Sleep‐disordered breathing in children with mucolipidosis

Mucolipidosis (ML) is a rare lysosomal storage disorder with a wide spectrum of disease severity according to the type. Sleep‐disordered breathing is recognized as a characteristic feature of ML but objective data are scarce. The aim of the study was to describe sleep data and medical management in children with ML α/β. All patients with ML α/β followed at a national reference center of ML were included. Five patients had ML II, one patient had ML III and one patient had ML II‐III. One patient was started on noninvasive ventilation (NIV) to allow extubation after prolonged invasive mechanical ventilation. The six other patients underwent sleep study at a median age of 1.8 years (range 4 months–17.4 years). Obstructive sleep apnea (OSA) was observed in all patients with a median apnea‐hypopnea index (AHI) of 36 events/hr (range 5–52) requiring continuous positive airway pressure (CPAP) or NIV. CPAP/NIV resulted in an improvement of nocturnal gas exchange and was continued in all patients with an excellent compliance. Two patients died. Systematic sleep studies are recommended at time of diagnosis in ML. CPAP or NIV are effective treatments of OSA, well tolerated, and may contribute to improve the quality of life of patients and caregivers.     

Sleep‐disordered breathing in children with pycnodysostosis

Upper airway obstruction is a common feature in pycnodysostosis and may cause obstructive sleep apnea (OSA). The aim of our study was to analyze sleep‐disordered breathing and respiratory management in children with pycnodysostosis. A retrospective review of the clinical charts and sleep studies of 10 consecutive children (three girls and seven boys) with pycnodysostosis seen over a time period of 10 years was performed. Six patients had severe OSA and/or nocturnal hypoventilation and were started on continuous positive airway pressure (CPAP) as a first treatment at a median age of 3.4 ± 2.6 years, because of the lack of indication of any surgical treatment. Three patients could be weaned after several years from CPAP after spontaneous improvement (two patients) or multiple upper airway surgeries (one patient). Three patients had upper airway surgery prior to their first sleep study with two patients still needing CPAP during their follow‐up. Only one patient never developed OSA. Patients with pycnodysostosis are at a high risk of severe OSA, underlying the importance of a systematic screening for sleep‐disordered breathing. Multidisciplinary care is mandatory because of the multilevel airway obstruction. CPAP is very effective and well accepted for treating OSA.     

Sleep‐disordered breathing in major depressive disorder

Individuals with major depressive disorder often experience obstructive sleep apnea. However, the relationship between depression and less severe sleep‐disordered breathing is unclear. This study examined the rate of sleep‐disordered breathing in depression after excluding those who had clinically significant sleep apnea (>5 apneas?h^?1). Archival data collected between 1991 and 2005 were used to assess the prevalence of sleep‐disordered breathing events in 60 (31 depressed; 29 healthy controls) unmedicated participants. Respiratory events were automatically detected using a program developed in‐house measuring thermal nasal air‐flow and chest pressure. Results show that even after excluding participants with clinically significant sleep‐disordered breathing, individuals with depression continue to exhibit higher rates of sleep‐disordered breathing compared with healthy controls (depressed group: apnea–hypopnea index mean = 0.524, SE = 0.105; healthy group: apnea–hypopnea index mean = 0.179, SE = 0.108). Exploratory analyses were also conducted to assess for rates of exclusion in depression studies due to sleep‐disordered breathing. Study exclusion of sleep‐disordered breathing was quantified based on self‐report during telephone screening, and via first night polysomnography. Results from phone screening data reveal that individuals reporting depression were 5.86 times more likely to report a diagnosis of obstructive sleep apnea than presumptive control participants. Furthermore, all of the participants excluded for severe sleep‐disordered breathing detected on the first night were participants with depression. These findings illustrate the importance of understanding the relationship between sleep‐disordered breathing and depression, and suggest that screening and quantification of sleep‐disordered breathing should be considered in depression research.     

