Is Pulse Oximetry Useful for Screening Neonates for Critical Congenital Heart Disease at High Altitudes?

A new algorithm DEtectS critical Congenital Heart Disease at different altitudes: ANDES-CHD study

BACKGROUND

Neonatal pulse oximetry screening (POS) algorithms for critical congenital heart disease (CCHD) have contributed towards decreasing neonatal mortality but cannot be applied at high altitudes. New POS algorithms at high altitudes are needed.

METHODS

This observational, prospective study included newborns born at different altitudes from 0 to 4380 meters above the sea level in Peru. Healthy newborns underwent neonatal preductal and postductal oximetry, echocardiography and telephonic follow-up up to 12 months of age. Newborns with CCHD underwent preductal and postductal oximetry at the time of telemedicine evaluation while located at the high-altitude hospital where they were born, and their diagnoses were confirmed with echocardiography locally or after arriving to the referral center. Two new algorithms were designed using clinically accepted neonatal oximetry cutoffs or the 5th and 10th percentiles for preductal and postductal oximetry values.

RESULTS

A total of 502 healthy newborns and 15 newborns with CCHD were enrolled. Echocardiography and telephonic follow-up were completed in 227 (45%) and 330 healthy newborns (65%), respectively. The algorithm based on clinically accepted cutoffs had a sensitivity of 92%, specificity of 73% and false positive rate of 27% The algorithm based on the 5th and 10th percentiles had a sensitivity of 80%, specificity of 88% and false positive rate of 12%.

CONCLUSIONS

Two algorithms that detect CCHD at different altitudes had adequate performance but high false positive rates.

Trajectories of oxygen saturation within 6-72 hours after birth in neonates at moderate altitude: a prospective longitudinal cohort study

BACKGROUND

Trajectories of pulse oxygen saturation (SpO2) within the first few days after birth are important to inform the strategy for identifying asymptomatic hypoxemic disease but remain poorly substantiated at higher altitudes.

METHODS

We performed a longitudinal cohort study with consecutive neonates at a local hospital in Luchun County, China, at an altitude of 1650 m between January and July 2020. We repeatedly measured the pre- and post-ductal SpO2 values at 6, 12, 18, 24, 36, 48, and 72 hours after birth for neonates without oxygen supplements. All neonates underwent echocardiography and were followed up to 42 days after discharge. We included neonates without hypoxemic diseases to characterize the trajectories of SpO2 over time using a linear mixed model. We considered the 2.5th percentile as the reference value to define hypoxemic conditions.

RESULTS

A total of 1061 neonates were enrolled. Twenty-five had non-cardiac hypoxemic diseases, with 84% (21/25) presenting with abnormal SpO2 within 24 hours. One had tetralogy of Fallot identified by echocardiography. Among the 1035 asymptomatic neonates, SpO2 values declined from 6 hours after birth, reached a nadir at 48 hours, and tended to level off thereafter, with identical patterns for both pre- and post-ductal SpO2. The reference percentile was 92% for both pre- and post-ductal SpO2 and was time independent.

CONCLUSIONS

A decline within 48 hours features SpO2 trajectories within the first 72 hours at moderate altitude. Our findings suggest that earlier screening may favorably achieve a benefit-risk balance in identifying asymptomatic hypoxemic diseases in this population.

Establishing the reference interval for pulse oxygen saturation in neonates at high altitudes: protocol for a multicentre, open, cross-sectional study

INTRODUCTION

Establishing the reference interval for pulse oxygen saturation (SpO₂) is essential for sensitively identifying neonatal hypoxaemia due to various causes. However, the reference interval for high altitudes has not yet been established, and existing studies have many limitations. This study will aim to establish the reference interval for various high altitudes and determine whether preductal and postductal measurements at the same altitude vary.

METHODS AND ANALYSIS

This is a multicentre, open, cross-sectional study, which will begin in February 2022. Approximately 2000 healthy full-term singleton neonates will be recruited from six hospitals (altitude ≥2000 m) in Qinghai Province, China. The participating hospitals will use a uniform pulse oximeter type. The measurements will be performed between 24 hours after birth and discharge. During the measurement, the neonate will be awake and quiet. Preductal and postductal measurements will be performed. The measurement time, site and results will be recorded and input, along with the collected basic information, into the perinatal cloud database. We will carry out strict quality control for basic information collection, measurement and data filing. We will perform descriptive statistics on the distribution range of the collected data, determine the lower limit value of the reference interval for each hospital and the corresponding altitude, perform curve fitting for the lower limit value, use the altitude as a covariate for the function corresponding to the fitted curve, establish the prediction equation and ultimately determine the reference intervals of each high altitude location.

ETHICS AND DISSEMINATION

Our protocol has been approved by the Medical Ethics Committee of all participating hospitals. We will publish our study results in academic conferences and peer-reviewed public journals.

TRIAL REGISTRATION NUMBER

NCT05115721.

Oxygen saturation and perfusion index screening in neonates at high altitudes: can PDA be predicted?

Screening critical congenital heart disease in neonates with 24-48 h of age could be made by oxygen saturation determination. Perfusion index may be used as an adjunct to pulse oximetry screening to detect non-cyanotic critical congenital heart disease cases such as a left heart outflow obstruction. We evaluate the results of combined screening for oxygen saturation and peripheral perfusion index at high altitudes. The study included 501 neonates older than gestational week 35. The mean oxygen saturation was lower than at sea level, and the screening test was positive in a total of 21 (4.2%) babies. Critical congenital heart diseases were not detected in any patient. A total of 10 (2%) babies were detected with PDA, nine (1.8%) of whom recorded a positive screening test. The prevalence of PDA was significantly higher in the positive screening test group when compared with those who underwent echocardiography due to clinical findings.Conclusion: The median peripheral perfusion index at high altitude was not lower than at sea level, while the mean oxygen saturation, in contrast, was lower than at sea level. The low partial oxygen pressure found at high altitudes leads to a variation in postnatal adaptation and an increased prevalence of PDA. Accordingly, oxygen saturation screening may serve to identify babies with PDA at high altitudes. What is Known: • Oxygen saturation is known to be low at high altitudes, and thus the rates of false positivity are high when screening for critical congenital heart disease. • High altitudes are also associated with an increased prevalence of simple congenital heart disease. What is New: • The peripheral perfusion index at high altitude is not lower than at sea level. • The prevalence of PDA is significantly higher in those with false positive screening results.

