Obstructive, mixed, and central apnea in the neonate: physiologic correlates

Etiology and Mechanism of Intermittent Hypoxemia Episodes in Spontaneously Breathing Extremely Premature Infants

OBJECTIVE

To evaluate the mechanisms leading to intermittent hypoxemia (IH) episodes in spontaneously breathing extremely premature infants at 32 weeks and 36 weeks postmenstrual age (PMA).

METHODS

We studied spontaneously breathing premature infants born at 23-28 weeks of gestational age who presented with IH episodes while on noninvasive respiratory support at 32 or 36 weeks PMA. Daytime recordings of arterial oxygen saturation (SpO2), esophageal pressure, respiratory inductive plethysmography of the abdomen, chest wall, and their sum were obtained during 4 hours at 32 weeks and 36 weeks PMA. IH episodes (SpO2 <90% for ≥5 seconds) and severe IH episodes (SpO2 < 80% for ≥5 seconds) were classified as resulting from apnea, active exhalation and breath holding, reduced tidal volume (VT), or reduced respiratory rate (RR) during the preceding 60 seconds.

RESULTS

Fifty-one infants with a mean gestational age of 25.9 ± 1.5 weeks and a mean birth weight of 846 ± 185 g were included. Of these, 31 and 41 were included in the analysis at 32 weeks and 36 weeks PMA, respectively. At both 32 weeks and 36 weeks PMA, greater proportions of all IH episodes and severe IH episodes were associated with active exhalation and breath holding than with apnea, reduced RR, or reduced VT. The severity and duration of the IH episodes did not differ between mechanisms.

CONCLUSIONS

In this group of premature infants, the predominant mechanism associated with daytime IH was active exhalation and breath holding. This etiology is more closely associated with behavioral factors than abnormal respiratory control and can have implications for prevention.

Lung volume changes during apnoeas in preterm infants

OBJECTIVE

Mechanisms of non-invasive high-frequency oscillatory ventilation (nHFOV) in preterm infants are unclear. We aimed to compare lung volume changes during apnoeas in preterm infants on nHFOV and nasal continuous positive airway pressure (nCPAP).

METHODS

Analysis of electrical impedance tomography (EIT) data from a randomised crossover trial comparing nHFOV with nCPAP in preterm infants at 26-34 weeks postmenstrual age. EIT data were screened by two reviewers to identify apnoeas ≥10 s. End-expiratory lung impedance (EELI) and tidal volumes (V_T) were calculated before and after apnoeas. Oxygen saturation (SpO₂) and heart rate (HR) were extracted for 60 s after apnoeas.

RESULTS

In 30 preterm infants, 213 apnoeas were identified. During apnoeas, oscillatory volumes were detectable during nHFOV. EELI decreased significantly during apnoeas (∆EELI nCPAP: -8.0 (-11.9 to -4.1) AU/kg, p<0.001; ∆EELI nHFOV: -3.4 (-6.5 to -0.3), p=0.03) but recovered over the first five breaths after apnoeas. Compared with before apnoeas, V_T was increased for the first breath after apnoeas during nCPAP (∆V_T: 7.5 (3.1 to 11.2) AU/kg, p=0.001). Falls in SpO₂ and HR after apnoeas were greater during nCPAP than nHFOV (mean difference (95% CI): SpO₂: 3.6% (2.7 to 4.6), p<0.001; HR: 15.9 bpm (13.4 to 18.5), p<0.001).

CONCLUSION

Apnoeas were characterised by a significant decrease in EELI which was regained over the first breaths after apnoeas, partly mediated by a larger V_T. Apnoeas were followed by a considerable drop in SpO₂ and HR, particularly during nCPAP, leading to longer episodes of hypoxemia during nCPAP. Transmitted oscillations during nHFOV may explain these benefits.

TRIAL REGISTRATION NUMBER

ACTRN12616001516471.

Central apnea detection in premature infants using machine learning

BACKGROUND AND OBJECTIVE

Apnea of prematurity is one of the most common diagnosis in neonatal intensive care units. Apneas can be classified as central, obstructive or mixed. According to the current international standards, minimal fluctuations or absence of fluctuations in the chest impedance (CI) suggest a central apnea (CA). However, automatic detection of reduced CI fluctuations leads to a high number of central apnea-suspected events (CASEs), the majority being false alarms. We aim to improve automatic detection of CAs by using machine learning to optimize detection of CAs among CASEs.

METHODS

Using an optimized algorithm for automated detection, all CASEs were detected in a population of 10 premature infants developing late-onset sepsis and 10 age-matched control patients. CASEs were inspected by two clinical experts and annotated as CAs or rejections in two rounds of annotations. A total of 47 features were extracted from the ECG, CI and oxygen saturation signals considering four 30 s-long moving windows, from 30 s before to 15 s after the onset of each CASE, using a moving step size of 5 s. Consecutively, new CA detection models were developed based on logistic regression with elastic net penalty, random forest and support vector machines. Performance was evaluated using both leave-one-patient-out and 10-fold cross-validation considering the mean area under the receiver-operating-characteristic curve (AUROC).

RESULTS

The CA detection model based on logistic regression with elastic net penalty returned the highest mean AUROC when features extracted from all four time windows were included, both using leave-one-patient-out and 10-fold cross-validation (mean AUROC of 0.88 and 0.90, respectively). Feature relevance was found to be the highest for features derived from the CI. A threshold for the false positive rate in the mean receiver-operating-characteristic curve equal to 0.3 led to a high percentage of correct detections for all CAs (78.2%) and even higher for CAs followed by a bradycardia (93.4%) and CAs followed by both a bradycardia and a desaturation (95.2%), which are more critical for the well-being of premature infants.