Age-related changes in cardiac autonomic control during sleep

Aging is commonly associated with decreased sleep quality and increased periodic breathing (PB) that can influence heart rate variability (HRV). Cardiac autonomic control, as inferred from HRV analysis, was determined, taking into account the sleep quality and breathing patterns. Two groups of 12 young (21.1 +/- 0.8 years) and 12 older (64.9 +/- 1.9 years) volunteers underwent electroencephalographic, cardiac, and respiratory recordings during one experimental night. Time and frequency domain indices of HRV were calculated in 5-min segments, together with electroencephalographic and respiratory power spectra. In the elderly, large R-R oscillations in the very-low frequency (VLF) range emerged, that reflected the frequency of PB observed in 18% of the sleep time. PB occurred more frequently during rapid eye movement sleep (REM) sleep and caused a significant (P < 0.02) increase in the standard deviation of normal R-R intervals (SDNN) and absolute low-frequency (LF) power. With normal respiratory patterns, SDNN, absolute VLF, LF, and high frequency (HF) power fell during each sleep stage (P < 0.01) compared with young subjects, with no significant sleep-stage dependent variations. An overall decrease (P < 0.01) in normalized HF/(LF + HF) was observed in the elderly, suggesting a predominant loss of parasympathetic activity which may be related to decreased slow-wave sleep duration. These results indicate that two distinct breathing features, implying different levels of autonomic drive to the heart, influence HRV in the elderly during sleep. The breathing pattern must be considered to correctly interpret HRV in the elderly.     

Unbiased categorical classification of pediatric sleep disordered breathing

Study Objectives:

To classify pediatric sleep disordered breathing (SDB) using unbiased approaches. In children, decisions regarding severity and treatment of SDB are conducted solely based on empirical observations. Although recognizable entities clearly exist under the SDB spectrum, neither the number of SDB categories nor their specific criteria have been critically defined.

Design:

retrospective cohort analysis and random prospective cohort

Setting:

community and clinical sample

Patients or Participants:

Urban 5- to 9-year-old community children undergoing overnight sleep study (NPSG), and a comparable prospectively recruited clinical SDB sample.

Interventions:

n/a

Measurements and Results:

Principal component analysis was used to identify the uniqueness of the polysomnographically derived measures that are routinely used in clinical settings: apnea-hypopnea index, apnea index, obstructive apnea index, nadir SpO₂, spontaneous arousal index and respiratory arousal index. These measures were then incorporated using unbiased data mining approaches to further characterize and discriminate across categorical phenotypes. Of 1,133 subjects, 52.8% were habitual snorers. Six categorical phenotypes clustered without any a priori hypothesis. Secondly, a non-hierarchical model that incorporated 6 NPSG-derived measures enabled unbiased identification of algorithms that predicted these 6 severity-based clusters. Thirdly, a hierarchical model was developed and performed well on all severity-based clusters. Classification and predictive models were subsequently cross-validated statistically as well as clinically, using 2 additional datasets that included 259 subjects. Modeling reached ∼93% accuracy in cluster assignment.

Conclusions:

Data-driven analysis of conventional NPSG-derived indices identified 6 distinct clusters ranging from a cluster with normal indices toward clusters with more abnormal indices. Categorical assignment of individual cases to any of such clusters can be accurately predicted using a simple algorithm. These clusters may further enable prospective unbiased characterization of clinical outcomes and of genotype-phenotype interactions across multiple datasets.

Citation:

Spruyt K; Verleye G; Gozal D. Unbiased categorical classification of pediatric sleep disordered breathing. SLEEP 2010;33(10):1341-1347.     

Association of cardiac autonomic function measures with severity of sleep-disordered breathing in a community-based sample

The goal of this study was to test the hypothesis that spectral indices of heart rate variability, such as high-frequency power (HFP), low-to-high frequency power (LHR), and their respiration-adjusted counterparts (HFPra, LHRra) are correlated with severity of sleep-disordered breathing (SDB), as quantified by the respiratory disturbance index (RDI). A total of 436 subjects, non-smoking, normotensive, and free of cardiovascular disease and diabetes were selected from the Sleep Heart Health Study (SHHS). Of these, 288 records with sufficiently high quality electrocardiogram signals were selected for further analysis [males/females: 221/67; age: 46.1 to 74.9 years; body mass index (BMI): 21.5 to 46.4 kg m⁻²; 0.3 < RDI < 85.0⁻¹]. From each polysomnogram, the respiration channels (thoracic and abdominal) and R-R interval (RRI) derived from the electrocardiogram were subjected to spectral analysis and autoregressive moving average modeling in consecutive 5-min segments. After adjusting for age and BMI, mean RRI was found to be negatively correlated with RDI in men in all sleep-wake states (all P  < 0.001). HFP and HFPra were negatively correlated with RDI in men only during wakefulness (all P  < 0.01). In women, LHR and LHRra were not correlated with RDI during wakefulness, but were positively correlated during non-rapid eye movement Stage 1 and 2 sleep (all P  < 0.01). These findings suggest that the indices of cardiac autonomic control are correlated with SDB severity, but gender and state affect the nature of these correlations. In both genders, however, vagal modulation of heart rate increases while sympathetic modulation decreases from wakefulness to sleep.     

