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Supplemental Oxygen Use in Ischemic Stroke Patients
Does Utilization Correspond to Need for Oxygen Therapy?
Arthur M. Pancioli, MD;
Mark J. Bullard, MD;
Mary E. Grulee, MD;
Edward C. Jauch, MD, MS;
David F. Perkis, MA
Arch Intern Med. 2002;162:49-52.
ABSTRACT
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Background In 1994, the American Heart Association Stroke Council concluded that
there were no data to support the routine use of supplemental oxygen in patients
who had a stroke. More recently, supplemental oxygen has been suggested to
be potentially detrimental. The purpose of this study was to determine the
extent of oxygen use in ischemic stroke patients and whether patients receiving
oxygen had indications for its use.
Methods A literature search was performed to generate a comprehensive list of
explicit criteria for supplemental oxygen use. When the literature disagreed,
the criteria were included in the list to overestimate rather than underestimate
the justification for oxygen use. A retrospective chart review of consecutive,
nonintubated, ischemic stroke patients admitted to a university hospital was
performed. Statistical tests and logistic regression models were constructed
to identify the presence of unjustified oxygen use within the sample. Hospital
charges were used to quantify opportunities for resource conservation.
Results A total of 167 patient charts were reviewed yielding a total of 600
inpatient days abstracted. One hundred two patients (61.1%) received oxygen
during some portion of their hospitalization. Of the 322 days that patients
received oxygen, 147 (45.6%) met at least 1 criterion for oxygen use. Of the
278 days that patients did not receive oxygen, 69 (24.8%) met at least 1 of
the criteria for oxygen use. There were 384 days for which no criteria were
met. Of these, a patient still received oxygen 45.6% of the time (175 days).
Factors associated with oxygen use included the presence of at least 1 justifying
criteria as well as increasing age and male sex. Withholding oxygen from those
not medically justified by the criteria could produce resource savings of
roughly 45%.
Conclusions Using a literature-based list of criteria for supplemental oxygen use,
only 45.6% of days of oxygen use were justified in our ischemic stroke population.
This study demonstrates that oxygen therapy is commonly given to ischemic
stroke patients without clear indication, and opportunities exist for substantial
resource conservation.
INTRODUCTION
IN 1994, the American Heart Association Stroke Council concluded that
there were no data to support the routine use of supplemental oxygen in patients
who had a stroke.1 While there are many explicit
criteria for oxygen utilization among inpatients, a diagnosis of ischemic
stroke alone is not adequate. More recently, investigators concluded that
supplemental oxygen should not routinely be given to non–hypoxic stroke
patients who experienced minor or moderate strokes. These authors state that
further research is needed to determine specific indications for oxygen supplementation
for patients who experienced severe strokes.2
In the United States, stroke is the third leading cause of death and
a leading cause of adult disability.3 In 1993,
Broderick et al4 estimated that there are 700 000
acute strokes per year in the United States. In 1993, it was determined that
more than $30 billion per year was spent on the care of stroke patients.5 Dollars spent in the first 30 days after a stroke
equal greater than 50% of the total costs in the first year after a stroke.6 As such, interventions designed to contain resource
utilization for these patients represent potentially significant economic
and resource savings.
With no proven rationale for supplemental oxygen use in ischemic stroke
patients, and the potential for harm, the practice of routine supplemental
oxygen therapy for these patients must be scrutinized. In addition, resource
utilization may be decreased if unjustified oxygen therapy is curtailed. Several
studies have shown that established guidelines for the use and discontinuation
of respiratory therapy result in decreased expenditures without increased
morbidity or mortality.7-9
METHODS
We performed an extensive MEDLINE search to review documented explicit
criteria for supplemental oxygen utilization.7, 10-13
From this review, a table of explicit criteria for oxygen utilization was
created (Table 1). When the literature
disagreed, criteria were included in the list to overestimate rather than
underestimate the justification for oxygen use.
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Table 1. Explicit Criteria for Supplemental Oxygen Therapy
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We designed a retrospective chart review data collection instrument
to gather demographic and oxygen utilization information including a daily
check for any of the explicit criteria for supplemental oxygen utilization.
The data instrument was tested independently in a series of 10 patients by
2 of the researchers to ensure interrater reliability and reproducibility.
Results of this initial evaluation of the data collection tool led to nonsubstantial
formatting changes for clarification only. The data instrument was retested
independently in a series of 5 patients by 2 of the researchers, yielding
excellent agreement. A computer interface for data entry was then developed.
