Pediatrics International (2016) 0, 1–4

doi: 10.1111/ped.13099

Original Article

Measurement of brain tissue oxygen saturation in term infants using a
new portable near-infrared spectroscopy device
Takaaki Watanabe, Masato Ito, Fuyu Miyake, Ryo Ogawa, Masanori Tamura and Fumihiko Namba
Department of Pediatrics, Saitama Medical Center, Saitama Medical University, Kawagoe, Saitama, Japan
Abstract

Background: A small oximeter with the probe attached to the examiner’s finger has been developed. The aim of
this study was to determine the feasibility of measuring regional oxygenation of the brain tissue using this device inhealthy term infants immediately after birth.
Methods: We conducted a prospective observational study. Using a new near-infrared spectroscopy (NIRS) device,
we measured changes in regional cerebral tissue oxygen saturation (crSO2) during the first 10 min of life in 32
healthy term infants after delivery. Arterial oxygen saturation (SpO2) was also simultaneously measured.
Results: Median crSO2 increased from 43% (1 min after birth) to 49% (4 min after birth); thereafter, no significant
changes were observed. Median SpO2 increased constantly from min 3 to min 7, from 77% to 92% and did notchange significantly after 8 min. A stable oxygen saturation signal was measured in 59% of infants (crSO2) and in
0% of infants (SpO2) at 1 min, and in 97% (crSO2) and in 78% (SpO2) at 3 min.
Conclusions: During the transition after birth, crSO2 can be more easily and quickly measured in healthy newborn
infants using the novel NIRS device than SpO2.

Key words arterial oxygen saturation, near-infrared spectroscopy, oximetry, regional cerebral tissue oxygen saturation, terminfant.
The seventh edition of the Neonatal Resuscitation Program
states that pulse oximetry should be used when resuscitation
can be anticipated, positive pressure ventilation is administered, central cyanosis persists beyond the first 5–10 min oflife, or supplementary oxygen is given.1 It provides arterial
oxygen saturation (SpO2) targets that resuscitation teams
should achieve. There is ongoing discussion, however, about
the use of supplemental oxygen during neonatal resuscitation
because the appropriate oxygen concentration during resuscitation in newborns remains unknown.2 Because the brain is oneof the most vulnerable organ systems to hypoxia–ischemia
during neonatal transition, a more direct, simple, non-invasive
way to assess oxygenation would be useful. One approach tomeasuring cerebral oxygenation is to measure regional cerebral tissue oxygen saturation (crSO2) using near infrared spectroscopy (NIRS), which is a well-described non-invasive
technique that uses the transparency of biological tissue tolight in the near-infrared spectrum to measure cerebral tissue
oxygenation.3–6 Studies have already been performed during
the neonatal transition,7 and several observational studies havedescribed changes in crSO2 during the first few minutes immediately after birth.8–10

Recently, Kanayama and Niwayama developed a small
oximeter with the probe attached to the examiner’s finger(KN-15; ASTEM, Kawasaki, Japan).11 This medical instrument consists of a probe with NIRS and a numerical display
device. The size of the sensor in the probe is <1 cm2. Thisprobe is attached to the examiner’s finger. Examiners canmeasure any site in the human body, even the organs within abody cavity during surgery, because the device is small andportable. The same group has previously investigated the characteristics of this oximetry technique and obtained clinicaldata during labor; they concluded that the mean crSO2 of thefetal head during labor significantly correlated with umbilicalcord arterial pH immediately after delivery.12 crSO2 during
the transition after birth, however, has not been evaluated in alarge group of patients using this device. The aim of this study
was therefore to measure crSO2 during the immediate transition after birth to determine the safety of this new small portable device and its correlation with SpO2, as well as to define
crSO2 reference ranges within the first 10 min after birth inhealthy term infants who do not need any medical support.

Correspondence: Fumihiko Namba, MD PhD, Department ofPediatrics, Saitama Medical Center, Saitama Medical University,
1981 Kamoda, Kawagoe, Saitama 350-8550, Japan. Email:nambaf@saitama-med.ac.jp
Received 25 May 2016; revised 8 July 2016; accepted 21 July
2016.

This prospective observational study was conducted at a tertiary center, the Division of Neonatology, Department of Pediatrics, Saitama Medical Center, Saitama Medical University,Japan, from November 2015 to March 2016. We included
newborn infants with gestational age (GA) ≥37 weeks after© 2016 Japan Pediatric Society