Respiratory polygraphy in children with sleep‐disordered breathing

At‐home respiratory polygraphy has been shown to be a reliable substitute for in‐laboratory polysomnography in adults for diagnosing obstructive sleep apnea, but this is less well studied in children. One aim of this study was to examine the quality of at‐home respiratory polygraphy in children with sleep‐disordered breathing and to evaluate the interrater reliability of the results. Another aim was to study whether calibrated respiratory inductance plethysmography (RIP) flow can be used for the scoring of respiratory events when the airflow measurements are unreliable. Children aged 4–10 years, with sleep‐disordered breathing, underwent at‐home respiratory polygraphy. Of 113 polygraphies, only 46% were of acceptable quality, with missing nasal airflow being the most common problem (40%). The median recorded time with artifact‐free signal present in three traces simultaneously was 228 min (0–610 min). Seventeen polygraphy studies were selected for further study. Each study was scored by two independent scorers, with and without the nasal airflow signal present, the latter relying on RIP flow for the scoring of respiratory events. The apnea–hypopnea index (AHI) from the four different measurements was compared using intraclass correlation coefficients (ICC). Comparison of the two scorers showed moderate agreement, with (ICC = 0.66) and without (ICC = 0.53) nasal airflow. One scorer had good agreement between AHI with and without nasal airflow (ICC = 0.81), whereas the other had poor agreement (ICC = 0.12). In conclusion, the scoring of respiratory events based on RIP flow is scorer dependent even for experienced scorers. The nasal airflow signal is frequently missing in paediatric respiratory polygraphies, which limits the usefulness of the method.     

Sleep‐disordered breathing and nocturnal hypoventilation in children with the MECP2 duplication syndrome: A case series and review of the literature

There is limited knowledge on the occurrence of respiratory manifestations and sleep‐disordered breathing in particular in children with the MECP2 duplication syndrome. Although sleep‐disordered breathing and nocturnal hypoventilation are currently not cited as an important symptom in these children, we present three cases who all had an abnormal breathing during sleep. In view of the consequences associated with sleep apnea and hypoventilation, we advise to perform a polysomnography in children with MECP2 duplication. Different treatment modalities (ENT surgery, CPAP, and non‐invasive ventilation) can be applied to successfully treat these conditions.     

Interaction effect of obstructive sleep apnea and periodic limb movements during sleep on heart rate variability

We aimed at assessing cardiac autonomic function by heart rate variability during sleep in patients with obstructive sleep apnea and periodic limb movements during sleep, and to compare it with that of patients with obstructive sleep apnea only, periodic limb movements during sleep only, and controls. We also aimed at investigating the interaction effect between apnea–hypopnea index and periodic limb movement index on heart rate variability. Four groups of patients (n = 42 each, total = 168) were identified based on the presence/absence of obstructive sleep apnea and periodic limb movements during sleep: + obstructive sleep apnea/? periodic limb movements during sleep (5 ≤ apnea–hypopnea index < 30 events per hr), ? obstructive sleep apnea/+ periodic limb movements during sleep (periodic limb movement index > 15 events per hr), + obstructive sleep apnea/+ periodic limb movements during sleep, ? obstructive sleep apnea/? periodic limb movements during sleep (controls). All groups were matched for age, sex and body mass index. Time‐ and frequency‐domain heart rate variability measures were calculated over 5‐min periods of stable stage 2 non‐rapid eye movement sleep. In patients with both obstructive sleep apnea and periodic limb movements during sleep, LFnu and LF/HF ratio were higher than in those with obstructive sleep apnea only, periodic limb movements during sleep only, and controls, while HFnu was the lowest among the four groups. LFnu, HFnu and LF/HF ratio were significantly and independently associated with minimal oxygen saturation in the + obstructive sleep apnea/+ periodic limb movements during sleep group. There was a significant interaction effect between apnea–hypopnea index and periodic limb movement index on LF/HF ratio (p = 0.038) in patients with obstructive sleep apnea. Patients with elevated apnea–hypopnea index and elevated periodic limb movement index exhibited higher sympathovagal balance compared with those with high apnea–hypopnea index and low periodic limb movement index, and compared with those with low apnea–hypopnea index (regardless of periodic limb movement index). Increased sympathetic activation and decreased parasympathetic control appear to be related to the severity of oxygen desaturation. Apnea–hypopnea index and periodic limb movement index had interactive effects on increased sympathovagal balance in patients with obstructive sleep apnea.     