All patients presenting to a large tertiary referral center with the
diagnosis of acute ischemic stroke for the calendar year 1998, a total of
210 patient records, were reviewed. We excluded patients who were never admitted
to the hospital, patients who were intubated, as well as 2 patients whose
charts were unavailable. A total of 167 patient charts were reviewed. Each
patient chart was abstracted for demographic and medical historical information.
This was followed by an abstraction of each inpatient day, identifying documentation
of oxygen utilization as well as any documentation relevant to any of the
explicit criteria that justified oxygen utilization. In keeping with the goal
of overestimating the justification of oxygen utilization, the explicit criteria
were considered met if a single measure was documented that met the criteria.
For example, if there was 1 measurement of a patient's respiratory rate greater
than 24/min, then that explicit criterion was considered met for that day.
For this study, prehospital documentation and supplemental oxygen use were
not considered. A patient's evaluation period in the emergency department
was considered part of the first hospital day.
The proportion of patients receiving oxygen without justifying criteria
was tested to determine if it was statistically different than 0 to confirm
or disprove the presence of resource savings opportunities. In addition, a
logistic regression model was implemented to determine statistically significant
relationships ( = .05) between the decision to give a patient oxygen
therapy (outcome variable) and factors from the patient charts (covariates)
including demographics, medical history, and whether the patient met at least
1 of the justifying criteria for oxygen use. The unit of analysis for the
regression was individual patient days where the patients in our sample had
varying hospital stay durations. The longest hospital stay measured was 17
days and the shortest was 1 day. Due to the unit of analysis, it was necessary
to account for the correlation of the outcome between days within each patient.
Generalized estimating equations were incorporated, assuming an autoregressive
correlation structure between days for each patient, to account for the correlation.
Finally, in an attempt to quantify savings opportunities, the total
charges along with the total respiratory charges for each patient were obtained
from hospital billing records. Unfortunately, the usefulness of this billing
data was questionable due to missing values and the likelihood of erroneous
values. For example, several patients received respiratory services and yet
had respiratory charges that were missing or equal to 0. Due to several discrepancies
in the billing data, we decided to use the standard charges (fees) for both
oxygen therapy setup and daily oxygen administration as proxies for actual
costs to approximate proportional savings opportunities for respiratory resources
due to oxygen therapy.
RESULTS
A total of 167 patient charts were abstracted. The geometric mean patient
age was 61 years. The patients were 47% male and 53% female. The patients
were 62% African American, 37% white, and 1% Asian/Pacific Islander.
CATEGORIZATION BASED ON CRITERIA
From the 167 patient charts reviewed, a total of 600 inpatient days
were abstracted. One hundred two (61.1%) of the 167 patients received oxygen
during some portion of their hospitalization. Forty-five (44.1%) of these
patients met at least 1 oxygen justification criterion on the day of oxygen
initiation. Of the 322 total days that patients received oxygen, 147 (45.6%)
met at least 1 of the criteria for oxygen use. Of the 278 days that patients
did not receive oxygen, 69 (24.8%) met at least 1 of the criteria for oxygen
use. Vital sign abnormalities such as a respiratory rate greater than 24/min
and tachycardia greater than 100/min were the most common explicit criteria
found. Table 2 lists the explicit
criteria for oxygen therapy and the number and percentage of patients who
met each criteria for hospital days during which at least 1 of the criteria
was met. Table 2 also provides
a breakout of this information by whether or not the patient was receiving
supplemental oxygen at the time the criterion was met.
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Table 2. Number of Days Meeting Explicit Criteria
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OXYGEN THERAPY ON DAYS WITH NO JUSTIFYING CRITERIA
Of the 600 inpatient days abstracted, 384 (64.0%) did not meet any of
the explicit criteria for oxygen use. Of the 384 days, patients still received
oxygen therapy on 175 days (45.6%) of the days. The 99% confidence interval
for this percentage is 39.7% to 51.5%. The confidence interval rejects any
hypothesis that this percentage is a very small number close to 0 and confirms
the presence of unjustified oxygen utilization based on the defined criteria.
OXYGEN THERAPY FACTORS
While oxygen use was not limited to patients with a justifying criterion,
logistic regression shows that meeting at least 1 criterion was significantly
associated with the decision to administer oxygen (Table 3). We expanded the analysis by using logistic regression
to simultaneously examine multiple factors. Factors associated with oxygen
use included presence of at least 1 justifying criterion, increasing age,
and male sex (Table 3).
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Table 3. Logistic Regression Results for Factors (Parameters) Associated
With Oxygen Use*
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CHARGE DATA
At the time of the study, the standard charges for oxygen administration
were a one-time setup fee of $29 for the visit and a daily fee of $34 for
oxygen. Based on these fees, total oxygen therapy charges for our sample were
$13 906. By administering oxygen to only patients in the sample for which
oxygen is justified by the criteria, a savings of $6274, or 45.1%, would be
realized based on 147 less days on oxygen and 44 less setup fees. Because
these totals do not include charges for other respiratory services that are
directly or indirectly related to a patient receiving oxygen, a savings of
45.1% would yield a higher absolute savings than the amounts reported herein.
