Arterial oxygen saturation profiles in healthy preterm infants

24-hour oxygen saturation recordings in preterm infants: editing artefact

AIM

To create editing guidelines for artefact removal in preterm infant pulse oximetry recordings.

METHODS

38 preterm infants ready for discharge home from the neonatal intensive care unit underwent 24-hour pulse oximetry recording using the Masimo^® Rad-8 device. An expert panel determined editing rules based on clinical protocols. For each recording, three reports were generated, 'raw' no editing, 'auto' using the software editing feature and 'manual' reviewed and edited according to the rules. Primary outcome measures were desaturation indices including desaturation index 3% and 4%. Secondary measures included heart rate, mean oxygen saturation and time below 90%.

RESULTS

While all oximetry outcomes differed significantly between editing modes, the majority were not considered likely to influence clinical management. Use of the auto editing compared to no editing did alter by >5%: Time spent <90% oxygen saturation and Desaturation index 4% >10 seconds. The use of manual editing removed extremely low pulse values that were considered unphysiological in this group of otherwise healthy infants.

CONCLUSION

We recommend that oximetry recordings to determine cardiorespiratory stability in newborn infants ready for discharge from the neonatal unit have software editing features applied. This will remove artefact without consuming time in a busy unit.

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.

A graphical method for comparing nocturnal oxygen saturation profiles in individuals and populations: Application to healthy infants and preterm neonates

STUDY OBJECTIVES

Pulse-oximetry (SpO₂ ) allows the identification of important clinical physiology. However, summary statistics such as mean values and desaturation incidence do not capture the complexity of the information contained within continuous recordings. The aim of this study was to develop an objective method to quantify important SpO₂ characteristics; and assess its utility in healthy infant and preterm neonate cohorts.

METHODS

An algorithm was developed to calculate the desaturation incidence, depth, and duration. These variables are presented using three plots: SpO₂ cumulative-frequency relationship; desaturation-depth versus incidence; desaturation-duration versus incidence. This method was applied to two populations who underwent nocturnal pulse-oximetry: (1) thirty-four healthy term infants studied at 2-weeks, 3, 6, 12, and 24-months of age and (2) thirty-seven neonates born <26 weeks and studied at discharge from NICU (37-44 weeks post-conceptual age).

RESULTS

The maturation in healthy infants was characterized by reduced desaturation index (27.2/h vs 3.3/h at 2-weeks and 24-months, P < 0.01), and increased percentage of desaturation events ≥6-s in duration (27.8% vs 43.2% at 2-weeks and 3-months, P < 0.01). Compared with term-infants, preterm infants had a greater desaturation incidence (54.8/h vs 27.2/h, P < 0.01), and these desaturations were deeper (52.9% vs 37.6% were ≥6% below baseline, P < 0.01). The incidence of longer desaturations (≥14-s) in preterm infants was correlated with healthcare utilization over the first 24-months (r = 0.63, P < 0.01).

CONCLUSIONS

This tool allows the objective comparison of extended oximetry recordings between groups and for individuals; and serves as a basis for the development of reference ranges for populations.

Oxygen saturation ranges for healthy newborns within 24 hours at 1800 m

There are minimal data to define normal oxygen saturation (SpO₂) levels for infants within the first 24 hours of life and even fewer data generalisable to the 7% of the global population that resides at an altitude of >1500 m. The aim of this study was to establish the reference range for SpO₂ in healthy term and preterm neonates within 24 hours in Nairobi, Kenya, located at 1800 m. A random sample of clinically well infants had SpO₂ measured once in the first 24 hours. A total of 555 infants were enrolled. The 5th-95th percentile range for preductal and postductal SpO₂ was 89%-97% for the term and normal birthweight groups, and 90%-98% for the preterm and low birthweight (LBW) groups. This may suggest that 89% and 97% are reasonable SpO₂ bounds for well term, preterm and LBW infants within 24 hours at an altitude of 1800 m.