CONCLUSIONS

Models based on machine learning can lead to improved CA detection with fewer false alarms.

Is Early Preventive Caffeine Safe and Effective in Premature Neonates? A Clinical Trial

Background

Advantages of caffeine for the treatment of apnea of prematurity (AOP) have prompted clinicians to use it as a preventive drug even before the occurrence of apnea.

Objective

To compare the effect of early preventive caffeine therapy with routine late preventive caffeine on the occurrence rate of apnea of prematurity, bronchopulmonary dysplasia (BPD) and related radiographic changes, necrotizing enterocolitis (NEC), intraventricular hemorrhage (IVH), and patent ductus arteriosus (PDA), the need for mechanical ventilation, the length of mechanical ventilation, and the length of hospitalization.

Materials and Methods

In this open randomized clinical trial study, 90 preterm neonates with the gestational age of 25-35 weeks were divided into 2 groups: group A received caffeine during the first two days of life (early preventive caffeine), while group B received caffeine during the third to the tenth day of life (late preventive caffeine). The occurrence rate of AOP and other outcomes were the primary outcomes. The adverse effects of caffeine in each group were the secondary outcomes.

Results

The total occurrence rate of AOP was significantly higher (32.6%) in the late group versus (6.8%) in the early group (p = 0.002). The total occurrence rate of BPD was also significantly higher (37%) in the late group versus (18.2%) in the early group (p = 0.047). On the other hand, we found a lower need for mechanical ventilation, shorter length of mechanical ventilation, shorter length of hospitalization, and a lower occurrence rate of PDA, NEC, and IVH in the early group that was not significant. No adverse effect of caffeine was observed in each group.

Conclusions

Early preventive caffeine administration was associated with a significantly lower occurrence rate of AOP, BPD, and BPD radiologic changes. As other outcomes occurred lesser in the early group that were not significant, future studies with more participants are recommended. This study has been registered at the Iranian Registry of Clinical Trials (IRCT20160827029535N8).

The effect of apnea length on vital parameters in apnea of prematurity - Hybrid observations from clinical data and simulation in a mathematical model

Apnea of prematurity (AOP) is a critical condition for preterm infants which can lead to several adverse outcomes. Despite its relevance, mechanisms underlying AOP are still unclear. In this work we aimed at improving the understanding of AOP and its physiologic responses by analyzing and comparing characteristics of real infant data and model-based simulations of AOP. We implemented an existing algorithm to extract apnea events originating from the central nervous system from a population of 26 premature infants (1248 h of data in total) and investigated oxygen saturation (SpO₂) and heart rate (HR) of the infants around these events. We then extended a previously developed cardio-vascular model to include the lung mechanics and gas exchange. After simulating the steady state of a preterm infant, which successfully replicated results described in previous literature studies, the extended model was used to simulate apneas with different lengths caused by a stop in respiratory muscles. Apneas identified by the algorithm and simulated by the model showed several similarities, including a far deeper decrease in SpO₂, with the minimum reached later in time, in case of longer apneas. Results also showed some differences, either due to how measures are performed in clinical practice in our neonatal intensive care unit (e.g. delayed detection of decline in SpO₂ after apnea onset due to signal averaging) or to the limited number of very long apneas (≥80 s) identified in our dataset.

Multichannel esophageal signals to monitor respiratory rate in preterm infants

BACKGROUND

Apnea of prematurity cannot be reliably measured with current monitoring techniques. Instead, indirect parameters such as oxygen desaturation or bradycardia are captured. We propose a Kalman filter-based detection of respiration activity and hence apnea using multichannel esophageal signals in neonatal intensive care unit patients.

METHODS

We performed a single-center observational study with moderately preterm infants. Commercially available nasogastric feeding tubes containing multiple electrodes were used to capture signals with customized software. Multichannel esophageal raw signals were manually annotated, processed using extended Kalman filter, and compared with standard monitoring data including chest impedance to measure respiration activity.

RESULTS

Out of a total of 405.4 h captured signals in 13 infants, 100 episodes of drop in oxygen saturation or heart rate were examined. Median (interquartile range) difference in respiratory rate was 0.04 (-2.45 to 1.48)/min between esophageal measurements annotated manually and with Kalman filter and -3.51 (-7.05 to -1.33)/min when compared to standard monitoring, suggesting an underestimation of respiratory rate when using the latter.

CONCLUSIONS

Kalman filter-based estimation of respiratory activity using multichannel esophageal signals is safe and feasible and results in respiratory rate closer to visual annotation than that derived from chest impedance of standard monitoring.

