Reference values for pulse oximetry recordings in healthy term neonates during their first 5 days of life

Mother's Bed Incline and Desaturation Episodes in Healthy Term Newborns during Early Skin-to-Skin Contact: A Multicenter Randomized Controlled Trial

INTRODUCTION

Early skin-to-skin contact (ESSC) is associated with rare, sudden, unexpected postnatal collapse episodes. Placing the newborn in ESSC closer to an upright position may reduce the risk of airway obstruction and improve respiratory mechanics. This study assessed whether a greater inclination of the mother's bed during ESSC would reduce the proportion of healthy term newborns (HTNs) who experienced episodes of pulse oximeter saturation (SpO2) <91%.

METHODS

We conducted a multicenter randomized controlled trial comparing the effect of the mother's bed incline, 45° versus 15°, on desaturation in HTNs during ESSC. Before delivery on 1,271 dyads, randomization was conducted, and stringent criteria to select healthy mothers and term newborns were monitored until after birth. Preductal SpO2 was continuously monitored between 10 min and 2 h after birth. The primary outcome was the occurrence of at least one episode of SpO2 <91%.

RESULTS

254 (20%) mother-infant dyads were eligible for analysis (45°, n = 126; 15°, n = 128). Overall, 57% (95% confidence interval [CI]: 51%-63%) of newborns showed episodes of SpO2 <91%. The proportion of infants with SpO2 <91% episodes was 52% in 45° and 62% in 15° (relative risk: 0.80; 95% CI: 0.6-1.07).

CONCLUSIONS

We did not show that a high mother bed inclination during ESSC led to significantly fewer HTNs who experienced episodes of SpO2 <91%. Desaturation episodes from 10 min to 2 h after birth occurred in more than half of HTNs.

Delivery room desaturations and bradycardia in the early postnatal period of healthy term neonates - a prospective observational study

OBJECTIVE

It has been suggested that desaturations and bradycardia precede acute life-threatening events (ALTE) and that ALTE is more common in the delivery room than later in life. However, frequency, duration and severity of desaturations in the first hours of life and additional risk factors have not readily been studied.

METHODS

Term neonates (n = 100) were monitored for the first two hours after birth by pulse oximetry. The impact of maternal and perinatal factors on the frequency and severity of desaturations (<85%) and bradycardia (<80/min) was evaluated.

RESULTS

Desaturations were detected in 30%, prolonged desaturations in 25% of infants. Desaturations were observed significantly more often in infants born by planned Cesarean section (pCs) compared to other modes of delivery (pCs 20/49; others 10/51; p = .029). Desaturations were also more frequent in infants diagnosed with neonatal infection (NI) or infants born to a mother with gestational diabetes (GDM), although not significantly. No bradycardia <80/min was detected.

CONCLUSIONS

In our collective 4% of healthy term neonates had prolonged, clinically relevant desaturations in the first hours after birth. The mode of delivery and maternal risk factors may increase the risk for these events. However, our cohort was too small to detect any ALTE or SIDS and determine potential risk factors for these events. Our data lay ground for a large-scale prospective trial to investigate whether the mode of delivery could be an indication for general pulse oximetry monitoring of newborn in the delivery room.

Intermittent hypoxia in preterm infants: Measurement using the desaturation index

OBJECTIVE

The aims of this study were to: (i) Determine in preterm infants at neonatal discharge the prevalence of intermittent hypoxia (IH), as measured by the oxygen desaturation index (DSI) recorded by pulse oximetry and (ii) Determine the change in values for very preterm infants at 1-month post discharge.

METHODS

Preterm infants were recruited from the Wellington regional neonatal intensive care unit (NICU) and 24-h pulse oximetry recordings performed immediately before discharge. Infants born <32 weeks gestational age (GA) had repeat oximetry 1-month post discharge. Oxygenation measures included the 3% and 4% desaturation (DSI 3%, DSI 4%) indices.

RESULTS

At discharge from the neonatal unit the median and interquartile range (IQR) for DSI 4% was 51 (31-74) events per hour with normal mean SpO₂ (median of 97.9% [97.2-98.8 IQR]). Episodes of IH 1 month post discharge decreased with improvements of between 42% and 57% seen for the three DSI measures. Infants <32 weeks GA had higher median DSI 3 and 4% values at discharge but differences when compared with late preterm infants were not significant.

