess the 3-Minute Walk Test, the Modified Borg Scale, and other variables in a
uniform manner. A standardized description of each assessment will be appended to the data collection
sheets. The research assistants will record their findings on data collection sheets (Appendix 1-2c).
There will be ongoing evaluation of the quality of the patient assessments judged by completeness of
data collection sheets and compliance in enrolling eligible patients. Staff will be provided regular
feedback of a general nature as well as specific review of any individual problems which may arise.
4.4.2 Selection of Variables The variables selected for assessment in the study were chosen by the
investigators based on their clinical experience and reports in the literature for CHF,28;69;70;124;125
COPD,43;77;126;127 CAP,46;48;51;128;129 and 3-Minute Walk Test.93-101 These variables are felt to be useful
in predicting whether or not patients are likely to suffer adverse events in the 14 days following the ED
visit. The inclusion of too many variables in the protocol would increase the burden for patients and
the assessors and lead to decreased compliance with the study. Several variables discussed in the
literature were felt to be not useful or not reliable and will not be included (e.g. cyanosis, gallop, rales,
wheezes,). The following sections list the variables to be collected and the proposed data Case Record
Form is shown in Appendix 1-2d.
4.4.3 Variables from History a) Demographic (age, gender); b) Past Medical History (congestive
heart failure, NYHA classification, angina, myocardial infarction, percutaneous coronary intervention,
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CABG, diabetes mellitus, chronic obstructive pulmonary disease, chronic renal disease, peripheral
vascular disease, cancer, chronic liver disease/cirrhosis, cerebrovascular disease, dementia, pacemaker,
current smoker, smoker pack-years, hypertension, atrial fibrillation, previous admission for respiratory
distress, previous intubation for respiratory distress); c) Medications (current oral antibiotic use, home
oxygen, current prednisone, chronic medications); d) Current Symptoms (dyspnea, duration of
dyspnea, pleuritic chest pain); and, e) Social factors (lives alone with no caregiver).
4.4.4 Variables from General Examination Some variables will be assessed on arrival and then
again at reassessment, 4 to 8 hours after the initial assessment. The exact time of reassessment will be
determined by the attending physician’s judgment that there has been sufficient time for response to
therapy and that the patient is well enough to undergo the 3-Minute Walk Test. a) Vital Signs on
arrival and after 4 - 8 hours (systolic blood pressure, heart rate, respiratory rate, temperature); b)
Oxygen Saturation on arrival and after 4-8 hours, by pulse oximetry on room air or home O2 level; c)
Altered Mental Status, defined as disorientation to place, person, or time; d) Quantity of Diuresis
after 4-8 hours (CHF patients); e) Ability to Intake Fluids Orally; and, f) Modified Borg Scale on
arrival and after 4 – 8 hours (Appendix 1-2c).130
4.4.5 The 3-Minute Walk Test The 3-Minute Walk Test assessment will be performed by trained
Registered Respiratory Therapists (RRT) or Registered Nurses (RN) at time of reassessment, i.e. 4-8
hours after initial assessment. Patients will be asked to walk at their own pace in the ED for a fixed
period of 3 minutes, regardless of the distance covered. Patients may use their normal walking aids
(e.g. cane or walker) but may not be physically supported by another person. Patients will use no
supplementary oxygen or will use their normal home oxygen flow level. The attending RRT or RN
will attach the study pulse oximeter to the patient’s finger and the oximeter will continually measure
heart rate and oxygen saturation levels, giving ongoing readouts and also keeping permanent
recordings. We will request purchase of specific recording oximeters in our study budget.
For safety reasons, the 3-Minute Walk Test will be discontinued immediately if: a) Patient
requests to stop for any reason or is unable to continue walking; b) Oxygen saturation decreases to less
than 86%; c) Heart rate exceeds 110 bpm; or d) Patient complains of chest pain.
