Intermittent Hypoxemia in Preterm Infants: A Potential Proinflammatory Process

The impact of intermittent hypoxemia on type 1 retinopathy of prematurity in preterm infants

BACKGROUND

Intermittent hypoxemia (IH) may influence retinopathy of prematurity (ROP) development in preterm infants, however, previous studies had mixed results. This study tests the hypothesis that increased IH is associated with Type 1 ROP; a stage beyond which treatment is indicated.

METHODS

IH was quantified by continuously monitoring oxygen saturation (SpO2) using high-resolution pulse oximeters during the first 10 weeks of life. Statistical analyses assessed the relationship and predictive ability of weekly and cumulative IH for Type 1 ROP development.

RESULTS

Most analyses showed no association between IH and Type 1 ROP adjusting for gestational age (GA) and birth weight (BW). However, cumulative IH of longer duration during weeks 5-10, 6-10, and 7-10 were significantly associated with Type 1 ROP adjusting for GA and BW, e.g., the adjusted odds ratio of Type 1 ROP was 2.01 (p = 0.03) for every 3.8 seconds increase in IH duration from week 6-10. IH did not provide statistically significant added predictive ability above GA and BW.

CONCLUSIONS

For most analyses there was no significant association between IH and Type 1 ROP adjusting for GA and BW. However, infants with longer IH duration during the second month of life had higher risk for Type 1 ROP.

IMPACT

The relationship and predictive ability of intermittent hypoxemia (IH) on retinopathy of prematurity (ROP) is controversial. This study shows no significant association between IH events and Type 1 ROP after adjusting for gestational age (GA) and birth weight (BW), except for cumulative IH of longer duration in the second month of life. In this cohort, IH does not provide a statistically significant improvement in ROP prediction over GA and BW. This study is the first to assess the cumulative impact of IH measures on Type 1 ROP. Interventions for reducing IH duration during critical postnatal periods may improve ROP outcomes.

Predicting Extubation Readiness in Preterm Infants Utilizing Machine Learning: A Diagnostic Utility Study

OBJECTIVE

The objective of this study was to predict extubation readiness in preterm infants using machine learning analysis of bedside pulse oximeter and ventilator data.

STUDY DESIGN

This is an observational study with prospective recordings of oxygen saturation (SpO2) and ventilator data from infants <30 weeks of gestation age. Research pulse oximeters collected SpO2 (1 Hz sampling rate) to quantify intermittent hypoxemia (IH). Continuous ventilator metrics were collected (4-5-minute sampling) from bedside ventilators. Data modeling was completed using unbiased machine learning algorithms. Three model sets were created using the following data source combinations: (1) IH and ventilator (IH + SIMV), (2) IH, and (3) ventilator (SIMV). Infants were also analyzed separated by postnatal age (infants <2 or ≥2 weeks of age). Models were compared by area under the receiver operating characteristic curve (AUC).

RESULTS

A total of 110 extubation events from 110 preterm infants were analyzed. Infants had a median gestation age and birth weight of 26 weeks and 825 g, respectively. Of the 3 models presented, the IH + SIMV model achieved the highest AUC of 0.77 for all infants. Separating infants by postnatal age increased accuracy further achieving AUC of 0.94 for <2 weeks of age group and AUC of 0.83 for ≥2 weeks group.

CONCLUSIONS

Machine learning analysis has the potential to enhance prediction accuracy of extubation readiness in preterm infants while utilizing readily available data streams from bedside pulse oximeters and ventilators.

Association between Intermittent Hypoxemia and NICU Length of Stay in Preterm Infants

INTRODUCTION

Length of hospitalization varies widely in preterm infants and can be affected by multiple maternal and neonatal factors including respiratory instability. Therefore, we aimed to determine the association between postnatal intermittent hypoxemia (IH) and prolonged hospitalization.

METHODS

This prospective single-center cohort study followed infants born at <31 weeks of gestational age through 2 years corrected age with detailed oxygen saturation data captured from days 7 to 30 of age.