Daytime sleepiness and neural cardiac modulation in sleep-related breathing disorders

Sleep-related breathing disorders are common causes of excessive daytime sleepiness, a socially and clinically relevant problem. Mechanisms responsible for daytime sleepiness are still largely unknown. We investigated whether specific alterations in autonomic cardiac modulation during sleep, commonly associated with sleep-related breathing disorders, are related to excessive daytime sleepiness. Fifty-three patients with sleep-related breathing disorders underwent nocturnal polysomnography. Excessive daytime sleepiness was diagnosed as a Multiple Sleep Latency Test response less than or equal to 600 s. We explored the relation of excessive daytime sleepiness, objectively determined, with indices of autonomic cardiac regulation, such as baroreflex sensitivity and heart rate variability, with polysomnographic indices of the severity of sleep-related breathing disorders and with quality of sleep. Patients with excessive daytime sleepiness, when compared with patients without, had significantly lower baroreflex sensitivity and significantly higher low-to-high frequency power ratio of heart rate variability during the different stages of nocturnal sleep. By contrast, no differences were found in indices quantifying the severity of sleep-related breathing disorders or sleep quality. We demonstrated that excessive daytime sleepiness is accompanied by a deranged cardiac autonomic control at night, the latter probably reflecting autonomic arousals not detectable in the EEG. As abnormal autonomic regulation is also known to be associated with increased cardiovascular risk, a possible relation between excessive daytime sleepiness and cardiovascular events in patients with sleep-related breathing disorders deserves to be investigated in future studies.     

Sleep‐disordered breathing in hypertensive disorders of pregnancy: a BMI‐matched study

Sleep‐disordered breathing is more common in hypertensive disorders during pregnancy; however, most studies have not adequately accounted for the potential confounding impact of obesity. This study evaluated the frequency of sleep‐disordered breathing in women with gestational hypertension and pre‐eclampsia compared with body mass index‐ and gestation‐matched normotensive pregnant women. Women diagnosed with gestational hypertension or pre‐eclampsia underwent polysomnography shortly after diagnosis. Normotensive controls body mass index‐matched within ±4 kg m^?2 underwent polysomnography within ±4 weeks of gestational age of their matched case. The mean body mass index and gestational age at polysomnography were successfully matched for 40 women with gestational hypertension/pre‐eclampsia and 40 controls. The frequency of sleep‐disordered breathing in the cases was 52.5% compared with 37.5% in the control group (P = 0.18), and the respiratory disturbance index overall did not differ (P = 0.20). However, more severe sleep‐disordered breathing was more than twice as common in women with gestational hypertension or pre‐eclampsia (35% versus 15%, P = 0.039). While more than half of women with a hypertensive disorder of pregnancy meet the clinical criteria for sleep‐disordered breathing, it is also very common in normotensive women of similar body mass index. This underscores the importance of adjusting for obesity when exploring the relationship between sleep‐disordered breathing and hypertension in pregnancy. More severe degrees of sleep‐disordered breathing are significantly associated with gestational hypertension and pre‐eclampsia, and sleep‐disordered breathing may plausibly play a role in the pathophysiology of pregnancy hypertension in these women. This suggests that more severe sleep‐disordered breathing is a potential therapeutic target for reducing the prevalence or severity of hypertensive disorders in pregnancy.     

Usefulness of cardiac parasympathetic index in CPAP‐treated patients with obstructive sleep apnea: A preliminary study

