Pediatric Pulmonology 27:423–427 (1999)
Diagnostic and Therapeutic
Methods
Relation Between Pulse Oximetry and Clinical
Score in Children With Acute Wheezing Less Than
24 Months
of Age
Dolores
Pavo´n, MD , 1
INT
ROD
UCT
ION
Jose Antonio Castro-Rodri´guez,
Rubilar, MD,11and Guido Girardi,
MD,1,2* Lilian
MD
Summary. The aim of this study was to determine the relation between
transcutaneous hemoglobin oxygen saturation, measured by pulse oximetry
(SpO2), and clinical score values in 138 infants (mean ± SD, 6.6 ± 5.5 months
of age) with acute wheezing episodes presenting in a primary care outpatient
setting. A single investigator evaluated the severity of the acute wheezing
episodes by assigning a clinical score and was unaware of the SpOvalues.
Another investigator measured SpO2values on all subjects. The mean (± SD)
SpO22value was 98.2 ± 1.1% for children with clinical scores of 2–5 (n = 32);
95.4 ± 1.5% for those with scores of 6–7 (n = 82), and 92.9 ± 2% for children
with scores of 8–10 (n = 24), ( P < 0.001 by Bonferroni’s multiple comparison,
when all two-way comparisons were done for each pair of results). The
clinical score showed a good correlation with SpO2(r = -0.76; 95% CI, -0.83
to -0.68). We conclude that if pulse oximetry is not available, it is
advisable to include oxygen in the
therapy of wheezy infants with clinical scores values 8. Pediatr Pulmonol.
1999; 27:423– 427. © 1999 Wiley-Liss, Inc.
Key words: pulse oximetry; clinical score; wheezing; therapy; oxygen; bronchiolitis.
score vs. SpO212in children under 2 years of age with acute wheezing.
usefulness of clinical scores for the evaluation of the 13In Chile, wheezing is the most common cause of pediatric
severity of acute wheezing episodes in infants has been shown visits to outpatient departments. Most of these visits occur at
in several studies.4,5However, there are conflicting data in the a primary-care level where pulse oximetry is not readily
literature.6This highlights the need for objective methods to available. We, therefore, designed the present study to
evaluate the severity of these episodes. Hypoxemia is the
correlate the clinical score used in Chile’s Acute Respiratory
primary early feature resulting from the pathophysiological Infection National Programwith
changes that occur in the children with airway obstruction,
and it is an important marker of disease severity.Pulse
1Pediatric Pulmonology Unit, Department of Pediatrics, Exequiel Gonza´les
oximetry is a simple noninvasive method, and it gives fast
Co´rtes Children’s Hospital, University of Chile, Santiago, Chile.
and fairly accurate assessment of arterial oxygen
saturation.6,7
2Pediatric Pulmonary Section, Respiratory Sciences Center, University of
Arizona, Tucson, Arizona.
There have been contradictory results in previous studies
which have tried to establish a correlation between clinical
This work was presented in part at the American Lung Association/
scoring systems and the degree of transcutaneous hemoglobin American Thoracic Society International Conference, May 16–21, 1997, San
oxygen saturation as measured by pulse oximetry (SpO2) in Francisco, CA.
children.4,5,8,10–124,8,9Only one study compared a clinicalThese
*Correspondence to: Jose Antonio Castro-Rodri´guez, M.D., Respiratory
studies were conducted using patients of different ages,
Center, Arizona Health Sciences Center, 1501 N. Campbell Ave.,
different respiratory diseases (e.g., pneumonia, bronchiolitis, Sciences
Tucson, AZ 85724. E-mail: jacastro@resp-sci.arizona.edu
or asthma), and different severities of disease (hospitalized vs. Received 31 August 1998; Accepted 15 December 1998.
ambulatory subjects) and patients were evaluated by several
observers.
1–3The
© 1999 Wiley-Liss, Inc.
424 Pavo´n et al.
TABLE 1—Modified TAL’s Clinical Score1
Respiratory rate
0 40 30 None2
None None
SpO2values in a group of young children with acute wheezing Abbreviations PaCOPartial pressure of carbon dioxide in arterial blood
PaO22Partial pressure of oxygen in arterial blood SpO2Transcutaneous
episodes seen in a primary care setting.
hemoglobin oxygen saturation
MATERIALS AND METHODS
In this cross-sectional study we evaluated 138 children (age
range, 1–24 months) who presented with acute wheezing
episodes to a single primary care center in Santiago (545 m
above sea level), from July to November 1995 (winter–spring
and the respiratory syncytial virus season). We did not
distinguish between asthma and bronchiolitis. All children
had a chest film. Children with a clinical and/or radiological
diagnosis of pneumonia, pulmonary or cardiac congenital
malformations, chronic pulmonary disease, malnutrition, or a
history of prematurity were excluded. The study was
approved by the local Ethics Committee, and verbal consent
of each parent was obtained.
