Changes in the heart rate variability in patients with obstructive sleep apnea and its response to acute CPAP treatment

Detection of preceding sleep apnea using ECG spectrogram during CPAP titration night: A novel machine-learning and bag-of-features framework

Obstructive sleep apnea (OSA) has a heavy health-related burden on patients and the healthcare system. Continuous positive airway pressure (CPAP) is effective in treating OSA, but adherence to it is often inadequate. A promising solution is to detect sleep apnea events in advance, and to adjust the pressure accordingly, which could improve the long-term use of CPAP treatment. The use of CPAP titration data may reflect a similar response of patients to therapy at home. Our study aimed to develop a machine-learning algorithm using retrospective electrocardiogram (ECG) data and CPAP titration to forecast sleep apnea events before they happen. We employed a support vector machine (SVM), k-nearest neighbour (KNN), decision tree (DT), and linear discriminative analysis (LDA) to detect sleep apnea events 30-90 s in advance. Preprocessed 30 s segments were time-frequency transformed to spectrograms using continuous wavelet transform, followed by feature generation using the bag-of-features technique. Specific frequency bands of 0.5-50 Hz, 0.8-10 Hz, and 8-50 Hz were also extracted to detect the most detected band. Our results indicated that SVM outperformed KNN, LDA, and DT across frequency bands and leading time segments. The 8-50 Hz frequency band gave the best accuracy of 98.2%, and a F1-score of 0.93. Segments 60 s before sleep events seemed to exhibit better performance than other pre-OSA segments. Our findings demonstrate the feasibility of detecting sleep apnea events in advance using only a single-lead ECG signal at CPAP titration, making our proposed framework a novel and promising approach to managing obstructive sleep apnea at home.

Obstructive sleep apnea heterogeneity and autonomic function: a role for heart rate variability in therapy selection and efficacy monitoring

Obstructive sleep apnea is a highly prevalent sleep-related breathing disorder, resulting in a disturbed breathing pattern, changes in blood gases, abnormal autonomic regulation, metabolic fluctuation, poor neurocognitive performance, and increased cardiovascular risk. With broad inter-individual differences recognised in risk factors, clinical symptoms, gene expression, physiological characteristics, and health outcomes, various obstructive sleep apnea subtypes have been identified. Therapeutic efficacy and its impact on outcomes, particularly for cardiovascular consequences, may also vary depending on these features in obstructive sleep apnea. A number of interventions such as positive airway pressure therapies, oral appliance, surgical treatment, and pharmaceutical options are available in clinical practice. Selecting an effective obstructive sleep apnea treatment and therapy is a challenging medical decision due to obstructive sleep apnea heterogeneity and numerous treatment modalities. Thus, an objective marker for clinical evaluation is warranted to estimate the treatment response in patients with obstructive sleep apnea. Currently, while the Apnea-Hypopnea Index is used for severity assessment of obstructive sleep apnea and still considered a major guide to diagnosis and managements of obstructive sleep apnea, the Apnea-Hypopnea Index is not a robust marker of symptoms, function, or outcome improvement. Abnormal cardiac autonomic modulation can provide additional insight to better understand obstructive sleep apnea phenotyping. Heart rate variability is a reliable neurocardiac tool to assess altered autonomic function and can also provide cardiovascular information in obstructive sleep apnea. Beyond the Apnea-Hypopnea Index, this review aims to discuss the role of heart rate variability as an indicator and predictor of therapeutic efficacy to different modalities in order to optimise tailored treatment for obstructive sleep apnea.

Novel metrics of sleep-disordered breathing are associated with outcome after ischemic stroke

OBJECTIVE/BACKGROUND

Standard measures of sleep-disordered breathing (SDB) that rely on count data may not sufficiently capture SDB severity or reflect downstream consequences of SDB. We hypothesized that novel metrics derived from pulse rate, oxygen saturation, and nasal pressure would be associated with stroke outcomes.

