Can we Replace Arterial Blood Gas Analysis by Pulse Oximetry in Neonates with Respiratory Distress Syndrome, who are Treated According to INSURE Protocol?

Abstract

Neonates with respiratory distress syndrome (RDS), who are treated according to INSURE protocol; require arterial blood gas (ABG) analysis to decide on appropriate management. We conducted this study to investigate the validity of pulse oximetry instead of frequent ABG analysis in the evaluation of these patients. From a total of 193 blood samples obtained from 30 neonates <1500 grams with RDS, 7.2% were found to have one or more of the followings: acidosis, hypercapnia, or hypoxemia. We found that pulse oximetry in the detection of hyperoxemia had a good validity to appropriately manage patients without blood gas analysis. However, the validity of pulse oximetry was not good enough to detect acidosis, hypercapnia, and hypoxemia.

Full text

Iran J Med Sci May 2015; Vol 40 No 3
IJMS
Vol 40, No 3, May 2015
264
Can we Replace Arterial Blood Gas Analysis by
Pulse Oximetry in Neonates with Respiratory
Distress Syndrome, who are Treated According
to INSURE Protocol?
Pedram Niknafs1, MD; Elahe Norouzi1,
MD; Bahareh Bahman Bijari1, MD;
Mohammad Reza Baneshi2, PhD
1Division of Neonatology, Afzalipour
Medical Center, Kerman University of
Medical Sciences, Kerman, Iran;
2Research Center for Modeling in Health,
Institute for Future Studies, Kerman
University of Medical Sciences, Kerman,
Iran
Correspondence:
Pedram Niknafs, MD;
Division of Neonatology,
Afzalipour Medical Center,
Imam Khomeini Highway,
Kerman, Iran
Tel / Fa x : +98 34 33222763
Email: pniknafs@yahoo.com
Received: 24 August 2013
Revised: 1 December 2013
Accepted: 6 December 2013
Abstract
Neonates with respiratory distress syndrome (RDS), who are
treated according to INSURE protocol; require arterial blood
gas (ABG) analysis to decide on appropriate management. We
conducted this study to investigate the validity of pulse oximetry
instead of frequent ABG analysis in the evaluation of these
patients. From a total of 193 blood samples obtained from 30
neonates <1500 grams with RDS, 7.2% were found to have one
or more of the followings: acidosis, hypercapnia, or hypoxemia.
We found that pulse oximetry in the detection of hyperoxemia
had a good validity to appropriately manage patients without
blood gas analysis. However, the validity of pulse oximetry was
not good enough to detect acidosis, hypercapnia, and hypoxemia.
Please cite this article as: Niknafs P, Norouzi E, Bahman Bijari B, Baneshi MR.
Can we Replace Arterial Blood Gas Analysis by Pulse Oximetry in Neonates with
Respirator y Distress Syndrome, who are Treated According to INSURE Protocol?
Iran J Med Sci. 2015;40(3):264-267.
Keywords ● Infant ● Respiratory distress syndrome ● Oximetry ●
Blood gaz analysis
Brief Report
Introduction
In neonates with birth weight <1500 grams, when the clinical
diagnosis of respiratory distress syndrome (RDS) is made based on
the respiratory symptoms and conrmatory studies (e.g. blood gas
analysis, chest x-ray, etc.), the appropriate management is to place
the patient under nasal continuous positive airway pressure (NCPAP).
If respiratory distress increases, surfactant is administered according
to INSURE protocol1 (transient intubation, surfactant administration,
rapid extubation to NCPAP2). These infants require an umbilical
artery catheter to obtain arterial blood gas (ABG) every 30 minutes
to 4 hours for accurate monitoring of gas exchange.3
Arterial blood gas analysis is the gold standard by which the
adequacy of oxygenation and ventilation are assessed.1 Although
umbilical catheterization is safe and well tolerated in most infants,
it is associated with serious complications which could be life
threatening.3-5
Pulse oximetry is a technique that indirectly determines
oxygenation in a continuous noninvasive manner. The percentage
of saturated hemoglobin is calculated from the difference between
light frequencies of the pulsatile ow as it passes beneath the
sensor at distal extremity of the infant.3,4
We did not nd any study regarding the validity of pulse oximetry as
a bedside monitoring in the assessment of neonates with birth weight

