Journal of Perinatology (2014) 34, 917–920 © 2014 Nature America, Inc. All rights reserved 0743-8346/14 www.nature.com/jp
ORIGINAL ARTICLE
Oxygen saturation profile in late-preterm and term infants: a prospective cohort study PS Shah, H Hakak, A Mohamed, J Shah, J Young and E Kelly OBJECTIVE: To determine oxygen saturation profile over 6 h monitoring period in healthy late-preterm and term neonates during the first 48 h of age, and to assess the impact of gestational age, birth weight and method of delivery on this profile. STUDY DESIGN: Prospective cohort study of measurement of SpO2 over 6 h in 20 late-preterm (35 to 36 weeks gestation) and 40 term infants within 12 to 48 h of birth was conducted. Infants with cardiorespiratory symptoms or need for cardiorespiratory support at birth were excluded. Percentage time spent at SpO2 >90% and ⩽ 90% was calculated by gestational age and birth weight. RESULT: Late-preterm infants and infants born weighing o 2.5 kg spent approximately 7% of the time at SpO2 ⩽ 90%; this time decreased as gestational age and birth weight increased. Time at SpO2 >90% was significantly different between late-preterm and term infants (93% (5%) vs 96% (3%); P = 0.002). Time at SpO2 >90% was not significantly different between males and females (95% (5%) vs 95% (4%), both n = 30; P = 0.72) or between vaginal births and cesarean births (95% (4%), n = 32, vs 95% (4%), n = 28; P = 0.39). Cumulative time with SpO2 o 90 was mean (s.d.) of 25 (18) in preterm vs 13 (10) min in term infants. CONCLUSION: Over a 6-h period healthy late-preterm and term infants spent significant time at SpO2 ⩽ 90%. Lower gestation and lower birth weight were associated with higher time at SpO2 ⩽ 90%. Journal of Perinatology (2014) 34, 917–920; doi:10.1038/jp.2014.107; published online 5 June 2014
INTRODUCTION Pulse oximetry is widely used in clinical practice to obtain data on oxygen saturation (SpO2). It is a non-invasive technique that requires no calibration and provides instantaneous data that correlates well with arterial oxygen measurements.1–3 Information on SpO2 in healthy full-term infants in the first4 and second5 months after birth, during infancy6 and during childhood7 has been published. However, these studies did not include infants younger than 48 h of age. Although investigators have obtained data from spot checks of SpO2 from infants immediately after birth or early postnatal period,8–11 no data exist from prolonged monitoring during the first 48 h of age and only a little continuous information on SpO2 over the first 96 h during periods of wakefulness, sleep and feeding is available. Many cardiorespiratory changes occur during the first few days of life; however, data on normal SpO2 values during this period of physiological transition are lacking. Spot checks of SpO2 indicate that during the first 24 h after birth newborn infants adapt their circulation to extrauterine life. After an initial increase in SpO2 during the first minutes of age, SpO2 stabilizes over next 20 to 24 h.12–15 Most studies report that mean SpO2 is approximately 97 to 98%, with the normal range from 94 to 100%.16 Rosvik et al.17 reported that in healthy newborns, levels of SpO2 measured between 2 and 24 h of life are negatively related to birth weight and related to mode of delivery. O’Brien et al.18 reported that the range of SpO2 during the first 24 h of life is similar to that previously reported during the first month of life. Our objective in this study was to determine oxygen saturation profile over a 6-h monitoring period among healthy late-preterm and term neonates between 12 and 48 h after birth and to assess the impact of gestational age and birth weight on this profile.
METHODS Study design and setting We conducted a prospective cohort study of 40 full-term and 20 latepreterm (35 and 36 weeks gestational age) infants at Mount Sinai Hospital Mother and Baby unit in Toronto. We planned to enroll equal numbers of infants from each subgroup of sex (male and female) and mode of delivery (vaginal delivery and cesarean section) to evaluate if there are any significant differences in SpO2 according to these variables.
Eligibility criteria Healthy neonates ready to be discharged home after an uneventful postnatal course were enrolled. We excluded neonates with congenital malformation; small for gestational age (birth weight o 3rd percentile); suspected cardiac anomaly; neonates who received any respiratory support at birth, such as positive pressure ventilation, continuous positive airway pressure to open lungs or oxygen; and neonates who had meconium aspiration at birth and needed intubation and suction below the vocal cords.
Procedure Neonates were enrolled between 12 and 48 h postnatal age in order to capture those who are healthy enough to be discharged. After obtaining parental consent, neonates were connected to a pulse oximeter for 6 h. Neonates were kept in their mother’s room during the entire study period. If the baby needed phototherapy, the probe was covered to prevent any interference of light on the probe sensor. During the recording no painful procedures were allowed (heel lance or venipuncture).
Oximeter and probes We used a Nellcor OxiMax N-600X pulse oximeter (Covidien, Mansfield, MA, USA) for the study. This monitor measures SpO2 between 1 and 100% and pulse rate from 20 to 250 b.p.m. and has an internal memory where
Department of Paediatrics, Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada. Correspondence: Dr PS Shah, Department of Pediatrics, Staff Neonatologist, Mount Sinai Hospital, University of Toronto, 19-231 F-600 University Avenue, Toronto, ON, Canada M5G 1X5. E-mail: [email protected] Received 14 March 2014; revised 23 April 2014; accepted 29 April 2014; published online 5 June 2014
Oxygen saturation profile in late-preterm/term infants PS Shah et al
918 recordings of SpO2 and pulse rate can be stored for up to 24 h. The machine measures SpO2 using highly accurate sensors (OxiMax MAX-N and OxiMax MAX-I). For SpO2 of 70 to 100% the sensors are accurate within ± digits, for SpO2 of 60 to 80% within ± 3 digits and for pulse rate of 20 to 250 within ± 3 digits.19 The OxiMax MAX-N sensor was used in infants weighing o 3 kg and was attached around the infant’s hand or foot, and the OxiMax MAX-I sensor was used in infants of ⩾ 3 kg and was attached around the thumb or big toe, according to the manufacturer’s instructions. The averaging time was 2 to 3 s. The sensor was covered from natural light. The machine runs on electricity and also has an internal battery that can run for 7 h and protects the data if the machine is accidentally unplugged. We set the SpO2 low alarm at 80% with no upper limit alarm, and the pulse rate low alarm at 80 b.p.m. This was to ensure that there were not many unnecessary false alarms to increase the workload for health-care practitioners and increase anxiety of parents. However, at the same time it was important to know if the infant had a SpO2 o80% or became bradycardic as it may help to identify any underlying severe illness. For most of the neonates the sensor was connected to the foot (except in a few neonates where it was connected to the right hand) after ensuring that there was no difference in pre- and post-ductal saturation. After 6 h of recording, the machine was connected to a computer to download the data using PROFOX oximetry software. The data were saved and printed for later analyses.