PATIENTS/METHODS

Shortly after ischemic stroke, participants in a population-based study were offered ApneaLink Plus testing. Signal analysis was used to generate 166 metrics from the nasal pressure cannula and finger probe, categorized as: autonomic (based on pulse rate variability), oximetry-derived, nasal pressure-derived, and mixed oxygen and nasal pressure-derived measures. Three-month outcome assessments included functional and cognitive outcomes and stroke recurrence. Tobit regression and Cox proportional hazards models were used to examine associations between each sleep apnea metric and the three outcomes, unadjusted and adjusted for multiple potential confounders. Models were adjusted for multiple comparisons.

RESULTS

Of the 530 participants, the median age was 65 (IQR: 57, 73), 49 % were female, and 64 % were Mexican American. Without covariate adjustment, 23 of 166 variables were associated with functional outcome, 43 were associated with cognitive outcome, and 1 was associated with stroke recurrence. After adjustment, 7 mixed, oximetry, or nasal pressure-based metrics and 1 autonomic metric were associated with functional outcome, but none was associated with cognitive outcome or stroke recurrence.

CONCLUSIONS

Many novel metrics of SDB were associated with important stroke outcomes, and 8 novel metrics were associated with functional outcome in adjusted models. This raises hypotheses about pathways by which SDB may negatively impact stroke outcomes.

The 24-Hour Cardiac Autonomic Activity in Patients With Allergic Rhinitis

BACKGROUND

Definitive knowledge of the 24-hour cardiac autonomic activity in patients with allergic rhinitis (AR) is lacking. Thus, we aimed to evaluate heart rate variability (HRV), which is used to measure cardiac autonomic activity by 24-hour Holter monitoring in patients with AR.

METHODS

We enrolled 32 patients who visited our clinic and were diagnosed with AR. The control group was selected four-fold (n = 128) by matching (age, sex, hypertension, and diabetes) in the AR group from a Holter registry in the cardiology department. The HRV results, which were measured using 24-hour Holter monitoring, were compared between the AR and control groups.

RESULTS

All time-domain parameters of HRV revealed no differences between the groups. However, among the frequency domain parameters of HRV, the low-frequency to high-frequency ratio and low-frequency power in normalized units were significantly lower in the AR group. Conversely, high-frequency power in normalized units was significantly higher in the AR group. In the multiple regression analysis, AR was independently associated with sympathetic withdrawal (adjusted odds ratio = 3.393, P = 0.020) after adjusting for age, sex, hypertension, diabetes mellitus, and hyperlipidemia.

CONCLUSIONS

The present findings suggest differences in cardiac autonomic activity which are related with sympathetic withdrawal in patients with AR compared with that in the normal population over 24 hours.

Oscillation of Sympathetic Activity in Patients with Obstructive Sleep Apnea during the First Hour of Sleep

(1) Background: Snoring is a cardinal symptom of obstructive sleep apnea (OSA) and has been suggested to potentially increase sympathetic activity. On the other hand, sleep itself usually leads to a decrease in sympathetic activity. Heart rate variability (HRV) analysis is a non-invasive technique used to assess autonomic nervous system function. However, there is limited research on the combined impact of sleep and snoring on sympathetic activity in individuals with OSA, particularly during the first hour of sleep (non-rapid eye movement sleep). The current study aims to investigate the net effect of sleep and snoring on sympathetic activity and explore factors that might contribute to increased sympathetic activity in individuals with OSA during the first hour of sleep. (2) Methods: The participants were referred from the outpatient department for OSA diagnosis and underwent whole-night polysomnography (PSG). Electrocardiogram (EKG) data from the PSG were downloaded for HRV analysis. HRV measurements were conducted in both the time and frequency domain, including the root mean square of successive differences between normal heartbeats (RMSSD) and the ratio of the absolute power of the low-frequency (LF) band (0.04-0.15 Hz) to the absolute power of the high-frequency (HF) band (0.15-0.4 Hz) (LF/HF ratio), respectively. (3) Results: A total of 45 participants (38 men and 7 women) were included in the analysis. The RMSSD gradually increased from 0-5 min to 50-60 min (p = 0.024), while the LF/HF ratio decreased (p < 0.001) during the first hour of sleep (non-rapid eye movement sleep). The LF/HF ratios of the "S" (snoring) episodes were compared with those of the pre-S episodes. An elevated LF/HF ratio during the S episode was associated with the first snoring episode occurring more than 20 min after lying down to sleep (Odds ratio, OR = 10.9, p = 0.004) and with patients diagnosed with severe OSA (OR = 5.01, p = 0.045), as determined by logistic regression. (4) Conclusions: The study observed an increase in the value of RMSSD and a decrease in the value of the LF/HF ratio during the first hour of sleep for patients with OSA. Higher LF/HF ratios were associated with the first occurrence of snoring while lying down for more than 20 min and with patients with severe OSA.