1The patients were accompanied by their mothers at all times.
After a period of adjustment for at least 5 min, and with the
child quiet, not crying, without fever, and breathing room air
only, one investigator (L.R.) evaluated the severity of the
acute wheezing episodes using a modified Tal’s clinical
score(the modification was only in the respiratory frequency
according to age;1314see Table 1). Respiratory frequency was
determined by observation of the thoracic movement over a
full minute. The degree of accessory muscle use was based on
the degree of intercostal or subcostal retraction. According to
the policy of Chile’s Acute Respiratory Infection National
Program, infants with clinical scores of 11–12 must be
referred immediately for hospitalization and, therefore, were
not included in the present study.We recently determined that
infants with a clinical score of 11–12
constituted no more than 3% of all wheezing infants (G.
Girardi, unpublished observations).
Simultaneously, and without knowing the result of the
clinical score, another investigator (D.P.) measured SpO2
with a pulse oximeter (Omheda Biox 3740, Louisville, CO)
using a pediatric probe placed on the big toe, with infant
quiet, awake, and in natural light. The maximum SpO2was
recorded after a period of at least three satisfactory sweeps of
the pulse wave were recorded (corroborating that the cardiac
frequency of the oximeter coincided with the simultaneously
taken heart rate by auscultation). For this study, we defined
hypoxemia as a SpO2value 91%. The data were analyzed
with the EpiInfo v.5.1 (CDDWHO) program. Student’s t-test was used to test the
significance of r or the difference between two means.
Bonferroni analysis was used for evaluations of multiple
comparisons and multiple regressions (Stata v.5.0, Corp.,
TX). Statistical significance was considered when P
0.05.
Score
RESULTS
One hundred thirty-eight infants (88 male, 50 female) with
a mean (± SD) age of 6.6 ± 5.5 months (range, 1–24 months)
were included in the analysis. For the entire population (n 4
138), the mean (± SD) SpO2value was 95.6 ± 2.3%, and the
clinical score value (mean ± SD) was 6.4 ± 1.4.
The mean (± SD) SpO2value was 98.2 ± 1.1% in children
with a score of 2–5, 95.4 ± 1.5% in those with a score of 6–7,
and 92.9 ± 2% in children with a score of 8–10, (P < 0.001 by
Bonferroni’s multiple comparison, when all two-way
comparisons were done for each pair of results; Table 2).
When we divided the population into three age groups (<3,
3–5, and 6 months of age), SpO2
values were still significantly different based on the clinical
score in each age group (P < 0.001 by Bonferroni’s
multiple comparison, when all two-way comparisons were
done for each pair of results; the only exception was
(per min) Wheezing CyanosisAccessory muscle use<6 mths 6 mths
with stethoscope Perioral with crying +
2 56–70 46–60 Inspiration and expirationwith stethoscope Perioral at rest ++
3 >70 >60 Audible withoutstethoscope Generalized at rest +++
1 41–55
31–45 End
expiration
1
14Score: mild, 5; moderate, 6–7; severe, 8–10; very severe, 11–12. Derived from Martínez et
al.,with the addition of an age-appropriate respiratory rate score.
2
If wheezes not audible due to a minimal air entry, consider score 3.
Pulse Oximetry and Wheezing 425
by Clinical Score and Age Group1
C
SpO2
l
T o t a l < 3 m o n ti h s 3 – 5 m o n t h s  6 m o n t h s X ± S D n
X ± S D n X ± S D n nX ± S D n
2–5 98.2 ± 1.1 32 98.1 ± 1.2 14 98.8 ± 1 i4 98.0 ± 1.1 14 6–7 95.4 ± 1.6 82 95.0 ± 1.4 18 95.5 ± 1.6
31 95.4 ± 2.4 33 8–10 92.9 ± 2 24 93.5 ±c0.7 2 92.0 ± 2.3 7 93.2 ± 3.8 17
a for each set of pairs in each age-group and the total group, SpO2for all pairs was
1When all two-way comparisons were done
l for Bonferroni’s multiple comparisons); the only exception was in the <3 months
significantly different (P < 0.001 corrected
age group between those children with clinical score 6–7 vs. 8–10 (P 4 0.15).
s
c
o
r
e
TABLE 3—Correlation (r) Between the Components of the
group, in which there was no difference Clinical Score vs. SpO2
TABLE 2—Average SpO2
in the <3 months age
in the clinical scores of 6–7 vs. 8–10, P 4 0.15, Table 2).