Reference Interval for Pulse Oxygen Saturation in Neonates at Different Altitudes: A Systematic Review

Introduction: The reference interval for pulse oxygen saturation (SpO₂) in neonates born at high altitudes has not been defined to date. The purpose of this study was to systematically review published studies and determine the reference interval of SpO₂ in neonates at different altitudes. Methods: Databases of PubMed, Embase, Cochrane Library, Clinicaltrials.Gov, Chinese National Knowledge Infrastructure Database, Wanfang Database, Chinese Science Technology Journals Database, and Chinese Clinical Trial Registry were searched for studies reporting SpO₂ in healthy neonates at different altitudes. Retrieval time was from inception of the database to August 16, 2021. The Agency for Healthcare Research and Quality checklist was used to evaluate the quality of studies. Python v3.8 was used to analyze the data. This systematic review was drafted in accordance with the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Results: Seven cross-sectional studies, published between 1991 and 2020, were identified. They were from US, Mexico, Israel, Ecuador, and China. Three studies were rated as high quality and four as moderate quality. The mean SpO₂ (with standard deviation or standard error) of neonates born in 40 different altitudes (ranging from 25 meters to 3,100 meters) were obtained. The prediction equation for calculation of the lower limit of the reference interval was established, and the reference intervals for SpO₂ at different altitudes were determined. Conclusions: In healthy neonates, the lower limit of the reference interval of SpO₂ decreases with increase in altitude. High-quality prospective studies are need to confirm our findings.

Revised threshold values for neonatal oxygen saturation at mild and moderate altitudes

AIM

The aim of this study was to determine reference values for oxygen saturation (SpO₂ ) in neonates at mild and moderate altitudes.

METHODS

Our study included 41 097 consecutively born, asymptomatic neonates from 35 hospitals, located in Yunnan, China, with altitudes ranging from 267 to 2202 m. Pre-and post-ductal SpO₂ of each neonate was measured at 24 hours of age and before hospital discharge. All study participants, according to the altitude of birth, were categorised into three groups: low (0-500 m), mild (500-1500 m) and moderate altitude (1500-2500 m).

RESULTS

Every 1000-m increase in altitude was associated with a 1.54 per cent decrease in mean SpO₂ . The means of pre-ductal SpO₂ at low, mild and moderate groups were 97.9%, 96.4% and 95.5%, respectively. We used the 2.5th percentile of SpO₂ distribution as the cut-off for neonatal SpO₂ screening and defined new cut-off values of ≤93% for mild altitudes, ≤92% for moderate altitudes and no adjustment for low altitudes.

CONCLUSION

We recommend revised cut-off values for neonatal SpO₂ at mild and moderate altitudes and provide new values for paediatricians to refer to when screening neonates for severe congenital heart or lung diseases.

Pulse oximetry in neonates at high altitudes: a modified Colorado protocol

Pulse oximetry for detecting critical CHD produces more false positive tests at high altitudes than at sea level, because at altitude the average resting saturation is lower and the variability is higher. This increases diagnostic difficulties, especially in small isolated communities without paediatric echocardio-graphy, and requires expensive transport to a regional medical centre. One way of reducing diagnostic errors is to measure arterial oxygen saturation while the infant is breathing 100% oxygen. In the absence of right-to-left shunting through the heart, the ductus, or the lungs, arterial oxygen tension will exceed 150 mmHg and arterial oxygen saturation will be 100%. With right-to-left shunting, arterial oxygen tension will be <100 mmHg, and thus <96% (usually much lower).

Pattern Analysis of Oxygen Saturation Variability in Healthy Individuals: Entropy of Pulse Oximetry Signals Carries Information about Mean Oxygen Saturation

Pulse oximetry is routinely used for monitoring patients' oxygen saturation levels with little regard to the variability of this physiological variable. There are few published studies on oxygen saturation variability (OSV), with none describing the variability and its pattern in a healthy adult population. The aim of this study was to characterize the pattern of OSV using several parameters; the regularity (sample entropy analysis), the self-similarity [detrended fluctuation analysis (DFA)] and the complexity [multiscale entropy (MSE) analysis]. Secondly, to determine if there were any changes that occur with age. The study population consisted of 36 individuals. The “young” population consisted of 20 individuals [Mean (±1 SD) age = 21.0 (±1.36 years)] and the “old” population consisted of 16 individuals [Mean (±1 SD) age = 50.0 (±10.4 years)]. Through DFA analysis, OSV was shown to exhibit fractal-like patterns. The sample entropy revealed the variability to be more regular than heart rate variability and respiratory rate variability. There was also a significant inverse correlation between mean oxygen saturation and sample entropy in healthy individuals. Additionally, the MSE analysis described a complex fluctuation pattern, which was reduced with age (p < 0.05). These findings suggest partial “uncoupling” of the cardio-respiratory control system that occurs with aging. Overall, this study has characterized OSV using pre-existing tools. We have showed that entropy analysis of pulse oximetry signals carries information about body oxygenation. This may have the potential to be used in clinical practice to detect differences in diseased patient subsets.