Methods

2 T Watanabe et al.
uncomplicated pregnancy. This group of patients was selected
because the study protocol would not alter the routine treatment of these infants. Term infants were observed routinelyfor 10 min on a resuscitation table. Infants requiring any
respiratory support or additional inspired oxygen during thetransition or with any suspected or known malformation wereexcluded. Infants delivered after vacuum-assisted delivery orforceps delivery were excluded. Only those infants who had
an uncomplicated transitional period were included. The
Ethics Committee of the Saitama Medical Center, Saitama
Medical University approved the project. Written informed
consent was obtained from the parents.
A KN-15 NIRS device was used to measure crSO2 (Fig. 1).
The transducer contains near-infrared light-emitting diodes(LED) and photodiodes. The detectors were placed 6 and
8 mm away from the LED. The KN-15 NIRS device calculates crSO2, which is expressed as percentage of oxygenatedhemoglobin/total hemoglobin. The transducer was positionedon the left frontoparietal area of the forehead of each infant,regardless of mode of delivery. Arterial oxygen saturation wasmeasured using a Neopulse device (Atom Medical, Tokyo,Japan). The transducer was placed on the right hand/wrist.
All variables were continuously stored for subsequent analysis.
crSO2 and SpO2 data were stored every 1 and 15 s,respectively.
Measurements were performed during the first 10 min afterbirth. A stopwatch was set off when the neonate was fully
delivered. All infants were dried and wrapped with warmed
towels. Immediately after arrival of the infant at the resuscitation table, two people applied the transducers. First, one sensor was placed on the left frontoparietal area of the forehead(to measure crSO2), and concurrently, transcutaneous pulse
oximetry was initiated on a preductal level (right hand, tomeasure SpO2). The infants were positioned supine and werebreathing room air. A neonatologist observed the transition ofthe newborn infants and recorded Apgar scores at 1 and5 min. After 10 min and a clinical assessment, the newborn
infant was handed to the parents.

Fig. 1 The oximeter probe attached to the examiner’s finger
measuring regional cerebral tissue oxygen saturation on the headof a newborn (KN-15 NIRS; ASTEM, Kawasaki, Japan). Photo
courtesy of ASTEM.
© 2016 Japan Pediatric Society

Statistical analysis

Median SpO2 and crSO2 were calculated for each minute afterbirth. Data are presented as median (IQR). Infant characteristics are presented as numbers and proportions for categoricalvariables and as mean  SD for continuous variables. To
compare patient characteristics, Student’s t-test was used.
Changes by minute were evaluated using Friedman’s analysisof variance and Holm’s post-hoc test of variance for repeatedmeasures. P < 0.05 was considered to be significant. Statistical analysis was performed using EZR (Saitama MedicalCenter, Jichi Medical University, Saitama, Japan).

Results
Of 46 neonates, 14 were excluded because of a lack ofrecorded SpO2 data. Both crSO2 and SpO2 data for 32 neonates, who were delivered between November 2015 andMarch 2016, were analyzed (GA, 38  1 weeks; birthweight,2771  314 g; Apgar score, 8/9; Table 1). By 1 min, thecrSO2 signal could be measured for approximately 60% ofinfants. Therefore, the data presentation begins at 1 min. The
data presentation of SpO2 begins at 3 min, because the SpO2
signal could be measured for at least 70% of infants by 3 min.
A stable oxygen saturation signal was measured in 59% ofinfants (crSO2) and in 0% of infants (SpO2) at 1 min, and in
97% (crSO2) and in 78% (SpO2) at 3 min. After 2 min, acrSO2 signal could be measured in >90% of infants, and after
4 min, an SpO2 signal could be measured in >90% of infants(Fig. 2). Median crSO2 increased from 43 in 1 min to 49 inTable 1 Subject characteristics
Characteristics

Term infants (n = 32)
Mean  SD or n (%)

Gestational age (weeks)
Vaginal delivery
Birthweight (g)Head circumference (cm)
Apgar scores at 1 min
Apgar scores at 5 min
pH umbilical artery38  14 (13)2771  314
33.3  1.2
8  0.45
9  0.44
7.32  0.04Fig. 2 Cumulative proportion of infants with measurement of(□) regional cerebral tissue oxygen saturation and (■) arterial
oxygen saturation.

NIRS crSO2 measurement in infants 3
4 min with no further statistical change. SpO2 increased from77 in 3 min to 92 in 7 min (Fig. 3).