Oxygen saturation profile of term equivalent extreme preterm infants at discharge - comparison with healthy term counterparts

AIM

Compare the oxygen saturation profiles before discharge of neonates born extremely preterm (<28 weeks), now at term equivalent age, with healthy term neonates and assess the impact of feeding on this profile in each group.

METHODS

We prospectively evaluated and compared the oxygen saturation profile in 15 very low birthweight infants at term equivalent age, ready to be discharged home without any oxygen and 15 term newborns after 48 hours of life. We also evaluated and compared the saturations of these two groups during a one-hour period during and after feeding.

RESULTS

Term equivalent preterm and term infants spent median 3% and 0%, respectively, of the time below 90% in a 12-hour saturation-recording period. Term infants spent a median 0.26% and 0.65% of the time in <90% saturation during feed time and no feed time, respectively. In contrast, preterm infants spent significantly more time <90% saturation (3.47% and 3.5% during feed time and no feed time, respectively).

CONCLUSION

Term equivalent preterm infants spent significantly more time in a saturation range <90% compared to term infants. Feeding had little effect on saturation profile overall within each group.

Nocturnal oxygen saturation profiles of healthy term infants

OBJECTIVE

Pulse oximetry is used extensively in hospital and home settings to measure arterial oxygen saturation (SpO2). Interpretation of the trend and range of SpO2 values observed in infants is currently limited by a lack of reference ranges using current devices, and may be augmented by development of cumulative frequency (CF) reference-curves. This study aims to provide reference oxygen saturation values from a prospective longitudinal cohort of healthy infants.

DESIGN

Prospective longitudinal cohort study.

SETTING

Sleep-laboratory.

PATIENTS

34 healthy term infants were enrolled, and studied at 2 weeks, 3, 6, 12 and 24 months of age (N=30, 25, 27, 26, 20, respectively).

INTERVENTIONS

Full overnight polysomnography, including 2 s averaging pulse oximetry (Masimo Radical).

MAIN OUTCOME MEASUREMENTS

Summary SpO2 statistics (mean, median, 5th and 10th percentiles) and SpO2 CF plots were calculated for each recording. CF reference-curves were then generated for each study age. Analyses were repeated with sleep-state stratifications and inclusion of manual artefact removal.

RESULTS

Median nocturnal SpO2 values ranged between 98% and 99% over the first 2 years of life and the CF reference-curves shift right by 1% between 2 weeks and 3 months. CF reference-curves did not change with manual artefact removal during sleep and did not vary between rapid eye movement (REM) and non-REM sleep. Manual artefact removal did significantly change summary statistics and CF reference-curves during wake.

CONCLUSIONS

SpO2 CF curves provide an intuitive visual tool for evaluating whether an individual's nocturnal SpO2 distribution falls within the range of healthy age-matched infants, thereby complementing summary statistics in the interpretation of extended oximetry recordings in infants.

Apnea of prematurity--perfect storm

With increased survival of preterm infants as young as 23 weeks gestation, maintaining adequate respiration and corresponding oxygenation represents a clinical challenge in this unique patient cohort. Respiratory instability characterized by apnea and periodic breathing occurs in premature infants because of immature development of the respiratory network. While short respiratory pauses and apnea may be of minimal consequence if oxygenation is maintained, they can be problematic if accompanied by chronic intermittent hypoxemia. Underdevelopment of the lung and the resultant lung injury that occurs in this population concurrent with respiratory instability creates the perfect storm leading to frequent episodes of profound and recurrent hypoxemia. Chronic intermittent hypoxemia contributes to the immediate and long term co-morbidities that occur in this population. In this review we discuss the pathophysiology leading to the perfect storm, diagnostic assessment of breathing instability in this unique population and therapeutic interventions that aim to stabilize breathing without contributing to tissue injury.

Recommendations for long-term home oxygen therapy in children and adolescents

OBJECTIVE

To advise pediatricians, neonatologists, pulmonologists, pediatric pulmonologists, and other professionals in the area on the main indications and characteristics of long-term home oxygen therapy in children and adolescents.