Cardiac autonomic indexes, including cardiac parasympathetic index and cardiac sympathetic index, have been reported to accurately identify patients with sleep disorders such as obstructive sleep apnea. Our study aimed to assess cardiac autonomic indexes in patients with obstructive sleep apnea before and during a single full‐night continuous positive airway pressure therapy using a combined approach. Our simultaneous heart rate variability‐polysomnographic study included 16 never‐treated obstructive sleep apnea patients. Two patients dropped out. Patients underwent combined recordings in two consecutive days, at baseline and during a single full‐night of acute continuous positive airway pressure treatment. We calculated cardiac parasympathetic index and cardiac sympathetic index as night/day ratio for high‐frequency and low‐frequency heart rate variability spectral components, respectively. Continuous positive airway pressure treatment significantly reduced cardiac autonomic indexes values in comparison with baseline values (cardiac parasympathetic index: p < .0001; cardiac sympathetic index: p = .001). After acute continuous positive airway pressure treatment, the percentage of decrease of cardiac parasympathetic index was greater than that of cardiac sympathetic index (51.02 ± 15.72 versus 34.64 ± 26.93). A positive statistical correlation was also found between decrease of cardiac parasympathetic index and decrease of apnea–hypopnea index after continuous positive airway pressure (p < .001). This study improves the knowledge on cardiac autonomic modulation during acute continuous positive airway pressure therapy in obstructive sleep apnea. Our results demonstrate that both autonomic indexes decreased significantly after a single‐night of acute continuous positive airway pressure therapy. Cardiac parasympathetic index more than cardiac sympathetic index was related to decrease of apnea–hypopnea index after continuous positive airway pressure therapy, thus representing a potential help in everyday clinical practice.     

Sleep disordered breathing (SDB) experiences associated with snoring in adult Nigerians

Background

Snorers often experience symptoms of sleep disordered breathing (SDB) which is largely undiagnosed in the population. Information on SDB experiences is needed to target high-risk individuals that may benefit from treatment of snoring.

Objective

This study compares the experience of the nighttime and daytime symptoms of SDB of habitual snorers with that of non-habitually snoring adult subjects in a tertiary health facility in Nigeria.

Methods

A cross-sectional, comparative, hospital based study was conducted. Berlin questionnaire was administered to consecutive adult patients (subjects) attending ENT Clinic of OOUTH, Sagamu, Nigeria. Based on the responses to their experience of snoring, the subjects were categorized as habitual snorers or non-habitual snorers. General physical examinations with emphases on the nose, throat and neck were performed on the subjects. The experiences of nighttime and daytime symptoms of SDB were recorded and those of habitual snorers compared to non-habitual snorers.

Results

One hundred and ninety- five subjects participated in the study. M:F =1.3:1. Overall prevalence of snoring was 37.9% and habitual snoring was 18.5%. Habitual snoring was significantly associated with age, marital status and obesity (BMI>=30.0). There were statistically significant increased odds of experiencing the nighttime and daytime symptoms of SDB in habitual snorers compared to non-habitual snorers.

Conclusion

Adults that snore habitually had significantly more nighttime and daytime symptoms of SDB compared to those who do not snore habitually. Habitual snoring predisposes adult subjects to experiencing symptoms of SDB.     

Impact of sleep‐disordered breathing in patients with acute myocardial infarction: a retrospective analysis

Sleep‐disordered breathing (SDB) is associated with an increased risk of cardiovascular events. Previous studies showed that severe SDB has a negative impact on myocardial salvage and progression of left ventricular dysfunction after acute myocardial infarction (AMI). This study investigated the frequency of SDB and the effects of SDB on left ventricular function after AMI. This retrospective study enrolled all patients with AMI who had undergone cardiorespiratory polygraphy for SDB diagnosis. The apnea–hypopnea index was used as a standard metric of SDB severity. SDB was classified as mild (apnea–hypopnea index >5 to <15 per h), moderate (≥15 to <30 per h) or severe (apnea–hypopnea index ≥30 per h). According to the majority of events, SDB was classified as predominant obstructive sleep apnea, central sleep apnea or mixed sleep apnea (mixed SDB). A total of 223 patients with AMI (112 with ST elevation and 111 without ST elevation; 63.2 ± 11.2 years, 82% male, left ventricular ejection fraction 49 ± 12%) were enrolled. SDB was present in 85.6%, and was moderate‐to‐severe in 63.2%; 40.8% had obstructive sleep apnea, 41.7% had central sleep apnea and 3.1% had mixed SDB. Left ventricular ejection fraction was lower in patients with AMI with severe SDB (45 ± 14%) versus those without SDB (57 ± 7%; P < 0.005). In addition, lower left ventricular ejection fraction (≤45%) was associated with increased frequency (apnea–hypopnea index ≥5 per h in 96%) and severity (apnea–hypopnea index ≥30 per h in 48%) of SDB in general and a higher percentage of central sleep apnea (57%) in particular. SDB is highly frequent in patients with AMI. SDB severity appeared to be linked to impaired left ventricular function, especially in patients with central sleep apnea.     

