Cardiorespiratory Monitoring Data to Predict Respiratory Outcomes in Extremely Preterm Infants

Effect of Intermittent Hypoxemia and Hyperoxemia during the Neonatal Period on Control of Breathing Function among Infants Born Extremely Preterm

OBJECTIVE

To evaluate the association between intermittent hypoxemia (IH) and hyperoxemia (HOX) during the first 28 days with peripheral and central chemoreception at 36 weeks of postmenstrual age among infants born extremely preterm.

STUDY DESIGN

For this observational study, 52 infants born at 23-28 weeks of gestational age were enrolled. Mean daily IH frequency (arterial oxygen saturation <80% for ≥10 seconds) and percent of time in HOX (arterial oxygen saturation ≥98% while the fraction of inspired oxygen was >0.21) were calculated for the first 28 days of life. At 36 weeks of postmenstrual age, respiratory control tests assessed peripheral chemoreception by ventilatory response to 100% O2 for 30 seconds in which decreased ventilation caused by inhibition of peripheral chemoreceptors reflects their contribution to respiratory drive. Central chemoreception was evaluated by ventilatory response to 4% inspired CO2 for 10 minutes.

RESULTS

Multivariable generalized linear models showed increasing IH and HOX were independently associated with an attenuated ventilatory response to 100% O2 at 36 weeks of postmenstrual age. IH and HOX were not significantly associated with an attenuated ventilatory response to CO2.

CONCLUSIONS

In these infants born extremely preterm, neonatal IH and HOX were independently associated with attenuated peripheral chemoreception at near-term corrected age. This may reflect reduced peripheral chemoreceptor oxygen sensitivity and may be in part responsible for persistence of respiratory instability in infants born preterm. Neonatal IH or HOX were not associated with reduced central chemoreception.

Tachycardia-Desaturation Episodes in Neonatal Intensive Care Unit Patients with and without Bronchopulmonary Dysplasia

Much attention has been paid to measuring physiological episodes of bradycardia-oxygen desaturation (BDs) in the neonatal intensive care unit (NICU). NICU patients also have spells of tachycardia-desaturation (TDs), but these have not been well-characterized. We hypothesized that TDs would be more common among infants with bronchopulmonary dysplasia (BPD). We aimed to quantify daily TDs compared to BDs in NICU patients across a range of gestational and postmenstrual ages (GA and PMA) and determine whether TDs are associated with BPD.We analyzed every 2-second heart rate (HR) and peripheral saturation of oxygen (SpO2) throughout the NICU stay of all infants with 24 to 39 weeks GA admitted to a single, level IV NICU from 2012 to 2015. BDs were defined in our prior work (HR <100 bpm for ≥4 seconds with concurrent SpO2 <80% for ≥10 seconds) and TDs as a 20% increase in HR from the previous 2-hour mean baseline and concurrent SpO2 <80% for ≥10 seconds. We calculated the median daily BDs and TDs across a range of GAs and PMAs. For infants ≤32 weeks GA, we compared TDs for those with and without BPD at 36 weeks PMA and discharge on supplemental oxygen.We analyzed 782,424 hours of HR and SpO2 data from 1,718 neonates, with a median of 271 hours analyzed per infant. TDs frequency increased with increasing PMA across all GAs. BDs occurred most frequently in infants <29 weeks GA and decreased as infants approached term equivalent age. For infants with ≤32 weeks GA, one or more TD per day from 33 to 35 weeks PMA was associated with BPD and home oxygen.Episodes of TD at the thresholds defined in this analysis occurred more frequently at later PMA and were more common in infants with BPD and those requiring home oxygen. · Desaturation episodes occur often in preterm infants.. · Bradycardia or tachycardia can coincide with desaturation.. · TD occurs later and with BPD..

Development and external validation of a machine learning model to predict bronchopulmonary dysplasia using dynamic factors

We hypothesized that incorporating postnatal dynamic factors would enhance the prediction accuracy of bronchopulmonary dysplasia in preterm infants. This retrospective cohort study included neonates born before 32 weeks of gestation at Seoul National University Hospital between 2013 and 2022. The primary outcome was moderate or severe bronchopulmonary dysplasia. We assessed both static perinatal risk factors and dynamic factors, such as respiratory support type, inspired oxygen concentration, and blood gas analysis results within the first 7 days. The model was developed using data from 546 infants born between 2013 and 2021, with internal validation on 75 infants born in 2022. External validation was based on 105 infants recruited at the Boramae Medical Center. The integrated prediction model, combining static and dynamic factors, showed superior predictive performance, with an area under the receiver operating characteristic curve (AUROC) of 0.841 in the development set, outperforming the static perinatal factor model. Internal validation confirmed the robustness of the integrated model (AUROC: 0.912 vs. 0.805, p < 0.0001). The performance was maintained in the external validation (AUROC: 0.814). Incorporating early respiratory support and blood gas analysis into predictive models substantially improved the accuracy of bronchopulmonary dysplasia prediction in preterm infants.