DATA SOURCE

A literature search was carried out in the MEDLINE/PubMed database (1990 to 2011). Additionally, references from selected studies were included. As consistent scientific evidence does not exist for many aspects, some of the recommendations were based on clinical experience.

DATA SYNTHESIS

Long-term home oxygen therapy has been a growing practice in pediatric patients and is indicated in bronchopulmonary dysplasia, cystic fibrosis, bronchiolitis obliterans, interstitial lung diseases, and pulmonary hypertension, among others. The benefits are: decrease in hospitalizations, optimization of physical growth and neurological development, improvement of exercise tolerance and quality of sleep, and prevention of pulmonary hypertension/cor pulmonale. The levels of oxygen saturation indicative for oxygen therapy differ from those established for adults with chronic obstructive pulmonary disease, and vary according to age and disease. Pulse oximetry is used to evaluate oxygen saturation; arterial blood gas is unnecessary. There are three available sources of oxygen: gas cylinders, liquid oxygen, and oxygen concentrators. The flows used are usually smaller, as are the number of hours/day needed when compared to the use in adults. Some diseases show improvement and oxygen therapy discontinuation is possible.

CONCLUSIONS

Long-term home oxygen therapy is increasingly common in pediatrics and has many indications. There are relevant particularities when compared to its use in adults, regarding indications, directions for use, and monitoring.

An exploratory investigation of some statistical summaries of oximeter oxygen saturation data from preterm babies

Aim. To explore the potential usefulness of the mean, standard deviation (SD), and coefficient of variation (CV = SD/mean) of oximeter oxygen saturations in the clinical care of preterm babies. Methods. This was an exploratory investigation involving 31 preterm babies at 36 weeks postmenstrual age. All babies were healthy, but two were considered to be clinically unstable and required greater attention. Each baby's oxygen saturations were recorded using an oximeter and summarized by the mean, SD, and CV. The potential usefulness of each measure was assessed by its ability to distinguish the two unstable babies from the others. This was achieved using box plots and hierarchical clustering together with the Calinski-Harabasz (CH) index to quantify clustering performance (higher CH index indicates stronger clustering outcome). Results. The box plots flagged both unstable babies as outliers and none of the other babies. Successful clustering of the stable and unstable babies was achieved using the CV (CH = 72.8) and SD (CH = 63.3) but not with the mean. Conclusion. Taking the box plots and clustering results together, it seems plausible that variability might be more effective than mean level for detecting instability in oxygen saturation in preterm babies and that the combination of variability and level through the CV might be even better.

Detection of previously unrecognized daytime desaturation in children with chronic lung disease

PRIMARY OBJECTIVE

The prime rationale of this research is to investigate the possible occurrence of previously unrecognized episodes of desaturation apparent in preterm infants with chronic lung disease as they freely move around a non-artificial environment.

RESEARCH DESIGN

The study comprises 58 hours of telemetric recordings of SpO2, heart rate, body movement and temperature, along with full ECG and photoplethysmographic waveforms for eight preterm subjects in their home environment. MAIN OUTCOME/RESULTS: The data is analysed for remarkable events, more particularly periods of spontaneous desaturation. Statistical results for all case studies are collated into a table along with examples of graphical analysis.

CONCLUSIONS

This study has shown that some patients are prone to episodes of hypoxemia during the course of normal daily activity or daytime sleep that would usually go unrecognized and that more effective management of supplemental oxygen treatment may be possible with continual unobtrusive monitoring.

Optimum oxygen therapy in preterm babies

Oxygen is the most commonly used therapy in neonatal nurseries as an integral part of respiratory support. The goal of oxygen therapy is to achieve adequate delivery of oxygen to the tissue without creating oxygen toxicity. Oxygen must have been given to newborn preterm babies more than any other medicinal product in the past 60 years. Despite this, we still know very little about how much oxygen these babies actually need, or how much oxygen is safe to give, especially in the first few weeks of life. Recent observational studies have raised concerns that giving oxygen to target the saturation at "physiological" levels in newborn preterm babies may do more harm than good, but to date, clinicians have not been able to resolve the uncertainties surrounding optimum oxygen therapy.

