Autonomic nervous function and low-grade inflammation in children with sleep-disordered breathing

BACKGROUND

The objective of the study was to assess the relationship between autonomic nervous function and low-grade inflammation in children with sleep-disordered breathing.

METHODS

We enrolled habitually snoring children aged 3-14 years for overnight polysomnography (PSG) and high-sensitivity C-reactive protein (hsCRP) measurement. Low-grade inflammation was defined as hsCRP >1.0 mg/L to <10.0 mg/L. An electrocardiogram recording was extracted from PSG. Heart rate variability was analyzed using time and frequency domain methods.

RESULTS

In total, 190 children were included, with 61 having primary snoring (PS), 39 mild obstructive sleep apnea (OSA), and 90 moderate-to-severe OSA. The average RR interval displayed a significant decline, whereas the low frequency/high frequency (LF/HF) ratio showed an increasing tendency in children with PS, mild OSA, and moderate-to-severe OSA. Mean RR was mainly influenced by age and the apnea hypopnea index (AHI) (all P < 0.01). AHI was an independent risk factor for the altered LF/HF ratio at all sleep stages except N3 stage (all P < 0.05). In the wake stage, low-grade inflammation was an independent risk factor of altered LF/HF ratio (P = 0.014).

CONCLUSIONS

Autonomic nervous function was impaired in children with OSA. The sympathetic-vagal balance was influenced by low-grade inflammation in the wake stage, whereas it was only affected by AHI when falling asleep.

IMPACT

We found that autonomic nervous function was impaired in children with OSA. We found that there was a negative correlation between systemic inflammation and autonomic nervous function in children with SDB only at wake stage. A negative association between systemic inflammation and autonomic nervous function was demonstrated in children in this study. Furthermore, altered LF/HF ratio maybe a good indicator of autonomic nervous dysfunction in children as it only correlated with the SDB severity, not with age.

Utilisation of machine learning to predict surgical candidates for the treatment of childhood upper airway obstruction

OBJECTIVE

To investigate the effect of adenotonsillectomy on OSAS symptoms based on a data-driven approach and thereby identify criteria that may help avoid unnecessary surgery in children with OSAS.

METHODS

In 323 children enrolled in the Childhood Adenotonsillectomy Trial, randomised to undergo either early adenotonsillectomy (eAT; N = 165) or a strategy of watchful waiting with supportive care (WWSC; N = 158), the apnea-hypopnea index, heart period pattern dynamics, and thoraco-abdominal asynchrony measurements from overnight polysomnography (PSG) were measured. Using machine learning, all children were classified into one of two different clusters based on those features. The cluster transitions between follow-up and baseline PSG were investigated for each to predict those children who recovered spontaneously, following surgery and those who did not benefit from surgery.

RESULTS

The two clusters showed significant differences in OSAS symptoms, where children assigned in cluster A had fewer physiological and neurophysiological symptoms than cluster B. Whilst the majority of children were assigned to cluster A, those children who underwent surgery were more likely to stay in cluster A after seven months. Those children who were in cluster B at baseline PSG were more likely to have their symptoms reversed via surgery. Children who were assigned to cluster B at both baseline and 7 months after surgery had significantly higher end-tidal carbon dioxide at baseline. Children who spontaneously changed from cluster B to A presented highly problematic ratings in behaviour and emotional regulation at baseline.

CONCLUSIONS

Data-driven analysis demonstrated that AT helps to reverse and to prevent the worsening of the pathophysiological symptoms in children with OSAS. Multiple pathophysiological markers used with machine learning can capture more comprehensive information on childhood OSAS. Children with mild physiological and neurophysiological symptoms could avoid AT, and children who have UAO symptoms post AT may have sleep-related hypoventilation disease which requires further investigation. Furthermore, the findings may help surgeons more accurately predict children on whom they should perform AT.

Adenotonsillectomy for paediatric sleep disordered breathing in Australia and New Zealand

AIMS

To review the contributions of Australian and New Zealand research on adenotonsillectomy for the treatment of symptoms of obstructed breathing during sleep (sleep disordered breathing, SDB) in children.

METHODS

A search of the scientific literature was conducted using the MEDLINE (Ovid), PubMed and Scopus databases in August 2020. The following search string was used: (tonsillectomy OR adenoidectomy OR adenotonsillectomy) AND (paediatric OR child) AND (Australia OR New Zealand). A focused internet search was additionally conducted on Google to identify grey literature.

RESULTS

Researchers from Australia and New Zealand have made important contributions to the understanding and improvement of adenotonsillectomy (AT), including its epidemiology, cost, surgical techniques and peri-operative safety. Rates of AT have fluctuated over the years, becoming the most common paediatric surgery today, with SDB becoming the most common indication. Research in Australia and New Zealand has also focussed on the impact of AT on quality of life, and behaviour, neurocognition and cardiovascular sequelae.

CONCLUSIONS

Australian and New Zealand researchers have played a significant role in understanding the epidemiology and improving the safety of AT. There are promising directions in research still to come, including better understanding of the reasons for geographical variation in surgery rates, developing more efficient pre-operative risk assessment tools and alternative treatment options for mild OSA.