Reimagining apnea monitoring in the neonatal ICU

PURPOSE OF REVIEW

This review outlines the prevalence and complications of apneas and intermittent hypoxemic events in preterm infants, examines current monitoring limitations in neonatal ICUs (NICUs), and explores emerging technologies addressing these challenges.

RECENT FINDINGS

New evidence from the Prematurity-Related Ventilatory Control (Pre-Vent) study, which analyzed cardiorespiratory data from 717 extremely preterm infants, exposes the varying frequency, duration, and severity of apneas, intermittent hypoxemia, bradycardias, and periodic breathing during hospitalization, and highlights the negative impact of intermittent hypoxemia on pulmonary outcomes at discharge. Although traditional monitoring methods cannot differentiate between apnea types and quantify their burden, recent advancements in sensor technologies and data integration hold promise for improving real-time detection and evaluation of apneas in the NICU. Notably, small wearable mechano-acoustic sensors could improve apnea monitoring through continuous detection of airflow and respiratory efforts. Additionally, integrating bedside physiological data with modalities such as near-infrared spectroscopy, diaphragmatic activity, and electrical impedance tomography could help predict adverse outcomes by monitoring regional oxygen saturation and lung function in relation to apneas.

SUMMARY

Enhancing our understanding of neonatal apneas and overcoming the current limitations in apnea monitoring through advanced sensor technologies and data integration could lead to more personalized management and improved outcomes for preterm infants.

Effects of liberal versus restrictive transfusion strategies on intermittent hypoxaemia in extremely low birthweight infants: secondary analyses of the ETTNO randomised controlled trial

OBJECTIVES

To compare the effect of liberal versus restrictive transfusion strategies on the proportion of time (%time) spent with intermittent hypoxaemia (IH, ie, arterial haemoglobin oxygen saturation measured by pulse oximetry (SpO2) <80% lasting ≥60 s) in the 'Effects of Transfusion Thresholds on Neurocognitive Outcome' (ETTNO) population, and to investigate whether infants with above-median exposure to IH might benefit more from liberal transfusion strategies than those with lower exposure.

DESIGN, SETTING, PATIENTS

Secondary analysis in all 554/1013 infants of <1000 g birth weight recruited into the ETTNO trial (mean gestational age 26.2 weeks) with >80% completeness of SpO2 recordings during postnatal days 8-49.

INTERVENTION

Randomly assigned liberal (n=268) or restrictive (n=286) transfusion strategies, defining transfusion triggers based on postnatal age and health status.

MAIN OUTCOME MEASURES

%time with IH, rate and mean duration of IH episodes during postnatal days 8-49. Interaction between exposure to IH and transfusion strategies with respect to ETTNO's composite primary outcome, death or disability at 24 months corrected age.

RESULTS

The median (quartile 1-quartile 3) %time with IH was similar between treatment groups (0.91% (0.13%-2.83%) with liberal vs 0.79% (0.16%-2.44%) with restrictive transfusions). There was no interaction between exposure to IH and transfusion strategies on outcome at 24 months.

CONCLUSIONS

In infants <1000 g birth weight, a liberal transfusion strategy did not reduce IH. Blood transfusions should not be administered 'liberally' to reduce IH or to improve neurocognitive outcome in infants with above-average exposure to IH.

TRIAL REGISTRATION NUMBER

NCT01393496.

Control of breathing in preterm infants on incubator oxygen or nasal cannula oxygen

BACKGROUND

Incubator oxygen may improve respiratory stability in preterm infants compared with nasal cannula oxygen.

METHODS

Single center randomized trial of infants <29 weeks' gestation on supplemental oxygen at ≥32 weeks' postmenstrual age. Infants were crossed-over every 24 hours for 96 hours between incubator oxygen and nasal cannula ≤1.0 L/kg/min. We measured episodes of intermittent hypoxemia (oxygen saturations (SpO2) < 85% ≥10 seconds), bradycardia, cerebral and abdominal hypoxemia, and end-tidal carbon dioxide.

RESULTS

We enrolled 25 infants with a gestational age of 26 weeks 4 days±15 days (mean ± SD) and birth weight 805 ± 202 grams. There were no differences in episodes of intermittent hypoxemia, bradycardia, or cerebral hypoxemia between groups. There were fewer episodes of abdominal hypoxemia <40% ≥10 seconds with incubator oxygen compared with nasal cannula (132 ± 130 versus 158 ± 125; p < 0.01). Time with SpO2 < 85% and abdominal hypoxemia was lower among infants on incubator oxygen. Carbon dioxide values were higher while on incubator oxygen (41 ± 11 versus 36 ± 10 mmHg; p < 0.02).