The RRT or RN will record the following data on the 3-Minute Walk Test form (Appendix 21c): a) Initial heart rate and oxygen saturation level, at rest; b) Highest heart rate and lowest oxygen
saturation level, during the 3 minutes of the walk test; c) Heart rate and oxygen saturation level, one
minute following the walk test; d) Inability to complete the walk test and the reason for not
completing (fatigue, dyspnea, chest pain, oxygen saturation level, heart rate).
4.4.6 Variables from Laboratory Tests We will collect results of routinely performed laboratory
tests but will not require non-routine tests other than BNP for CHF patients. a) Routine Chemistry
(blood urea nitrogen, creatinine, sodium, potassium, glucose, CO2); b) B-type Natriuretic Peptide
(BNP) for CHF patients only (not routinely collected in Canadian hospitals – will reimburse hospitals);
c) Hematology (hemoglobin, white blood cell count); d) Arterial blood gases - pCO2, pO2, pH
(optional at discretion of treating physician; not routine management for all patients); e) ECG
Abnormalities – acute or potentially serious findings (infarction, ischemia, atrial fibrillation/flutter,
ventricular tachycardia, a-v conduction disturbance, intraventricular conduction disturbance); f) Chest
X-ray Findings – relevant acute or serious findings by final radiology report (pulmonary congestion,
pleural effusion, cardiomegaly, pneumonia, pneumonia number of lobes); g) Spirometry (FEV1, FVC,
peak flow on arrival and at 4 – 8 hours – COPD only).
4.4.7 Interobserver Reliability Interobserver reliability of the predictor variables will NOT be
evaluated as most variables are discrete and clear-cut with little need for subjective interpretation. The
only exception is the 3-Minute Walk Test and we believe that it is not appropriate to ask some patients
to repeat this assessment for a second observer.
4.4.8 Data Collection The patient assessment data, as described above, will comprise the predictor
variables for the data analyses and will be collected from the following sources: a) ED Health
Record, including physician, nursing, and RRT notes; b) Ambulance Call Report (if applicable);
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c) Hospital Health Record; d) 3-Minute Walk Test Form, to be completed by study RRT or RN
(Appendix 1-2c). e) Case Record Form, to be completed by site research assistant (Appendix 1-2d).
4.5 Outcome Measures
4.5.1 Primary Outcome The primary outcome measure will be “adverse event” defined as any of the
following within 14 days of the ED visit, regardless of whether or not the patient is admitted to
hospital:
a) Death from any cause;
b) Admission to a Monitored Unit (including intensive care units, coronary care units, acute
monitoring units, or stepdown units);
c) Endotracheal Intubation;
d) Need for Non-Invasive Ventilation (e.g. BiPAP) after hospital admission, unless on BiPAP at
home;
e) Myocardial infarction as defined by international consensus standards.131;132 Either one of the
following criteria satisfies the diagnosis for an acute, evolving or recent MI: 1) Typical rise and
gradual fall (troponin) or more rapid rise and fall (CK-MB) of biochemical markers of myocardial
necrosis with at least one of the following: a) ischemic symptoms; b) development of pathologic Q
waves on the ECG; c) ECG changes indicative of ischemia (ST segment elevation or depression); or d)
coronary artery intervention (e.g., coronary angioplasty). 2) Pathologic findings of an acute MI;
f) Relapse for patients who are discharged on the initial ED visit. Relapse is defined as a return to the
ED for any related medical problem within 14 days, i.e. worsening dyspnea, fever, sepsis, chest pain,
inability to ambulate.43 For every suspected relapse we will review the ED health record to determine
that the return visit was for a related medical problem.
Hence, adverse events may occur both in patients who are initially admitted to hospital or who
are initially discharged from the ED. The simple act of hospital admission does not constitute an
adverse event as admission practices may vary from hospital to hospital and may also be influenced by
social factors and bed availability.
