Heart rate variability, sympathetic and vagal balance and EEG arousals in upper airway resistance and mild obstructive sleep apnea syndromes

Impaired post-sleep apnea autonomic arousals in patients with drug-resistant epilepsy

OBJECTIVE

Sudden and unexpected deaths in epilepsy (SUDEP) pathophysiology may involve an interaction between respiratory dysfunction and sleep/wake state regulation. We investigated whether patients with epilepsy exhibit impaired sleep apnea-related arousals.

METHODS

Patients with drug-resistant (N = 20) or drug-sensitive (N = 20) epilepsy and obstructive sleep apnea, as well as patients with sleep apnea but without epilepsy (controls, N = 20) were included. We explored (1) the respiratory arousal threshold based on nadir oxygen saturation, apnea-hypopnea index, and fraction of hypopnea among respiratory events; (2) the cardiac autonomic response to apnea/hypopnea quantified as percentages of changes from the baseline in RR intervals (RRI), high (HF) and low (LF) frequency powers, and LF/HF.

RESULTS

The respiratory arousal threshold did not differ between groups. At arousal onset, RRI decreased (-9.42%) and LF power (179%) and LF/HF ratio (190%) increased. This was followed by an increase in HF power (118%), p < 0.05. The RRI decrease was lower in drug-resistant (-7.40%) than in drug-sensitive patients (-9.94%) and controls (-10.91%), p < 0.05. LF and HF power increases were higher in drug-resistant (188%/126%) than in drug-sensitive patients (172%/126%) and controls (177%/115%), p < 0.05.

CONCLUSIONS

Cardiac reactivity following sleep apnea is impaired in drug-resistant epilepsy.

SIGNIFICANCE

This autonomic dysfunction might contribute to SUDEP pathophysiology.

Acute Effect of Positive Airway Pressure on Heart Rate Variability in Obstructive Sleep Apnea

Autonomic dysregulation is associated with cardiovascular consequences in obstructive sleep apnea (OSA). This study aimed to investigate the effect of acute continuous positive airway pressure (CPAP) treatment on autonomic activity and to identify factors contributing to heart rate variability (HRV) changes in OSA. Frequency domain HRV parameters were calculated and compared between the baseline polysomnography and during the CPAP titration in 402 patients with moderate to severe OSA. There were significant reductions in total power, very low-frequency band power, low-frequency band power, and high-frequency band power during the CPAP titration as compared to the baseline polysomnography. This tendency was pronounced in male patients with severe OSA. Multivariate analysis found that changes in the apnea-hypopnea index and oxygen saturation were significantly associated with changes in sympathetic and parasympathetic activity, respectively. This study demonstrated that HRV parameters significantly changed during the CPAP titration, indicating a beneficial effect of CPAP in the restoration of sympathetic and parasympathetic hyperactivity in OSA. Prospective longitudinal studies should determine whether long-term CPAP treatment aids in maintaining the long-lasting improvement of the autonomic functions, thereby contributing to the prevention of cardiovascular and cerebrovascular diseases in patients with OSA.

Information-Based Similarity of Ordinal Pattern Sequences as a Novel Descriptor in Obstructive Sleep Apnea Screening Based on Wearable Photoplethysmography Bracelets

Obstructive sleep apnea (OSA) is a common respiratory disorder associated with autonomic nervous system (ANS) dysfunction, resulting in abnormal heart rate variability (HRV). Capable of acquiring heart rate (HR) information with more convenience, wearable photoplethysmography (PPG) bracelets are proven to be a potential surrogate for electrocardiogram (ECG)-based devices. Meanwhile, bracelet-type PPG has been heavily marketed and widely accepted. This study aims to investigate the algorithm that can identify OSA with wearable devices. The information-based similarity of ordinal pattern sequences (OP_IBS), which is a modified version of the information-based similarity (IBS), has been proposed as a novel index to detect OSA based on wearable PPG signals. A total of 92 PPG recordings (29 normal subjects, 39 mild-moderate OSA subjects and 24 severe OSA subjects) were included in this study. OP_IBS along with classical indices were calculated. For severe OSA detection, the accuracy of OP_IBS was 85.9%, much higher than that of the low-frequency power to high-frequency power ratio (70.7%). The combination of OP_IBS, IBS, CV and LF/HF can achieve 91.3% accuracy, 91.0% sensitivity and 91.5% specificity. The performance of OP_IBS is significantly improved compared with our previous study based on the same database with the IBS method. In the Physionet database, OP_IBS also performed exceptionally well with an accuracy of 91.7%. This research shows that the OP_IBS method can access the HR dynamics of OSA subjects and help diagnose OSA in clinical environments.

The multisystemic effects of oral appliance therapy for obstructive sleep apnea: A narrative review

Obstructive sleep apnea (OSA) is a chronic condition accompanied by repeated obstruction of the upper airway during sleep despite respiratory efforts, resulting in intermittent hypoxemia, altered sleep structure, and sympathetic activation. Previous studies have shown a significant association between OSA and general health issues such as cardiovascular diseases, endocrine disorders, neurocognitive function decline, and poor quality of life. Continuous positive airway pressure (CPAP) has been considered as the first line treatment for OSA. However, accumulating evidence supports the role of oral appliance (OA) therapy, including mandibular advancement devices, as an alternative option for snoring and OSA patients who do not comply with or refuse CPAP usage. Despite a generally favorable outcome of OA therapy for OSA related respiratory indices, studies focusing on the impact of systemic effects of OA therapy in OSA patients are relatively scarce compared with the extensive literature focusing on the systemic effects of CPAP. Therefore, this article aimed to provide an overview of the current evidence regarding the multisystemic effects of OA therapy for OSA.

Obstructive Sleep Apnoea Syndrome Screening Through Wrist-Worn Smartbands: A Machine-Learning Approach

Purpose

A large portion of the adult population is thought to suffer from obstructive sleep apnoea syndrome (OSAS), a sleep-related breathing disorder associated with increased morbidity and mortality. International guidelines include the polysomnography and the cardiorespiratory monitoring (CRM) as diagnostic tools for OSAS, but they are unfit for a large-scale screening, given their invasiveness, high cost and lengthy process of scoring. Current screening methods are based on self-reported questionnaires that suffer from lack of objectivity. On the contrary, commercial smartbands are wearable devices capable of collecting accelerometric and photoplethysmographic data in a user-friendly and objective way. We questioned whether machine-learning (ML) classifiers trained on data collected through these wearable devices would help predict OSAS severity.

Patients and Methods

Each of the patients (n = 78, mean age ± SD: 57.2 ± 12.9 years; 30 females) underwent CRM and concurrently wore a commercial wrist smartband. CRM's traces were scored, and OSAS severity was reported as apnoea hypopnoea index (AHI). We trained three pairs of classifiers to make the following prediction: AHI <5 vs AHI ≥5, AHI <15 vs AHI ≥15, and AHI <30 vs AHI ≥30.

Results

According to the Matthews correlation coefficient (MCC), the proposed algorithms reached an overall good correlation with the ground truth (CRM) for AHI <5 vs AHI ≥5 (MCC: 0.4) and AHI <30 vs AHI ≥30 (MCC: 0.3) classifications. AHI <5 vs AHI ≥5 and AHI <30 vs AHI ≥30 classifiers' sensitivity, specificity, positive predictive values (PPV), negative predictive values (NPV) and diagnostic odds ratio (DOR) are comparable with the STOP-Bang questionnaire, an established OSAS screening tool.

Conclusion

Machine learning algorithms showed an overall good performance. Unlike questionnaires, these are based on objectively collected data. Furthermore, these commercial devices are widely distributed in the general population. The aforementioned advantages of machine-learning algorithms applied to smartbands' data over questionnaires lead to the conclusion that they could serve a population-scale screening for OSAS.