Mean (s.d.) of SpO2 in the entire cohort was 96.5% (1.4). However, 55 out of 60 patients had at least one documented episode of SpO2 o 88% lasting for >20 s and all of them had at least one episode of SpO2 o 88% lasting for >10 s. Percentage time spent with SpO2 >90% and ⩽ 90% is depicted in Figure 1 according to gestational age, and in Figure 2 according to birth weight. As seen from the figures, late-preterm infants and infants of o 2.5 kg birth weight spent approximately 7% of the time with SpO2 ⩽ 90% and this time was reduced with increasing gestational age and birth weight. There was a significant difference in percentage time with SpO2 >90% between late-preterm infants (93% (5%), n = 20) and term infants (96% (3%), n = 40; P = 0.002). In terms of cumulative timing, preterm infants spent mean (s.d.) of 25 (18) minutes with SpO2 o90 as compared with term infants who spent 13 (10) minutes over 6 h. It is noteworthy that even full-term infants spent around 3 to 4% of the time with SpO2 ⩽ 90%. Tables 1 and 2 summarize the SpO2 profiles in different
Data collection The following variables were collected: gestational age, birth weight, sex, mode of delivery, percentage of time SpO2 values were >90% and ⩽ 90%, mean SpO2 during the study period and mean pulse rate during the study period. The episodes of desaturations were screened to remove events which were due to poor signal conductance secondary to motion artifact, changing diapers, feeding or excessive motion.
Statistical analyses Sample size was based on convenience as this study aimed to establish a nomogram and we did not have any baseline data as no previous study has evaluated ongoing monitoring over a prolonged period. Mean SpO2 values with 95% confidence interval for each gestational age and birth weight stratum were calculated and plotted. The proportion of time SpO2 values were >90% and ⩽ 90% were calculated and plotted. Mean SpO2 values were compared for gestational age subgroups (full-term vs. preterm), gender subgroups (male vs. female) and for mode of delivery subgroups (normal delivery and cesarean section). Student’s t-test and one-way analysis of variance were used to detect difference in the groups. A P value o0.05 was considered significant.
RESULTS Over an 8-month period (May 2012 to December 2012), 400 parents were approached for consent, 93 neonates were recruited (23.3%). In most cases the reason for refusal was because parents wanted to leave the hospital as they were ready for discharge. We did not monitor infants under constant supervision over 6 h period as that would have affected bonding, breastfeeding and routine care, and did not collect data on sleep-awake state during the study period. Because of loss of connection or signal, 32 infants were excluded as less than 6 h of data were recorded and the main purpose of the study was to obtain good signal over 6 h. One neonate had significant desaturation to o80% for prolonged periods of time and was excluded from the study and admitted to the neonatal intensive care unit. No specific diagnosis was made and the patient eventually improved and was discharged home. The remaining 60 neonates were included in the study and included 20 late-preterm infants (9 born at 35 weeks gestation and 11 born at 36 weeks gestation) and 40 term infants (> 37 weeks gestational age). The number of male and female neonates was equal in both the late-preterm and term groups. Thirty two neonates were delivered vaginally and 28 by cesarean section. The median (interquartile range) age at the start of recording was 22 h (15 to 31 h). Journal of Perinatology (2014), 917 – 920
Figure 1. Scatterplot of SpO2 profile according to gestational age. Bold line represents mean and light lines represent 95% confidence interval around the mean.
Figure 2. Scatterplot of SpO2 profile according to birth weight. Bold line represent mean and light lines represent 95% confidence interval around the mean. © 2014 Nature America, Inc.
Oxygen saturation profile in late-preterm/term infants PS Shah et al
919 Table 1.
Mean time spent with SpO2 above 90% and below 90% according to gestational age n
Gestational age at birth, weeks 35–36
Mean (s.d.) Median (range) Mean (s.d.) Median (range) Mean (s.d.) Median (range) Mean (s.d.) Median (range)
37–8 39–41 Total
Table 2.