CONCLUSIONS

Preterm infants have frequent episodes of IH as measured by the 3% and 4% DSI when deemed otherwise ready for discharge home. Further research in a larger cohort of very preterm infants and also in term infants is needed to determine the significance of this finding.

Heart rate, respiratory rate, apnoeas and peripheral arterial oxygen saturation in healthy term neonates during quiet sleep

AIM

This study compiled percentiles for cardiorespiratory parameters in healthy term neonates during quiet sleep.

METHODS

We enrolled 215 healthy term neonates born at Hannover Medical School, Germany, between October 2011 and March 2013. They were prospectively observed on the maternity ward at a median age of two days using six-hour recordings of pulse oximeter plethysmography, oxygen saturation, thoracic breathing movements and electrocardiogram during sleep in a supine position. We examined their heart rate, respiratory rate and oxygen saturation during quiet sleep, plus bradycardias, apnoeas lasting at least four-seconds and desaturations below 85%.

RESULTS

The 3rd, 50th and 97th percentiles were calculated as follows: heart rate 87, 112 and 133 beats per minute, respiratory rate 32, 44 and 57 per minute and oxygen saturation 94, 98 and 100%. Desaturations, apnoeas and bradycardias below 80 beats per minute were common and recorded in 54%, 98% and 30% of participants. In contrast, only 7% experienced bradycardias of less than two-thirds of the baseline heart rate and 5% experienced apnoeas exceeding 15 seconds.

CONCLUSION

Our results will facilitate the evidence-based valuation of cardiorespiratory parameters in term neonates and help validate the significance of cardiorespiratory events in preterm infants at discharge.

The use of overnight oximetry in neonates: A literature review

There is much debate between neonatologists and paediatricians about appropriate oxygen saturation targets for babies with chronic neonatal lung disease (CNLD). Overnight oximetry is used to guide the fraction of inspired oxygen to use. We did this literature review to examine the current literature on the use of overnight oximetry in term infants, preterm infants and babies with CNLD (especially relevant to ex-preterm babies with CNLD going home on oxygen). We reviewed the literature from January 1990 to October 2017 by searching the following databases: Cochrane Central Register of Controlled Trials, The Joanna Briggs Institute, CINAHL, MEDLINE, Scopus, EMBASE, ProQuest and Science Direct. Sixteen articles were included in the review. The literature available on overnight oximetry in neonates is limited, it is not contemporary, and it reports studies that did not use oximeters with modern software for data collection and analysis. It is imperative that reference ranges be defined for overnight oximetry parameters so that babies are not inadvertently administered inappropriate amounts of oxygen.

Caffeine decreases intermittent hypoxia in preterm infants nearing term-equivalent age

OBJECTIVE

To determine whether intermittent hypoxia (IH) persisting after 36 weeks postmenstrual age (PMA) can be attenuated using caffeine doses sufficient to maintain caffeine concentrations >20 μg ml^-1.

STUDY DESIGN

Twenty-seven infants born <32 weeks were started on caffeine citrate at 10 mg kg^-1 day^-1 when clinical caffeine was discontinued. At 36 weeks PMA, the dose was increased to 14 or 20 mg kg^-1 day^-1 divided twice a day (BID) to compensate for progressively increasing caffeine metabolism. Caffeine concentrations were measured weekly. The extent of IH derived from continuous pulse oximetry was compared to data from 53 control infants.

RESULT

The mean (s.d.) gestational age of enrolled infants was 27.9±2 weeks. Median caffeine levels were >20 μg ml^-1 on study caffeine doses. IH was significantly attenuated through 38 weeks PMA compared with the control group.

CONCLUSION

Caffeine doses of 14 to 20 mg kg^-1 day^-1 were sufficient to maintain caffeine concentrations >20 μg ml^-1 and reduce IH in preterm infants at 36 to 38 weeks PMA.