Association of sleep‐disordered breathing with decreased cognitive function among patients with dementia

Sleep is known to be essential for proper cognitive functioning. Sleep disturbance, especially respiratory disturbance during sleep, is a risk factor for the development of dementia. However, it is not known whether hypopnoea during sleep is related to severity of cognitive function in patients already diagnosed with dementia. Considering the high prevalence of sleep problems in aged people, it is important to determine if hypopnoea during sleep contributes to dementia. In addition, it would be desirable to develop a feasible method for objectively evaluating sleep in patients with dementia. For this purpose, a simple sleep recorder that employs single or dual bioparameter recording, which is defined as a type‐4 portable monitor, is suitable. In this study, a type‐4 sleep recorder was used to evaluate respiratory function during sleep in 111 patients with dementia, and data suggesting a possible relationship with cognitive function levels were examined. Multivariate logistic regression was used to investigate the association of severity of dementia with sleep‐disordered breathing, age, diabetes, dyslipidaemia and hypertension. It was found that the respiratory disturbance index was associated with severity of cognitive dysfunction in our subjects. Furthermore, patients younger than 80 years were more susceptible to lower cognitive function associated with sleep‐disordered breathing than patients 80 years old or over, because an increase in the respiratory disturbance index was associated with deteriorated cognitive function only in the former age group. These results suggest that proper treatment of sleep apnea is important for the preservation of cognitive function, especially in patients with early‐stage dementia.     

Cardiac autonomic dynamics during sleep are lost in patients with TIA and stroke

Ischaemic stroke is accompanied by important alterations of cardiac autonomic control, which have an impact on stroke outcome. In sleep, cardiac autonomic control oscillates with a predominant sympathetic modulation during REM sleep. We aimed to assess cardiac autonomic control in different sleep stages in patients with ischaemic stroke. Forty‐five patients enrolled in the prospective, multicentre SAS‐CARE study but without significant sleep‐disordered breathing (apnea–hypopnea index < 15/hr) and without atrial fibrillation were included in this analysis. The mean age was 56 years, 68% were male, 76% had a stroke (n = 34, mean National Institutes of Health Stroke Scale [NIHSS] score of 5, 11 involving the insula) and 24% (n = 11) had a transitory ischaemic attack. Cardiac autonomic control was evaluated using three different tools (spectral, symbolic and entropy analysis) according to sleep stages on short segments of 250 beats in all patients. Polysomnographic studies were performed within 7 days and 3 months after the ischaemic event. No significant differences in cardiac autonomic control between sleep stages were observed in the acute phase and after 3 months. Predominant vagal modulation and decreased sympathetic modulation were observed across all sleep stages in ischaemic stroke involving the insula. Patients with ischaemic stroke and transitory ischaemic attack present a loss of cardiac autonomic dynamics during sleep in the first 3 months after the ischaemic event. This change could represent an adaptive phenomenon, protecting the cardiovascular system from the instabilities of autonomic control, or a risk factor for stroke, which precedes the ischaemic event.     

Respiratory sinus arrhythmia during sleep in children with upper airway obstruction

Upper airway obstruction during adulthood is associated with cardiovascular morbidity; cardiovascular consequences of childhood upper airway obstruction are less well established. This study aimed at investigating the effect of childhood upper airway obstruction on respiratory sinus arrhythmia as a measure of cardiac vagal modulation during night‐time sleep. Overnight polysomnography was conducted in 40 healthy children (20 M; age: 7.5 ± 2.6 years; body mass index percentile: 60.7 ± 26.4%) and 40 children with upper airway obstruction (24 M; age: 7.5 ± 2.7 years; body mass index percentile: 65.8 ± 31.9%). We used the phase‐averaging technique to compute respiratory sinus arrhythmia amplitude and phase delay. To study sleep stage effects and the effect of upper airway obstruction, respiratory sinus arrhythmia was measured during all artefact‐free sleep episodes, and after exclusion of respiratory events. A significant increase in respiratory sinus arrhythmia amplitude and phase delay was observed during stage 4 sleep as compared with rapid eye movement sleep in both groups (amplitude: controls = 0.10 ± 0.03 versus 0.07 ± 0.02 s, P < 0.01, respectively, and upper airway obstruction = 0.07 ± 0.03 versus 0.05 ± 0.03 s, P < 0.05, respectively; phase delay: controls = 3.1 ± 0.1 versus 3.0 ± 0.1 rad, P < 0.05, respectively, and upper airway obstruction = 3.13 ± 0.04 versus 3.04 ± 0.08 rad, P < 0.01, respectively). A significant association between respiratory sinus arrhythmia and apnea/hypopnea index was observed during stage 2 sleep in children with upper airway obstruction. Compared with healthy controls, a significant decrease in respiratory sinus arrhythmia amplitude during stage 2 sleep was observed in children with upper airway obstruction (0.09 ± 0.03 versus 0.06 ± 0.03 s, P < 0.05). However, this difference was not apparent when respiratory events were excluded from analysis. Importantly, respiratory sinus arrhythmia showed a strong negative correlation with body mass index. In conclusion, night‐time respiratory sinus arrhythmia in children is sleep stage dependent and normal during quiet sleep in children with relatively mild upper airway obstruction.     