Synchronization of the Processes of Autonomic Control of Blood Circulation in Humans Is Different in the Awake State and in Sleep Stages

The influence of higher nervous activity on the processes of autonomic control of the cardiovascular system and baroreflex regulation is of considerable interest, both for understanding the fundamental laws of the functioning of the human body and for developing methods for diagnostics and treatment of pathologies. The complexity of the analyzed systems limits the possibilities of research in this area and requires the development of new tools. Earlier we propose a method for studying the collective dynamics of the processes of autonomic control of blood circulation in the awake state and in different stages of sleep. The method is based on estimating a quantitative measure representing the total percentage of phase synchronization between the low-frequency oscillations in heart rate and blood pressure. Analysis of electrocardiogram and invasive blood pressure signals in apnea patients in the awake state and in different sleep stages showed a high sensitivity of the proposed measure. It is shown that in slow-wave sleep the degree of synchronization of the studied rhythms is higher than in the awake state and lower than in sleep with rapid eye movement. The results reflect the modulation of the processes of autonomic control of blood circulation by higher nervous activity and can be used for the quantitative assessment of this modulation.

Sleep Apnea Classification Algorithm Development Using a Machine-Learning Framework and Bag-of-Features Derived from Electrocardiogram Spectrograms

BACKGROUND

Heart rate variability (HRV) and electrocardiogram (ECG)-derived respiration (EDR) have been used to detect sleep apnea (SA) for decades. The present study proposes an SA-detection algorithm using a machine-learning framework and bag-of-features (BoF) derived from an ECG spectrogram.

METHODS

This study was verified using overnight ECG recordings from 83 subjects with an average apnea-hypopnea index (AHI) 29.63 (/h) derived from the Physionet Apnea-ECG and National Cheng Kung University Hospital Sleep Center database. The study used signal preprocessing to filter noise and artifacts, ECG time-frequency transformation using continuous wavelet transform (CWT), BoF feature generation, machine-learning classification using support vector machine (SVM), ensemble learning (EL), k-nearest neighbor (KNN) classification, and cross-validation. The time length of the spectrogram was set as 10 and 60 s to examine the required minimum spectrogram window time length to achieve satisfactory accuracy. Specific frequency bands of 0.1-50, 8-50, 0.8-10, and 0-0.8 Hz were also extracted to generate the BoF to determine the band frequency best suited for SA detection.

RESULTS

The five-fold cross-validation accuracy using the BoF derived from the ECG spectrogram with 10 and 60 s time windows were 90.5% and 91.4% for the 0.1-50 Hz and 8-50 Hz frequency bands, respectively.

CONCLUSION

An SA-detection algorithm utilizing BoF and a machine-learning framework was successfully developed in this study with satisfactory classification accuracy and high temporal resolution.

Does continuous positive airway pressure therapy benefit patients with coronary artery disease and obstructive sleep apnea? A systematic review and meta-analysis

The prevalent co‐morbidity of coronary artery disease (CAD) and obstructive sleep apnea (OSA) has attracted great interest. However, effects of continuous positive airway pressure (CPAP) in patients with OSA and CAD for cardiovascular outcomes and deaths are still controversial. Usage of CPAP among patients with CAD and OSA could decrease the risk of cardiovascular events and death in adults. PubMed, EMBASE, Web of science, and Cochrane Library were systematically searched. Studies that described association of CPAP treatment with cardiovascular events in CAD and OSA patients were included. The main outcome was the major adverse cardiovascular events (MACE), including all‐cause death, cardiovascular death, myocardial infarction (MI), stroke, and repeat revascularization. Summary relative risks (risk ratios [RRs]) and 95% confidence intervals (CIs) of outcomes were pooled and heterogeneity was assessed with the I² statistic. Nine studies enrolling 2590 participants with OSA and CAD were included and extracted data. There was significant association of CPAP with reduced risk of MACE (RR, 0.73, 95% CI [0.55, 0.96]), particularly among those with AHI less than 30 events/h (RR, 0.43, 95% CI [0.22, 0.84]). Similarly, the same result was found in all‐cause death (RR, 0.66, 95% CI, [0.46, 0.94]) and cardiovascular death (RR, 0.495, 95% CI [0.292, 0.838]). Our data suggested that CPAP usage, compared to usual care, was associated with reduced risks of cardiovascular outcomes or death in patients with OSA and CAD, particularly in the subgroup with AHI less than 30 events/h, which still needs further studies to confirm.

Can dynamic and static pupillary responses be used as an indicator of autonomic dysfunction in patients with obstructive sleep apnea syndrome?

PURPOSE

We aimed to reveal whether static and dynamic pupillary responses can be used for the detection of autonomic nervous system (ANS) dysfunction in patients with obstructive sleep apnea syndrome (OSAS).

METHODS

We included in this study patients with OSAS, who were divided into three groups according to the apnea-hypopnea index (AHI) (group 1, mild [n = 20]; group 2, moderate [n = 20]; and group 3, severe [n = 20]), and healthy controls (group 4, n = 20). Pupillary responses were measured using a pupillometry system.

RESULTS

Static (mesopic PD, P = 0.0019; low photopic PD, P = 0.001) and dynamic pupil responses (resting diameter, P = 0.004; amplitude of pupil contraction, P < 0.001; duration of pupil contraction, P = 0.022; velocity of pupil contraction, P = 0.001; and velocity of pupil dilation, P = 0.012) were affected in patients with different OSAS severities. Also, AHI was negatively correlated with mesopic PD (P = 0.008), low photopic PD (P = 0.003), resting diameter (P = 0.001), amplitude of pupil contraction (P < 0.001), duration of pupil contraction (P = 0.011), velocity of pupil contraction (P < 0.001), and velocity of pupil dilation (P = 0.001).

CONCLUSION

We detected pupil responses innervated by the ANS were affected in the OSAS patients. This effect was more significant in the severe OSAS patients. Therefore, the pupillometry system can be an easily applicable, noninvasive method to detect ANS dysfunction in the OSA patients.

Atrial Fibrillation (Part 1): Pathophysiology, Risk Factors, and Therapeutic Basis

A fibrilação atrial é a arritmia sustentada mais comum na prática clínica com predileção pelas faixas etárias mais avançadas. Com o envelhecimento populacional, as projeções para as próximas décadas são alarmantes. Além de sua importância epidemiológica, a fibrilação atrial é destacada por suas repercussões clínicas, incluindo fenômenos tromboembólicos, hospitalizações e maior taxa de mortalidade. Seu mecanismo fisiopatológico é complexo, envolvendo uma associação de fatores hemodinâmicos, estruturais, eletrofisiológicos e autonômicos. Desde os anos 1990, o estudo Framingham em análises multivariadas já demonstrou que, além da idade, a presença de hipertensão, diabetes, insuficiência cardíaca e doença valvar é preditor independente dessa normalidade do ritmo. Entretanto, recentemente, vários outros fatores de risco estão sendo implicados no aumento do número de casos de fibrilação atrial, tais como sedentarismo, obesidade, anormalidades do sono, tabagismo e uso excessivo de álcool. Além disso, as mudanças na qualidade de vida apontam para uma redução na recorrência de fibrilação atrial, tornando-se uma nova estratégia para o tratamento de excelência dessa arritmia cardíaca. A abordagem terapêutica envolve um amplo conhecimento do estado de saúde e hábitos do paciente, e compreende quatro pilares principais: mudança de hábitos de vida e tratamento rigoroso de fatores de risco; prevenção de eventos tromboembólicos; controle da frequência; e controle do ritmo. Pela dimensão de fatores envolvidos no cuidado ao paciente portador de fibrilação atrial, ações integradas com equipes multiprofissionais estão associadas aos melhores resultados clínicos.

Electrophysiological features in acromegaly: re-thinking the arrhythmic risk?