CONCLUSION

There was no difference in intermittent hypoxemia between incubator and nasal cannula oxygen among preterm infants on supplemental oxygen. Infants had higher levels of carbon dioxide while on incubator oxygen, which may have improved some measures of respiratory stability. CLINCALTRIALS.

GOV IDENTIFIERS

NCT03333174 and NCT03174301.

IMPACT STATEMENT

In this randomized cross-over trial of preterm infants on supplemental oxygen, incubator oxygen did not decrease episodes of intermittent hypoxemia compared with nasal cannula oxygen. Incubator oxygen reduced time with oxygen saturations less than 85%, reduced abdominal hypoxemia, and increased carbon dioxide levels. Differences in measures of respiratory stability on incubator oxygen may be partly due to higher carbon dioxide levels compared with nasal cannula oxygen. The mode of supplemental oxygen administration may impact control of breathing in preterm infants through its effect on hypopharyngeal oxygen stability and carbon dioxide levels.

Neonatal Sequential Organ Failure Assessment Score Predicts Respiratory Outcomes in Preterm Newborns with Late-Onset Sepsis: A Retrospective Study

INTRODUCTION

Neonatal sequential organ failure assessment (nSOFA) score predicts mortality in preterm newborns. The aim of the study was to assess whether nSOFA score could predict respiratory outcomes in preterm infants with late-onset sepsis (LOS).

METHODS

This retrospective, observational, single-center study enrolled infants with gestational age <32 weeks born between January 2016 and June 2023 who experienced an episode of LOS during NICU stay. The primary outcome was death or bronchopulmonary dysplasia (BPD); secondary outcomes were BPD, death or mechanical ventilation (MV) on day 5 after the onset of LOS, and MV on day 5 after the onset of LOS. The nSOFA score was assessed at the onset of LOS and after 6 ± 1, 12 ± 3, and 24 ± 3 h.

RESULTS

Neonatal SOFA score was significantly higher in patients who developed each outcome versus those who did not at all timings. Maximal nSOFA score during the first 24 h after onset of LOS was an independent predictive factor for death or BPD (p = 0.007), BPD (p = 0.009), and death or MV on day 5 (p = 0.009), areas under the curve (AUC) were 0.740 (95% CI: 0.656-0.828), 0.700 (95% CI: 0.602-0.800), and 0.800 (95% CI: 0.710-0.889), respectively. Maximal nSOFA score also predicted moderate to severe BPD (p = 0.019) and death or moderate to severe BPD (p < 0.001). Maximal nSOFA ≥4 was associated with odds ratio (OR) of 7.37 (95% CI: 2.42-22.44) for death or BPD, 4.86 (95% CI: 1.54-15.28) for BPD, and 7.99 (95% CI: 3.47-18.36) for death or MV on day 5. AUC of the predicting model was 0.895 (95% CI: 0.801-0.928) for BPD, 0.897 (95% CI: 0.830-0.939) for death or BPD, 0.904 (95% CI: 0.851-0.956) for MV on day 5, 0.923 (95% CI: 0.892-0.973) for death or MV on day 5.

CONCLUSION

Maximal nSOFA score during the first 24 h after the onset of LOS predicts respiratory outcomes and allows identification of patients who may crucially benefit from lung-protective measures.

The association of gene polymorphisms of adenosine and dopamine receptors with the response to caffeine citrate treatment in infants with apnea of prematurity: a prospective nested case-control study

BACKGROUND

To investigate the potential influence of adenosine and dopamine receptor genes polymorphisms in combination with clinical factors on the response of preterm infants to caffeine citrate treatment in apnea of prematurity (AOP).

METHODS

A prospective nested case-control study enrolled 221 preterm infants with gestational age < 34 weeks. These infants were divided into the response (n = 160) and the non-response groups (n = 61). 22 single-nucleotide polymorphisms in adenosine and dopamine receptor genes were genotyped. The basic characteristics and clinical outcomes of the two groups were compared. Univariate logistic regression analysis was performed to evaluate the differences in genotype distribution between the groups. Multivariable logistic regression analysis was performed to identify independent risk and protective factors and develop a nomogram to predict caffeine citrate response in preterm infants.