A physiologic reduced oxygen protocol decreases the incidence of threshold retinopathy of prematurity

PURPOSE

To report the incidence of threshold retinopathy of prematurity (ROP) in very low birth weight premature infants from three neonatal intensive care units (NICUs) before and after implementation of a physiologic reduced oxygen protocol (PROP).

METHODS

PROSPECTIVE, OBSERVATIONAL STUDY OF DATA FROM THREE NICUS: Cedars-Sinai Medical Center (CSMC), Los Angeles; Good Samaritan Hospital (GSH), Los Angeles; and National University Hospital (NUH), Singapore. PROP was implemented to keep oxygen saturation values by pulse oximeter (SpO2) between 83% and 93% (as described in Pediatrics 2003;111:339-345). The incidence of threshold ROP in the year before and the year after implementation of PROP was compared. Data from the transition year were not included in the analysis.

RESULTS

THE INCIDENCE OF THRESHOLD ROP DECREASED IN EACH CENTER: CSMC, 3.3% to 0.0% (3/92 to 0/88); GSH, 14.8% to 4.9% (8/54 to 2/41); and NUH, 6.7% to 0.0% (3/45 to 0/30). Overall, the incidence of threshold ROP decreased from 7.3% to 1.3%. (P <.05). The 95% confidence interval was 4.3% to 12% for the pre-PROP group and 0.05% to 4.76% for the post-PROP group.

CONCLUSIONS

Physiologic hypoxia is the normal fetal state. Exposure of newborn premature infants to hyperoxia down-regulates retinal vascular endothelial growth factor. This arrests the normal retinal vascular migration and causes vaso-obliteration, the first phase of ROP. The hypothesis is that maintaining SpO2 values between 83% and 93% in the immediate postgestation life, combined with strict control of oxygen fluctuations, prevents the early vaso-obliterative phase and subsequent development of severe ROP. Significant reduction of threshold disease after implementation of PROP in all three centers supports the hypothesis.

[Oxygen therapy in the neonatal period]

Although oxygen has been widely used in the neonatal period for many years, and although serious complications such as retinopathy of the premature infant have been directly attributed to its use, there persists a degree of uncertainty about the optimal level of oxygen which should be used or target levels to achieve. There is a great variability in current practices. Some theoretical data and recent clinical results question uncontrolled use of oxygen during the neonatal period. Controlled studies comparing the effects of strategies with different target levels for oxygen saturation are planned to provide evidence-based answers to these questions.

Management of infants with chronic lung disease of prematurity in the United Kingdom

The management of chronic lung disease of prematurity (CLD) is challenging for the neonatologist. There are few well-powered randomised controlled trials to inform practice and longer-term outcomes of some interventions have only recently been identified (for example the possible association between the use of corticosteroids and neurodevelopmental abnormalities). As a result, many neonatologists rely on empirical management derived from the evidence available. We describe, in this article, our own approach to the management of CLD, and acknowledge that practice may vary between units within the United Kingdom.

Twelve-month prospective study of oxygen saturation measurements among term and preterm infants

BACKGROUND

Optimising home oxygen delivery in infants has important logistical and safety implications. This can be aided by having a suitable reference range of normal values for arterial oxygen saturation using pulse oximetry (SpO(2)).

OBJECTIVES

To describe oxygenation profiles in healthy preterm and term infants in relation to gestational and postnatal age, to extend reference values to guide home oxygen therapy.

STUDY DESIGN

Prospective monitoring of SpO(2) for 4 hours at 3 monthly intervals of 34 term, and 53 preterm healthy infants, took place over a 12-month period using an Ohmeda Biox 3700e pulse oximeter and data logger.

RESULTS

Group mean and 5th percentiles were used to construct cumulative frequency curves at each time interval, representing the normal reference range of SpO(2) profiles for term and preterm infants over time.