BACKGROUND

Acromegaly is disease associated with a specific cardiomyopathy. Hitherto, it has been widely understood that acromegaly carries an increased risk of arrhythmia.

PURPOSE

In this review we show that evidences are limited to a small number of case-control studies that reported increased rates of premature ventricular beats (PVB) but no more significant arrhythmia. In contrast, there are several studies that have reported impaired preclinical markers of arrhythmia, including reduced heart rate variability, increased late potentials, QT interval dispersion, impaired heart rate recovery after physical exercise and left ventricular dysynchrony. Whilst these markers are associated with an adverse cardiovascular prognosis in the general population, they do not have a high independent positive predictive accuracy for arrhythmia. In acromegaly, case reports have described sudden cardiac death, ventricular tachyarrhythmia and advanced atrio-ventricular block that required implantation of a cardio-defibrillator or permanent pacemaker. Treatment with somatostatin analogues can reduce cardiac dysrhythmia in some cases by reducing heart rate, PVBs and QT interval. Pegvisomant reduces mean heart rate. Pasireotide is associated with QT prolongation. In the absence of good quality data on risk of arrhythmia in acromegaly, the majority of position statements and guidelines suggest routine 12-lead electrocardiography (ECG) and transthoracic echocardiography (TTE) in every patient at diagnosis and then follow up dependent on initial findings.

Effects of Aircraft Noise Exposure on Heart Rate during Sleep in the Population Living Near Airports

Background Noise in the vicinity of airports is a public health problem. Many laboratory studies have shown that heart rate is altered during sleep after exposure to road or railway noise. Fewer studies have looked at the effects of exposure to aircraft noise on heart rate during sleep in populations living near airports. Objective The aim of this study was to investigate the relationship between the sound pressure level (SPL) of aircraft noise and heart rate during sleep in populations living near airports in France. Methods In total, 92 people living near the Paris-Charles de Gaulle and Toulouse-Blagnac airports participated in this study. Heart rate was recorded every 15 s during one night, using an Actiheart monitor, with simultaneous measurements of SPL of aircraft noise inside the participants' bedrooms. Energy and event-related indicators were then estimated. Mixed linear regression models were applied, taking into account potential confounding factors, to investigate the relationship between energy indicators and heart rate during sleep measured every 15 s. Event-related analyses were also carried out in order to study the effects of an acoustic event associated with aircraft noise on heart rate during sleep. Results The more the SPL from all sources (L_Aeq,15s) and the SPL exceeded for 90% of the measurement period (L_A90,15s) increased, the more heart rate also increased. No significant associations were observed between the maximum 1-s equivalent SPL associated with aircraft overflight (L_Amax,1s) and differences between the heart rate recorded during or 15 or 30 s after an aircraft noise event and that recorded before the event. On the other hand, a positive and significant association was found between L_Amax,1s and the heart rate amplitude calculated during an aircraft noise event. Results were unchanged when analyses were limited to participants who had lived more than five years in their present dwelling. Conclusion Our study shows that exposure to the maximum SPL linked to aircraft overflight affect the heart rate during sleep of residents near airports. However, further studies on a larger number of participants over several nights are needed to confirm these results.

Reduction in Parasympathetic Tone During Sleep in Children With Habitual Snoring

Introduction: Changes in the autonomic nervous system due to Obstructive Sleep Apnea (OSA) during the life span have been described. Some pediatric studies have shown cardiovascular effects in children who do not fit the criteria for OSA; namely children with mild sleep disordered breathing. Objective: We investigated heart rate variability (HRV) during sleep in children with chronic snoring and flow limitation events during sleep. Methods: Ten children and adolescents with chronic snoring and an apnea hypopnea index < 1, associated to high Respiratory Index, and 10 controls matched for age, gender, and Tanner stage were monitored following one night of habituation in the sleep laboratory. HRV was studied at each sleep stage. The time and frequency domains were calculated for each 5-min period. Results: All patients were chronic heavy snorers. They presented an apnea hypopnea index = 0.8, respiratory disturbance index = 10.2/h with lowest O2 saturation 96.1 ± 2.4%. The total power of HRV was decreased in all stages (p < 0.05). There was also a decrease in NN50 and pNN50 during all sleep stages compared to healthy controls (p = 0.0003 and p = 0.03, respectively). Conclusion: A reduction in parasympathetic tone was found in the patient group. This may represent an autonomic impairment during sleep in children with mild SDB. A reduction in HRV in children with habitual snoring could be associated with possible increases in cardiovascular risk in adulthood. Significance: The study indicates that children with habitual snoring have important parasympathetic tone changes during sleep.

Autonomic regulation during sleep and wakefulness: a review with implications for defining the pathophysiology of neurological disorders

Cardiovascular and respiratory parameters change during sleep and wakefulness. This observation underscores an important, albeit incompletely understood, role for the central nervous system in the differential regulation of autonomic functions. Understanding sleep/wake-dependent sympathetic modulations provides insights into diseases involving autonomic dysfunction. The purpose of this review was to define the central nervous system nuclei regulating sleep and cardiovascular function and to identify reciprocal networks that may underlie autonomic symptoms of disorders such as insomnia, sleep apnea, restless leg syndrome, rapid eye movement sleep behavior disorder, and narcolepsy/cataplexy. In this review, we examine the functional and anatomical significance of hypothalamic, pontine, and medullary networks on sleep, cardiovascular function, and breathing.

Aberrant Interhemispheric Connectivity in Obstructive Sleep Apnea-Hypopnea Syndrome

Objective

To determine the changes in interhemispheric functional coordination in patients with obstructive sleep apnea–hypopnea syndrome (OSAHS) relative to controls, using a recently introduced method of analysis: voxel-mirrored homotopic connectivity (VMHC).

Methods

Twenty-nine patients with OSAHS and twenty-six normal sex-, age-, and education-matched controls were recruited and resting-state functional magnetic resonance imaging data were obtained. We employed VMHC to analyze the interhemispheric functional connectivity differences between groups. The z-values of alterations in VMHC in brain region were correlated with clinical characteristics.

Results

Compared with controls, patients with OSAHS had significantly higher scores for body mass index (t = 5.749, P < 0.001), apnea–hypopnea index (AHI; t = 7.706, P < 0.001), oxygen desaturation index (t = 6.041, P < 0.001), and Epworth sleepiness scale (t = 3.711, P < 0.001), but significantly lower scores on the Rey–Osterrieth complex figure test-immediate recall (t = −3.727, P < 0.05). On the same basis, the VMHC showed significant increases in bilateral calcarine cortex and precuneus. Moreover, significant, positive correlations were found in only these areas between the AHI and the VMHC change coefficients (r = 0.399, P = 0.032; r = 0.378, P = 0.043).

Conclusion

We found a memory defect in patients with OSAHS. The correlation between the abnormal VMHC and the AHI in patients with OSAHS suggested that AHI might be a key factor in cognitive dysfunction, which might offer new insights into the neural pathophysiology underlying OSAHS-related cognitive deficits.

Heart Rate Variability Responses of Individuals With and Without Saline-Induced Obstructive Sleep Apnea

STUDY OBJECTIVES

Postoperative development of obstructive sleep apnea (OSA) has been attributed to the fluid overloaded state of patients during the postoperative period. In this context, alterations in cardiac autonomic regulation caused by OSA may explain the increased postoperative risk for adverse cardiovascular events. This study tests the hypothesis that individuals with fluid overload-induced OSA will experience autonomic dysregulation, compared to those without fluid overload-induced OSA.

METHODS

Twenty-one normotensive, nonobese (mean body mass index 24.5 kg/m²) males (mean age 37 years) underwent a sleep study. Participants were randomly assigned to infusion with saline during sleep either at the minimum rate (control) or as a bolus of 22 mL/kg body weight (intervention). Participants were blinded to the intervention and crossed over to the other study arm after 1 week. Measures of heart rate variability were calculated from electrocardiography recordings presaline and postsaline infusion in the intervention arm. Heart rate variability measures computed were: standard deviation of the RR interval; root mean square of successive differences; low-frequency, high-frequency, and total power; and the ratio of low-frequency to high-frequency power.