Infants with viral bronchiolitis demonstrate two distinct patterns of nocturnal oxyhaemoglobin desaturation

AIM

This study aimed to demonstrate that viral bronchiolitis is associated with intermittent oxygen saturation of haemoglobin (SpO2 ) drops (≥3%) and low basal SpO2 between episodes of haemoglobin desaturation.

METHODS

Infants with bronchiolitis underwent pulse oximetry during the first night following hospital admission and a subgroup of them underwent repeat oximetry before hospital discharge. Oximetry was also performed in infants with partial upper airway obstruction (UAO) and without lung disease and in control participants without UAO or lung disease.

RESULTS

We enrolled 53 infants: 21 with bronchiolitis, 11 with UAO and 21 healthy controls. Participants with bronchiolitis had lower basal SpO2 (median 93.7% [10th-90th percentiles: 91.1-96.8]) than the subjects with UAO (96.9% [95.3-98.1]; p < 0.01) or the controls (98.7% [96.9-99.3]; p < 0.01). The bronchiolitis group was not different from the UAO group regarding the desaturation index (23.3 episodes/hour [10.3-46.6] and 15.5 episodes/hour [5.4-36.4], respectively; p = 0.08), but differed significantly from the controls (3.1 episodes/hour [0.3-5.5]; p < 0.01). The basal SpO2 and desaturation index improved in 10 subjects with bronchiolitis who had follow-up oximetry before discharge, but these indices remained abnormal when compared to values in the control group.

CONCLUSION

Bronchiolitis was characterised by low nocturnal basal SpO2 and intermittent SpO2 drops.

Pulse oximetry measures a lower heart rate at birth compared with electrocardiography

OBJECTIVE

To examine the effect of time after birth on heart rate (HR) measured by pulse oximetry (PO) (HRPO) and electrocardiography (ECG) (HRECG).

STUDY DESIGN

HRECG and HRPO (collected at maximum sensitivity) were assessed in 53 term and preterm infants at birth. ECG electrodes and a PO sensor were attached as soon as possible and HRECG and HRPO were compared every 30 seconds from 1-10 minutes after birth. Data were compared using a Wilkinson signed-rank test. Clinical relevance (eg, HR <100 beats per minute [bpm] was tested using a McNemar test).

RESULTS

Seven hundred fifty-five data pairs were analyzed. Median (IQR) gestational age was 37 (31-39) weeks. Mean (SD) starting time of PO and ECG data collection was 99 (33) vs 82 (26) seconds after birth (P = .001). In the first 2 minutes after birth, HRPO was significantly lower compared with HRECG (94 (67-144) vs 150 (91-153) bpm at 60 seconds (P < .05), 81 (60-109) vs 148 (83-170) bpm at 90 seconds (P < .001) and 83 (67-145) vs 158 (119-176) at 120 seconds (P < .001). A HR <100 bpm was more frequently observed with a PO than ECG in the first 2 minutes (64% vs 27% at 60 seconds (P = .05), 56% vs 26% at 90 seconds (P < .05) and 53% vs 21% at 120 seconds (P < .05). HR by ECG was verified by ultrasound for outflow from a subset of infants.

CONCLUSIONS

In infants at birth, HRPO is significantly lower compared with ECG with clinically important differences in the first minutes.

A conversion formula for comparing pulse oximeter desaturation rates obtained with different averaging times

Objective

The number of desaturations determined in recordings of pulse oximeter saturation (SpO₂) primarily depends on the time over which values are averaged. As the averaging time in pulse oximeters is not standardized, it varies considerably between centers. To make SpO₂ data comparable, it is thus desirable to have a formula that allows conversion between desaturation rates obtained using different averaging times for various desaturation levels and minimal durations.

Methods

Oxygen saturation was measured for 170 hours in 12 preterm infants with a mean number of 65 desaturations <90% per hour of arbitrary duration by using a pulse oximeter in a 2–4 s averaging mode. Using 7 different averaging times between 3 and 16 seconds, the raw red-to-infrared data were reprocessed to determine the number of desaturations (D). The whole procedure was carried out for 7 different minimal desaturation durations (≥1, ≥5, ≥10, ≥15, ≥20, ≥25, ≥30 s) below SpO₂ threshold values of 80%, 85% or 90% to finally reach a conversion formula. The formula was validated by splitting the infants into two groups of six children each and using one group each as a training set and the other one as a test set.