RESULTS

Preterm infants in the non-response group had lower gestational age, lower birth weight, longer periods of oxygen supplementation and caffeine citrate use, and higher incidence of patent ductus arteriosus (PDA), bronchopulmonary dysplasia (BPD), neonatal respiratory distress syndrome (NRDS), retinopathy of prematurity (ROP), and brain injury (P < 0.05 for all). The ADORA1 rs10920573, ADORA2B rs2015353, ADORA3 rs10776728, DRD3 rs7625282, and DRD3 rs6280 gene polymorphisms were associated with caffeine citrate response in preterm infants (PFDR < 0.05 for all). The ADORA1 rs10920573 CC (aOR, 3.51; 95% CI, 1.34-9.25) and DRD3 rs6280 CT genotypes (aOR, 3.19; 95% CI, 1.53-6.65) were independent risk factors for non-response, whereas greater gestational age (aOR, 0.631; 95% CI, 0.53-0.75) was an independent protective factor for response. The concordance index of the nomogram was 0.764 (95% CI, 0.687-0.842), and the calibration and decision curve analysis indicated the nomogram had excellent predict performance.

CONCLUSIONS

Adenosine receptor gene and dopamine receptor gene polymorphisms influence caffeine citrate treatment response in AOP. By combining genetic and clinical variables, it is possible to predict the response to caffeine citrate treatment in preterm infants.

Achieved oxygen saturations and risk for bronchopulmonary dysplasia with pulmonary hypertension in preterm infants

OBJECTIVE

Characterisation of oxygen saturation (SpO2)-related predictors that correspond with both bronchopulmonary dysplasia-associated pulmonary hypertension (BPD-PH) development and survival status in infants with BPD-PH may improve patient outcomes. This investigation assessed whether (1) infants with BPD-PH compared with infants with BPD alone, and (2) BPD-PH non-survivors compared with BPD-PH survivors would (a) achieve lower SpO2 distributions, (b) have a higher fraction of inspired oxygen (FiO2) exposure and (c) have a higher oxygen saturation index (OSI).

DESIGN

Case-control study between infants with BPD-PH (cases) and BPD alone (controls) and by survival status within cases.

SETTING

Single-centre study in the USA.

PATIENTS

Infants born at <29 weeks' gestation and on respiratory support at 36 weeks' postmenstrual age.

EXPOSURES

FiO2 exposure, SpO2 distributions and OSI were analysed over the week preceding BPD-PH diagnosis.

MAIN OUTCOMES AND MEASURES

BPD-PH, BPD alone and survival status in infants with BPD-PH.

RESULTS

40 infants with BPD-PH were compared with 40 infants with BPD alone. Infants who developed BPD-PH achieved lower SpO2 compared with infants with BPD (p<0.001), were exposed to a higher FiO2 (0.50 vs 0.34; p=0.02) and had a higher OSI (4.3 vs 2.6; p=0.03). Compared with survivors, infants with BPD-PH who died achieved a lower SpO2 (p<0.001) and were exposed to a higher FiO2 (0.70 vs 0.42; p=0.049).

CONCLUSIONS

SpO2-related predictors differed between infants with BPD-PH and BPD alone and among infants with BPD-PH by survival status. The OSI may provide a non-invasive predictor for BPD-PH in preterm infants.

Establishment and validation of apnea risk prediction models in preterm infants: a retrospective case control study

BACKGROUND

Apnea is common in preterm infants and can be accompanied with severe hypoxic damage. Early assessment of apnea risk can impact the prognosis of preterm infants. We constructed a prediction model to assess apnea risk in premature infants for identifying high-risk groups.

METHODS

A total of 162 and 324 preterm infants with and without apnea who were admitted to the neonatal intensive care unit of Xiamen University between January 2018 and December 2021 were selected as the case and control groups, respectively. Demographic characteristics, laboratory indicators, complications of the patients, pregnancy-related factors, and perinatal risk factors of the mother were collected retrospectively. The participants were randomly divided into modeling (n = 388) and validation (n = 98) sets in an 8:2 ratio. Least Absolute Shrinkage and Selection Operator (LASSO) and multivariate logistic regression analyses were used to independently filter variables from the modeling set and build a model. A nomogram was used to visualize models. The calibration and clinical utility of the model was evaluated using consistency index, receiver operating characteristic (ROC) curve, calibration curve, and decision curve, and the model was verified using the validation set.

RESULTS

Results of LASSO combined with multivariate logistic regression analysis showed that gestational age at birth, birth length, Apgar score, and neonatal respiratory distress syndrome were predictors of apnea development in preterm infants. The model was presented as a nomogram and the Hosmer-Lemeshow goodness of fit test showed a good model fit (χ2=5.192, df=8, P=0.737), with Nagelkerke R2 of 0.410 and C-index of 0.831. The area under the ROC curve and 95% CI were 0.831 (0.787-0.874) and 0.829 (0.722-0.935), respectively. Delong's test comparing the AUC of the two data sets showed no significant difference (P=0.976). The calibration curve showed good agreement between the predicted and actual observations. The decision curve results showed that the threshold probability range of the model was 0.07-1.00, the net benefit was high, and the constructed clinical prediction model had clinical utility.