RESULTS

Although presaline infusion values were similar, postsaline infusion values of the standard deviation of the RR interval and high-frequency power were lower in the group whose apnea-hypopnea index increased in response to saline infusion, compared to the group whose apnea-hypopnea index did not increase in response to saline infusion (P < .05 for both).

CONCLUSIONS

Fluid overload-induced OSA is accompanied by a reduction in heart rate variability, consistent with vagal withdrawal. Future work should explore autonomic dysregulation in the postoperative period and its association with adverse events.

Relationship between autonomic cardiovascular control and obstructive sleep apnoea in persons with spinal cord injury: a retrospective study

Study design

Retrospective study.

Objective

To determine if there is an association between obstructive sleep apnoea (OSA) and blood pressure (BP) pattern or heart rate variability (HRV) in people with spinal cord injury (SCI).

Setting

A state-based spinal cord service in Victoria, Australia.

Methods

We identified 42 subjects who had ambulatory BP monitoring (ABPM) within 6 months of a diagnostic sleep study at Austin Hospital between 2009 and 2014. Markers for autonomic function, including circadian BP pattern and HRV were extracted from the ABPM study database. Apnoea/hypopnoea index (AHI), arousals/hour and oxygen desaturation index were extracted from the sleep study database. Subjects with a nocturnal systolic BP dipping more than 10% of daytime value were defined as dippers, between 10 and 0% were non-dippers and those with a higher night than day systolic BP were reverse dippers. Severity of OSA is classified as non-OSA (AHI < 5), mild (AHI 5-15), moderate (AHI 15-30) and severe (AHI > 30).

Results

Subjects (n = 42) were predominantly male (85.7%), aged 44 ± 15.4 (mean ± SD), with a BMI of 24.4 ± 5.7 (mean ± SD) and mainly tetraplegic (92.9%). There was no difference in AHI, oxygen desaturation index or arousals/hour between dippers, non-dippers and reverse dippers. None of the HRV parameters differed between dippers, non-dippers and reverse dippers. No differences were found in 24 h, night-time, daytime or nocturnal dip in BP between subjects with non-OSA, mild, moderate and severe OSA.

Conclusion

We found no relationship between BP pattern or HRV and the severity of OSA in persons with SCI.

Characteristics and Consequences of Non-apneic Respiratory Events During Sleep

Rationale

Current scoring criteria of non-apneic events (ie, hypopnea) require the presence of oxyhemoglobin desaturation and/or arousal. However, other sleep study parameters may help to identify abnormal respiratory events (REs) and assist in making more accurate diagnosis.

Objectives

To investigate whether non-apneic REs without desaturation or cortical arousal are associated with respiratory and cardiac consequences.

Methods

Thirteen participants with sleep disturbances (snoring and/or excessive day time sleepiness), were screened using attended in laboratory polysomnography (PSG) while monitoring pressure and airflow via a nasal mask with an attached pneumotach. To separate the contribution of the upper airway resistance (RUA) and total pulmonary resistance (RL), supraglottic and esophageal pressures were measured using Millar pressure catheters. RL and RUA were calculated during baseline and hypopneas. RL was defined as the resistive pressure divided by the maximal flow during inspiration and expiration. Hypopnea was defined 30% decrease in flow with 3% desaturation and/or cortical arousal. REs was defined as 30% decrease in the flow without desaturation and/or cortical arousal. In eight subjects continuous positive airway pressure (CPAP) was titrated to optimal pressure. R-R interval (RRI) was defined as consecutive beat-to-beat intervals on single lead electrocardiograph (ECG) during baseline, RE/hypopnea and on optimal CPAP.

Results

REs associated with increased expiratory RUA (14.6 ± 11.3 vs. 7.5 ± 4.5 cmH2O L-1 s-1; p < .05), and increased expiratory RL relative to baseline (29.2 ± 14.6 vs. 20.9 ± 11.0 and 23.7 ± 12.1 vs. 14.3 ± 5.6 cmH2O L-1 s-1 during inspiration and expiration, respectively; p < .05). RRI decreased significantly following RE and hypopnea relative to baseline (804.8 ± 33.1 vs. 806.4 ± 36.3 vs. 934.3 ± 45.8 ms; p < .05). Optimal CPAP decreased expiratory RUA (4.0 ± 2.5 vs. 7.5 ± 4.5 cmH2O L-1 s-1; p < .05), decreased inspiratory RL (12.6 ± 14.1 vs. 7.5 ± 4.5 cmH2O L-1 s-1; p < .05), and allowed RRI to return to baseline (p < .05). RRI dips index was an independent predictor of sleep-disordered breathing (SDB) when non-apneic REs were accounted for in symptomatic patients (p < .05).

Conclusions

Non-apneic REs without cortical arousal or desaturation are associated with significant respiratory and heart rate changes. Optimal CPAP and the reduction of resistive load are associated with the normalization of heart rate indicating potential clinical benefit.

Exploring the Abnormal Modulation of the Autonomic Systems during Nasal Flow Limitation in Upper Airway Resistance Syndrome by Hilbert-Huang Transform

Patients with nasal flow limitation and upper airway resistance syndrome (UARS) during sleep can present with low blood pressure and disturbing symptoms associated with hypervagotony. We hypothesized that the dynamic changes of the autonomic system related to inspiratory flow limitation can be quantified by the developed analytic technique applied on beat-to-beat heart rate (RR intervals) and finger photoplethysmography (PPG).

Sleep disturbances in irritable bowel syndrome: a systematic review

BACKGROUND

Sleep disturbances are well-documented among persons with irritable bowel syndrome (IBS). Difficulty in falling asleep, shorter sleep time, frequent arousal and awakenings, or non-restorative sleep are the most common manifestations. Sleep disturbances are also related to a higher risk of having IBS. Some researchers have provided evidence of a positive association between poorer subjective sleep quality and increased severity and frequency in gastrointestinal (GI) symptoms in those with IBS. However, findings from studies using objective sleep and activity measures, such as polysomnography and actigraphy, are inconclusive.

PURPOSE

This systematic review of the literature between 1990 and 2015 evaluates the evidence of sleep disturbances in adults with IBS and their relationship with GI symptoms.

Inflammatory cytokines in pediatric obstructive sleep apnea

Pediatric obstructive sleep apnea (OSA) is associated with chronic systemic inflammation and with cognitive impairments. This study aimed to investigate the status of proinflammatory cytokines, particularly interleukin 17 (IL-17) and interleukin 23 (IL-23) and cognition in pediatric OSA.Controls and OSA children participated in the study. Exclusion criteria were adenotonsillectomy, heart, neurological and severe psychiatric diseases, craniofacial syndromes, and obesity. Polysomnogram was followed by serum testing for inflammatory markers and neurocognitive tests such as continuous performance task (CPT) and Wisconsin card sorting test, questionnaires, analyses of plasma high-sensitivity C-reactive protein (HS-CRP), tumor necrosis factor alpha (TNF-α), interleukin 1 (IL-1), interleukin 6 (IL-6), IL-17, and IL-23.Seventy-nine, 4 to 12-year-old subjects in 2 groups ended the study: 47 nonobese OSA children (mean age = 7.84 ± 0.56 years, body mass index [BMI] = 16.95 ± 0.47 kg/m, BMI z-score = 0.15 ± 0.21, and mean apnea-hypopnea index [AHI] = 9.13 ± 1.67 events/h) and 32 healthy control children (mean age = 7.02 ± 0.65 years, with BMI = 16.55 ± 0.58 kg/m, BMI z-score = -0.12 ± 0.27, and mean AHI = 0.41 ± 0.07 event/h) were enrolled. Serum cytokine analyses showed significantly higher levels of HS-CRP, IL-17, and IL-23 in OSA children (P = 0.002, P = 0.024, and P = 0.047). Regression test showed significant influence of HS-CRP, TNF-α, IL-6, IL-17, and specifically IL-23, with the continuous performance test and Wisconsin card sorting test.OSA children have abnormal levels of IL-17, an interleukin related to T helper 17 cells, a T helper cell involved in development of autoimmunity and inflammation. This high expression level may contribute to the complications of pediatric OSA; we also found a significant influence of inflammatory cytokines, particularly IL-23, on abnormal neurocognitive testing.