o3000 3000–3499
Total
16 24 60
93.0 94.3 96.8 96.4 96.1 97.4 95.2 96
(5.2) (78–99) (1.8) (94–100) (3.4) (87–100) (4.0) (78–100)
% Time with SpO2 ⩽ 90% 6.9 5.7 3.2 3.6 4.0 3.4 4.8 4
(5.1) (1–22) (1.8) (0.3–6.4) (3.3) (0.2–14) (4.0) (0–22)
Minutes spent with SpO2 o90 in 6 h 25 20 11 13 14 12 17 14
(18) (4–80) (6) (1–23) (12) (1–49) (14) (1–80)
Mean time spent with SpO2 above 90% and below 90% according to birth weight n
Birth weight, g
>3500
20
% Time with SpO2 >90%
Mean (s.d.) Median (range) Mean (s.d.) Median (range) Mean (s.d.) Median (range) Mean (s.d.) Median (range)
22 24 14 60
% Time with SpO2 >90% 93.4 94.7 96.2 96.0 96.5 97 95.2 96
(5.4) (78–99) (2.7) (88–100) (2.4) (91–99) (4.0) (78–100)
gestational age and birth weight categories over the study duration. There was no difference in percentage time with SpO2 >90% between males (95% (5%), n = 30) and females (95% (4%), n = 30; P = 0.72); or between vaginal births (95% (4%), n = 32) and cesarean births (95% (4%), n = 28; P = 0.39). Desaturation events (SpO2 o 85% lasting for >20 s) occurred in two late-preterm infants (three episodes each) and four term infants (three episodes each in three infants and four episodes in one infant). DISCUSSION In this prospective evaluation of healthy late-preterm and term infants, we identified that late-preterm infants spent an average of 7% of the time and term infants an average of 4% of the time with SpO2 ⩽ 90% over a 6-h monitoring period. Low birth weight infants and infants of o 3 kg birth weight also spent >6% of time with SpO2 ⩽ 90%. There was no impact of gender or mode of birth on proportion of time spent with SpO2 ⩽ 90%. Spot checking of saturation is recommended by the American Academy of Pediatrics for every newborn prior to discharge.20 This is indicated to diagnose critical congenital heart diseases prior to discharge of an infant. However, prolonged monitoring is not indicated routinely for healthy and stable infants. Our findings are concordant with existing knowledge that spot checks in the majority of stable late-preterm and term infants without cardiovascular malformations are highly likely to reveal SpO2 of >90%.4 However, our study clearly indicates that if the monitoring is prolonged for a sufficient period of time, especially in latepreterm infants, it is likely an infant may spend approximately 7% of the total time at lower oxygen saturations. This could be problematic for correct implementation of the car-seat challenge or any equivalent monitoring to assess cardiorespiratory stability of infants prior to discharge. Lack of standardization and uniform criteria for car-seat failure complicates the matter and marked variation between units for definition may have stem from the lack of normative data.21 © 2014 Nature America, Inc.
% Time with SpO2 ⩽ 90% 6.5 5.2 3.8 3.9 3.6 3.1 4.8 4.0
(5.3) (0.622) (2.7) (0.2–12) (2.5) (0.7–9) (4.0) (0–22)
Minutes spent with SpO2 o90 in 6 h 24 19 14 14 13 11 17 14
(19) (2–80) (10) (1–43) (9) (3–32) (14) (1–80)
The long-term importance of desaturations and apnea is unclear even in preterm infants. This makes it difficult to identify criteria for safe discharge of preterm neonates. Similar to our study, Willett et al.22 reported that term babies spent 4.8% of the time with SpO2 o 90% and 1.4% of the time with SpO2 o 85%. In another study, the same authors23 reported that preterm infants had on average of 11 episodes in a 90-min recording when SpO2 was o 80%. Bass et al.24 also reported that 18% of preterm infants had SpO2 o 90% in car-seat testing. Finally, Young et al.25 reported a 24% car-seat failure rate using the pre-determined criteria listed above, and suggested that all preterm neonates should have car-seat testing prior to discharge. Our study provides evidence for development of guidelines for routine monitoring of late-preterm infants in a car seat. Currently, statements from professional societies26,27 suggest that two or more episodes of desaturation of o88% for 10 s or more are considered significant; however, this may lead to unnecessary admissions, prolonged hospital stay and increased anxiety among parents and affect infant bonding, attachment and breastfeeding. In our series during prolonged monitoring over 6 h, all babies, including term and preterm neonates had at least one episode of desaturation lasting >10 s, which calls into question the validity of such criteria. Our study suggests arguments for either testing all infants or liberalizing criteria for unsatisfactory results. However, we must caution that during car-seat testing, infant is put in a fixed position, with very little room for movement and head in proper position so as not to obstruct airway and so on, whereas in our monitoring infant was allowed to continue routine activities including feeding, diaper change and all routine posturing. Strengths of our study include the use of prospective evaluation, 6-h long monitoring for all neonates and inclusion of late-preterm infants. However, we must acknowledge the limitations of our study. The sample size in each subgroup was small; however, the overall sample size was sufficient enough to generate a trend evaluation. The Nellcor oximeter we used recorded all desaturations of >4% at any given time, thus we could not count the total number of significant desaturations. Journal of Perinatology (2014), 917 – 920
Oxygen saturation profile in late-preterm/term infants PS Shah et al
920 Status of infants during the study period with respect to sleep/ wake state was not recorded. Many infants needed to be excluded because complete 6 h evaluation was not obtained, thus, limiting generalizability. However, we are not expecting this test to become standard for clinical purpose anyway. Additionally, we did not follow-up on these children after discharge to ascertain whether any issues arose post-discharge that might have been related to higher time spent with SpO2 o 90%; however, we have not heard from any parents regarding subsequent admission and diagnosis of congenital heart disease. CONCLUSION There is a relative deficiency of normative neonatal data in the literature, especially for late-preterm infants for whom monitoring in a car seat is suggested by the American Academy of Pediatrics and Canadian Pediatrics Society. In this prospective evaluation of healthy late-preterm and term infants we identified that latepreterm infants spent significant time at SpO2 ⩽ 90% over a 6-h monitoring period conducted between 12 and 48 h after birth. In particular, lower gestational age and lower birth weight were associated with higher time at SpO2 ⩽ 90%. Evaluation of the longterm outcomes of infants that demonstrate a higher degree of SpO2 instability is needed. CONFLICT OF INTEREST The authors declare no conflict of interest.
ACKNOWLEDGEMENTS We sincerely thank the parents who agreed to participate in this study. We also thank Kostandina Floras and Karla Sarmiento, both respiratory therapists at Mount Sinai Hospital, for their support during the conduct of the study. We also thank the staff nurses in Mother–Baby unit at Mount Sinai Hospital for their support during this study. We acknowledge the support from Covidien, USA, for their provision of a Nellcor Oximeter and software for the purpose of the study. Covidien was not involved in study design or conduct, data analysis and interpretation or the decision to publish these results. We would like to thank Dr Ruth Warre, Scientific Editor, at the Maternal–Infant Care Research Centre, Mount Sinai Hospital for critical review and editing of this manuscript. The Maternal–Infant Care Research Centre is supported by the Ministry of Health and Long-Term Care, Ontario. Dr Prakesh Shah is supported by an Applied Research Chair in Reproductive and Child Health Services and Policy Research funded by the Canadian Institutes of Health Research.