CONCLUSIONS

Our risk prediction model based on gestational age, birth length, Apgar score 10 min post-birth, and neonatal respiratory distress syndrome was validated in many aspects and had good predictive efficacy and clinical utility.

Extended CPAP or low-flow nasal cannula for intermittent hypoxaemia in preterm infants: a 24-hour randomised clinical trial

OBJECTIVE

Optimal timing of continuous positive airway pressure (CPAP) cessation in preterm infants remains undetermined. We hypothesised that CPAP extension compared with weaning to low-flow nasal cannula (NC) reduces intermittent hypoxaemia (IH) and respiratory instability in preterm infants meeting criteria to discontinue CPAP.

DESIGN

Single-centre randomised clinical trial.

SETTING

Level 4 neonatal intensive care unit.

PATIENTS

36 infants <34 weeks' gestation receiving CPAP≤5 cmH2O and fraction of inspired oxygen (FiO2) ≤0.30 and meeting respiratory stability criteria.

INTERVENTIONS

Extended CPAP was compared with weaning to low-flow NC (0.5 L/kg/min with a limit of 1.0 L/min) for 24 hours.

OUTCOMES

The primary outcome was IH (number of episodes with SpO2<85% lasting ≥10 s). Secondary outcomes included: coefficient of variability of SpO2, proportion of time in various SpO2 ranges, episodes (≥10 s) with SpO2<80%, median cerebral and renal oxygenation, median effective FiO2, median transcutaneous carbon dioxide and bradycardia (<100/min for≥10 s).

RESULTS

The median (IQR) episodes of IH per 24-hour period was 20 (6-48) in the CPAP group and 76 (18-101) in the NC group (p=0.03). Infants continued on CPAP had less bradycardia, time with SpO2 <91% and <85%, and lower FiO2 (all p<0.05). There were no statistically significant differences in IH<80%, median transcutaneous carbon dioxide or median cerebral or renal oxygenation.

CONCLUSION

In preterm infants meeting respiratory stability criteria for CPAP cessation, extended CPAP decreased IH, bradycardia and other hypoxaemia measures compared with weaning to low-flow NC during the 24-hour intervention.

TRIAL REGISTRATION NUMBER

NCT04792099.

Apnea, Intermittent Hypoxemia, and Bradycardia Events Predict Late-Onset Sepsis in Infants Born Extremely Preterm

OBJECTIVE

The objective of this study was to examine the association of cardiorespiratory events, including apnea, periodic breathing, intermittent hypoxemia (IH), and bradycardia, with late-onset sepsis for extremely preterm infants (<29 weeks of gestational age) on vs off invasive mechanical ventilation.

STUDY DESIGN

This is a retrospective analysis of data from infants enrolled in Pre-Vent (ClinicalTrials.gov identifier NCT03174301), an observational study in 5 level IV neonatal intensive care units. Clinical data were analyzed for 737 infants (mean gestational age: 26.4 weeks, SD 1.71). Monitoring data were available and analyzed for 719 infants (47 512 patient-days); of whom, 109 had 123 sepsis events. Using continuous monitoring data, we quantified apnea, periodic breathing, bradycardia, and IH. We analyzed the relationships between these daily measures and late-onset sepsis (positive blood culture >72 hours after birth and ≥5-day antibiotics).

RESULTS

For infants not on a ventilator, apnea, periodic breathing, and bradycardia increased before sepsis diagnosis. During times on a ventilator, increased sepsis risk was associated with longer events with oxygen saturation <80% (IH80) and more bradycardia events before sepsis. IH events were associated with higher sepsis risk but did not dynamically increase before sepsis, regardless of ventilator status. A multivariable model including postmenstrual age, cardiorespiratory variables (apnea, periodic breathing, IH80, and bradycardia), and ventilator status predicted sepsis with an area under the receiver operator characteristic curve of 0.783.

CONCLUSION

We identified cardiorespiratory signatures of late-onset sepsis. Longer IH events were associated with increased sepsis risk but did not change temporally near diagnosis. Increases in bradycardia, apnea, and periodic breathing preceded the clinical diagnosis of sepsis.

The global burden of disease attributable to preterm birth and low birth weight in 204 countries and territories from 1990 to 2019: An analysis of the Global Burden of Disease Study

Background

Preterm birth and low birth weight (PBLBW), recognised globally as primary contributors to infant mortality in children under five, have not been sufficiently investigated in terms of their worldwide impact. In this study we aimed to thoroughly evaluate the contemporary trends in disease burden attributable to PBLBW.

Methods

We analysed data from 204 countries and territories between 1990-2019, as sourced from the 2019 Global Burden of Disease Study. We analysed the global incidence of mortality and disability-adjusted life years (DALYs) associated with PBLBW, stratified by age, gender, year, and geographic location, alongside the socio-demographic index (SDI). We calculated the annual percentage changes to evaluate the dynamic trends over time. We employed a generalised linear model and scrutinised the relationship between the SDI and the disease burden attributed to PBLBW.