Upper Airway Resistance Syndrome Patients Have Worse Sleep Quality Compared to Mild Obstructive Sleep Apnea

Purpose

To compare sleep quality and sustained attention of patients with Upper Airway Resistance Syndrome (UARS), mild Obstructive Sleep Apnea (OSA) and normal individuals.

Methods

UARS criteria were presence of excessive daytime sleepiness (Epworth Sleepiness Scale—ESS—≥ 10) and/or fatigue (Modified Fatigue Impact Scale—MFIS—≥ 38) associated to Apnea/hypopnea index (AHI) ≤ 5 and Respiratory Disturbance Index (RDI) > 5 events/hour of sleep or more than 30% of total sleep time with flow limitation. Mild OSA was considered if the presence of excessive daytime sleepiness (ESS ≥ 10) and/or fatigue (MFIS ≥ 38) associated to AHI ≥ 5 and ≤ 15 events/hour. “Control group” criteria were AHI < 5 events/hour and RDI ≤ 5 events/hour and ESS ≤ 9, without any sleep, clinical, neurological or psychiatric disorder. 115 individuals (34 UARS and 47 mild OSA patients and 34 individuals in “control group”), adjusted for age, gender, body mass index (BMI) and schooling years, performed sleep questionnaires and sustained attention evaluation. Psychomotor Vigilance Task (PVT) was performed five times (each two hours) from 8 a.m. to 4 p.m.

Results

UARS patients had worse sleep quality (Functional Outcomes of Sleep Questionnaire—FOSQ—and Pittsburgh Sleep Quality Index—PSQI: p < 0.05) and more fatigue than mild OSA patients (p = 0.003) and scored significantly higher in both Beck inventories than “control group” (p < 0.02). UARS patients had more lapses early in the morning (in time 1) compared to the results in the afternoon (time 5) than mild OSA (p = 0.02). Mild OSA patients had more lapses in times 2 than in time 5 compared to “control group” (p = 0.04).

Conclusions

UARS patients have a worse sleep quality, more fatigue and a worse early morning sustained attention compared to mild OSA. These last had a worse sustained attention than controls.

Serum Vitamin D Is Significantly Inversely Associated with Disease Severity in Caucasian Adults with Obstructive Sleep Apnea Syndrome

STUDY OBJECTIVES

To evaluate vitamin D (25(OH)D) levels in obstructive sleep apnea syndrome (OSAS) and possible relationships to OSAS severity, sleepiness, lung function, nocturnal heart rate (HR), and body composition. We also aimed to compare the 25(OH)D status of a subset of OSAS patients compared to controls matched for important determinants of both OSAS and vitamin D deficiency (VDD).

METHODS

This was a cross-sectional study conducted at an urban, clinical sleep medicine outpatient center. We recruited newly diagnosed, Caucasian adults who had recently undergone nocturnal polysomnography. We compared body mass index (BMI), body composition (bioelectrical impedance analysis), neck circumference, sleepiness (Epworth Sleepiness Scale), lung function, and vitamin D status (serum 25-hydrpoxyvitamin D (25(OH)D) across OSAS severity categories and non-OSAS subjects. Next, using a case-control design, we compared measures of serum 25(OH)D from OSAS cases to non-OSAS controls who were matched for age, gender, skin pigmentation, sleepiness, season, and BMI.

RESULTS

106 adults (77 male; median age = 54.5; median BMI = 34.3 kg/m(2)) resident in Dublin, Ireland (latitude 53°N) were recruited and categorized as non-OSAS or mild/moderate/severe OSAS. 98% of OSAS cases had insufficient 25(OH)D (< 75 nmol/L), including 72% with VDD (< 50 nmol/L). 25(OH)D levels decreased with OSAS severity (P = 0.003). 25(OH)D was inversely correlated with BMI, percent body fat, AHI, and nocturnal HR. Subsequent multivariate regression analysis revealed that 25(OH)D was independently associated with both AHI (P = 0.016) and nocturnal HR (P = 0.0419). Our separate case-control study revealed that 25(OH)D was significantly lower in OSAS cases than matched, non-OSAS subjects (P = 0.001).

CONCLUSIONS

We observed widespread vitamin D deficiency and insufficiency in a Caucasian, OSAS population. There were significant, independent, inverse relationships between 25(OH)D and AHI as well as nocturnal HR, a known cardiovascular risk factor. Further, 25(OH)D was significantly lower in OSAS cases compared to matched, non-OSAS subjects. We provide evidence that 25(OH)D and OSAS are related, but the role, if any, of replenishment has not been investigated.

[The syndrome of increased upper airways resistance: What are the clinical features and diagnostic procedures?]

The upper airway resistance syndrome "UARS" is a poorly defined entity, often described as a moderate variant of the obstructive sleep apnea syndrome. It is associated with respiratory effort-related arousal, absence of obstructive sleep apnea, and absence of significant desaturation. It is a relatively common condition that predominantly affects non-obese young adults, with no predominance in either sex. The degree of upper airway collapsibility during sleep of patients with UARS is intermediate between that of normal subjects and that of patients with mild-to-moderate sleep apnea syndrome. Craniofacial and palatal abnormalities are often noted. Patients frequently complain of a functional somatic syndrome, especially daytime sleepiness and chronic fatigue. Polysomnography with esophageal pressure measurements remains the gold standard diagnostic test. The absence of any neurological abnormality gives UARS a good prognosis and it is potentially reversible if treated early. However, some studies suggest that untreated UARS has an increased risk of arterial hypertension. It can also evolve into obstructive sleep apnea.

Prevalence and associations of respiratory-related leg movements: the MrOS sleep study

OBJECTIVES

Obstructive respiratory events often terminate with an associated respiratory-related leg movement (RRLM). Such leg movements are not scored as periodic leg movements (periodic limb movements during sleep, PLMS), although the criteria for distinguishing RRLM from PLMS differ between the American Academy of Sleep Medicine (AASM) and the World Association of Sleep Medicine (WASM)/ International Restless Legs Syndrome Study Group (IRLSSG) scoring manuals. Such LMs may be clinically significant in patients with obstructive sleep apnea (OSA). The prevalence and correlation of RRLM in men with OSA were examined.

METHODS

A case-control sample of 575 men was selected from all men with an apnea-hypopnea index (AHI, ≥3% desaturation criteria) ≥ 10 and good data from piezoelectric leg movement sensors at the first in-home sleep study in the MrOS cohort (mean age = 76.8 years). Sleep studies were rescored for RRLMs using five different RRLM definitions varying in both latency of leg movement onset from respiratory event termination and duration of the leg movement. The quartile of RRLM% (the number of RRLM/the number of hypopneas + apneas) was derived.

RESULTS

The nonparametric densities of RRLM% were most influenced by alterations in the latency rather than the duration of the LM. The most liberal RRLM definition (latency 0-5 s, duration 0.5-10 s) led to a median RRLM% of 23.4 (interquartile range 12.41, 37.12) in this sample. The average AHI and arousal index increased as the quartile of RRLM% increased, as well as the prevalence of chronic obstructive pulmonary disease (COPD). The prevalence of those with a history of hypertension decreased as RRLM% increased. The non-Caucasian race was associated with lower RRLM%.