Results

Based on the linear relationship found between the logarithm of the desaturation rate and the logarithm of the averaging time, the conversion formula is: D₂ = D₁ (T₂/T₁)^c, where D₂ is the desaturation rate for the desired averaging time T₂, and D₁ is the desaturation rate for the original averaging time T₁, with the exponent c depending on the desaturation threshold and the minimal desaturation duration. The median error when applying this formula was 2.6%.

Conclusion

This formula enables the conversion of desaturation rates between different averaging times for various desaturation thresholds and minimal desaturation durations.

Under-recognition of alarms in a neonatal intensive care unit

BACKGROUND

Treatment decisions for apnoea of prematurity (AOP) are usually based on nursing staff's documentation of pulse oximeter and heart rate alarms.

OBJECTIVE

In an observational study, to compare the accuracy of oxygen saturation (SpO2) and heart rate alarm documentation, and the resulting interventions by nursing staff, with objectively registered events using polysomnographic and video recording.

METHODS

Data on 21 preterm neonates (12 male) with a diagnosis of AOP were analysed. Nursing staff's desaturation (<80% SpO2) and bradycardia (<80/min) alarm documentation was compared with events registered objectively using simultaneous polysomnography. Interventions by nursing staff were evaluated using 24 h video recordings and compared with their chart documentation. Nursing staff had been unaware that the polygraphic and video recordings would be used subsequently for this purpose.

RESULTS

Median (minimum-maximum) postnatal age was 15.5 (3-65) days. 968 SpO2 desaturation events and  415 bradycardias were documented by polysomnography. Nursing staff registered 23% of these desaturation events, and 60% of bradycardias (n=223, and n=133, respectively). Intraclass correlation coefficient (95% CI) between objectively measured desaturation events and those documented by nursing staff was 0.14 (-0.31 to 0.53); and for bradycardias 0.51 (0.11 to 0.78). 225 nursing staff interventions were registered on video, of which 87 (39%) were documented.

CONCLUSIONS

The alarm documentation by neonatal intensive care unit staff does not appear to be sufficiently accurate to permit further understanding and treatment of AOP. It is unclear if the alarms missed here would have led to clinical consequences had they been documented.

Newborn oxygen saturation at mild altitude versus sea level: implications for neonatal screening for critical congenital heart disease

AIM

To determine the normal SpO2 in healthy term newborns at mild altitude (MA, 780 metres) compared with sea level (SL), within the context of universal screening for critical congenital heart disease (CCHD).

METHODS

We studied 199 (119 at MA and 80 at SL) consecutively born healthy newborns. SpO2 recordings were at 24-72 h using Masimo SET Radical-7 on the right hand and left foot.

RESULTS

Mean SpO2 was lower at MA compared with SL in the right hand (97.86 ± 1.58 vs 98.28 ± 1.41, p = 0.05) and left foot (98.49 ± 1.35 vs 98.90 ± 1.16, p = 0.03). No infant with SpO2 <95% had CCHD. Extrapolating with predicted regression lines set at 95% CI, a SpO2 cut-off of 95% would result in up to 3.5 times more false-positive screens at MA compared with SL.

CONCLUSIONS

At MA, SpO2 is approximately 0.4% lower compared with SL. Our study supports the AAP recommendation suggesting algorithm cut-offs may need adjustment in high-altitude nurseries and suggest broadening it to MA as well.

Altitude, oxygen and the definition of bronchopulmonary dysplasia

OBJECTIVE

The definition of bronchopulmonary dysplasia (BPD) among very-low birth weight (VLBW) infants is based upon oxygen requirement at 36 weeks gestation, but oxygen may be required at altitude because of hypoxia. This study determined the effect of altitude on BPD rates.

STUDY DESIGN

For 63 VLBW infants at high altitude, oxygen concentrations were measured by a hood oxygenation test (HOT) and BPD rates were determined with altitude adjustment.