COMMENT
While it seems to be intuitive that providing oxygen to a patient with
an ischemic stroke would be beneficial, paradigms in clinical practice that
are not evidence based should be questioned. Recent expert panel reports document
the lack of utility for oxygen in patients without specified criteria.1 In addition, one recent report detailed the potential
harm in this practice.2 We have generated a
comprehensive list of explicit criteria that would tend to overestimate, rather
than underestimate, the number of inpatient days for which oxygen use is justified.
Even with very inclusive criteria, 54% of the days during which a patient
received oxygen in our study did not meet a single one of the criteria.
Notably, of the 278 days that patients did not receive oxygen, 69 days
(24.8%) met at least 1 of the criteria for oxygen use. It is impossible to
determine from our review whether these patients would have benefited from
supplemental oxygen. For this review, justification criteria for oxygen therapy
were purposefully extremely liberal to define a lower boundary for the potential
resource savings if oxygen therapy were based on explicit criteria. This study
was not designed to evaluate the patient outcomes relative to oxygen utilization
or the potential benefit of oxygen therapy for patients with ischemic stroke.
To confirm cost and resource savings opportunities, it must first be
shown that a significant percentage of the inpatient days during which oxygen
therapy is unjustified result in oxygen utilization. The confidence interval
determined for this percentage shows with 99.5% confidence that there are
at least 40% such cases in our study, thus demonstrating a significant percentage
of unjustified oxygen utilization in one cohort of stroke patients.
While the presence of at least 1 of the justifying criteria was not
an absolute determinant for oxygen therapy in our group of patients, a logistic
regression reveals that it is a statistically significant factor. Our regression
also determines statistically significant parameter estimates for age and
male sex as factors. While this analysis does not imply that age and sex are
direct inputs into the decision to administer oxygen, it does appear that
they are directly or indirectly related to the decision in some manner. Criteria-based
treatment guidelines might diminish the effect of such confounding factors.
Results of our study have revealed a significant potential for savings
through the review of oxygen utilization in ischemic stroke patients. Using
charge data, our study showed that 45% of oxygen therapy charges, as well
as other related respiratory charges, could be saved. While there is clearly
a disparity between charge data and potential cost savings with decreased
resource utilization, the fact that only 46% of the days for which oxygen
was utilized can be medically justified by the previously described criteria
offers a significant hope of cost savings through decreased utilization of
respiratory services.
Our study is limited because it is a retrospective chart review. While
the documentation for each individual patient day was carefully reviewed for
any criteria for oxygen use, it is possible that a patient met a criterion
that was not recorded by a physician, nurse, or respiratory therapist.
There are also limitations to estimating the true potential cost savings
or "cost-effectiveness" of decreasing inappropriate oxygen utilization for
stroke patients. The definition of cost-effectiveness is "a change in health
care resources used (ie, incremental cost) relative to a change in health
outcomes (ie, incremental effectiveness) if a new intervention is adopted
over the alternative."14 For this study, the
true cost of oxygen utilization is an unknown; charges are often higher than
actual cost, while some services are also underestimated by charges secondary
to such procedures as cross-subsidization. When more than half of all oxygen
utilization cannot be considered medically justified by a very broad sweeping
and inclusive series of criteria, however, there is significant hope for a
potential diminution of oxygen utilization, and the resources involved, for
these patients.
Like so many disease processes, certain paradigms exist in clinical
practice that may or may not have scientific or clinical validity. Automatic
oxygen utilization for an ischemic process, while inherently pleasing, is
unlikely to be medically justified for all patients. This study highlights
one example where a careful look at clinical practice may offer a significant
opportunity for resource utilization reduction for a disease of enormous proportion.
AUTHOR INFORMATION
Accepted for publication April 18, 2001.
Corresponding author and reprints: Arthur M. Pancioli, MD, Department
of Emergency Medicine, University of Cincinnati College of Medicine, 231 Albert
Sabin Way, Cincinnati, OH 45267-0769 (e-mail: Arthur.Pancioli{at}uc.edu).
From the Department of Emergency Medicine, University of Cincinnati
College of Medicine (Drs Pancioli, Bullard, and Jauch), Institute for Health
Policy and Health Services Research (Mr Perkis), and Department of Pediatrics,
Children's Hospital Medical Center (Dr Grulee), Cincinnati, Ohio.
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