CONCLUSION

Within an elderly sample with moderate to severe OSA, piezoelectric-defined RRLM% is associated with a number of sleep-related and demographic factors. Further study of the optimal definition, predictors, and consequences of RRLM is warranted.

Cardiac autonomic control in the obstructive sleep apnea

INTRODUCTION

The sympathetic activation is considered to be the main mechanism involved in the development of cardiovascular diseases in obstructive sleep apnea (OSA). The heart rate variability (HRV) analysis represents a non-invasive tool allowing the study of the autonomic nervous system. The impairment of HRV parameters in OSA has been documented. However, only a few studies tackled the dynamics of the autonomic nervous system during sleep in patients having OSA.

AIMS

To analyze the HRV over sleep stages and across sleep periods in order to clarify the impact of OSA on cardiac autonomic modulation. The second objective is to examine the nocturnal HRV of OSA patients to find out which HRV parameter is the best to reflect the symptoms severity.

METHODS

The study was retrospective. We have included 30 patients undergoing overnight polysomnography. Subjects were categorized into two groups according to apnea-hypopnea index (AHI): mild-to-moderate OSAS group (AHI: 5-30) and severe OSAS group (AHI>30). The HRV measures for participants with low apnea-hypopnea indices were compared to those of patients with high rates of apnea-hypopnea across the sleep period and sleep stages.

RESULTS

HRV measures during sleep stages for the group with low rates of apnea-hypopnea have indicated a parasympathetic activation during non-rapid eye movement (NREM) sleep. However, no significant difference has been observed in the high AHI group except for the mean of RR intervals (mean RR). The parasympathetic activity tended to increase across the night but without a statistical difference. After control of age and body mass index, the most significant correlation found was for the mean RR (p=0.0001, r=-0.248).

CONCLUSION

OSA affects sympathovagal modulation during sleep, and this impact has been correlated to the severity of the disease. The mean RR seemed to be a better index allowing the sympathovagal balance appreciation during the night in OSA.

A Comparison of Personality Characteristics and Psychiatric Symptomatology between Upper Airway Resistance Syndrome and Obstructive Sleep Apnea Syndrome

OBJECTIVE

To investigate the personality characteristics of patients with upper airway resistance syndrome (UARS) and those of patients with obstructive sleep apnea syndrome (OSAS).

METHODS

Eighty-eight patients with UARS and 365 patients with OSAS participated. All patients had a diagnostic full-night attended polysomnography (PSG) and completed the Athens Insomnia Scale (AIS), Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), Symptom Checklist-90-Revision (SCL-90-R) and Eysenck Personality Questionnaire (EPQ).

RESULTS

The UARS group scored significantly higher than the OSAS group on the ESS, AIS, and PSQI (p<0.001). The scores of all SCL-90-R subscales in the UARS group were significantly higher than those in the OSA group (all p<0.001, except for somatization, p=0.016). Patients with UARS scored lower on EPQ-E (extroversion/introversion) (p=0.006) and EPQ-L (lie) (p<0.001) than those with OSA. UARS patients also showed higher scores on EPQ-P (psychoticism) (p=0.002) and EPQ-N (neuroticism) (p<0.001) than OSAS patients.

CONCLUSION

Our results suggest that patients with UARS have worse subjective sleep quality than OSAS patients in spite of their better PSG findings. UARS patients tend to have more neurotic and sensitive personalities than patients with OSAS, which may be a cause of the clinical features of UARS.

An overlooked cause of resistant hypertension: upper airway resistance syndrome - preliminary results

OBJECTIVE

Upper airway resistance syndrome is a sleep-disordered breathing syndrome that is characterized by repetitive arousals resulting in sympathetic overactivity. We aimed to determine whether upper airway resistance syndrome was associated with poorly controlled hypertension.

METHODS

A total of 40 patients with resistant hypertension were enrolled in the study. All of the patients underwent polysomnographic examinations and 24-hour ambulatory blood pressure monitoring to exclude white coat syndrome and to monitor treatment efficiency. Among 14 upper airway resistance syndrome patients, 2 patients had surgically correctable upper airway pathologies, while 12 patients were given positive airway pressure therapy.

RESULTS

All patients underwent polysomnographic examinations; 22 patients (55%) were diagnosed with obstructive sleep apnea and 14 patients (35%) were diagnosed with upper airway resistance syndrome, according to American Sleep Disorders Association criteria. The patients with upper airway resistance syndrome were younger and had a lower body mass index compared with other patients, while there were no difference between the blood pressure levels and the number of antihypertensive drugs. The arousal index was positively correlated with systolic blood pressure level (p=0.034; rs=0.746), while the Epworth score and AHI were independent of disease severity (p=0.435, rs=0.323 and p=0.819, rs=-0.097, respectively). Eight patients were treated with positive airway pressure treatment and blood pressure control was achieved in all of them, whereas no pressure reduction was observed in four untreated patients.

CONCLUSIONS

We conclude that upper airway resistance syndrome is a possible secondary cause of resistant hypertension and that its proper treatment could result in dramatic blood pressure control.

Mean platelet volume in patients with obstructive sleep apnea and its relationship with simpler heart rate derivatives

Some studies show increased mean platelet volume (MPV) in obstructive sleep apnea (OSA). The aim of this study was to evaluate MPV in OSA patients without cardiovascular risk factors and the possible association of heart rate derivatives with MPV. A total of 82 patients (aged 30–70 years) were divided into 2 groups according to the presence of either OSA or non-OSA as the control group. The OSA group consisted of 52 patients and the control group consisted of 30 subjects. Neither group was significantly different in terms of MPV values as well as heart rate (HR) derivatives such as minimum HR, maximum HR, the difference between maximum HR and minimum HR, mean HR, and heart rate performance index (HRPI) [(HR max. − HR min.)/HR mean] (P > 0.05 for all variables). In multivariate analysis, platelet count and percentages of recording time spent at arterial oxygen saturation < 90% significant variables are associated with MPV (β ± SE: −0.004 ± 0.002, 95% CI, −0.008 to −0.001; P = 0.034) and (β ± SE: 2.93 ± 1.93, 95% CI, 0.167 to 5.69; P = 0.038). Consequently, our findings predominantly suggest that there is a casual and reciprocal interaction between MPV and autonomic activation.

Heart rate variability evaluation of Emfit sleep mattress breathing categories in NREM sleep

OBJECTIVE

Heart rate variability (HRV) analysis of obstructive sleep apnea patients reveals an increase in sympathetic activity. Sleep disordered breathing (SDB) can be also assessed with sleep mattress sensors, as the Emfit sensor, by dividing the signal into different breathing categories. In addition to normal breathing (NB) and periodic apneas/hypopneas (POB), the sleep mattress unveils a breathing category consisting of sustained partial obstruction (increased respiratory resistance, IRR). The aim of our study was to evaluate HRV during these three breathing categories in NREM sleep.

METHODS

53 patients with suspected SDB underwent an overnight polysomnography with an Emfit mattress. The Emfit signal was scored in 3-min epochs according to the established rules. The NB, POB, and IRR epochs were combined to as long NB, POB and IRR periods as possible and HRV was calculated from at least 6-min epochs.

RESULTS

The meanHR did not differ between the breathing categories. HRV parameters revealed an increase in sympathetic activity during POB. The mean LF/HF ratio was highest during POB (3.0) and lowest during IRR (1.3). During NB it was 1.7 (all p-values ⩽ 0.001). Interestingly sympathetic activity decreased and parasympathetic activity increased during IRR as compared to NB (the mean HF power was 1113.8 ms(2) during IRR and 928.4 ms(2) during NB).

CONCLUSIONS

The HRV findings during POB resembled HRV results of sleep apnea patients but during sustained prolonged partial obstruction a shift towards parasympathetic activity was achieved.