4.5.2 Outcome Assessment Assessment of the primary outcome measure, adverse event, will be
made by research staff, blinded to the patient status for the predictor variables. The following source
documents will be used: a) ED health records; b) Hospital health records; c) Computerized
hospital patient tracking and record system, available at all participating sites; d) Review of death
records from the provincial coroner’s offices. The availability of these data has been assured by
representatives of the Coroner’s Offices in Ontario and Medical Examiner’s Office in Alberta
(Appendix 1-1). Final determination of adverse event status will be made by a panel of investigators,
who will be blinded to the predictor variables of the patients. These physician investigators are
specialists in emergency medicine, internal medicine, and respirology.
4.5.3 Secondary Outcome: Preventability The secondary outcome will be determination of
whether adverse events were preventable, i.e. could have been avoided. If a patient suffers an adverse
event, a research assistant will review the source documents described above (Section 4.5.2) and will
extract additional information regarding the event: circumstances surrounding, treatment received by
patient, whether the patient responded to the treatment, and the treating physician’s opinion pertaining
to the cause of the outcome (if recorded). A blinded case summary will be prepared for the index ED
visit. Two physicians will independently review the case summary and make three ratings. First they
will rate whether the outcome was related to the same disease process that led to the patient’s index ED
visit. Second, they will rate whether the outcome was due to treatment. Third, for cases rated adverse
events, they will rate whether it was avoidable. For the purposes of this study, the two physicians must
agree. If they disagree, then a third physician will perform the ratings and make a final judgment.
4.6 Data Analysis
4.6.1 Analysis Plan Each major patient cohort, i.e. CHF, COPD, and CAP, will be analyzed
separately. Hence, we will develop three separate predictive models for CHF, COPD, and CAP but
will use an identical approach for each. For patients with overlapping diagnoses, the panel of
investigators will review the cases and attempt to determine the most responsible diagnosis for that
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visit. Each predictor variable, including the 3-Minute Walk Test (components and ability to complete)
will be evaluated for its univariate association with the primary outcome. Those variables found to be
strongly associated with the outcome measure (P < 0.05) will be combined using recursive partitioning.
4.6.2 Univariate Analysis Univariate analyses will be used to determine the strength of association
between each variable and the primary outcome. This will aid selection of the best variables for the
multivariate analyses. The appropriate univariate technique will be chosen according to the type of
data: for nominal data, the chi-square test with continuity correction; for ordinal variables, the MannWhitney U test; and, for continuous variables, the unpaired 2-tailed t-test, using pooled or separate
variance estimates as appropriate.
4.6.3 Multivariate Analysis Recursive partitioning analyses will derive models to predict the
primary outcome, adverse event, as defined in Section 4.5.1, separately for each of the three study
cohorts. The objective will be to find the best combinations of predictor variables that are highly
sensitive for detecting the outcome measure while achieving the maximum possible specificity. To be
clinically acceptable, the model must be nearly 100% sensitive. The derived models must be easy to
use by clinicians and should contain as few variables as possible. A model will only be acceptable,
therefore, if it fulfils these criteria: a) 99% or greater sensitivity for adverse event, b) highest possible
specificity (which ideally leads to reduction in hospital admission), and c) has no more than six
component variables. Assuming more than one model meets the minimum acceptable criteria, the best
model will be the one which has the highest specificity and the fewest number of component variables.
Recursive partitioning will be performed using KnowledgeSEEKER V5 Software (Angoss
Software, Toronto).133-136 We have had extensive experience in using recursive partitioning to develop
four validated ED clinical decision rules (ankle, knee, cervical spine, and minor head injuries). Our
experience suggests that recursive partitioning is much more suitable than logistic regression when the
objective is to correctly classify one outcome group at the expense of the other, i.e. where high
sensitivity is more important than overall accuracy. Identification of all or most adverse events is the
priority of the model building and misclassification of some cases without adverse events will be quite
acceptable. We can deliberately drive the analysis to correctly classify the adverse event outcome
group at the expense of the group with good outcomes. We can also deliberately avoid complex
models with significant interactions that would be difficult for clinicians to interpret or apply.