265
Pulse oximetr y versus ABG in RDS
Iran J Med Sci May 2015; Vol 40 No 3
lower than 1500 grams with RDS. Therefore, we
conducted this study to investigate the diagnostic
value of pulse oximetry in detecting acidosis,
hypercapnia, hypoxemia, and hyperoxemia.
Patien ts and M ethods
This was a prospective diagnostic test study (carried
out at the Afzalipour Medical Center in Kerman-Iran,
from October 2011 to March 2012) on 30 preterm
infants with moderately severe RDS weighing less
than 1500 grams at birth.
6
Neonates in whom
surfactant had been introduced as INSURE protocol
met the criteria for the study. These infants were
placed under bubble NCPAP with FiO2 of 40-50%
and CPAP of 5-6 cmH2O after INSURE procedure.
Umbilical or peripheral artery catheter was
inserted for all patients and ABG according to
the patient status was obtained every 30 minutes
to 4 hours (OPTI CCA-TS blood gas analyzer,
OPTI Medical Company, USA). All patients were
monitored continuously, physical examination
was done repeatedly, and pulse oximetry was
performed by a probe at distal extremity (SpO
2
Masimo set, NOVIN S1800 patient monitor, Saadat
Co., Ltd., Iran). In this study, blood gas analysis
was the gold standard. pH higher than 7.20, PaO2
equal to 50-80 mmHg, PaCO
2
less than 60 mmHg,
and oxygen saturation in the range of 85 -95%
were considered as normal values.7
Variables including pH, PaO
2
, PaCO
2
, oxygen
saturation, as well as gestational age, birth
weight, and gender of the infant were recorded.
SPSS 19 was used to analyze the data. To
assess the degree of dependency among
observations of the same patients, we estimated
the ICC value by the applied multilevel analysis.
Sensitivity, specicity, positive predictive and
negative predictive values were extracted from
2×2 contingency tables of results.8
In this study, any abnormality in blood gas
analysis including low pH, high PaCO2, low
PaO2, and high PaO2 was considered as “disease/
condition”, and SpO
2
value by pulse oximetry was
considered as “test”.
The study protocol received approval from the
Ethics Committee of Kerman University of Medical
Sciences with the code number 323/90/K, and all
patients provided written informed consent prior
to participation.
Results
Among 30 preterm infants who were studied, 14
(46.7%) were female and 16 (53.3%) were male.
Mean gestational age at birth was 311/7-week, with
minimum of 27-week and maximum of 351/7-week.
Mean birth weight was 1340 grams, with the range
of 900 to 1500 grams.
193 ABG specimens were obtained from the
infants through umbilical or peripheral arterial
catheters. Of the 193 blood samples, only 14
specimens (7.2%) were found to have one or
more of acidosis, hypercapnia, and hypoxemia.
Acidosis (pH<7.20) was found in 10 specimens
from a total of 193. Sensitivity of pulse oximeter in
the estimation of acidosis was 40% and its specicity
was 100%. Positive predictive value and negative
predictive value of pulse oximetry in the prediction
of acidosis were 100% and 96.8%, respectively.
From 193 ABG specimens, hypercapnia
(PaCO2>60) was found in six specimens.
Sensitivity of pulse oximetry with a cut-off point
of 85% in the detection of hypercapnia was 50%.
Specicity of pulse oximetry in the prediction of
normocapnia was 99.6%. Positive predictive value
and negative predictive value of pulse oximetry
for PaCO2 were 75% and 98.4%, respectively.
From 193 specimens, four showed hypoxemia
(PaO2<50) by blood gas analysis. Sensitivity of
pulse oximetry in the detection of hypoxemia
was 75% and its specicity was 99.5%. Positive
predictive value and negative predictive value
of pulse oximetry for hypoxemia were 75% and
98.5%, respectively.
In the evaluation of hyperoxemia (PaO2>80),
from 193 ABG specimens, 61 had PaO
2
higher than
80 (hyperoxemia). Sensitivity of pulse oximetry in
the detection of hyperoxemia was 83% and its
specicity was 92.4%. Positive predictive value
and negative predictive value for hyperoxemia
were 83% and 92.4%, respectively (table 1).
Discussion
In a study performed by Witting et al., sensitivity
Table 1: Prediction of ABG abnormalities by pulse oximetry in neonates with RDS
Acidosis
(pH<7.20)
Hypercapnia
(PaCO2>60)
Hypoxemia
(PaO2<50)
Hyperoxemia
(PaO2>80)
Cut-off point SpO2 (%) 85 85 85 95
Sensitivity (%) 40 50 75 83
Specicity (%) 100 99.6 99.5 92.4
PPV (%) 100 75 75 83
NPV (%) 96.8 98.4 98.5 92.4
NPV: Negative predictive value; PPV: Positive predictive value