CONCLUSIONS

These data may be used to test the benefits in the home or hospital of having a reference range of normal values for cumulative SpO(2).

Neonatal cardiorespiratory monitoring techniques

Episodes of apnoea, desaturation and bradycardia are a common occurrence in preterm infants and are known to persist after hospital discharge. These events are typically detected by clinical bedside monitoring, but the type and number of events depend on alarm settings, the inclusion of continuous pulse oximetry and the mode of respiratory monitoring used. The long term effects of cardiorespiratory events remain controversial; however, some studies have suggested an association between prolonged apnoea and morbidity such as impaired neurodevelopmental outcome. Common clinical practice requires an event-free period before hospital discharge, although the specific length of time varies between institutions. Therefore, with the current demand to shorten hospital stay, the possible persistence of cardiorespiratory events after hospital discharge and the potential consequences of these events, cardiorespiratory monitoring remains a subject of considerable interest. Since cardiorespiratory event detection is dependent on the mode of monitoring used, this chapter will focus on both the respiratory patterns and types of cardiorespiratory events that occur in the infant population and the modalities of cardiorespiratory monitoring currently available to detect these events.

Controversy surrounding the use of home oxygen for premature infants with bronchopulmonary dysplasia

OBJECTIVE

To determine the criteria used in the current practice of neonatology for the initiation of home oxygen therapy in premature infants with bronchopulmonary dysplasia and to compare these criteria with the available literature regarding the use of home oxygen therapy.

STUDY DESIGN

Participants in the December 2000 meeting of the Vermont Oxford Network were surveyed regarding their current use of home oxygen therapy for infants with bronchopulmonary dysplasia.

RESULTS

Surveys were returned by 181 out of 297 participants. Pulse oximetry saturation (SpO2) thresholds for the initiation of home oxygen therapy varied widely from <84% to <98%. The most common threshold was <90% chosen by only 43% of the respondents. Additionally, 22% of the respondents did not initiate therapy until the oxygen saturation in room air was below 88%. Once on oxygen therapy, the target SpO2 also varied widely from >84% to >98%, with only 27% of respondents aiming for an SpO2 of >94%.

CONCLUSIONS

There is a clear lack of consensus among neonatologists regarding the initiation of home oxygen therapy for bronchopulmonary dysplasia. Furthermore, the criteria used for home oxygen therapy varies widely with the majority of neonatologists surveyed using oxygen saturation levels not supported by the literature. We speculate that a significant underutilization of home oxygen therapy exists for infants with bronchopulmonary dysplasia.

Safety, reliability, and validity of a physiologic definition of bronchopulmonary dysplasia

OBJECTIVE

Bronchopulmonary dysplasia (BPD) is the focus of many intervention trials, yet the outcome measure when based solely on oxygen administration may be confounded by differing criteria for oxygen administration between physicians. Thus, we wished to define BPD by a standardized oxygen saturation monitoring at 36 weeks corrected age, and compare this physiologic definition with the standard clinical definition of BPD based solely on oxygen administration.

METHODOLOGY

A total of 199 consecutive very low birthweight infants (VLBW, 501 to 1500 g birthweight) were assessed prospectively at 36+/-1 weeks corrected age. Neonates on positive pressure support or receiving >30% supplemental oxygen were assigned the outcome BPD. Those receiving < or =30% oxygen underwent a stepwise 2% reduction in supplemental oxygen to room air while under continuous observation and oxygen saturation monitoring. Outcomes of the test were "no BPD" (saturations > or =88% for 60 minutes) or "BPD" (saturation < 88%). At the conclusion of the test, all infants were returned to their baseline oxygen. Safety (apnea, bradycardia, increased oxygen use), inter-rater reliability, test-retest reliability, and validity of the physiologic definition vs the clinical definition were assessed.