The variables chosen by the best models for each condition will constitute the decision rules
for selecting which patients with CHF, COPD, and CAP should be admitted. The decision rules will
be presented in clear narrative form that does not require computation or use of statistical aids. A
hypothetical example of a decision rule is as follows: "Stable patients with exacerbation of CHF in the
ED should be admitted to hospital if they demonstrate any one of these findings: (i) age 80 or greater;
(ii) resting heart rate of 100 or greater after ED treatment; (iii) diuresis of less than 250 ml, 4 hours
after treatment; or (iv) inability to successfully complete the “3-Minute Walk Test."
4.6.4 Classification Performance The derived rules will be cross-validated by comparing the
classification of each patient to their actual status for the primary outcome, adverse event. This will
allow an estimate, with 95% confidence intervals, of the sensitivity and specificity of the rules. More
robust prospective validations will be carried out on new cohorts of patients in a future phase II study.
4.7 Sample Size
4.7.1 Feasibility Based on pilot studies in Ottawa and Edmonton, we can estimate for each of the
CHF, COPD, and CAP patient groups, the number of eligible patients available, current admission
rates, and the incidence of adverse events.
a) CHF: Table 3 indicates that in a 3-month period at one Ottawa ED site, 77 eligible patients
were seen with an admission rate of 38% and an adverse event rate of 29%. Hence, with a projected
50% recruitment rate and extrapolating to 4 sites over 24 months, we can expect to enroll 1,200
patients with 456 adverse events over a 2-year period.
b) COPD: Table 3 indicates that in a 3-month period at one Ottawa ED site, 40 eligible
patients were seen with an admission rate of 30% and an adverse event rate of 20%. Hence, with a
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projected 50% recruitment rate and extrapolating to 4 sites over 24 months, we can expect to enroll
640 patients with 128 adverse events over a 2-year period.
c) CAP: From the 1-year patient review at the University of Alberta Hospital site, 364 eligible
patients were seen with an admission rate of 75% and an estimated adverse event rate of 16%. Hence,
with a projected 50% recruitment rate and extrapolating to 4 sites over 24 months, we can expect to
enroll 1,200 patients with 192 adverse events over a 2-year period.
4.7.2 Patients Required We plan to enrol a total of 3,040 patients over the 2-year enrolment period.
Since no hypothesis is being tested, sample size is based on estimation of the precision of the
sensitivity of the derived rules and on the stability of the multivariate models. The sample size has to
accommodate the large number of potential clinical variables and the large number of evaluating
physicians. Our primary goal is to enrol sufficient numbers of adverse event cases to be able to develop
decision rules with nearly 100% sensitivity and upper and lower limits of the 95% confidence intervals
at 100% and 97.0% respectively. The condition with the lowest number of adverse events available is
COPD and hence can be considered to drive the recruitment period for this study. A 24-month
recruitment period will yield an estimated 128 adverse events for COPD. CHF and COPD will have
more adverse event cases and can be expected to have rules with even more precision of sensitivity.
4.8 Methodological Issues
4.8.1 Should We Have Included Both Admitted and Discharged Patients? We have carefully
considered the issue of including both admitted and discharged patients in this study. We recognize
that that admission status may confound the likelihood of an adverse event occurring. Some admitted
patients will not suffer adverse events because they receive more intensive therapy in hospital. In
contrast, the same patients might have suffered adverse events if they had been discharged from the
ED. Nevertheless, we believe that the best approach is to include admitted patients so that we can
adequately address the specificity of the new rules as well as their sensitivity. In other words, our
objectives are to develop decision rules that ensure appropriate admission of patients at high risk (i.e.
sensitivity) as well as ensuring the admission of a minimal number of patients at low risk (i.e.
specificity). In addition, admission practices likely vary considerably among different hospitals and the
inclusion criteria for the study would not likely be consistently applied from site to site.