Perinatal Hypoxemia and Oxygen Sensing

The development of the control of breathing begins in utero and continues postnatally. Fetal breathing movements are needed for establishing connectivity between the lungs and central mechanisms controlling breathing. Maturation of the control of breathing, including the increase of hypoxia chemosensitivity, continues postnatally. Insufficient oxygenation, or hypoxia, is a major stressor that can manifest for different reasons in the fetus and neonate. Though the fetus and neonate have different hypoxia sensing mechanisms and respond differently to acute hypoxia, both responses prevent deviations to respiratory and other developmental processes. Intermittent and chronic hypoxia pose much greater threats to the normal developmental respiratory processes. Gestational intermittent hypoxia, due to maternal sleep-disordered breathing and sleep apnea, increases eupneic breathing and decreases the hypoxic ventilatory response associated with impaired gasping and autoresuscitation postnatally. Chronic fetal hypoxia, due to biologic or environmental (i.e. high-altitude) factors, is implicated in fetal growth restriction and preterm birth causing a decrease in the postnatal hypoxic ventilatory responses with increases in irregular eupneic breathing. Mechanisms driving these changes include delayed chemoreceptor development, catecholaminergic activity, abnormal myelination, increased astrocyte proliferation in the dorsal respiratory group, among others. Long-term high-altitude residents demonstrate favorable adaptations to chronic hypoxia as do their offspring. Neonatal intermittent hypoxia is common among preterm infants due to immature respiratory systems and thus, display a reduced drive to breathe and apneas due to insufficient hypoxic sensitivity. However, ongoing intermittent hypoxia can enhance hypoxic sensitivity causing ventilatory overshoots followed by apnea; the number of apneas is positively correlated with degree of hypoxic sensitivity in preterm infants. Chronic neonatal hypoxia may arise from fetal complications like maternal smoking or from postnatal cardiovascular problems, causing blunting of the hypoxic ventilatory responses throughout at least adolescence due to attenuation of carotid body fibers responses to hypoxia with potential roles of brainstem serotonin, microglia, and inflammation, though these effects depend on the age in which chronic hypoxia initiates. Fetal and neonatal intermittent and chronic hypoxia are implicated in preterm birth and complicate the respiratory system through their direct effects on hypoxia sensing mechanisms and interruptions to the normal developmental processes. Thus, precise regulation of oxygen homeostasis is crucial for normal development of the respiratory control network. © 2021 American Physiological Society. Compr Physiol 11:1653-1677, 2021.

Caffeine for the Treatment of Apnea in the Neonatal Intensive Care Unit: A Systematic Overview of Meta-Analyses

BACKGROUND

Caffeine is a common treatment for neonatal intensive care management of the developmental complication of apnea of prematurity in preterm infants. There are several systematic reviews (SRs) on the performance of caffeine in the treatment of apnea. The evidence provided by those, however, is depressed by an information overload due to high heterogeneity in the characteristics as well as the quality of these SRs.

OBJECTIVE

The aim was to provide a systematic overview of SRs on the use of caffeine for the management of neonatal apnea. Such overviews are a recent method used to assess and filter top evidence among SRs, enabling enhanced access to targeted information of interest.

METHODS

A comprehensive literature search was conducted via EMBASE, Cochrane Database of Systematic Reviews (CDSR), and PubMed since inception to January 2020. Two reviewers independently conducted study selection and data extraction, and assessed the quality of methods and the risk of bias in included SRs based on A Measurement Tool to Assess Systematic Reviews (AMSTAR-2) and Risk of Bias in Systematic Reviews (ROBIS) tools. Extracted data related to study type, characteristics, patients, intervention, comparator, regimen, and outcome measures.

RESULTS

Seven SRs with meta-analyses (SRMAs) were included in the current overview, involving a total of 63,315 neonates. SRMAs included randomized clinical and observational studies, with various types of patients, comparators, and outcomes. The quality of SRMAs ranged from critically low (n = 1), low (n = 1), moderate (n = 2), to high (n = 3), and the risk of bias was unclear (n = 2), low (n = 4), and high (n = 1). The effectiveness of caffeine with regard to treatment success and the rate of apnea was not significantly different from that of theophylline or doxapram in two SRMAs. Against control, in one SRMA, while caffeine reduced the rate of failure as well as the need for pressure ventilation, it did not significantly reduce mortality. This comparative effectiveness of caffeine was based on high-quality SRMAs with a low risk of bias. The effectiveness against apnea seems to be enhanced via the administration of early (0-2 days) or high doses of caffeine in one and three SRMAs, respectively. This, nevertheless, was based on lower-quality SRMAs with a higher risk of bias. Safety outcomes were mostly based on comparative SRMAs of different drug regimens, whereby, less tachycardia and lower risk for complications were reported with lower and earlier caffeine administrations, respectively. The evidence behind this, however, was limited in quantity and quality.

CONCLUSION

While limited in quantity, there is evidence of non-inferior effectiveness of caffeine against other methylxanthines or doxapram for the management of apnea in neonates. Owing to the limited quality, however, limited evidence exists in support of an optimal administration regimen for caffeine. Further controlled studies are, therefore, needed to confirm the comparative usefulness of caffeine as well as to assess its different potential regimens, including in relation to safety.

Effects of Nasal Continuous Positive Airway Pressure on Cerebral Hemodynamics in Preterm Infants

Background: To evaluate the effects of pressure levels on cerebral hemodynamics in premature infants receiving nasal continuous positive airway pressure (nCPAP) during the first 3 days of life. Methods: Forty-four preterm infants treated with nCPAP were divided into two groups: very preterm infants [gestational age 1 (GA1), GA < 32 weeks, n = 24] and moderate/late preterm infants (GA2 group, GA 32-37 weeks, n = 20). During monitoring, pressure levels were set at 4 → 6 → 8 → 4 cmH₂O, and cerebral hemodynamics was assessed by near-infrared spectroscopy (NIRS). Vital signs, peripheral oxygen saturation (SpO₂) and transcutaneous carbon dioxide pressure (TcPCO₂) were simultaneously recorded. Results: Pressures of 4-8 cmH₂O had no significant influence on cerebral hemodynamics, TcPCO₂, SpO₂ or other vital signs. The tissue oxygenation index (TOI), the difference between oxygenated hemoglobin (ΔHbO₂) and deoxygenated hemoglobin (ΔHHb) (ΔHbD), and cerebral blood volume (ΔCBV) were all significantly positively correlated with gestational and post-natal age, with fluctuations being greater in the GA1 group. ΔHbD and ΔCBV were also significantly positively correlated with TcPCO₂. Conclusions: No significant differences were observed in cerebral hemodynamics when the nCPAP pressure was set to 4-8 cmH₂O.

High versus standard dose caffeine for apnoea: a systematic review

BACKGROUND

Placebo-controlled trials have shown that caffeine is highly effective in treating apnoea of prematurity and reduces the risk of bronchopulmonary dysplasia (BPD) and neurodevelopmental impairment (NDI).