SIGNIFICANCE

The findings encourage the use of sleep mattresses in SDB diagnostics. In addition the findings suggest that sustained partial obstruction represents its own SDB entity.

Impact of successful treatment of acromegaly on overnight heart rate variability and sleep apnea

BACKGROUND

Successful treatment of acromegaly improves disease-related cardiovascular mortality and morbidity, but its effects on autonomic modulation of the heart rate are unknown.

OBJECTIVES

We documented treatment-induced changes in time-domain heart rate variability, taking into account the confounding effects of obstructive sleep apnea.

PATIENTS AND METHODS

Sixteen consecutive patients (12 males, aged 43 ± 12 y) with newly diagnosed acromegaly underwent overnight (12:00-7:00 am) cardiac Holter recordings coupled with polysomnography. Data were obtained before and 10 ± 6 months after successful treatment of acromegaly.

RESULTS

IGF-1 levels fell from 807 ± 333 to 207 ± 69 μg/L and normalized in all patients. Seven patients (44%) had obstructive sleep apnea (apnea-hypopnea index 33 ± 21/h) at baseline. Treatment had no significant effect on polysomnographic indices. After treatment, increases were noted in the normal-to-normal heart period (NN), SD-NN, the percentage of NN differing from the previous NN by greater than 50 msec, and the root mean square of successive differences in NN (each P < .05). These heart rate variability results were not influenced by the type of treatment, and there was no relationship between changes in NN and changes in the apnea-hypopnea index (P = .58).

CONCLUSION

Early after successful treatment of acromegaly, we observed increased parasympathetic modulation/decreased sympathetic modulation of the nighttime heart rate, an effect that seems unrelated to changes in sleep apnea status. Treatments aimed at normalizing IGF-1 may improve cardiovascular homeostasis through improved cardiac autonomic nervous system modulation.

Heart rate variability is augmented in patients with positional obstructive sleep apnea, but only supine LF/HF index correlates with its severity

PURPOSE

Data on cardiac autonomic functioning, as expressed by heart rate variability (HRV), in patients with positional obstructive sleep apnea (p-OSA) disorder are lacking. The purpose of the study was to compare HRV indices between sleep segments derived from supine body position and another body position with and without apneic events, respectively. Our intention was to find some correlation between HRV indices and the pathophysiological characteristics of the corresponding temporal period.

METHODS

Nocturnal polysomnograms derived from twenty-seven patients (22 men) with documented positional apnea were retrospectively reviewed. Patients never treated for OSA and free from diseases/drugs altering HRV were examined. Data from total sleep studies were collected. Two N2 sleep segments, from supine body position with sleep-disordered breathing (SDB) and another body position without SDB were analyzed. Apneic events (namely, apneas, hypopneas, and respiratory effort-related arousals (RERAs)), arousals, number of desaturations, minimum pulse oximetry (SaO2min), time domain variables (average RR, SDNN, SDSD, RMSSD, pNN50, and HRV triangular index) and frequency domain variables (VLF, LF, HF, TP, LF/HF) were recorded for both temporal periods.

RESULTS

With the exception of average RR and HF, all other variables were significantly higher in segments with SDB. Only LF/HF_supine ratio was positively correlated with the apneic_supine_index (t = 3.13, p < 0.01) and negatively correlated with SaO2min (t = -2.9, p < 0.01) and the desaturation_supine_index (t = -2.5, p = 0.02). Arousals were negatively correlated with SaO2min (t = -2.8, p < 0.01).

CONCLUSIONS

SDB augments autonomic tone in patients with p-OSA, but only LF/HF correlates with its severity and might be used as a screening tool in the future. On the contrary, parasympathetic tone, as reflected by HF, remains constant in both periods.

Chronic intermittent hypoxia and hypercapnia inhibit the hypothalamic paraventricular nucleus neurotransmission to parasympathetic cardiac neurons in the brain stem

Obstructive sleep apnea is associated with chronic intermittent hypoxia/hypercapnia (CIHH) episodes during sleep that heighten sympathetic and diminish parasympathetic activity to the heart. Although one population of neurons in the paraventricular nucleus of the hypothalamus strongly influences sympathetic tone and has increased activity after CIHH, little is known about the role of this pathway to parasympathetic neurons and how this network is altered in CIHH. We hypothesized that CIHH inhibits the excitatory pathway from the paraventricular nucleus of the hypothalamus to parasympathetic cardiac vagal neurons in the brain stem. To test this hypothesis, channelrhodopsin was selectively expressed, using viral vectors, in neurons in the paraventricular nucleus of the hypothalamus and channelrhodopsin-expressing fibers were photoactivated to evoke postsynaptic currents in cardiac vagal neurons in brain stem slices. Excitatory postsynaptic currents were diminished in animals exposed to CIHH. The paired-pulse and prolonged facilitation of the postsynaptic current amplitudes and frequencies evoked by paired and bursts of photoactivation of channelrhodopsin fibers, respectively, occurred in unexposed rats but were blunted in CIHH animals. In response to an acute challenge of hypoxia/hypercapnia, the amplitude of postsynaptic events was unchanged during, but increased after hypoxia/hypercapnia in unexposed animals. In contrast, postsynaptic currents were inhibited during hypoxia/hypercapnia in rats exposed to CIHH. In conclusion, the excitatory pathway to cardiac vagal neurons is diminished in response to both acute and chronic exposures to hypoxia/hypercapnia. This could elicit a reduced cardioprotective parasympathetic activity and an enhanced risk of adverse cardiovascular events in episodes of apnea and chronic obstructive sleep apnea.

Evaluation and validation of a method for determining platelet catecholamine in patients with obstructive sleep apnea and arterial hypertension

Background

Measurements of plasma and urinary catecholamine are susceptible to confounding factors that influence the results, complicating the interpretation of sympathetic nervous system (SNS) activity in the Obstructive sleep apnea (OSA) and arterial hypertension (HYP) conditions.

Objective

In this study, we validated a test for platelet catecholamine and compared the catecholamine levels (adrenaline and noradrenaline) in urine, plasma and platelets in patients with OSA and HYP compared with controls.

Methods

In the validation, 30 healthy, nonsmoking volunteers who were not currently undergoing treatment or medication were selected as the control group. One hundred fifty-four individuals (114 OSA, 40 non-OSA) were consecutively selected from the outpatient clinic of the Sleep Institute and underwent clinical, polysomnographic and laboratory evaluation, including the urinary, plasma and platelet levels of adrenaline (AD) and noradrenaline (NA). Patients were then allocated to groups according to the presence of OSA and/or hypertension.

Results

A logistic regression model, controlled for age and BMI, showed that urinary AD and urinary NA were risk factors in the OSA+HYP group and the HYP group; however, the model showed higher levels of platelet NA for OSA without HYP. After 1 year of CPAP (continuous upper airway pressure) treatment, patients (n = 9) presented lower levels of urinary NA (p = 0.04) and platelet NA (p = 0.05).

Conclusion

Urinary NA and AD levels were significantly associated with the condition of hypertension with and without OSA, whereas platelet NA with OSA without comorbidity. These findings suggest that platelet catecholamine levels might reflect nocturnal sympathetic activation in OSA patients without hypertension.

Acute effects of autoadjusting and fixed continuous positive airway pressure treatments on cardiorespiratory coupling in obese patients with obstructive sleep apnea

BACKGROUND

Treatment with positive airway pressure devices improved signs and symptoms of obstructive sleep apnea syndrome (OSA); however, auto-adjusting positive pressure (APAP) device was not as effective as continuous positive airway pressure (CPAP) in reducing arterial blood pressure and insulin resistance. The role played by autonomic cardiac regulation remains to be clarified. We aimed to test the effects of CPAP and APAP on autonomic regulation and cardiorespiratory coupling during sleep.