Discussion
We analyzed changes in crSO2 using a novel NIRS systemand simultaneous changes in SpO2 during the transition after
birth in a group of healthy term infants. The range of crSO2 interm infants was between 43% and 58%, and reached a plateau after 4 min. Previous studies have reported crSO2 range
in term and preterm infants between 57% and 79% during thefirst few days of life.8,10,13–17 Fauchere et al.10 published dataon crSO2 in 20 newborn term infants after cesarean section(CS), with a different NIRS device (NIRO 300, Hamamatsu,Japan). Urlesberger et al.18 conducted a prospective observational study in 61 term infants and measured crSO2 using anINVOS 5100 near-infrared spectrometer (Somanetics, Troy,MI, USA). They reported a very similar trend for crSO2, buttheir crSO2 data were higher than the present ones. A possible
reason for this difference in crSO2 may be the use of different
NIRS devices. NIRS measurement in healthy term infants during the transition after birth using the present new device,
KN-15, was safe and feasible.
Several studies have evaluated normal SpO2 immediately
after birth. Kamlin et al.19 studied SpO2 after birth in healthy
infants with GA ≥31 weeks and obtained SpO2 readings by
1 min of life in 53% of their cohort. Rabi et al.20 documented
SpO2 in healthy newborns with GA ≥35 weeks during unassisted transition in the delivery room and found that the median time to obtain stable SpO2 readings after probe placement
was 82 s. Nuntnarumit et al.21 studied 75 newborns with median GA 35 weeks and birthweight 2390 g, and found that themedian time from birth to obtain reliable SpO2 and heart rate
values was 160 s. We recorded SpO2 every 15 s in healthy
newborn infants with GA ≥37 weeks during the transition
after birth, and obtained SpO2 readings by 1 min and 2 min oflife in 0% and in 31% of the cohort, respectively (Fig. 2); furthermore, the median time from birth to obtain SpO2 was
150 s (IQR, 116–169 s), which is very similar to the Nuntnarumit et al. data. In contrast, a stable crSO2 signal wasmeasured relatively quickly. Urlesberger et al.18 were able tomeasure crSO2 in 92% of 59 healthy term infants by 3 minafter elective CS delivery using an INVOS 5100 near-infrared
spectrometer. Fauchere et al.10 reported crSO2 during immediate postnatal adaptation in 20 healthy newborn infants delivered at term by elective CS, and the median age at theinitiation of NIRS measurement was 2 min after birth (range,1–4 min). In the present study, after the infant was placed ona radiant warmer, crSO2 was detected immediately when thesensor was placed on the left frontoparietal area of the forehead. The crSO2 readings were obtained by 1 and 2 min oflife in 59% and in 94% of the cohort, respectively, and the
median time from birth to obtain crSO2 was 57 s (IQR, 50–78 s), which was much shorter than for SpO2 (i.e. 150 s; IQR,116–169 s).
The sector of wearable health technology is generating,apparently, endless interest. The use of low-cost, wearable
monitoring devices or wearable biosensors that allow constantmonitoring of physiological signals is essential for theadvancement of both the diagnosis and treatment of disease as
well as for monitoring in active lifestyles. Wearable, wirelessfingertip pulse oximetry devices for arterial saturation measurement are already available for smart phones, and fetal/
neonatal crSO2 can now be measured via finger-mounted
oximeter.11 In the present study, we have confirmed the safety
and feasibility of this novel device to measure crSO2 in
healthy newborn infants. There is a concern, however, about
its use in newborn infants at the resuscitation table, particularly in those requiring resuscitation. Because this fingermounted tissue oximetry probe was first developed to beattached to the physician’s finger to obtain tissue oxygen saturation of the fetal head during the second stage of labor,12 atleast one physician or midwife is needed to measure crSO2 for
one resuscitated newborn baby. Therefore, a new probe, suchas an SpO2 probe or electrocardiogram electrode, should be
developed for this device so that it can also be placed directlyon the head of newborn babies.
The present study was limited only by its small size, particularly because only a small proportion of neonates were vaginally delivered (only 13%). This is due to the characteristicsof the present institute, one of the largest Japanese tertiary
neonatal units, where the rates of normal vaginal delivery areFig. 3 (a) Regional cerebral tissue and (b) arterial oxygen saturation. *P < 0.05, **P < 0.01 compared with the endpoint (min 10).
© 2016 Japan Pediatric Society

4 T Watanabe et al.
very low. Despite these limitations, the present study has confirmed the ease, simplicity, and safety of this finger-based
device to obtain quick and reliable crSO2 measurements. We
believe that this novel oximetry probe will provide new information for the management of newborns during the transition
after birth.
In conclusion, crSO2 can be measured in healthy term newborn infants during the transition after birth using this novel
NIRS device even more easily and quickly than SpO2. Therewas an increase in crSO2 during the first 4 min of life. This
new NIRS instrument could be used as an alternative to or in
combination with pulse oximetry during neonatal resuscitation.

Acknowledgments
The authors thank the following for their excellent technicalsupport: Mr Hikaru Suzuki and Ms Aya Takiguchi (ASTEM,Kawasaki, Japan), and Dr Mari Mukai and Dr Naohiro
Kanayama (Department of Obstetrics and Gynecology, Hamamatsu University School of Medicine). This study was supported by a grant from The Ministry of Health Labour andWelfare.

Disclosure
A KN-15 NIRS device was leased from ASTEM (Kawasaki,Japan).

Author contributions
M.T. and F.N. designed the study; T.W., M.I., F.M., R.O., andF.N. collected and analyzed data; T.W. and F.N. drafted themanuscript; M.I., F.M., R.O., and M.T. critically reviewed
the manuscript; all authors read and approved the finalmanuscript.

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