OBJECTIVE

To identify, appraise and summarise studies investigating the modulating effect of different caffeine dosages.

METHODS

A systematic review identified all randomised controlled trials (RCTs) comparing a high versus a standard caffeine treatment regimen in infants with a gestational age <32 weeks, by searching the main electronic databases and abstracts of the Pediatric Academic Societies. Studies comparing caffeine to placebo or theophylline only were excluded. Primary outcomes were BPD and mortality at 36 weeks postmenstrual age. Secondary key-outcome was neurodevelopmental outcome at 12 and 24 months corrected age. Meta-analysis was performed using RevMan 5.3.

RESULTS

Six RCTs including 620 infants were identified. Meta-analysis showed a significant decrease in BPD, the combined outcome BPD or mortality, and failure to extubate in infants allocated to a higher caffeine dose. No differences were found in mortality alone and NDI. The quality of the outcome measures were deemed low to very low according to the Grading of Recommendations Assessment, Development and Evaluation guidelines.

CONCLUSIONS

Although this review suggests that administering a higher dose of caffeine might enhance its beneficial effect on death or BPD, firm recommendations on the optimal caffeine dose cannot be given due to the low level of evidence. A large RCT is urgently needed to confirm or refute these findings and determine the optimal dose of caffeine.

Classifying Apnea of Prematurity by Transcutaneous Electromyography of the Diaphragm

BACKGROUND

Treatment of apnea is highly dependent on the type of apnea. Chest impedance (CI) has inaccuracies in monitoring respiration, which compromises accurate apnea classification. Electrical activity of the diaphragm measured by transcutaneous electromyography (EMG) is feasible in preterm infants and might improve the accuracy of apnea classification.

OBJECTIVES

To compare the accuracy of apnea classification based on diaphragmatic EMG (dEMG) and CI tracings in preterm infants.

METHODS

Fifteen cases of central apnea, 5 of obstructive apnea, and 10 of mixed apnea were selected from recordings containing synchronized continuous tracings of respiratory inductive plethysmography (RIP), airway flow, heart rate (HR), oxygen saturation (SpO2), and breathing activity measured by dEMG and CI. Twenty-two assessors (neonatologists, pediatricians-in-training, and nurses) classified each apnea twice; once based on dEMG, HR, and SpO2 tracings, and once based on CI, HR, and SpO2. The assessors were blinded to the type of respiratory tracing (dEMG or CI) and to the RIP and flow tracings.

RESULTS

In total 1,320 assessments were performed, and in 71.1% the apnea was classified correctly. Subgroup analysis based on respiratory tracing showed that 74.8% of the dEMG tracings were classified correctly compared to 67.3% of the CI tracings (p < 0.001). This improved apnea classification based on dEMG was present for central (86.7 vs. 80.3%, p < 0.02) and obstructive (56.4 vs. 32.7%, p < 0.001) apnea. The improved apnea classification based on dEMG tracing was independent of the type of assessor.

CONCLUSION

Transcutaneous dEMG improves the accuracy of apnea classification when compared to CI in preterm infants, making this technique a promising candidate for future monitoring systems.

Doxapram Treatment for Apnea of Prematurity: A Systematic Review

BACKGROUND

Apnea of prematurity (AOP) is a common complication of preterm birth, for which caffeine is the first treatment of choice. In case of persistent AOP, doxapram has been advocated as an additional therapy.

OBJECTIVE

To identify and appraise all existing evidence regarding efficacy and safety of doxapram use for AOP in infants born before 34 weeks of gestational age.

METHODS

All studies reporting on doxapram use for AOP were identified by searching electronic databases, references from relevant studies, and abstracts from the Societies for Pediatric Research. Two reviewers independently assessed study eligibility and quality, and extracted data on study design, patient characteristics, efficacy and safety outcomes.

RESULTS

The randomized controlled trials showed less apnea during doxapram treatment when compared to placebo, but no difference in treatment effect when compared to theophylline. No serious adverse effects were reported. We identified 28 observational studies consisting mainly of cohort studies and case series (n = 1,994). There was considerable heterogeneity in study design and quality. Most studies reported a positive effect of doxapram on apnea rate. A few studies reported on long-term outcomes with conflicting results. A range of possible doxapram-related short-term adverse effects were reported, sometimes associated with the use of higher doses.

CONCLUSION

Based on the limited number of studies and level of evidence, no firm conclusions on the efficacy and safety of doxapram in preterm infants can be drawn. For this reason, routine use cannot be recommended. A large multicenter randomized controlled trial is urgently needed to provide more conclusive evidence.

The potential of methylxanthine-based therapies in pediatric respiratory tract diseases

Caffeine, theophylline and theobromine are the most known methylxanthines as they are present in coffee, tea and/or chocolate. In the last decades, a huge experimental effort has been devoted to get insight into the variety of actions that these compounds exert in humans. From such knowledge it is known that methylxanthines have a great potential in prevention, therapy and/or management of a variety of diseases. The benefits of methylxanthine-based therapies in the apnea of prematurity and their translational potential in pediatric affections of the respiratory tract are here presented.

Sleep and breathing in premature infants at 6 months post-natal age

Background

Poor sleep contributes to the developmental problems seen in preterm infants. We evaluated sleep problems in preterm infants 6 months of post-gestational age using the subjective Brief Infant Sleep Questionnaire (BISQ) and objective sleep tests. We also compared the sleep of premature infants with that of full-term infants.