4.8.2 Can We Improve Upon the PORT PSI Criteria for CAP? While the PORT PSI guidelines
have been validated, we believe they have significant weaknesses as described in Section 2.3.3. These
guidelines were only developed to predict mortality and not important morbidity. Unfortunately, the
guidelines are cumbersome, difficult to remember, and do not include variables considered important
to emergency physicians. In particular, the PORT PSI does not assess oxygen saturation by pulse
oximetry, either at rest or during ambulation. We are confident that we can develop better guidelines.
4.8.3 Should We Have Used “Admission to a Monitored Unit” as an Adverse Event? We
recognize that there is a risk that “Admission to a Monitored Unit” as one of the criteria for “Adverse
Event” may be somewhat subjective and variable from site to site. Nevertheless, we believe that this is
an important criterion that almost always reflects the severity of illness of admitted patients. It is likely
that such patients would suffer significant morbidity or death if they had been discharged.
4. Study Organization and Timeline (see budget module)
5. RELEVANCE
In Canada, both patient safety and hospital overcrowding are important healthcare issues.
Management of older patients presenting to the ED with acute dyspnea due to CHF, COPD, and CAP
is a common problem. This study will develop clinical decision rules for the hospital admission of
these patients. We expect these guidelines, once validated, will be widely used and will improve the
efficiency of hospital admission practices and will also improve the safety of ED patient disposition
decisions. Future research will validate and implement these clinical decision rules. This will
ultimately improve and standardize admission practices for these patients, diminishing both
unnecessary admissions as well as unsafe discharge decisions.
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6. TABLES AND FIGURES
Table 1. Characteristics of the 40 ‘3-Minute Walk Test’ Patients with Congestive Heart
Failure, Chronic Obstructive Pulmonary Disease, or Stable Chest Pain
CHF
(N=16)
75
56 – 91
63
COPD
(N=9)
69
53 – 83
44
Chest Pain
(N=15)
63
53 – 83
67
Overall
(N=40)
69
53 – 91
60
Vitals signs on arrival
Temperature (ºC)
Heart rate (beats/min)
Respiratory rate (breaths/min)
Systolic blood pressure (mmHg)
SaO2 on room air (% sat)
36.2
91
20
147
96
36.7
89
25
147
96
35.9
75
18
143
98
36.2
85
20
146
97
Past medical history (%)
Coronary artery disease and/or angina
CABG and/or PCI
Congestive heart failure
Hypertension
Prior myocardial infarction
Chronic obstructive pulmonary disease
Lung and/or other cancers
69
56
100
56
44
0
13
22
22
11
44
44
100
11
87
47
7
53
47
7
0
58
45
45
53
45
25
8
Chest X-ray findings (%)
Nil acute or normal
Congestive heart failure
Chronic obstructive pulmonary disease
Infiltrate/pneumonia
13
75
0
6
22
0
44
33
60
0
0
0
32
30
10
10
Electrocardiogram findings (%)
Nil acute or normal
Acute ischemia
Atrial fibrillation or flutter
69
6
19
56
0
0
87
0
7
73
3
10
Walk test (%)
Completed walk test
Duration of walk test [mean] (min)
Experienced chest pain during test
Given nitroglycerin during test
69
2.8
0
0
89
2.9
0
0
100
3
0
0
85
2.9
0
0
Outcome measures (%)
Admitted to hospital
BiPAP required
Intubation required
Myocardial infarction
Relapse
Deceased
25
0
0
0
25
0
22
0
0
11
22
11
0
0
0
0
0
0
15
0
0
3
15
3
Mean Age (years)
Range
Male gender (%)
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Table 2.