REFERENCES 1 Southall DP, Bignall S, Stebbens VA, Alexander JR, Rivers RP, Lissauer T. Pulse oximeter and transcutaneous arterial oxygen measurements in neonatal and paediatric intensive care. Arch Dis Child 1987; 62(9): 882–888. 2 Jennis MS, Peabody JL. Pulse oximetry: an alternative method for the assessment of oxygenation in newborn infants. Pediatrics 1987; 79(4): 524–528. 3 Mok J, Pintar M, Benson L, McLaughlin FJ, Levison H. Evaluation of noninvasive measurements of oxygenation in stable infants. Crit Care Med 1986; 14(11): 960–963. 4 Poets CF, Stebbens VA, Lang JA, O'Brien LM, Boon AW, Southall DP. Arterial oxygen saturation in healthy term neonates. Eur J Pediatr 1996; 155(3): 219–223.
Journal of Perinatology (2014), 917 – 920
5 Stebbens VA, Poets CF, Alexander JR, Arrowsmith WA, Southall DP. Oxygen saturation and breathing patterns in infancy. 1: Full term infants in the second month of life. Arch Dis Child 1991; 66(5): 569–573. 6 Poets CF, Stebbens VA, Southall DP. Arterial oxygen saturation and breathing movements during the first year of life. J Dev Physiol 1991; 15(6): 341–345. 7 Poets CF, Stebbens VA, Samuels MP, Southall DP. Oxygen saturation and breathing patterns in children. Pediatrics 1993; 92(5): 686–690. 8 Harris AP, Sendak MJ, Donham RT. Changes in arterial oxygen saturation immediately after birth in the human neonate. J Pediatr 1986; 109(1): 117–119. 9 House JT, Schultetus RR, Gravenstein N. Continuous neonatal evaluation in the delivery room by pulse oximetry. J Clin Monit 1987; 3(2): 96–100. 10 Porter KB, Goldhamer R, Mankad A, Peevy K, Gaddy J, Spinnato JA. Evaluation of arterial oxygen saturation in pregnant patients and their newborns. Obstet Gynecol 1988; 71(3 Pt 1): 354–357. 11 Dimich I, Singh PP, Adell A, Hendler M, Sonnenklar N, Jhaveri M. Evaluation of oxygen saturation monitoring by pulse oximetry in neonates in the delivery system. Can J Anaesth 1991; 38(8): 985–988. 12 Dawson JA, Davis PG, O'Donnell CP, Kamlin CO, Morley CJ. Pulse oximetry for monitoring infants in the delivery room: a review. Arch Dis Child Fetal Neonatal Ed 2007; 92(1): F4–F7. 13 Kamlin CO, O'Donnell CP, Davis PG, Morley CJ. Oxygen saturation in healthy infants immediately after birth. J Pediatr 2006; 148(5): 585–589. 14 Mariani G, Dik PB, Ezquer A, Aguirre A, Esteban ML, Perez C et al. Pre-ductal and post-ductal O2 saturation in healthy term neonates after birth. J Pediatr 2007; 150 (4): 418–421. 15 Rabi Y, Yee W, Chen SY, Singhal N. Oxygen saturation trends immediately after birth. J Pediatr 2006; 148(5): 590–594. 16 Levesque BM, Pollack P, Griffin BE, Nielsen HC. Pulse oximetry: what's normal in the newborn nursery? Pediatr Pulmonol 2000; 30(5): 406–412. 17 Rosvik A, Oymar K, Kvaloy JT, Berget M. Oxygen saturation in healthy newborns; influence of birth weight and mode of delivery. J Perinat Med 2009; 37(4): 403–406. 18 O'Brien LM, Stebbens VA, Poets CF, Heycock EG, Southall DP. Oxygen saturation during the first 24 hours of life. Arch Dis Child Fetal Neonatal Ed 2000; 83(1): F35–F38. 19 Mannheimer PD, Asbaugh NA. and the Nellcor Technical Staff. Nellcor OxiMax Pulse Oximeter Accuracy, 2011. Covidien, MA, USA. 20 Mahle WT, Newburger JW, Matherne GP, Smith FC, Hoke TR, Koppel R et al. Role of pulse oximetry in examining newborns for congenital heart disease: a scientific statement from the American Heart Association and American Academy of Pediatrics. Circulation 2009; 120(5): 447–458. 21 Davis NL, Zenchenko Y, Lever A, Rhein L. Car seat safety for preterm neonates: implementation and testing parameters of the infant car seat challenge. Acad Pediatr 2013; 13(3): 272–277. 22 Willett LD, Leuschen MP, Nelson LS, Nelson RM Jr. Risk of hypoventilation in premature infants in car seats. J Pediatr 1986; 109(2): 245–248. 23 Willett LD, Leuschen MP, Nelson LS, Nelson RM Jr. Ventilatory changes in convalescent infants positioned in car seats. J Pediatr 1989; 115(3): 451–455. 24 Bass JL, Mehta KA, Camara J. Monitoring premature infants in car seats: implementing the American Academy of Pediatrics policy in a community hospital. Pediatrics 1993; 91(6): 1137–1141. 25 Young B, Shapira S, Finer N. Predischarge car seat safety study for premature infants. Paediatrics Child Health 1996; 1: 202–205. 26 Safe transportation of premature and low birth weight infants. American Academy of Pediatrics. Committee on Injury and Poison Prevention and Committee on Fetus and Newborn. Pediatrics 1996; 97(5): 758–760. 27 McMillan D, Fetus and Newborn Committee CPS. Assessment of babies for car seat safety before hospital discharge. Paediatrics Child Health 2000; 5(1): 53–56.