Results

In 2019, the global age-standardised rate of deaths and DALYs related to PBLBW showed significant declines. Over the period 1990-2019, both death and DALY rates displayed substantial downward trends, with similar change trends observed for both females and males. Age-specific ratios revealed a decrease in PBLBW-related deaths and DALYs with increasing age, primarily during the neonatal stages (zero to 27 days). The leading three causes of PBLBW-related DALYs in 2019 were neonatal disorders, lower respiratory infections, and sudden infant death syndrome. Furthermore, the association between SDI and PBLBW-related DALYs indicated that the age-standardised DALY rates in 204 countries and territories worldwide were negatively correlated with SDI in 2019. From 1990 to 2019, the age-standardised DALY rates decreased linearly in most regions, except sub-Saharan Africa.

Conclusions

The persistent global burden of disease associated with PBLBW is particularly pronounced in neonates aged less than 28 days and in regions with low SDI. In this study, we highlighted the critical need for tailored interventions aimed at mitigating the detrimental effects of PBLBW to attain specific sustainable development goals, particularly those centred on enhancing child survival and overall well-being.

Pulse oximetry signal loss during hypoxic episodes in preterm infants receiving automated oxygen control

The aim of this study was to analyze signal loss (SL) resulting from low signal quality of pulse oximetry-derived hemoglobin oxygen saturation (SpO2) measurements during prolonged hypoxemic episodes (pHE) in very preterm infants receiving automatic oxygen control (AOC). We did a post hoc analysis of a randomized crossover study of AOC, programmed to set FiO2 to "back-up FiO2" during SL. In 24 preterm infants (median (interquartile range)) gestational age 25.3 (24.6 to 25.6) weeks, recording time 12.7 h (12.2 to 13.6 h) per infant, we identified 76 pHEs (median duration 119 s (86 to 180 s)). In 50 (66%) pHEs, SL occurred for a median duration of 51 s (33 to 85 s) and at a median frequency of 2 (1 to 2) SL-periods per pHE. SpO2 before and after SL was similar (82% (76 to 88%) vs 82% (76 to 87%), p = 0.3)).  Conclusion: SL is common during pHE and must hence be considered in AOC-algorithm designs. Administering a "backup FiO2" (which reflects FiO2-requirements during normoxemia) during SL may prolong pHE with SL.  Trial registration: The study was registered at www.

CLINICALTRIALS

gov under the registration no. NCT03785899.

WHAT IS KNOWN

• Previous studies examined SpO2 signal loss (SL) during routine manual oxygen control being rare, but pronounced in lower SpO2 states. • Oxygen titration during SL is unlikely to be beneficial as SpO2 may recover to a normoxic range.

WHAT IS NEW

• Periods of low signal quality of SpO2 are common during pHEs and while supported with automated oxygen control (SPOC), FiO2 is set to a back-up value reflecting FiO2 requirements during normoxemia in response to SL, although SpO2 remained below target until signal recovery. • FiO2 overshoots following pHEs were rare during AOC and occurred with a delayed onset; therefore, increased FiO2 during SL does not necessarily lead to overshoots.

Longitudinal effects of early exposure to intermittent hypoxia on autonomic cardiovascular control in very preterm infants

INTRODUCTION

Cardiorespiratory control is immature in infants born preterm compared to those born at term. Animal studies have shown that repetitive hypoxia associated with periodic breathing can alter autonomic control. We aimed to elucidate if the amount of time spent with apnoea and periodic breathing in the neonatal unit was associated with longitudinal changes in autonomic control assessed using heart rate variability.

METHODS

Twenty-nine very preterm infants (10 M 19F) were studied during supine daytime sleep on 4 occasions. Study 1: 32-36 weeks post menstrual age (PMA) (n = 29), Study 2: 36-40 weeks PMA (n = 27), Study 3: 3-months corrected age (CA) (n = 20) and Study 4: 6-months CA (n = 26). The percentage total sleep time (%TST) spent having apnoeas in active (AS) and quiet sleep (QS) at each study was calculated. Total power, low frequency (LF, sympathetic + parasympathetic activity) high frequency (HF, parasympathetic activity), and LF/HF (sympathovagal balance) were calculated. Infants were divided into two groups based on the %TST spent with apnoeas above and below the median in AS and QS at Study 1. Data were normalised and compared with two-way ANOVA with Bonferroni post-hoc tests.

RESULTS

When apnoeas were included in the analysis, in QS Total power and HF power were higher, and when apnoeas were excluded HF power was higher in QS but lower in AS in the above median group at Study 4.