266
Niknafs P, Norouzi E, Bahman Bijari B, Baneshi MR
Iran J Med Sci May 2015; Vol 40 No 3
and specicity of room-air pulse oximetry (with
SpO2≥96%) in detecting moderate hypercapnia
(PaCO2>50) in patients admitted to emergency ward
were 96% and 39%, respectively. They concluded
that room-air oxygen saturation below 95% could
alert the physician to the onset of hypoventilation.9
In another study, Ritonga et al. assessed
the validity of pulse oximetry in the estimation
of hypoxemia and hyperoxemia in neonates
and children. Pulse oximetry test (with cut-off
point 91%) for detecting hypoxemia in neonates
(PaO2<35 mmHg) had a sensitivity of 81%, and
specicity of 79%. Pulse oximetry test with cut-off
point 95% for detecting hyperoxemia (PaO2>50)
had a sensitivity of 78% and specicity of 66%.
They concluded that the validity of pulse oximetry
in the detection of hypoxemia in neonates was
fairly good, but, it was not good enough to be used
in the estimation of hyperoxemia in neonates.10
In a study performed by Bakr et al., the
diagnostic value of fetal pulse oximetry in
comparison with fetal scalp blood gas in predicting
neonatal outcome was assessed and it was found
that these two tests were favorably comparable.
11
In another study, Carruthers et al. compared
arterial blood gas analysis with oxygen saturation
by pulse oximetry in the assessment of acute
asthma. They concluded that, in SpO2>92%,
respiratory failure is not probable and ABG
analysis is not necessary.12
In our study, the diagnostic value of pulse
oximetry in the detection of hyperoxemia was high.
None of the infants with SpO2 value greater than
95% were acidotic or hypercapnic. So, one can
rely on SpO
2
values for further management of
patients with high SpO
2
(>95%), which is sensitive
for hyperoxemia, and decrease FiO2 o r CPA P.
The validity of pulse oximetry in predicting
hypoxemia in our study was not good. In cases
that were hypoxemic according to blood gas,
the sensitivity of pulse oximetry was 75%. This
means that hypoxemia detection by contenting
oneself with pulse oximetry alone; one would
miss hypoxemia in 25% of cases.
The sensitivity of pulse oximetry in the
detection of acidosis in our study was only 40%.
In other words, the prediction of acidosis by pulse
oximetry alone will result in missing acidosis in
60% of cases.
In the present study, the sensitivity of pulse
oximetry in detecting hypercapnia was 50%. In
other words, based on SpO2 by simultaneous
pulse oximetry alone, half of hypercapnic patients
would be missed.
Therefore, in patients with SpO2 values lower
than 95%, arterial blood gas measurements
should be performed, and according to ABG
results, increasing FiO2 or CPAP, surfactant
administration, or initiation of mechanical
ventilation should be done.
Conclusion
Pulse oximetry in the detection of hyperoxemia in
neonates <1500 grams with RDS, who are treated
according to INSURE protocol, has a good validity
to appropriately manage the patient without blood
gas analysis. However, the validity of pulse oximetry
is not good enough to be used to detect acidosis,
hypercapnia, and hypoxemia.
Acknowledgment
We are grateful to the nursing staff of NICU at the
Afzalipour Medical Center for their help to carry out
this research. In addition, we appreciate the support
of the Deputy for Research Affairs at Kerman
University of Medical Sciences.
Conict of Interest: None declared.
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