Methods

The study included 68 6-month-old full-term healthy infants and 191 premature infants born at <37 weeks gestation. All parents completed the BISQ-Chinese version and sleep diaries. At the same time, all premature infants were submitted to one night of polysomnography (PSG) in the sleep laboratory and also were set up with an actigraph kept for 7 days. Statistical analyses were performed using correlation coefficients and the t-test with SPSS version 18 to compare questionnaire responses with other subjective and objective measures of sleep.

Results

The sleep problems indicated in the subjective questionnaire for the premature infants, particularly: “the nocturnal sleep duration, number of night awakenings, daytime sleep duration, duration of time with mouth breathing, and loud-noisy breathing” had significant correlations with sleep diaries, actigraphy and PSG results. The BISQ showed that duration of infant’s sleeping on one side, nocturnal sleep duration, being held to fall asleep, number of nighttime awakenings, daytime sleep duration, subjective consideration of sleep problems, loud-noisy breathing, and duration spent crying during the night were significantly different between the premature infants and the term infants. PSG confirmed the presence of a very high percentage (80.6%) of premature infants with AHI > 1 event/hour as indicated by the questionnaire.

Conclusion

Premature infants have more sleep problems than full-term infants, including the known risk of abnormal breathing during sleep, which has been well demonstrated already with the BISQ-Chinese (CBISQ).

Electronic supplementary material

The online version of this article (doi:10.1186/s12887-014-0303-6) contains supplementary material, which is available to authorized users.

Current definitions for neonatal apnoea: are they evidence based?

Apnoea is defined as cessation of breathing with implicit pathophysiology. This review considers definitions of neonatal apnoea currently available and explores the evidence to support their use. For preterm and term infants, apnoea definitions appear arbitrary, are not supported by guidelines and vary from study to study. Although most alarms on infant breathing monitors are set to alert after a respiratory pause >20s duration is detected, this time period is the equivalent of 17 missed breaths in a preterm infant. Apnoea is likely to be better defined by associated consequence than by pause duration alone in this age group; however, the degree of change in heart rate or oxygen saturation that defines a respiratory pause as pathological is yet to be defined. Further research is required to determine the characteristics that differentiate respiratory events of clinical consequence from normal respiratory variability in term and preterm infants.

Cerebral desaturations in preterm infants: a crossover trial on influence of oxygen saturation target range

OBJECTIVE

To test the hypothesis that a higher pulsoximetric arterial oxygen saturation (SpO2) target range is associated with reduced cerebral tissue oxygen desaturations from baseline during events of hypoxaemia or bradycardia.

DESIGN

Randomised crossover trial.

SETTING

Single tertiary care neonatal intensive care unit.

PATIENTS

Sixteen preterm infants with severe intermittent hypoxaemia or bradycardia.

INTERVENTIONS

SpO2 target was set to 80-92% and 85-96% for 4 h each in random sequence. On a subsequent day, the target sequence was reversed and the study was repeated.

MAIN OUTCOME MEASURES

We simultaneously recorded cerebral tissue oxygen saturation (cerebral StO2), SpO2 and heart rate. Cerebral StO2 was measured by near infrared spectroscopy. The primary outcome was the cumulative cerebral StO2 desaturation score representing the area below a cerebral StO2 baseline value before onset of each hypoxaemic or bradycardic event.

RESULTS

During low SpO2 target range the median (IQR) cumulative cerebral StO2 desaturation score was higher (27384 (15825-37396) vs 18103 (6964-32946), p=0.011) and the mean (±SD) number of events was higher (29.1 (±15.3) vs 21.1 (±11.4), p=0.001). More time was spent with SpO2 below 80% (57.2 (±24.8) min vs 34.0 (±29.6) min, p=0.006). Total time of hyperoxaemia (defined as SpO2 ≥97% and ≥99%, respectively) and total time with cerebral StO2 <60% and <55% were similar.

CONCLUSIONS

A lower SpO2 target range was associated with a greater cumulative cerebral StO2 desaturation score, caused by more frequent SpO2 desaturations. However, time at very low cerebral StO2 was not affected. Episodes of hyperoxaemia were not reduced.

Apnea as the sole manifestation of a seizure attributable to meningioangiomatosis of the temporal lobe in an infant

An 8-month-old boy presented with periods of apnea occurring several times daily. Initial clinical and radiologic evaluations could not identify a cause for these episodes. Video electroencephalographic monitoring indicated interictal high-voltage θ and δ activity over the right frontotemporal area. A short ictal run of δ activity over the same region was registered during a brief apneic spell. Cranial magnetic resonance imaging revealed a lesion anteromedial in the right temporal lobe. After epilepsy surgery, anatomopathologic examination indicated meningioangiomatosis. This case demonstrates that a focal lesion in the temporal lobe can present during infancy with apnea as sole seizure manifestation, without other clear clinical evidence.

Body positioning for spontaneously breathing preterm infants with apnoea

BACKGROUND

It has been proposed that the use of body positioning may be a more effective way to reduce clinically significant apnoea than the use of more invasive measures.

OBJECTIVES

To determine the effect of body positioning on cardiorespiratory functioning in spontaneously breathing preterm infants with clinically significant apnoea.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2011), MEDLINE (1966 to March 2011), EMBASE (1988 to March 2011) and CINAHL (1988 to March 2011), abstracts of conference proceedings and citations of published articles.

SELECTION CRITERIA

All studies in which infants or their sequence of body positioning was randomised or quasi-randomised. We included cross-over studies.

DATA COLLECTION AND ANALYSIS

We performed assessment of trial quality, data extraction and synthesis of data using standard methods of the Cochrane Neonatal Review Group.