Association of 3-Minute Walk Test Patient Characteristics and Findings with
Outcomes
Good
Outcome
(N=28)
Adverse
Outcome
(N=12)
Diagnosis (%)
Congestive heart failure
Chronic obstructive pulmonary disease
Stable chest pain
29
18
54
67
33
0
Gender – Male (%)
57
67
0.73
69 (53 – 91)
70 (56 – 82)
0.66
81
20
149
78
97
94
21
138
76
95
0.13
0.43
0.30
0.73
0.19
Past Medical History (%)
Coronary artery disease
Coronary artery bypass graft
Angioplasty
Chronic obstructive pulmonary disease
Congestive heart failure
Prior myocardial infarction
Lung cancer
46
14
29
21
36
36
4
53
58
17
33
67
67
8
0.73
<0.01
0.69
0.45
0.09
0.09
0.52
Support (%)
Caregiver at home
Cardiologist
54
36
67
67
0.50
0.09
CXR findings (%)
Congestive heart failure
Chronic obstructive pulmonary disease
Nil acute or normal
21
4
39
50
25
25
ECG – abnormal findings (%)
18
25
0.49
Walk test results (%)
Completed
SaO2 < 90% at 3 minutes
96
0
58
25
<0.01
<0.01
Age [mean (range)] (yrs)
Vitals on arrival (mean values)
Heart rate (beats/min)
Respiratory rate (breaths/min)
Systolic blood pressure (mmHg)
Diastolic blood pressure (mmHg)
SaO2 – room air (N=27:11)
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P value
<0.01
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Table 3. Summary of Patient Characteristics and Findings for CHF and COPD Patients seen
over 3 Months at Ottawa Hospital Civic Campus ED
Age, mean
Range (years)
Gender – Male (%)
Vitals on arrival
Temperature (°C) [N=69:39]
Heart rate (beats/min) [N=73:40]
Respiratory rate (breaths/min) [N=66:34]
Systolic blood pressure (mmHg) [N=75:40]
SaO2 on room air (%) [N=62:30]
History
Duration of shortness of breath (days) [N=64:38]
Emergency Department Medications (%)
ACE inhibitor
Angiontensin II receptor blocker
Beta blocker
Calcium channel blocker
Anti-arrhythmic
ASA
Heparin
Coumadin
Diuretic
Vasodilator
Inhaled beta agonist
Inhaled anticholinergic
Inhaled steroid
Oral steroid
Antibiotic
Past medical history
Coronary artery disease
COPD
Congestive heart failure
Lung cancer
Other active cancer
Diabetes (type 1)
CXR findings
Nil acute
CHF
Infiltrate/pneumonia
COPD
Pleural effusion
ECG findings
Nil acute
Abnormal
Outcome Measures (%)
Admission on 1st visit
Adverse Event
BiPAP after admission
Intubation
Myocardial infarction
Relapse
Deceased
Admitted after relapse (N = 15: 6)
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CHF (N=77)
74.5
50.4 – 101.6
64
COPD (N=40)
72.9
50.6 – 88.2
35
36.2
77
23
139
96
36.6
92
23
142
95
10.3
5.5
1
0
3
1
3
4
3
1
71
8
6
3
0
0
10
0
0
0
0
0
0
0
0
5
0
90
88
0
33
23
49
13
96
4
3
25
15
100
25
3
5
3
12
78
5
0
3
35
3
30
15
3
65
32
48
18
38
29
3
1
5
19
8
60
30
20
0
3
0
15
5
33
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Research Proposal
Figure.
Comparison of The 3-Minute Walk Test Results of Patients With and Without
Adverse Outcomes for a) Dyspnea, b) Respiratory Rate, c) Heart Rate, and d)
Oxygen Saturation Measurements
22
3
2
1
No adverse outcome
Adverse outcome(s)
Respiratory Rate (breaths/min)
Modified Borg Scale
4
0
21
20
19
18
17
16
15
14
13
Baseline
1 minute
2 minutes
3 minutes
4 minutes
Baseline
1 minute
2 minutes
Time
4 minutes
3 minutes
4 minutes
Time
Figure a
Figure b
95
97
90
96
Oxygen Saturation (%)
Heart Rate (beats/min)
3 minutes
85
80
75
70
95
94
93
92
Baseline
1 minute
2 minutes
3 minutes
4 minutes
Baseline
1 minute
2 minutes
Time
Figure c
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Time
Figure d
Stiell, Ian G
Research Proposal
7. REFERENCES
(1) Canadian Association of Emergency Physicians, National Emergency Nurses Affiliation. Joint position
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