CONCLUSION

This study provides new evidence that short apnoeas, particularly periodic breathing, which is currently not detected or treated in the neonatal unit can affect autonomic cardiovascular control.

Highly comparative time series analysis of oxygen saturation and heart rate to predict respiratory outcomes in extremely preterm infants

Objective.Highly comparative time series analysis (HCTSA) is a novel approach involving massive feature extraction using publicly available code from many disciplines. The Prematurity-Related Ventilatory Control (Pre-Vent) observational multicenter prospective study collected bedside monitor data from>700extremely preterm infants to identify physiologic features that predict respiratory outcomes.Approach. We calculated a subset of 33 HCTSA features on>7 M 10 min windows of oxygen saturation (SPO2) and heart rate (HR) from the Pre-Vent cohort to quantify predictive performance. This subset included representatives previously identified using unsupervised clustering on>3500HCTSA algorithms. We hypothesized that the best HCTSA algorithms would compare favorably to optimal PreVent physiologic predictor IH90_DPE (duration per event of intermittent hypoxemia events below 90%).Main Results.The top HCTSA features were from a cluster of algorithms associated with the autocorrelation of SPO2 time series and identified low frequency patterns of desaturation as high risk. These features had comparable performance to and were highly correlated with IH90_DPE but perhaps measure the physiologic status of an infant in a more robust way that warrants further investigation. The top HR HCTSA features were symbolic transformation measures that had previously been identified as strong predictors of neonatal mortality. HR metrics were only important predictors at early days of life which was likely due to the larger proportion of infants whose outcome was death by any cause. A simple HCTSA model using 3 top features outperformed IH90_DPE at day of life 7 (.778 versus .729) but was essentially equivalent at day of life 28 (.849 versus .850).Significance. These results validated the utility of a representative HCTSA approach but also provides additional evidence supporting IH90_DPE as an optimal predictor of respiratory outcomes.

Effects of bradycardia, hypoxemia and early intubation on bronchopulmonary dysplasia in very preterm infants: An observational study

BACKGROUND

Bronchopulmonary dysplasia (BPD) is the most common pulmonary complication in preterm infants.

OBJECTIVES

The study aimed to explore the effects of bradycardia, hypoxemia, and early intubation on BPD in very preterm infants.

METHODS

This is a prospective observational cohort study. Preterm infants with a mean gestational age of 28.67 weeks were recruited from two level III neonatal intensive care units (NICUs) in Taiwan. Continuous electrocardiography was used to monitor heart rates and oxygen saturation (SpO2). Infants were monitored for heart rates of <100 beats per minute and SpO2 levels of <90 % lasting for 30 s. Generalized estimating equations were used to analyze the effects of bradycardia, hypoxemia, and early intubation on BPD in very preterm infants. Model fit was visually assessed using receiver operating characteristic curve analysis.

RESULTS

Bradycardia, hypoxemia, and early intubation significantly increased the odds of BPD among the preterm infants (N = 39) during NICU stay; the odds ratios for bradycardia, hypoxemia, and early intubation for BPD versus non-BPD were 1.058, 1.013, and 29.631, respectively (all p < 0.05). A model combining bradycardia, hypoxemia, and early intubation accurately predicted BPD development (area under the curve = 0.919).

CONCLUSIONS

Bradycardia, hypoxemia, and early intubation significantly increased the odds of BPD among very preterm infants during NICU stay. The model combining bradycardia, hypoxemia, and early intubation accurately predicted BPD development.

Elevated Urine Hyaluronan Concentrations Are Associated with an Unfavorable Respiratory Outcome in Preterm Neonates at 40 Weeks Postmenstrual Age

INTRODUCTION

Hyaluronan (HA) is a major component of the extracellular matrix. Increased pulmonary HA concentrations are associated with several respiratory disorders and is a pathophysiological feature of lung disease. We investigated whether elevated urine HA is a biomarker of an unfavorable 40-week respiratory outcome in preterm infants.

METHODS

Infants comprised a cohort of preterm neonates <31 weeks gestational age (GA) from the Prematurity-Related Ventilatory Control (Pre-Vent) multicenter study. HA was quantified in urine obtained at 1 week and 1 month of age. Respiratory status at 40 weeks post-menstrual age (PMA) was classified as unfavorable [either (1) deceased at or before 40 weeks PMA, (2) an inpatient on respiratory medication, O2 or other respiratory support at 40 weeks, or (3) discharged prior to 40 weeks on medications/O2/other respiratory support], or favorable (alive and previously discharged, or inpatient and off respiratory medications, off O2, and off other respiratory support at 40 weeks PMA). The association between urine HA and the unfavorable 40 week PMA outcome was examined using a multivariate logistic generalized estimation equation model.

RESULTS

Infants with higher HA at 1 week (but not 1 month) showed increased odds of unfavorable respiratory outcome at 40 weeks PMA (OR [95% CI] = 1.87 per 0.01 mg [1.27, 2.73]).