MAIN RESULTS

Five studies (N = 114) were eligible for inclusion. None of the individual studies or the meta-analyses showed a reduction in apnoea, bradycardia, oxygen desaturation or oxygen saturation with body positioning (supine versus prone; prone versus right lateral; prone versus left lateral; right lateral versus left lateral; prone horizontal versus prone head elevated; right lateral horizontal versus right lateral head elevated and left lateral horizontal versus left lateral head elevated).

AUTHORS' CONCLUSIONS

There is insufficient evidence to determine the role of body positioning on apnoea, bradycardia, oxygen desaturation and oxygen saturation. Large randomised controlled trials are needed to determine the effect of body positioning on cardiorespiratory function in spontaneously breathing preterm infants.

Indications for home apnea monitoring (or not)

Although there is a large body of literature describing infants who experience apnea of prematurity and apparent life-threatening events, there is no consensus regarding the use of home monitoring. This article focuses on issues that affect decision making regarding the use of home monitors in these two groups of infants and reviews existing data to guide a decision to discontinue monitoring at hospital discharge or to prescribe monitoring in the home.

Factors influencing apnea and bradycardia of prematurity - implications for neurodevelopment

BACKGROUND

Apnea and bradycardia of prematurity (ABP) are possible risks towards damage of the developing brain.

OBJECTIVES

To characterize the influence of neonatal factors on ABP and to determine the relationship of ABP to neurodevelopmental outcome.

METHODS

ABP was described in very low birth weight infants (n = 83) using the frequency and severity of ABP episodes with a clinical score considering heart rate, oxygenation, duration and interventions performed during each episode. Neonatal factors were analyzed for their relationship to ABP using regression analysis. Neurodevelopment was investigated using the Mental Developmental Index (MDI) and Psychomotor Developmental Index (PDI) of the Bayley Scales of Infant Development II at a corrected age of 13 months. Power of ABP parameters to predict outcome was assessed by logistic regression analysis.

RESULTS

ABP typically started within the first week after birth. Spontaneous resolution occurred at a postmenstrual age (PMA) of 36.0 +/- 2.2 (31.1-44.1) weeks. A delayed resolution (>36 weeks PMA) and a higher average daily ABP score during a defined developmental period (31-37 weeks PMA) were associated with a higher incidence of unfavorable outcome (MDI or PDI <69 or death).

CONCLUSION

ABP is an age-specific phenomenon. However, more severe courses than expected for PMA or the resolution at a later PMA indicated an increased risk of neurodevelopmental disturbances at a corrected age of 13 months.

Apnea in infants

OBJECTIVE

The main objective of this study was to describe frequency of risk factors in newborns who present different types of apnea in polysomnographic (PSG) recordings in neonatal care units.

METHODS

The study was carried out in neonatal care units of a perinatal tertiary level institution in Mexico City between August 2002 and August 2003. Infants were selected from among 223 infants if they presented any type of apnea event in sleep PSG recordings.

RESULTS

Nearly 25% of patients from a neonatal care unit presented apnea events. Infants with apnea showed lower values of age, weight, and cephalic perimeter at birth than infants without apnea, but did not show more neurologic risk factors. Central apnea events were more frequent in infants with preterm birth (birthweight < 1,500 g), obstructive apnea events were observed in infants with hyperbilirubinemia and gastro-esophageal reflux, while mixed events were seen in infants with sepsis, and hyperbilirubinemia. Sleep PSG recordings detected that 36% of infants with apnea have no previous clinic suspicion of the problem.

CONCLUSION

Central events of apnea were found more frequent in infants with preterm birth, obstructive events in newborns with hyperbilirubinemia and gastroesophagic reflux, while infants mixed apnea had more frequent hyperbilirubinemia and sepsis.

Effect of prone and supine position on sleep, apneas, and arousal in preterm infants

OBJECTIVE

Prematurely born compared with term born infants are at increased risk of sudden infant death syndrome, particularly if slept prone. The purpose of this work was to test the hypothesis that preterm infants with or without bronchopulmonary dysplasia being prepared for neonatal unit discharge would sleep longer and have less arousals and more central apneas in the prone position.

METHODS

This was a prospective observational study in a tertiary NICU. Twenty-four infants (14 with bronchopulmonary dysplasia) with a median gestational age of 27 weeks were studied at a median postconceptional age of 37 weeks. Video polysomnographic recordings of 2-channel electroencephalogram, 2-channel electro-oculogram, nasal airflow, chest and abdominal wall movements, limb movements, electrocardiogram, and oxygen saturation were made in the supine and prone positions, each position maintained for 3 hours. The duration of sleep, sleep efficiency (total sleep time/total recording time), and number and type of apneas, arousals, and awakenings were recorded.

RESULTS

Overall, in the prone position, infants slept longer, had greater sleep efficiency (89.5% vs 72.5%), and had more central apneas (median: 5.6 vs 2.2), but fewer obstructive apneas (0.5 vs 0.9). The infants had more awakenings (9.7 vs 3.5) and arousals per hour (13.6 vs 9.0) when supine. There were similar findings in the bronchopulmonary dysplasia infants.

CONCLUSIONS

Very prematurely born infants studied before neonatal unit discharge sleep more efficiently with fewer arousals and more central apneas in the prone position, emphasizing the importance of recommending supine sleeping after neonatal unit discharge for prematurely born infants.

Apnea is not prolonged by acid gastroesophageal reflux in preterm infants

OBJECTIVE

To examine the temporal relationship between apnea and gastroesophageal reflux (GER) and to assess the effect of GER on apnea duration.

METHODS

A total of 119 preterm infants underwent 12-hour cardiorespiratory monitoring studies using respiratory inductance plethysmography, heart rate, oxygen saturation (SaO2), and esophageal pH. The studies were scored for GER (pH <4 for > or =5 seconds) and apnea > or =15 seconds or > or =10 seconds that occurred within 30 seconds of GER. Apnea > or =10 seconds was used to assess whether GER would prolong apnea duration.