RESULT

BPD rates before and after altitude adjustment were 71.8 and 26.7%, respectively. Of oxygen-dependent infants analyzed by HOT, 33.3% needed room air. HOT oxygen requirement correlated with gestational age of last apnea episode (r=0.42, P<0.001).

CONCLUSION

Although BPD rates may be adjusted for altitude with the HOT, the test does not accurately predict clinical oxygen need. Persistent requirement for supplemental oxygen beyond that needed in the HOT may be partially due to immaturity of respiratory control mechanisms.

Neonatal management and safe discharge of late and moderate preterm infants

Late and moderate preterm infants form the majority of admissions for prematurity to special care neonatal nurseries. Although at risk for acute disorders of prematurity, they do not suffer the serious long term risks and chronic illnesses of the extremely premature. The special challenges addressed here are of transition and of thermal adaptation, nutritional compensation for postnatal growth restriction, the establishment of early feeding, and the avoidance of post-discharge jaundice or apnea. These 'healthy' premature infants provide challenges for discharge planning, in that opportunities may be available for discharge well before the expected date of delivery, which should be pursued. Barriers to early discharge are rigid conservative protocols and unwarranted investigations; facilitators of discharge are individualized care by nurses expert in cue-based feeding, early management of the thermal environment, support of family preferences and encouragement of mother-baby interactions. Safe discharge depends on recognizing these opportunities and applying strategies to address them.

Reference values of nocturnal oxygenation for use in outpatient oxygen weaning protocols in premature infants

OBJECTIVE

To define reference ranges for oxygen saturation (SpO(2) ) values in healthy full-term infants in the first days of life and in preterm infants off supplemental oxygen as they approach neonatal intensive care unit (NICU) discharge.

METHODS

From April 2009 to March 2010, we enrolled convenience samples of full-term infants from the newborn nursery and former preterm infants who did not require supplemental oxygen at the time of discharge from the NICU. Overnight SpO(2) and signal quality recordings were obtained and analyzed for duration of artifact-free recording time (AFRT), time (s) with SpO(2) less than several different target saturations (90-95%), and number of falls in SpO(2) by ≥4% and ≥10%.

RESULTS

We studied 102 full-term infants and 52 preterm infants. Preterm and full-term infants spent similar amounts of time less than 90%, 91%, 92%, 93%, 94%, and 95% although preterm infants had more falls in SpO(2) by ≥4% per hour of AFRT. Over 67% of term and preterm infants spent less than 6% of their time below 93%.

CONCLUSION

These data represent reference SpO(2) ranges for both preterm infants not requiring supplemental oxygen at NICU discharge and full-term infants in the first days of life. As we currently lack guidelines dictating the optimal target oxygen saturations for infants and the acceptable maximal time that they can safely spend below set target saturations, our data may serve as a guide to interpreting SpO(2) recordings of premature outpatient infants who are weaning from supplemental oxygen.

First day of life reference values for pleth variability index in spontaneously breathing term newborns

BACKGROUND

The perfusion index (PI), derived from the pulse oximetry signal, has been shown to be an accurate predictor for identifying high illness severity in neonates. The plethysmographic variability index (PVI) is a measure of the dynamic change in PI occurring during a complete respiratory cycle.

OBJECTIVES

The aim of this study was to establish the reference range of PVI in spontaneously breathing term newborns.

METHODS

PI and PVI values were assessed in 242 term newborns during the first day of life.

RESULTS

The median PVI value on the first day of life was 20% [95% confidence interval (CI) for the mean 19-20%; inter-quartile range 15 (95% CI 15-16) - 24 (95% CI 23-24)]. The 10th and 90th percentile cutoff values were 12% (95% CI 11-12) and 28% (95% CI 27-29), respectively, with the 97.5th percentile of 35% (95% CI 34-38). PVI was also significantly influenced by the behavioral status of the newborn, and was positively correlated with PI and pulse rate, while it was inversely correlated with oxygen saturation (p < 0.0001).

CONCLUSIONS

Our findings suggest: (1) evaluation of PVI values is an easily applicable, noninvasive procedure for monitoring early postnatal respiratory changes in newborns, and (2) the feasibility of a noninvasive pulse-oximeter postnatal screening for early identification of adverse neonatal cardiorespiratory outcomes.