© 2014 Nature America, Inc.
ORIGINAL ARTICLE
Oxygen saturation profile in late-preterm and term infants: a prospective cohort study PS Shah, H Hakak, A Mohamed, J Shah, J Young and E Kelly OBJECTIVE: To determine oxygen saturation profile over 6 h monitoring period in healthy late-preterm and term neonates during the first 48 h of age, and to assess the impact of gestational age, birth weight and method of delivery on this profile. STUDY DESIGN: Prospective cohort study of measurement of SpO2 over 6 h in 20 late-preterm (35 to 36 weeks gestation) and 40 term infants within 12 to 48 h of birth was conducted. Infants with cardiorespiratory symptoms or need for cardiorespiratory support at birth were excluded. Percentage time spent at SpO2 >90% and ⩽ 90% was calculated by gestational age and birth weight. RESULT: Late-preterm infants and infants born weighing o 2.5 kg spent approximately 7% of the time at SpO2 ⩽ 90%; this time decreased as gestational age and birth weight increased. Time at SpO2 >90% was significantly different between late-preterm and term infants (93% (5%) vs 96% (3%); P = 0.002). Time at SpO2 >90% was not significantly different between males and females (95% (5%) vs 95% (4%), both n = 30; P = 0.72) or between vaginal births and cesarean births (95% (4%), n = 32, vs 95% (4%), n = 28; P = 0.39). Cumulative time with SpO2 o 90 was mean (s.d.) of 25 (18) in preterm vs 13 (10) min in term infants. CONCLUSION: Over a 6-h period healthy late-preterm and term infants spent significant time at SpO2 ⩽ 90%. Lower gestation and lower birth weight were associated with higher time at SpO2 ⩽ 90%. Journal of Perinatology (2014) 34, 917–920; doi:10.1038/jp.2014.107; published online 5 June 2014
INTRODUCTION Pulse oximetry is widely used in clinical practice to obtain data on oxygen saturation (SpO2). It is a non-invasive technique that requires no calibration and provides instantaneous data that correlates well with arterial oxygen measurements.1–3 Information on SpO2 in healthy full-term infants in the first4 and second5 months after birth, during infancy6 and during childhood7 has been published. However, these studies did not include infants younger than 48 h of age. Although investigators have obtained data from spot checks of SpO2 from infants immediately after birth or early postnatal period,8–11 no data exist from prolonged monitoring during the first 48 h of age and only a little continuous information on SpO2 over the first 96 h during periods of wakefulness, sleep and feeding is available. Many cardiorespiratory changes occur during the first few days of life; however, data on normal SpO2 values during this period of physiological transition are lacking. Spot checks of SpO2 indicate that during the first 24 h after birth newborn infants adapt their circulation to extrauterine life. After an initial increase in SpO2 during the first minutes of age, SpO2 stabilizes over next 20 to 24 h.12–15 Most studies report that mean SpO2 is approximately 97 to 98%, with the normal range from 94 to 100%.16 Rosvik et al.17 reported that in healthy newborns, levels of SpO2 measured between 2 and 24 h of life are negatively related to birth weight and related to mode of delivery. O’Brien et al.18 reported that the range of SpO2 during the first 24 h of life is similar to that previously reported during the first month of life. Our objective in this study was to determine oxygen saturation profile over a 6-h monitoring period among healthy late-preterm and term neonates between 12 and 48 h after birth and to assess the impact of gestational age and birth weight on this profile.
METHODS Study design and setting We conducted a prospective cohort study of 40 full-term and 20 latepreterm (35 and 36 weeks gestational age) infants at Mount Sinai Hospital Mother and Baby unit in Toronto. We planned to enroll equal numbers of infants from each subgroup of sex (male and female) and mode of delivery (vaginal delivery and cesarean section) to evaluate if there are any significant differences in SpO2 according to these variables.
Eligibility criteria Healthy neonates ready to be discharged home after an uneventful postnatal course were enrolled. We excluded neonates with congenital malformation; small for gestational age (birth weight o 3rd percentile); suspected cardiac anomaly; neonates who received any respiratory support at birth, such as positive pressure ventilation, continuous positive airway pressure to open lungs or oxygen; and neonates who had meconium aspiration at birth and needed intubation and suction below the vocal cords.
Procedure Neonates were enrolled between 12 and 48 h postnatal age in order to capture those who are healthy enough to be discharged. After obtaining parental consent, neonates were connected to a pulse oximeter for 6 h. Neonates were kept in their mother’s room during the entire study period. If the baby needed phototherapy, the probe was covered to prevent any interference of light on the probe sensor. During the recording no painful procedures were allowed (heel lance or venipuncture).
Oximeter and probes We used a Nellcor OxiMax N-600X pulse oximeter (Covidien, Mansfield, MA, USA) for the study. This monitor measures SpO2 between 1 and 100% and pulse rate from 20 to 250 b.p.m. and has an internal memory where
Department of Paediatrics, Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada. Correspondence: Dr PS Shah, Department of Pediatrics, Staff Neonatologist, Mount Sinai Hospital, University of Toronto, 19-231 F-600 University Avenue, Toronto, ON, Canada M5G 1X5. E-mail: [email protected] Received 14 March 2014; revised 23 April 2014; accepted 29 April 2014; published online 5 June 2014
Oxygen saturation profile in late-preterm/term infants PS Shah et al
918 recordings of SpO2 and pulse rate can be stored for up to 24 h. The machine measures SpO2 using highly accurate sensors (OxiMax MAX-N and OxiMax MAX-I). For SpO2 of 70 to 100% the sensors are accurate within ± digits, for SpO2 of 60 to 80% within ± 3 digits and for pulse rate of 20 to 250 within ± 3 digits.19 The OxiMax MAX-N sensor was used in infants weighing o 3 kg and was attached around the infant’s hand or foot, and the OxiMax MAX-I sensor was used in infants of ⩾ 3 kg and was attached around the thumb or big toe, according to the manufacturer’s instructions. The averaging time was 2 to 3 s. The sensor was covered from natural light. The machine runs on electricity and also has an internal battery that can run for 7 h and protects the data if the machine is accidentally unplugged. We set the SpO2 low alarm at 80% with no upper limit alarm, and the pulse rate low alarm at 80 b.p.m. This was to ensure that there were not many unnecessary false alarms to increase the workload for health-care practitioners and increase anxiety of parents. However, at the same time it was important to know if the infant had a SpO2 o80% or became bradycardic as it may help to identify any underlying severe illness. For most of the neonates the sensor was connected to the foot (except in a few neonates where it was connected to the right hand) after ensuring that there was no difference in pre- and post-ductal saturation. After 6 h of recording, the machine was connected to a computer to download the data using PROFOX oximetry software. The data were saved and printed for later analyses.