RESULTS

There were 6255 episodes of GER. Only 1% of GER episodes were associated with apnea > or =15 seconds, and there was no difference in apnea rate before, during, or after GER. There was also no difference in rate of apnea > or =10 seconds before versus during GER; however, there was a decrease in apnea rate immediately after GER. The presence of GER during apnea did not prolong apnea duration, and GER had no effect on the lowest SaO2 or heart rate during apnea.

CONCLUSION

There is no evidence of a temporal relationship between acid-based GER and apnea in preterm infants. In addition, GER does not prolong apnea duration and does not exacerbate the resultant decrease in heart rate and SaO2.

Prone or supine for infants with chronic lung disease at neonatal discharge?

OBJECTIVE

To determine whether infants with chronic lung disease (CLD), ready for neonatal unit discharge, maintain cardiorespiratory stability while sleeping supine.

METHODS

Subjects were 15 infants born < 32 weeks gestational age (GA) and ready for discharge from the regional tertiary neonatal intensive care unit. Polysomnography recordings of sleep state, heart rate, arterial oxygen saturation, respiratory effort and nasal/oral airflow were taken prone and supine for up to 3 h post feed with the first position randomly allocated. The main outcome measures were oxygen saturation and apnoea hypopnoea index (AHI).

RESULTS

Seven infants (median GA 27 weeks, birthweight 945 g) had CLD and eight infants (median GA 29 weeks, birthweight 1160 g) did not. CLD infants were more mature at study than non-CLD infants (median 39 vs 36 weeks, P = 0.019). Neither oxygen saturation nor AHI were position dependent and no group differences were noted with respect to CLD status. There was a significant interaction of GA and sleep position with less-mature infants spending less time in quiet sleep (QS) in supine position (P = 0.006). These less-mature infants also had a higher AHI (P = 0.033). As expected, the AHI and arousal index (AI) were higher in active sleep (P < or = 0.001, P = 0.013, respectively) and mean oxygen saturation was lower (P = 0.001).

CONCLUSIONS

The supine position appears appropriate for very preterm infants with CLD going home from the neonatal unit. Respiratory instability on neonatal discharge is more likely to be associated with immaturity than CLD.

Cardiorespiratory events detected by home memory monitoring and one-year neurodevelopmental outcome

OBJECTIVE

To determine if infants with cardiorespiratory events detected by home memory monitoring during early infancy have decreased neurodevelopmental performance.

STUDY DESIGN

Infants (n = 256) enrolled in the Collaborative Home Infant Monitoring Evaluation also completed the Bayley Scales of Infant Development II at 92 weeks' postconceptional age. Infants were classified as having 0, 1 to 4, or 5+ cardiorespiratory events. Events were defined as apnea >or=20 seconds or heart rate <60 to 80 bpm or <50 to 60 bpm, for >or=5 to 15 seconds, depending on age.

RESULTS

For term infants, having 0, 1 to 4, and 5+ cardiorespiratory events was associated with unadjusted mean Mental Developmental Index (MDI) values (+/-SD) of 103.6 (10.6), 104.2 (10.7), and 97.7 (10.9), respectively, and mean Psychomotor Developmental Index (PDI) values of 109.5 (16.6), 105.8 (16.5), and 100.2 (17.4). For preterm infants, having 0, 1 to 4, and 5+ cardiorespiratory events was associated with unadjusted mean MDI values of 100.4 (10.3), 96.8 (11.5), and 95.8 (10.6), respectively, and mean PDI values of 91.7 (19.2), 93.8 (15.5), and 94.4 (17.7). The adjusted difference in mean MDI scores with 5+ events compared with 0 events was 5.6 points lower in term infants ( P = .03) and 4.9 points lower in preterm infants ( P = .04).

CONCLUSIONS

Having 5+ conventional events is associated with lower adjusted mean differences in MDI in term and preterm infants.

Treatment of apnea of prematurity

In the last decade, knowledge regarding the neurodevelopment and functional aspects of the respiratory centers during postnatal maturation has increased substantially. However, an increase in such knowledge has not provided a basis for change in practice. The diagnosis of apnea of prematurity (AOP) is one of exclusion. All causes of secondary apnea must be ruled out before initiating treatment for AOP. Treatment will depend on the etiology as well as effectiveness and tolerability of the treatment by the patient. The primary goal of any treatment of AOP is to prevent the frequency of apnea lasting >20 seconds, and/or those that are shorter, but associated with cyanosis and bradycardia. The clinical management of AOP is not much different today than it was two decades ago, with pharmacologic and nonpharmacologic treatment options remaining the mainstay of therapy. Methylxanthines are still the most widely used pharmacologic agents. Due to the wider therapeutic index of caffeine and ease of once daily administration, it should be the preferred agent. Doxapram, or nonpharmacologic treatment measures such as nasal continuous positive airway pressure, may be considered in infants who are unresponsive to methylxanthine treatment alone. Treatment should be continued until there is complete resolution of apnea, and for some time thereafter. The choice of method for weaning treatment remains one of individual physician preference. Discharge from hospital after apnea requires close monitoring and some infants will require home apnea monitors. The decision to provide a home apnea monitor should be individualized for each patient, depending on the effectiveness of treatment and clinical response.

Cardiorespiratory events in preterm infants referred for apnea monitoring studies

BACKGROUND

Episodes of apnea, desaturation, and bradycardia are common in preterm infants. Such infants who have persistent cardiorespiratory events detected by clinical bedside monitoring often are referred for overnight apnea monitoring studies.

OBJECTIVE

To characterize apnea, bradycardia, and desaturation events in infants referred for an overnight apnea monitoring study and compare them with corresponding events in control infants of similar age and weight with no bedside monitor alarms.