Clinical score r* Components
The correlation coefficient between total clinical score and Cyanosis -0.38 Respiratory rate -0.41 Wheezing -0.52 Accessory muscles use
SpO2was r 4 -0.76 (P < 0.0001; 95% CI, -0.83 to -0.68). The -0.55 Total score: -0.76
correlation of each component of the clinical score and
*P < 0.0001, for all components and total score.
SpO2was also significant (P < 0.0001): wheezing r 4 -0.52,
cyanosis r 4 -0.38, accessory muscle use r 4 -0.55, and
respiratory frequency r 4 -0.41 (Table 3). Age did not
influence this correlation (data not shown). In the more
severely affected patients (clinical score 8–10), the correlation
between SpOand clinical score was r 4 -0.57 (P 4 0.004).
The linear regression model between SpO22and clinical score
was y 4 103.5147–1.2421x (Fig. 1). A clinical score 8
had 100% sensitivity, 86.4% specificity, and 100% negative
predictive value to detect hypoxemia (SpO291%).
DISCUSSION
The clinical score originally described by Tal et al.1
has been used in many clinical trials.3,15–17In the present
study, using a modified Tal’s clinical scorein a large number
of infants with acute wheezing without pneumonia, we
demonstrated a good correlation (r 4 -0.76; 95% CI, -0.83 to
-0.68; P < 0.0001) between our modified Tal’s score and
SpO2144,5. The correlation was maintained in all three age
groups (<3, 3–5, and 6 months), and remained
significant (r 4 -0.57, P 4 0.004) in infants with severe
wheezing (clinical score 8–10). The good correlation found in
our study was due, in part, to the fact that only one
investigator evaluated the clinical score in all patients, in
contrast to other studies where there were several observers
with wide variations in scoring between them.We also used a
selected population defined as outpatients up to 2 years of age
with acute exacerbation of wheezing and without pneumonia,
instead of a population with a wide age range,4,55,9and with
different types 6,9,10and severities of respiratory illness.
A clinical score similar to that applied in the present study
was used in 71 pediatric asthmatic outpatients (mean ± SD,
10 ± 2.6 years of age), in whom a strong
Fig. 1. Correlation between clinical score and
SpO2.
correlation (r 4 -0.7, P 0.001) between asthma severity
and SpO2was demonstrated.128showed a poor correlation
between SpOHowever, in other studies using different
methodologies in the assessment of clinical severity of
disease, contradictory results appeared. For example, using a
different clinical score, Alario et al.2
9and acute wheezing episodes (r 4 -0.36, P 0.01) in
74 infants (mean age, 16.1 months; range, 1–36 months). In
contrast, Dawsonshowed a good correlation (r 4 -0.76, P
0.0001) in 41 hospitalized asthmatic children (mean
age, 5.5 years; range, 3–13 years) between the same
parameters. Studies of children with different respiratory
diseases have given variable results. Wang et al. could not
demonstrate a significant correlation (r 4 -0.04) between
SpO2and a clinical score similar to the one we used, in 58
infants hospitalized for pneumonia
426 Pavo´n et al.
3use
such testing in the evaluation of acute wheezing.
Therefore, disease severity is usually established on clinical
4(mean age, 12.3 months) and bronchiolitis (mean age, 6.6
grounds.
months).
13In Chile, most children with acute wheezing episodes are
A single clinical sign will not be very indicative of severity treated in a primary-care setting.Due to inadequate resources,
of airway obstruction, but a combination of signs may provide
many of those centers do not have pulse oximetry available to
more valid information, considering the complex relationship determine the need to add oxygen to bronchodilator therapy.
between the pathophysiological and the clinical features of
If pulse oximetry is not available, we conclude that it is
acute asthma. Our study showed a better correlation when it
advisable to include oxygen in the therapy of any infant with
considered the clinical score as a whole, instead of each
an acute wheezing episode who has a clinical score 8.
isolated element of the score (Table 3). Margolis et al. took
Using our criteria may result in a few infants receiving
27 elements of a clinical score in 312 infants with acute lower
oxygen unnecessarily, but on the other hand, all hypoxemic
respiratory tract infection (mean age 4 months, 87%
children will be identified.
bronchiolitis) and could not demonstrate a correlation with
hypoxemia (SpO25<95%). However, when they used a group
of five clinical characteristics, the sensitivity was 88%, the ACKNOWLEDGMENTS
specificity was 90%, and the negative predictive value was We thank Dr. Asher Tal, M.D. (Ben-Gurion University of
the Negev, Israel), and Dr. Mark A. Brown, M.D.
80%.
(Respiratory Sciences Center, University of Arizona), for
their advice and critical reviews.
As in other studies,we found that respiratory frequency had
one of the lowest correlations (r 4 -0.41, P < 0.0001) with
SpO25. In contrast, in children with pneumonia, the
correlation between respiratory rate and SpO2
2
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