Mean (s.d.) of SpO2 in the entire cohort was 96.5% (1.4). However, 55 out of 60 patients had at least one documented episode of SpO2 o 88% lasting for >20 s and all of them had at least one episode of SpO2 o 88% lasting for >10 s. Percentage time spent with SpO2 >90% and ⩽ 90% is depicted in Figure 1 according to gestational age, and in Figure 2 according to birth weight. As seen from the figures, late-preterm infants and infants of o 2.5 kg birth weight spent approximately 7% of the time with SpO2 ⩽ 90% and this time was reduced with increasing gestational age and birth weight. There was a significant difference in percentage time with SpO2 >90% between late-preterm infants (93% (5%), n = 20) and term infants (96% (3%), n = 40; P = 0.002). In terms of cumulative timing, preterm infants spent mean (s.d.) of 25 (18) minutes with SpO2 o90 as compared with term infants who spent 13 (10) minutes over 6 h. It is noteworthy that even full-term infants spent around 3 to 4% of the time with SpO2 ⩽ 90%. Tables 1 and 2 summarize the SpO2 profiles in different
Data collection The following variables were collected: gestational age, birth weight, sex, mode of delivery, percentage of time SpO2 values were >90% and ⩽ 90%, mean SpO2 during the study period and mean pulse rate during the study period. The episodes of desaturations were screened to remove events which were due to poor signal conductance secondary to motion artifact, changing diapers, feeding or excessive motion.
Statistical analyses Sample size was based on convenience as this study aimed to establish a nomogram and we did not have any baseline data as no previous study has evaluated ongoing monitoring over a prolonged period. Mean SpO2 values with 95% confidence interval for each gestational age and birth weight stratum were calculated and plotted. The proportion of time SpO2 values were >90% and ⩽ 90% were calculated and plotted. Mean SpO2 values were compared for gestational age subgroups (full-term vs. preterm), gender subgroups (male vs. female) and for mode of delivery subgroups (normal delivery and cesarean section). Student’s t-test and one-way analysis of variance were used to detect difference in the groups. A P value o0.05 was considered significant.
RESULTS Over an 8-month period (May 2012 to December 2012), 400 parents were approached for consent, 93 neonates were recruited (23.3%). In most cases the reason for refusal was because parents wanted to leave the hospital as they were ready for discharge. We did not monitor infants under constant supervision over 6 h period as that would have affected bonding, breastfeeding and routine care, and did not collect data on sleep-awake state during the study period. Because of loss of connection or signal, 32 infants were excluded as less than 6 h of data were recorded and the main purpose of the study was to obtain good signal over 6 h. One neonate had significant desaturation to o80% for prolonged periods of time and was excluded from the study and admitted to the neonatal intensive care unit. No specific diagnosis was made and the patient eventually improved and was discharged home. The remaining 60 neonates were included in the study and included 20 late-preterm infants (9 born at 35 weeks gestation and 11 born at 36 weeks gestation) and 40 term infants (> 37 weeks gestational age). The number of male and female neonates was equal in both the late-preterm and term groups. Thirty two neonates were delivered vaginally and 28 by cesarean section. The median (interquartile range) age at the start of recording was 22 h (15 to 31 h). Journal of Perinatology (2014), 917 – 920
Figure 1. Scatterplot of SpO2 profile according to gestational age. Bold line represents mean and light lines represent 95% confidence interval around the mean.
Figure 2. Scatterplot of SpO2 profile according to birth weight. Bold line represent mean and light lines represent 95% confidence interval around the mean. © 2014 Nature America, Inc.
Oxygen saturation profile in late-preterm/term infants PS Shah et al
919 Table 1.
Mean time spent with SpO2 above 90% and below 90% according to gestational age n
Gestational age at birth, weeks 35–36
Mean (s.d.) Median (range) Mean (s.d.) Median (range) Mean (s.d.) Median (range) Mean (s.d.) Median (range)
37–8 39–41 Total
Table 2.