RESULTS

A total of 199 VLBW were assessed, of whom 45 (36%) were diagnosed with BPD by the clinical definition of oxygen use at 36 weeks corrected age. The physiologic definition identified 15 infants treated with oxygen who successfully passed the saturation monitoring test in room air. The physiologic definition diagnosed BPD in 30 (24%) of the cohort. All infants were safely studied. The test was highly reliable (inter-rater reliability, kappa=1.0; test-retest reliability, kappa=0.83) and highly correlated with discharge home in oxygen, length of hospital stay, and hospital readmissions in the first year of life.

CONCLUSIONS

The physiologic definition of BPD is safe, feasible, reliable, and valid and improves the precision of the diagnosis of BPD. This may be of benefit in future multicenter clinical trials.

Occurrence of oxygen desaturation events during preterm infant bottle feeding near discharge

AIMS

The purpose of this study was to examine the occurrence, severity, pattern, and moderators of oxygen desaturation during preterm infant bottle feeding near the time of discharge from the neonatal intensive care unit (NICU) when fed by mothers.

STUDY DESIGN

Twenty-two very low birthweight (VLBW) infants [birthweight 1155+/-293 g, gestational age (GA) 28.1+/-2.0, postconceptional age (PCA) 36.5+/-1.6 weeks] were videotaped being bottle-fed by their mothers. Most infants (86%) were discharged within 6 days of the study. Oxygen saturation was continuously monitored and infant feeding behaviors were coded. Oxygen desaturation events (SpO(2)<90%) were identified and analyzed.

RESULTS

Infants averaged 10.8 events during feeding (range 1-28, S.D. 8.9) and spent, on average, 20% of their feeding time (range 0-70%, S.D. 17.98%) with oxygen levels below 90%. One hundred forty of the desaturation events (59%) were classified as mild (SpO(2) 85-89), 47 events (20%) were classified as moderate (SpO(2) 81-84), and 51 events (21%) were classified as severe (SpO(2)</=80). Events were evenly distributed across infants' feeding time. Receiving supplemental oxygen, beginning the feeding with a higher baseline SpO(2), and being of older PCA predicted lower percentage of feeding time with SpO(2) below 90% (R(2)=0.57). Receiving supplemental oxygen and beginning the feeding with a higher baseline SpO(2) predicted less number of desaturation events during the feeding (R(2)=0.44). Despite similar baseline SpO(2) levels, infants who were on supplemental oxygen had 50% less oxygen desaturation events and spent 33% less time with SpO(2) less than 90%.

CONCLUSION

VLBW infants continue to have desaturation events during feeding when fed by their mothers near the time of discharge. Further research is needed to understand the effect of hypoxemia on the preterm infant's development of oral feeding skills, to study the effects of supplemental oxygen during feeding, and to further develop interventions to minimize desaturation during feeding.

Pulse oximetry, severe retinopathy, and outcome at one year in babies of less than 28 weeks gestation

AIM

To determine whether differing policies with regard to the control of oxygen saturation have any impact on the number of babies who develop retinopathy of prematurity and the number surviving with or without signs of cerebral palsy at one year.

METHODS

An examination of the case notes of all the 295 babies who survived infancy after delivery before 28 weeks gestation in the north of England in 1990-1994.

RESULTS

Babies given enough supplemental oxygen to maintain an oxygen saturation of 88-98%, as measured by pulse oximetry, for at least the first 8 weeks of life developed retinopathy of prematurity severe enough to be treated with cryotherapy four times as often as babies only given enough oxygen to maintain an oxygen saturation of 70-90% (27.2% v 6.2%). Surviving babies were also ventilated longer (31.4 v 13.9 days), more likely to be in oxygen at a postmenstrual age of 36 weeks (46% v 18 %), and more likely to have a weight below the third centile at discharge (45% v 17%). There was no difference in the proportion who survived infancy (53% v 52%) or who later developed cerebral palsy (17% v 15%). The lowest incidence of retinopathy in the study was associated with a policy that made little use of arterial lines.

CONCLUSIONS

Attempts to keep oxygen saturation at a normal "physiological" level may do more harm than good in babies of less than 28 weeks gestation.