RESULTS

51/164 (31%) of infants were discharged after 400/7 weeks of corrected gestational age (CGA). A greater average daily number of IH events (OR per 10 events/day 1.33 [95% CI 1.03-1.72]), duration of events (OR per minute 1.14 [1.07-1.21]), and percent time with oxygen saturation <80% (OR per percent 1.88 [1.25-2.85]) on days 7-30 of age were all significantly associated with prolonged hospitalization past 400/7 weeks CGA. In survival analyses, infants with a greater average daily number of IH events (HR per 10 events/day 0.89 [0.81-0.98]), percent time with oxygen saturation <80% (HR per percent 0.79 [0.67-0.94]), and duration of events (HR per minute 0.93 [0.91-0.95]) on days 7-30 of age all had significantly lower probability of earlier discharge. In addition, there was a significant interaction with gestational age; the association between IH and prolonged hospitalization was stronger in more mature infants (p = 0.024).

CONCLUSIONS

Physiological instability on days 7-30 of age, as manifested by IH, is significantly associated with prolonged hospitalization. IH likely represents both a marker of initial severity of illness and the beginning of biological cascades, leading to prematurity-associated morbidities.

A Wearable Fiber-Free Optical Sensor for Continuous Monitoring of Neonatal Cerebral Blood Flow and Oxygenation

Impact

The innovative DSCFO technology may serve as a low-cost wearable sensor for continuous bedside monitoring of multiple cerebral hemodynamic parameters in neonatal intensive care units.Concurrent DSCFO and DCS measurements of CBF variations in neonatal piglet models generated consistent results.No consistent correlation patterns were observed among peripheral and cerebral monitoring parameters in preterm neonates, suggesting the importance of multi-parameter measurements for understanding deep insights of peripheral and cerebral regulations during IH events.Integrating and correlating multiple cerebral functional parameters with clinical outcomes may identify biomarkers for prediction and management of IH associated brain injury.

Background

Unstable cerebral hemodynamics places preterm infants at high risk of brain injury. We adapted an innovative, fiber-free, wearable diffuse speckle contrast flow-oximetry (DSCFO) device for continuous monitoring of both cerebral blood flow (CBF) and oxygenation in neonatal piglets and preterm infants.

Methods

DSCFO uses two small laser diodes as focused-point and a tiny CMOS camera as a high-density two-dimensional detector to detect spontaneous spatial fluctuation of diffuse laser speckles for CBF measurement, and light intensity attenuations for cerebral oxygenation measurement. The DSCFO was first validated against the established diffuse correlation spectroscopy (DCS) in neonatal piglets and then utilized for continuous CBF and oxygenation monitoring in preterm infants during intermittent hypoxemia (IH) events.

Results

Consistent results between the DSCFO and DCS measurements of CBF variations in neonatal piglets were observed. IH events induced fluctuations in CBF, cerebral oxygenation, and peripheral cardiorespiratory vitals in preterm infants. However, no consistent correlation patterns were observed among peripheral and cerebral monitoring parameters.

Conclusions

This pilot study demonstrated the feasibility of DSCFO technology to serve as a low-cost wearable sensor for continuous monitoring of multiple cerebral hemodynamic parameters. The results suggested the importance of multi-parameter measurements for understanding deep insights of peripheral and cerebral regulations.

Automatic oxygen control for reducing extremes of oxygen saturation: a randomised controlled trial

OBJECTIVE

The objective of this study was to evaluate the efficacy of the automatic oxygen control (A-Fio₂) in reducing the percentage of time spent in severe hypoxaemia (Spo₂ <80%) in preterm infants for the time period on invasive ventilation and/or nasal continuous positive airway pressure (NCPAP) delivered by AVEA ventilator.

DESIGN

A parallel arm randomised controlled trial.

SETTING

A level-III neonatal intensive care unit.

PATIENTS

Preterm infants (<33 weeks birth gestation) who received invasive ventilation or NCPAP in the first 72 hours of age.

INTERVENTIONS

A-Fio₂ vs manual (M-Fio₂) oxygen control.