DISCUSSION AND CONCLUSION

Neonatal urine screening for HA could identify infants at risk for death or need for respiratory support at term-corrected age (40 weeks PMA). The relationship between elevated HA at 1 week and an unfavorable 40 week outcome was stronger in infants with lower GA.

Apnea, Intermittent Hypoxemia, and Bradycardia Events Predict Late-Onset Sepsis in Extremely Preterm Infants

Objectives

Detection of changes in cardiorespiratory events, including apnea, periodic breathing, intermittent hypoxemia (IH), and bradycardia, may facilitate earlier detection of sepsis. Our objective was to examine the association of cardiorespiratory events with late-onset sepsis for extremely preterm infants (<29 weeks' gestational age (GA)) on versus off invasive mechanical ventilation.

Study Design

Retrospective analysis of data from infants enrolled in Pre-Vent (ClinicalTrials.gov identifier NCT03174301), an observational study in five level IV neonatal intensive care units. Clinical data were analyzed for 737 infants (mean GA 26.4w, SD 1.71). Monitoring data were available and analyzed for 719 infants (47,512 patient-days), of whom 109 had 123 sepsis events. Using continuous monitoring data, we quantified apnea, periodic breathing, bradycardia, and IH. We analyzed the relationships between these daily measures and late-onset sepsis (positive blood culture >72h after birth and ≥5d antibiotics).

Results

For infants not on a ventilator, apnea, periodic breathing, and bradycardia increased before sepsis diagnosis. During times on a ventilator, increased sepsis risk was associated with longer IH80 events and more bradycardia events before sepsis. IH events were associated with higher sepsis risk, but did not dynamically increase before sepsis, regardless of ventilator status. A multivariable model predicted sepsis with an AUC of 0.783.

Conclusion

We identified cardiorespiratory signatures of late-onset sepsis. Longer IH events were associated with increased sepsis risk but did not change temporally near diagnosis. Increases in bradycardia, apnea, and periodic breathing preceded the clinical diagnosis of sepsis.

Highly comparative time series analysis of oxygen saturation and heart rate to predict respiratory outcomes in extremely preterm infants

Objective

Highly comparative time series analysis (HCTSA) is a novel approach involving massive feature extraction using publicly available code from many disciplines. The Prematurity-Related Ventilatory Control (Pre-Vent) observational multicenter prospective study collected bedside monitor data from > 700 extremely preterm infants to identify physiologic features that predict respiratory outcomes. We calculated a subset of 33 HCTSA features on > 7M 10-minute windows of oxygen saturation (SPO2) and heart rate (HR) from the Pre-Vent cohort to quantify predictive performance. This subset included representatives previously identified using unsupervised clustering on > 3500 HCTSA algorithms. Performance of each feature was measured by individual area under the receiver operating curve (AUC) at various days of life and binary respiratory outcomes. These were compared to optimal PreVent physiologic predictor IH90 DPE, the duration per event of intermittent hypoxemia events with threshold of 90%.

Main Results

The top HCTSA features were from a cluster of algorithms associated with the autocorrelation of SPO2 time series and identified low frequency patterns of desaturation as high risk. These features had comparable performance to and were highly correlated with IH90_DPE but perhaps measure the physiologic status of an infant in a more robust way that warrants further investigation. The top HR HCTSA features were symbolic transformation measures that had previously been identified as strong predictors of neonatal mortality. HR metrics were only important predictors at early days of life which was likely due to the larger proportion of infants whose outcome was death by any cause. A simple HCTSA model using 3 top features outperformed IH90_DPE at day of life 7 (.778 versus .729) but was essentially equivalent at day of life 28 (.849 versus .850). These results validated the utility of a representative HCTSA approach but also provides additional evidence supporting IH90_DPE as an optimal predictor of respiratory outcomes.

The role of oxygen in the development and treatment of bronchopulmonary dysplasia

Oxygen (O2) is crucial for both the development and treatment of one of the most important consequences of prematurity: bronchopulmonary dysplasia (BPD). In fetal life, the hypoxic environment is important for alveolar development and maturation. After birth, O2 becomes a double-edged sword. While O2 is needed to prevent hypoxia, it also causes oxidative stress leading to a plethora of morbidities, including retinopathy and BPD. The advent of continuous O2 monitoring with pulse oximeters has allowed clinicians to recognize the narrow therapeutic margins of oxygenation for the preterm infant, but more knowledge is needed to understand what these ranges are at different stages of the preterm infant's life, including at birth, in the neonatal intensive care unit and after hospital discharge. Future research, especially in innovative technologies such as automated O2 control and remote oximetry, will improve the understanding and treatment of the O2 needs of infants with BPD.