Consequences of paediatric sleep disordered breathing: contributions from Australian and New Zealand investigators

AIMS

To highlight the contributions of Australian and New Zealand researchers to the identification of the consequences of paediatric sleep disordered breathing (SDB).

METHODS

A search was conducted in PubMed using the terms "sleep disordered breathing" "child" and "Australia or New Zealand". All abstracts were reviewed and those which focused on the consequences of SDB have been included.

RESULTS

Australasian research into the consequences of SDB has grown exponentially over the last 35 years. SDB has significant adverse consequences for quality of life, behaviour, neurocognition and the cardiovascular system and the Australasian research studies investigating these are summarised.

CONCLUSIONS

Australian and New Zealand researchers have played a significant role in understanding the consequences of paediatric SDB and the mechanisms which underpin these. The research conducted "Downunder" has led the world in this field of research and will continue to provide evidence to improve the lives of children not only in Australasia but around the world.

Effect of adenotonsillectomy for childhood obstructive sleep apnea on nocturnal heart rate patterns

Study Objectives

To assess the effect of adenotonsillectomy for relieving obstructive sleep apnea syndrome (OSAS) symptoms in children on cardiac autonomic modulation.

Methods

In 354 children enrolled in the Childhood Adenotonsillectomy Trial, randomized to undergo either early adenotonsillectomy (eAT; N = 181) or a strategy of watchful waiting with supportive care (WWSC; N = 173), nocturnal heart rate control was analyzed during quiet, event-free sleep at baseline and at 7 months using overnight polysomnography (PSG). The relative frequency of patterns indicating monotonous changes in heart rate was quantified.

Results

Children who underwent eAT demonstrated a significantly greater reduction in heart rate patterns postsurgery than the WWSC group. On assessing those heart rate patterns regarding normalization of clinical PSG, heart patterns were reduced to a similar level in both groups. In children whose AHI normalized spontaneously, heart rate patterns were already significantly less frequent at baseline, suggesting that upper airway obstruction was milder in this group at the outset.

Conclusions

Adenotonsillectomy reduces monotonous heart rate patterns throughout quiet event-free sleep, reflecting a reduction in cardiac autonomic modulation. Heart rate pattern analysis may help quantifying the effect of OSAS on autonomic nervous system activity in children. Clinical Trial Registration: The study was registered at Clinicaltrials.gov (#NCT00560859).

A Method for Estimating Pulse Wave Amplitude Variability in children with Sleep Disordered Breathing

Sleep disordered breathing (SDB) is a common pediatric disorder, which results in increasing respiratory workload during sleep, restless night time sleep and excessive daytime sleepiness. It has significant negative effects on children with SDB on their physical growth and cognitive related developments. Chronic autonomic activation was suggested to be one of the possible key drivers causing cardiovascular structural changes in SDB children and increasing the risk of developing cardiovascular disease in their future. The aim of this study was to investigate the effect of SDB on autonomic activation changes in children, by analyzing the pulse wave amplitude (PWA) dynamics using a simple envelope estimation method extracting PWA from PPG signal.Children with SDB (n = 40) showed a significantly a wider dynamic distribution in PWA compare to matched controls (n = 40), which suggests a higher and stronger level of autonomic response in SDB children.In conclusion, the PWA dynamic is altered in children with SDB during sleep and indicate changes in autonomic activation.

Circadian Dysregulation: The Next Frontier in Obstructive Sleep Apnea Research

OBJECTIVE

To review the effects of the circadian clock on homeostasis, the functional interaction between the circadian clock and hypoxia-inducible factors, and the role of circadian dysregulation in the progression of cardiopulmonary disease in obstructive sleep apnea (OSA).

DATA SOURCES

The MEDLINE database was accessed through PubMed.

REVIEW METHODS

A general review is presented on molecular pathways disrupted in OSA, circadian rhythms and the role of the circadian clock, hypoxia signaling, crosstalk between the circadian and hypoxia systems, the role of the circadian clock in cardiovascular disease, and implications for practice. Studies included in this State of the Art Review demonstrate the potential contribution of the circadian clock and hypoxia in animal models or human disease.

CONCLUSIONS

Molecular crosstalk between the circadian clock and hypoxia-inducible factors has not been evaluated in disease models of OSA.

IMPLICATIONS FOR PRACTICE

Pediatric OSA is highly prevalent and, if left untreated, may lead to cardiopulmonary sequelae. Changes in inflammatory markers that normally demonstrate circadian rhythmicity are also seen among patients with OSA. Hypoxia-inducible transcription factors interact with core circadian clock transcription factors; however, the interplay between these pathways has not been elucidated in the cardiopulmonary system. This gap in knowledge hinders our ability to identify potential biomarkers of OSA and develop alternative therapeutic strategies. A deeper understanding of the mechanisms by which OSA impinges on clock function and the impact of clock dysregulation on the cardiopulmonary system may lead to future advancements for the care of patients with OSA. The aim of this review is to shed light on this important clinical topic.