OUTCOMES

The primary outcome of the study was percentage of time spent in severe hypoxaemia (Spo₂ <80%).

RESULTS

44 infants were randomised to either A-Fio₂ or M-Fio₂ arm and continued in the study for the period of respiratory support (invasive ventilation and/or NCPAP). The total number of study days in A-Fio2 and M-Fio₂ arm were 194 and 204 days, respectively. The percentage of time spent in Spo₂ <80% was significantly lower with A-Fio₂ compared with M-Fio₂ (median of 0.1% (IQR: 0.07-0.7) vs 0.6% (0.2-2); p=0.03). The number of prolonged episodes (>60 s) of Spo₂ <80% per day was also significantly lower in A-Fio₂ (0.3 (0.0-2) vs 2 (0.6-6); p=0.02).

CONCLUSION

A-Fio₂ was associated with statistically significant reduction in the percentage of time spent in severe hypoxaemia when compared with M-Fio₂ in preterm infants receiving respiratory support.

TRIAL REGISTRATION NUMBER

NCT04223258.

The relationship between intermittent hypoxemia events and neural outcomes in neonates

This brief review examines 1) patterns of intermittent hypoxemia in extremely preterm infants during early postnatal life, 2) the relationship between neonatal intermittent hypoxemia exposure and outcomes in both human and animal models, 3) potential mechanistic pathways, and 4) future alterations in clinical care that may reduce morbidity. Intermittent hypoxemia events are pervasive in extremely preterm infants (<28 weeks gestation at birth) during early postnatal life. An increased frequency of intermittent hypoxemia events has been associated with a range of poor neural outcomes including language and cognitive delays, motor impairment, retinopathy of prematurity, impaired control of breathing, and intraventricular hemorrhage. Neonatal rodent models have shown that exposure to short repetitive cycles of hypoxia induce a pathophysiological cascade. However, not all patterns of intermittent hypoxia are deleterious and some may even improve neurodevelopmental outcomes. Therapeutic interventions include supplemental oxygen, pressure support and pharmacologic drugs but prolonged hyperoxia and pressure exposure have been associated with cardiopulmonary morbidity. Therefore, it becomes imperative to distinguish high risk from neutral and/or even beneficial patterns of intermittent hypoxemia during early postnatal life. Identification of such patterns could improve clinical care with targeted interventions for high-risk patterns and minimal or no exposure to treatment modalities for low-risk patterns.

Microglia-Mediated Neurodegeneration in Perinatal Brain Injuries

Perinatal brain injuries, including encephalopathy related to fetal growth restriction, encephalopathy of prematurity, neonatal encephalopathy of the term neonate, and neonatal stroke, are a major cause of neurodevelopmental disorders. They trigger cellular and molecular cascades that lead in many cases to permanent motor, cognitive, and/or behavioral deficits. Damage includes neuronal degeneration, selective loss of subclasses of interneurons, blocked maturation of oligodendrocyte progenitor cells leading to dysmyelination, axonopathy and very likely synaptopathy, leading to impaired connectivity. The nature and severity of changes vary according to the type and severity of insult and maturation stage of the brain. Microglial activation has been demonstrated almost ubiquitously in perinatal brain injuries and these responses are key cell orchestrators of brain pathology but also attempts at repair. These divergent roles are facilitated by a diverse suite of transcriptional profiles and through a complex dialogue with other brain cell types. Adding to the complexity of understanding microglia and how to modulate them to protect the brain is that these cells have their own developmental stages, enabling them to be key participants in brain building. Of note, not only do microglia help build the brain and respond to brain injury, but they are a key cell in the transduction of systemic inflammation into neuroinflammation. Systemic inflammatory exposure is a key risk factor for poor neurodevelopmental outcomes in preterm born infants. Based on these observations, microglia appear as a key cell target for neuroprotection in perinatal brain injuries. Numerous strategies have been developed experimentally to modulate microglia and attenuate brain injury based on these strong supporting data and we will summarize these.