Effects of exercise training on autonomic modulation and mood symptoms in patients with obstructive sleep apnea

We evaluated the effects of exercise training (ET) on the profile of mood states (POMS), heart rate variability, spontaneous baroreflex sensitivity (BRS), and sleep disturbance severity in patients with obstructive sleep apnea (OSA). Forty-four patients were randomized into 2 groups, 18 patients completed the untrained period and 16 patients completed the exercise training (ET). Beat-to-beat heart rate and blood pressure were simultaneously collected for 5 min at rest. Heart rate variability (RR interval) was assessed in time domain and frequency domain (FFT spectral analysis). BRS was analyzed with the sequence method, and POMS was analyzed across the 6 categories (tension, depression, hostility, vigor, fatigue, and confusion). ET consisted of 3 weekly sessions of aerobic exercise, local strengthening, and stretching exercises (72 sessions, achieved in 40±3.9 weeks). Baseline parameters were similar between groups. The comparisons between groups showed that the changes in apnea-hypopnea index, arousal index, and O₂ desaturation in the exercise group were significantly greater than in the untrained group (P<0.05). The heart rate variability and BRS were significantly higher in the exercise group compared with the untrained group (P<0.05). ET increased peak oxygen uptake (P<0.05) and reduced POMS fatigue (P<0.05). A positive correlation (r=0.60, P<0.02) occurred between changes in the fatigue item and OSA severity. ET improved heart rate variability, BRS, fatigue, and sleep parameters in patients with OSA. These effects were associated with improved sleep parameters, fatigue, and cardiac autonomic modulation, with ET being a possible protective factor against the deleterious effects of hypoxia on these components in patients with OSA.     

Pulse transit time as a surrogate measure of changes in systolic arterial pressure in children during sleep

Pulse transit time has been proposed as a surrogate measure of systolic arterial pressure, as it is dependent upon arterial stiffness. Past research has shown that pulse transit time has a significant inverse relationship to systolic arterial pressure in adults; however, studies in children are limited. This study aimed to explore the relationship between systolic arterial pressure and pulse transit time in children during sleep. Twenty‐five children (13.1 ± 1.6 years, 48% male) underwent overnight polysomnography (PSG) with a simultaneous recording of continuous systolic arterial pressure and photoplethysmography. Pulse transit time was calculated as the time delay between the R‐wave peak of the electrocardiogram (ECG) to the 50% point of the upstroke of the corresponding photoplethysmography waveform; 500 beats of simultaneous systolic arterial pressure and pulse transit time were analysed in each sleep stage for each child. Pulse transit time was normalized to each subject's mean wake pulse transit time. The ability of pulse transit time to predict systolic arterial pressure change was determined by linear mixed‐effects modelling. Significant negative correlations between pulse transit time and systolic arterial pressure were found for individual children for each sleep stage [mean correlations for cohort: non‐rapid eye movement (NREM) sleep 1 and 2 r = ?0.57, slow wave sleep (SWS) r = ?0.76, REM r = ?0.65, P < 0.01 for all]. Linear mixed‐model analysis demonstrated that changes in pulse transit time were a significant predictor of changes in systolic arterial pressure for each sleep stage (P < 0.001). The model of pulse transit time‐predicted systolic arterial pressure closely tracked actual systolic arterial pressure changes over time. This study demonstrated that pulse transit time was accurate in tracking systolic arterial pressure changes over time. Thus, the use of pulse transit time as a surrogate measure of changes in systolic arterial pressure in children is a valid, non‐invasive and inexpensive method with many potential applications.