o3000 3000–3499
Total
16 24 60
93.0 94.3 96.8 96.4 96.1 97.4 95.2 96
(5.2) (78–99) (1.8) (94–100) (3.4) (87–100) (4.0) (78–100)
% Time with SpO2 ⩽ 90% 6.9 5.7 3.2 3.6 4.0 3.4 4.8 4
(5.1) (1–22) (1.8) (0.3–6.4) (3.3) (0.2–14) (4.0) (0–22)
Minutes spent with SpO2 o90 in 6 h 25 20 11 13 14 12 17 14
(18) (4–80) (6) (1–23) (12) (1–49) (14) (1–80)
Mean time spent with SpO2 above 90% and below 90% according to birth weight n
Birth weight, g
>3500
20
% Time with SpO2 >90%
Mean (s.d.) Median (range) Mean (s.d.) Median (range) Mean (s.d.) Median (range) Mean (s.d.) Median (range)
22 24 14 60
% Time with SpO2 >90% 93.4 94.7 96.2 96.0 96.5 97 95.2 96
(5.4) (78–99) (2.7) (88–100) (2.4) (91–99) (4.0) (78–100)
gestational age and birth weight categories over the study duration. There was no difference in percentage time with SpO2 >90% between males (95% (5%), n = 30) and females (95% (4%), n = 30; P = 0.72); or between vaginal births (95% (4%), n = 32) and cesarean births (95% (4%), n = 28; P = 0.39). Desaturation events (SpO2 o 85% lasting for >20 s) occurred in two late-preterm infants (three episodes each) and four term infants (three episodes each in three infants and four episodes in one infant). DISCUSSION In this prospective evaluation of healthy late-preterm and term infants, we identified that late-preterm infants spent an average of 7% of the time and term infants an average of 4% of the time with SpO2 ⩽ 90% over a 6-h monitoring period. Low birth weight infants and infants of o 3 kg birth weight also spent >6% of time with SpO2 ⩽ 90%. There was no impact of gender or mode of birth on proportion of time spent with SpO2 ⩽ 90%. Spot checking of saturation is recommended by the American Academy of Pediatrics for every newborn prior to discharge.20 This is indicated to diagnose critical congenital heart diseases prior to discharge of an infant. However, prolonged monitoring is not indicated routinely for healthy and stable infants. Our findings are concordant with existing knowledge that spot checks in the majority of stable late-preterm and term infants without cardiovascular malformations are highly likely to reveal SpO2 of >90%.4 However, our study clearly indicates that if the monitoring is prolonged for a sufficient period of time, especially in latepreterm infants, it is likely an infant may spend approximately 7% of the total time at lower oxygen saturations. This could be problematic for correct implementation of the car-seat challenge or any equivalent monitoring to assess cardiorespiratory stability of infants prior to discharge. Lack of standardization and uniform criteria for car-seat failure complicates the matter and marked variation between units for definition may have stem from the lack of normative data.21 © 2014 Nature America, Inc.
% Time with SpO2 ⩽ 90% 6.5 5.2 3.8 3.9 3.6 3.1 4.8 4.0
(5.3) (0.622) (2.7) (0.2–12) (2.5) (0.7–9) (4.0) (0–22)
Minutes spent with SpO2 o90 in 6 h 24 19 14 14 13 11 17 14
(19) (2–80) (10) (1–43) (9) (3–32) (14) (1–80)
The long-term importance of desaturations and apnea is unclear even in preterm infants. This makes it difficult to identify criteria for safe discharge of preterm neonates. Similar to our study, Willett et al.22 reported that term babies spent 4.8% of the time with SpO2 o 90% and 1.4% of the time with SpO2 o 85%. In another study, the same authors23 reported that preterm infants had on average of 11 episodes in a 90-min recording when SpO2 was o 80%. Bass et al.24 also reported that 18% of preterm infants had SpO2 o 90% in car-seat testing. Finally, Young et al.25 reported a 24% car-seat failure rate using the pre-determined criteria listed above, and suggested that all preterm neonates should have car-seat testing prior to discharge. Our study provides evidence for development of guidelines for routine monitoring of late-preterm infants in a car seat. Currently, statements from professional societies26,27 suggest that two or more episodes of desaturation of o88% for 10 s or more are considered significant; however, this may lead to unnecessary admissions, prolonged hospital stay and increased anxiety among parents and affect infant bonding, attachment and breastfeeding. In our series during prolonged monitoring over 6 h, all babies, including term and preterm neonates had at least one episode of desaturation lasting >10 s, which calls into question the validity of such criteria. Our study suggests arguments for either testing all infants or liberalizing criteria for unsatisfactory results. However, we must caution that during car-seat testing, infant is put in a fixed position, with very little room for movement and head in proper position so as not to obstruct airway and so on, whereas in our monitoring infant was allowed to continue routine activities including feeding, diaper change and all routine posturing. Strengths of our study include the use of prospective evaluation, 6-h long monitoring for all neonates and inclusion of late-preterm infants. However, we must acknowledge the limitations of our study. The sample size in each subgroup was small; however, the overall sample size was sufficient enough to generate a trend evaluation. The Nellcor oximeter we used recorded all desaturations of >4% at any given time, thus we could not count the total number of significant desaturations. Journal of Perinatology (2014), 917 – 920
Oxygen saturation profile in late-preterm/term infants PS Shah et al
920 Status of infants during the study period with respect to sleep/ wake state was not recorded. Many infants needed to be excluded because complete 6 h evaluation was not obtained, thus, limiting generalizability. However, we are not expecting this test to become standard for clinical purpose anyway. Additionally, we did not follow-up on these children after discharge to ascertain whether any issues arose post-discharge that might have been related to higher time spent with SpO2 o 90%; however, we have not heard from any parents regarding subsequent admission and diagnosis of congenital heart disease. CONCLUSION There is a relative deficiency of normative neonatal data in the literature, especially for late-preterm infants for whom monitoring in a car seat is suggested by the American Academy of Pediatrics and Canadian Pediatrics Society. In this prospective evaluation of healthy late-preterm and term infants we identified that latepreterm infants spent significant time at SpO2 ⩽ 90% over a 6-h monitoring period conducted between 12 and 48 h after birth. In particular, lower gestational age and lower birth weight were associated with higher time at SpO2 ⩽ 90%. Evaluation of the longterm outcomes of infants that demonstrate a higher degree of SpO2 instability is needed. CONFLICT OF INTEREST The authors declare no conflict of interest.
ACKNOWLEDGEMENTS We sincerely thank the parents who agreed to participate in this study. We also thank Kostandina Floras and Karla Sarmiento, both respiratory therapists at Mount Sinai Hospital, for their support during the conduct of the study. We also thank the staff nurses in Mother–Baby unit at Mount Sinai Hospital for their support during this study. We acknowledge the support from Covidien, USA, for their provision of a Nellcor Oximeter and software for the purpose of the study. Covidien was not involved in study design or conduct, data analysis and interpretation or the decision to publish these results. We would like to thank Dr Ruth Warre, Scientific Editor, at the Maternal–Infant Care Research Centre, Mount Sinai Hospital for critical review and editing of this manuscript. The Maternal–Infant Care Research Centre is supported by the Ministry of Health and Long-Term Care, Ontario. Dr Prakesh Shah is supported by an Applied Research Chair in Reproductive and Child Health Services and Policy Research funded by the Canadian Institutes of Health Research.