METHODS

Twelve-hour bedside apnea monitoring studies were performed on 68 preterm infants before hospital discharge. This population included 35 infants who were referred by their attending physicians because of persistent bedside monitor alarms (referral group) and 33 infants who had no documented cardiorespiratory events for at least 2 days before the study (control group). Each study monitored respiration via respiratory inductance plethysmography, oxygen saturation (Sao2), and heart rate. Events were defined as meeting 1 of the following criteria: apnea > or =20 seconds, bradycardia < or =80 beats per minute, or Sao2 < or =80%.

RESULTS

The incidence of apnea > or =20 seconds was low, with no significant difference between infant groups. Referral infants exhibited a higher occurrence of desaturation episodes (20 +/- 6 vs 6 +/- 3 episodes/12-hour study) and a higher occurrence of bradycardia episodes (4.3 +/- 0.8 vs 1.1 +/- 0.3 episodes/12-hour study) than controls. These episodes of desaturation and bradycardia were always preceded by a respiratory pause, which was shorter in the referral infants (10.0 +/- 0.4 seconds vs 12.0 +/- 1.0 seconds). Baseline Sao2 was lower in referrals than controls (95 +/- 1% vs 98 +/- 1%), and the incidence of periodic breathing was significantly higher.

CONCLUSIONS

Infants referred for apnea monitoring studies because of persistent bedside monitor alarms have very infrequent prolonged apnea but a higher frequency of desaturation and bradycardia in response to short respiratory pauses than infants without persistent bedside monitor alarms. Referral infants also exhibit a lower baseline Sao2. These abnormalities in oxygenation and cardiorespiratory control may be markers for subtle residual lung disease or functional central nervous system abnormalities.

Acetazolamide treatment for infantile central sleep apnea

Central sleep apnea is a common respiratory pattern in healthy neonates. Nevertheless, frequent central sleep apnea associated with drops in oxygen saturation may contribute to infantile morbidity. Recently, low-dose acetazolamide was shown to reduce symptomatic central sleep apnea in adults. We treated 12 infants, median conceptional age 42 weeks (range, 40-44 weeks), with central sleep apnea. In all cases, the central apnea index was >40/h total sleeping time (apnea > or = 3 sec). The cumulative duration of drops in oxygen saturation below 90% was more than 3 min/h total sleeping time. All individuals received acetazolamide 7 mg/kg/day (orally, divided in three doses) for 11 weeks. Polysomnography was begun 10 hours before the first dose and continued for 10 hours after the third dose. Polysomnography was repeated after 6 weeks of treatment and 1 week after acetazolamide therapy was discontinued. Comparison of the respiratory patterns before and after treatment (10-hour recording after the third dose) showed a decrease in the median central apnea index from 74/h (range, 42-152/h) to 13/h (range, 6-49/h). The median of the cumulative duration of drops in oxygen saturation below 90% decreased from 3.6 min/h (range, 3.1-9.2 min/h) to 0.07 min/h (range, 0-0.5 min/h). Basal oxygen saturation increased from 95 (92-97%) to 98% (96-99%). This improvement was maintained in the final polysomnography (12 weeks after therapy was begun and 1 week after completion of the 11-week course). No adverse effects were noted. We conclude that low-dose acetazolamide treatment may be useful for the treatment of central infantile sleep apnea associated with hypoxemia.

Apnea of prematurity: diagnosis, implications for care, and pharmacologic management

Apnea is a disorder of respiratory control commonly seen in premature infants. Several mechanisms have been proposed to explain apnea, and many clinical conditions have been associated with its development. Apnea of prematurity is seen in infants less than 37 weeks gestation, with the incidence increasing as gestational age decreases. Expert and consistent nursing care is essential for management of premature infants with apnea. This article reviews the differential diagnosis, pathogenesis, and implications for care of apnea of prematurity.

Second-degree atrioventricular heart block after doxapram administration

Doxapram, a respiratory stimulant, is used to treat idiopathic apnea of prematurity. The side effects reported are minimal. We present three cases of second-degree atrioventricular block caused by QT interval prolongation associated with doxapram administration. All three infants returned to normal sinus rhythm after doxapram administration was stopped.

Cardiorespiratory adaptation during sleep in infants and children

The cardiorespiratory control system undergoes functional maturation after birth. Until this process is completed, the cardiorespiratory system is unstable, placing infants at risk for cardiorespiratory disturbances, especially during sleep. The profound influence of states of alertness on respiratory and cardiac control has been the focus of intense scrutiny during the last decade. The effects of rapid-eye movement (REM) sleep on various mechanisms involved in cardiorespiratory control are of particular significance during the postnatal period since newborns spend much of their time in this sleep state. In fullterm newborns, REM sleep occupies more than 50% of total sleep time, and this percentage is even greater in preterm newborns. From term to six months of age, the proportion of REM sleep decreases. Since respiratory and cardiac disturbances are known to occur selectively during REM sleep, the predominance of REM sleep may be a risk factor for abnormal sleep-related events during early infancy. Awareness of these developmental changes in sleep patterns is important for clinicians dealing with problems such as apparent life-threatening events (ALTE), sudden infant death syndrome (SIDS), and/or cardiorespiratory responses to respiratory disorders. Our current understanding of respiratory and cardiac control rests mainly on studies conducted during the first months of life. There is a paucity of data on late infancy and early childhood. The present paper will review available data on how sleep affects 1) ventilatory mechanics, in particular of the upper airways and the chest wall; ventilation and apnea; gas exchange; chemoreceptor function; and arousal responses; 2) changes in heart rate and heart rate variability, and the occurrence and mechanisms of bradycardia.