METHODS

We retrospectively analyzed full-night polysomnographic studies. 19 patients newly diagnosed with severe OSA (AHI>30) and 7 obese subjects without OSA (CON) were enrolled. Each OSA subject was assigned to CPAP or APAP treatment and underwent a sleep study after 1 week of treatment. Spectral and cross-spectral analyses of heart rate variability (HRV) and respiration were performed to assess autonomic profile and coherence (K2) between respiration and HF oscillation during sleep in CPAP, APAP and CON groups.

RESULTS

In CPAP and CON, LFnu and LF/HF, markers of sympathetic modulation, decreased from N2 to N3 and increased during REM sleep (p<0.001), while in APAP group, sympathetic modulation was significantly higher compared with those of CPAP and CON during all sleep stages. K2 values were lower in APAP compared with those in CPAP and CON.

CONCLUSION

APAP treatment was characterized by a greater sympathetic activation and it was associated with a lower cardio-respiratory coupling compared with CPAP. This might account for the different effects on cardiovascular risk factors induced by the two treatments.

Cardiac sympathetic modulation in response to apneas/hypopneas through heart rate variability analysis

Autonomic dysfunction is recognized to contribute to cardiovascular consequences in obstructive sleep apnea/hypopnea syndrome (OSAHS) patients who present predominant cardiovascular sympathetic activity that persists during wakefulness. Here, we examined 1) the factors that influence sympathetic cardiac modulation in response to apneas/hypopneas; and 2) the influence of autonomic activity during apneas/hypopneas on CA. Sixteen OSAHS patients underwent in-hospital polysomnography. RR interval (RR) and RR spectral analysis using wavelet transform were used to study parasympathetic (high frequency power: HF(WV)) and sympathetic (low frequency power: LF(WV) and LF(WV)/HF(WV) ratio) activity before and after apnea/hypopnea termination. Autonomic cardiac modulations were compared according to sleep stage, apnea/hypopnea type and duration, arterial oxygen saturation, and presence of CA. At apnea/hypopnea termination, RR decreased (p<0.001) while LF(WV) (p = 0.001) and LF(WV)/HF(WV) ratio (p = 0.001) increased. Only RR and LF(WV)/HF(WV) ratio changes were higher when apneas/hypopneas produced CA (p = 0.030 and p = 0.035, respectively) or deep hypoxia (p = 0.023 and p = 0.046, respectively). Multivariate statistical analysis showed that elevated LF(WV) (p = 0.006) and LF(WV)/HF(WV) ratio (p = 0.029) during apneas/hypopneas were independently related to higher CA occurrence. Both the arousal and hypoxia processes may contribute to sympathetic cardiovascular overactivity by recurrent cardiac sympathetic modulation in response to apneas/hypopneas. Sympathetic overactivity also may play an important role in the acute central response to apneas/hypopneas, and in the sleep fragmentation.

Quantitative analysis of live-cell growth at the shoot apex of Arabidopsis thaliana: algorithms for feature measurement and temporal alignment

Study of the molecular control of organ growth requires establishment of the causal relationship between gene expression and cell behaviors. We seek to understand this relationship at the shoot apical meristem (SAM) of model plant Arabidopsis thaliana. This requires the spatial mapping and temporal alignment of different functional domains into a single template. Live-cell imaging techniques allow us to observe real-time organ primordia growth and gene expression dynamics at cellular resolution. In this paper, we propose a framework for the measurement of growth features at the 3D reconstructed surface of organ primordia, as well as algorithms for robust time alignment of primordia. We computed areas and deformation values from reconstructed 3D surfaces of individual primordia from live-cell imaging data. Based on these growth measurements, we applied a multiple feature landscape matching (LAM-M) algorithm to ensure a reliable temporal alignment of multiple primordia. Although the original landscape matching (LAM) algorithm motivated our alignment approach, it sometimes fails to properly align growth curves in the presence of high noise/distortion. To overcome this shortcoming, we modified the cost function to consider the landscape of the corresponding growth features. We also present an alternate parameter-free growth alignment algorithm which performs as well as LAM-M for high-quality data, but is more robust to the presence of outliers or noise. Results on primordia and guppy evolutionary growth data show that the proposed alignment framework performs at least as well as the LAM algorithm in the general case, and significantly better in the case of increased noise.

Increased sympathetic and decreased parasympathetic cardiac tone in patients with sleep related alveolar hypoventilation

OBJECTIVE

To assess autonomic function by heart rate variability (HRV) during sleep in patients with sleep related alveolar hypoventilation (SRAH) and to compare it with that of patients with obstructive sleep apnea (OSA) and control patients.

DESIGN

Cross-sectional study.

SETTING

Sleep Unit, University Hospital of University of Navarra.

PATIENTS

Fifteen idiopathic and obesity related-SRAH patients were studied. For each patient with SRAH, a patient with OSA, matched in age, sex, body mass index (BMI), minimal oxygen saturation (SatO2), and mean SatO2 was selected. Control patients were also matched in age, sex, and BMI with patients with OSA and those with SRAH, and in apnea/hypopnea index (AHI) with patients with SRAH.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Time- and frequency-domain HRV measures (R-R, standard deviation of normal-to-normal RR interval [SDNN], very low frequency [VLF], low frequency [LF], high frequency [HF], LF/HF ratio) were calculated across all sleep stages as well as during wakefulness just before and after sleep during a 1-night polysomnography. In patients with SRAH and OSA, LF was increased during rapid eye movement (REM) when compared with control patients, whereas HF was decreased during REM and N1-N2 sleep stages. The LF/HF ratio was equally increased in patients with SRAH and OSA during REM and N1-N2. Correlation analysis showed that LF and HF values during REM sleep were correlated with minimal SatO2 and mean SatO2.

CONCLUSIONS

Patients with SRAH exhibited an abnormal cardiac tone during sleep. This fact appears to be related to the severity of nocturnal oxygen desaturation. Moreover, there were no differences between OSA and SRAH, supporting the hypothesis that autonomic changes in OSA are primarily related to a reduced nocturnal oxygen saturation, rather than a consequence of other factors such as nocturnal respiratory events.

Respiratory effort-related arousals contribute to sympathetic modulation of heart rate variability

PURPOSE

Sympathetic activation induced by sleep-disordered breathing may contribute to cardiovascular morbidity. However, the apnea-hypopnea index (AHI) excludes respiratory effort-related arousals (RERAs) associated with inspiratory flow limitation without oxygen desaturation. We sought to determine whether RERAs are associated with sympathetic activation.

METHODS

Twenty-five adults (12 males, 13 females) with AHI < 10/h and RERA index >5/h were included in this study. Power spectral density analysis was performed on two non-contiguous 10-min segments containing inspiratory flow limitation and arrhythmia-free electrocardiogram during N2 sleep. One segment contained RERA; the other did not, NO-RERA. Spectral power was described in a low-frequency domain (LF; 0.04-0.15 Hz), primarily sympathetic modulation, and a high frequency domain (HF; 0.15-0.4 Hz), parasympathetic modulation.

RESULTS

Analyses of LF and HF powers were made using normalized and absolute values. LF power was greater during RERA compared to NO-RERA (50.3 vs. 30.1 %, p < 0.001) whereas HF power was greater during NO-RERA compared to RERA (69.9 vs. 49.7 %, p < 0.001). The LF/HF ratio was greater during RERA than NO-RERA (1.01 vs. 0.43, p < 0.001). Gender differences emerged using absolute values of power: The percentage increase in LF power during RERA relative to NO-RERA was significantly greater for females than males, 247.6 vs. 31.9 %, respectively (p < 0.02).

CONCLUSIONS

RERAs are associated with a marked increase in cardiac sympathetic modulation, especially in females. Patients with a high RERA index, even in the setting of a low or normal AHI, may be exposed to elevated sympathetic tone during sleep.