REFERENCES 1 Southall DP, Bignall S, Stebbens VA, Alexander JR, Rivers RP, Lissauer T. Pulse oximeter and transcutaneous arterial oxygen measurements in neonatal and paediatric intensive care. Arch Dis Child 1987; 62(9): 882–888. 2 Jennis MS, Peabody JL. Pulse oximetry: an alternative method for the assessment of oxygenation in newborn infants. Pediatrics 1987; 79(4): 524–528. 3 Mok J, Pintar M, Benson L, McLaughlin FJ, Levison H. Evaluation of noninvasive measurements of oxygenation in stable infants. Crit Care Med 1986; 14(11): 960–963. 4 Poets CF, Stebbens VA, Lang JA, O'Brien LM, Boon AW, Southall DP. Arterial oxygen saturation in healthy term neonates. Eur J Pediatr 1996; 155(3): 219–223.
Journal of Perinatology (2014), 917 – 920
5 Stebbens VA, Poets CF, Alexander JR, Arrowsmith WA, Southall DP. Oxygen saturation and breathing patterns in infancy. 1: Full term infants in the second month of life. Arch Dis Child 1991; 66(5): 569–573. 6 Poets CF, Stebbens VA, Southall DP. Arterial oxygen saturation and breathing movements during the first year of life. J Dev Physiol 1991; 15(6): 341–345. 7 Poets CF, Stebbens VA, Samuels MP, Southall DP. Oxygen saturation and breathing patterns in children. Pediatrics 1993; 92(5): 686–690. 8 Harris AP, Sendak MJ, Donham RT. Changes in arterial oxygen saturation immediately after birth in the human neonate. J Pediatr 1986; 109(1): 117–119. 9 House JT, Schultetus RR, Gravenstein N. Continuous neonatal evaluation in the delivery room by pulse oximetry. J Clin Monit 1987; 3(2): 96–100. 10 Porter KB, Goldhamer R, Mankad A, Peevy K, Gaddy J, Spinnato JA. Evaluation of arterial oxygen saturation in pregnant patients and their newborns. Obstet Gynecol 1988; 71(3 Pt 1): 354–357. 11 Dimich I, Singh PP, Adell A, Hendler M, Sonnenklar N, Jhaveri M. Evaluation of oxygen saturation monitoring by pulse oximetry in neonates in the delivery system. Can J Anaesth 1991; 38(8): 985–988. 12 Dawson JA, Davis PG, O'Donnell CP, Kamlin CO, Morley CJ. Pulse oximetry for monitoring infants in the delivery room: a review. Arch Dis Child Fetal Neonatal Ed 2007; 92(1): F4–F7. 13 Kamlin CO, O'Donnell CP, Davis PG, Morley CJ. Oxygen saturation in healthy infants immediately after birth. J Pediatr 2006; 148(5): 585–589. 14 Mariani G, Dik PB, Ezquer A, Aguirre A, Esteban ML, Perez C et al. Pre-ductal and post-ductal O2 saturation in healthy term neonates after birth. J Pediatr 2007; 150 (4): 418–421. 15 Rabi Y, Yee W, Chen SY, Singhal N. Oxygen saturation trends immediately after birth. J Pediatr 2006; 148(5): 590–594. 16 Levesque BM, Pollack P, Griffin BE, Nielsen HC. Pulse oximetry: what's normal in the newborn nursery? Pediatr Pulmonol 2000; 30(5): 406–412. 17 Rosvik A, Oymar K, Kvaloy JT, Berget M. Oxygen saturation in healthy newborns; influence of birth weight and mode of delivery. J Perinat Med 2009; 37(4): 403–406. 18 O'Brien LM, Stebbens VA, Poets CF, Heycock EG, Southall DP. Oxygen saturation during the first 24 hours of life. Arch Dis Child Fetal Neonatal Ed 2000; 83(1): F35–F38. 19 Mannheimer PD, Asbaugh NA. and the Nellcor Technical Staff. Nellcor OxiMax Pulse Oximeter Accuracy, 2011. Covidien, MA, USA. 20 Mahle WT, Newburger JW, Matherne GP, Smith FC, Hoke TR, Koppel R et al. Role of pulse oximetry in examining newborns for congenital heart disease: a scientific statement from the American Heart Association and American Academy of Pediatrics. Circulation 2009; 120(5): 447–458. 21 Davis NL, Zenchenko Y, Lever A, Rhein L. Car seat safety for preterm neonates: implementation and testing parameters of the infant car seat challenge. Acad Pediatr 2013; 13(3): 272–277. 22 Willett LD, Leuschen MP, Nelson LS, Nelson RM Jr. Risk of hypoventilation in premature infants in car seats. J Pediatr 1986; 109(2): 245–248. 23 Willett LD, Leuschen MP, Nelson LS, Nelson RM Jr. Ventilatory changes in convalescent infants positioned in car seats. J Pediatr 1989; 115(3): 451–455. 24 Bass JL, Mehta KA, Camara J. Monitoring premature infants in car seats: implementing the American Academy of Pediatrics policy in a community hospital. Pediatrics 1993; 91(6): 1137–1141. 25 Young B, Shapira S, Finer N. Predischarge car seat safety study for premature infants. Paediatrics Child Health 1996; 1: 202–205. 26 Safe transportation of premature and low birth weight infants. American Academy of Pediatrics. Committee on Injury and Poison Prevention and Committee on Fetus and Newborn. Pediatrics 1996; 97(5): 758–760. 27 McMillan D, Fetus and Newborn Committee CPS. Assessment of babies for car seat safety before hospital discharge. Paediatrics Child Health 2000; 5(1): 53–56.
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