Clinical, polysomnographic, and heart rate variability in highland obstructive sleep apnea patients responding to one-night nocturnal oxygen supplementation: A post-hoc analysis from a randomized, crossover trial

OBJECTIVE

/Background: This study aimed to explore the clinical, polysomnographic, and heart rate variability (HRV) characteristics of highland obstructive sleep apnea (OSA) patients receiving one-night nocturnal oxygen supplementation (NOS) and to identify factors predicting response.

PATIENTS/METHODS

Thirty-four highland OSA patients living in Shangri-La were randomly assigned to receive NOS and sham oxygen in a randomized, placebo-controlled, crossover trial. Clinical assessments, polysomnography, and HRV were measured. A responder was defined as a ≥50% reduction in apnea-hypopnea index (AHI) with NOS compared with sham oxygen.

RESULTS

Eighteen participants responded and 16 did not respond, with a median (interquartile range [IQR]) age of 46.5 (36.5-53.0) and 48.0 (44.3-53.3) years, respectively. The median treatment effect (95% CI) on total AHI was -23.2/h (-30.0 to -17.5) and -12.0/h (-16.6 to -7.6) in responders and non-responders (p = 0.004), with similar effects on oxygen desaturation index. The mean OAH duration was prolonged by 7 s in responders together with improved sleep quality and daytime blood pressure. The mean OAH duration at baseline predicted responses to NOS with a sensitivity and specificity of 88.9% and 68.7% (AUC 0.809) at a cut-off point of 24.9 s. Changes in HRV parameters were negatively correlated with changes in mean oxygen saturation and daytime systolic blood pressure only in responders.

CONCLUSIONS

NOS significantly improved OSA severity and clinical outcomes in responders, which was related to improvements in parasympathetic activity. Highlanders with shorter mean OAH may be suitable candidates for NOS. These findings provide new information about tailored treatment strategies for highland OSA patients.

An Obstructive Sleep Apnea - A Novel Public Health Threat

In patients with obstructive sleep apnea (OSA) during obstructive events, episodes of hypoxia and hypercapnia may modulate the autonomic nervous system (ANS) by increasing sympathetic tone and irritability, which contributes to sympathovagal imbalance and ultimately dysautonomia. Because OSA can alter ANS function through biochemical changes, we can assume that heart rate variability (HRV) will be altered in patients with OSA. Most studies show that in both the time and frequency domains, patients with OSA have higher sympathetic components and lower parasympathetic dominance than healthy controls. These results confirm autonomic dysfunction in these patients, but also provide new therapeutic directions. Respiratory methods that modulate ANS, e.g., cardiorespiratory biofeedback, could be beneficial for these patients. Heart rate variability assessment can be used as a tool to evaluate the effectiveness of OSA treatment due to its association with autonomic impairment.

The effect of obstructive sleep apnea therapy on cardiovascular autonomic function: a systematic review and meta-analysis

STUDY OBJECTIVES

Autonomic function is impaired in obstructive sleep apnea (OSA) and may mediate the association between OSA and cardiovascular risk. We investigated the effect of OSA therapy on autonomic function through a systematic review and meta-analysis of intervention studies.

METHODS

A systematic search using three databases (Medline, Embase, and Scopus) was performed up to December 9, 2020. Studies of OSA patients ≥ 18 years with autonomic function assessed before and after treatment with positive airway pressure, oral appliance, positional therapy, weight loss, or surgical intervention were included for review. Random effects meta-analysis was carried out for five groups of autonomic function indices. Risk of bias was assessed using the Cochrane Collaboration tool.

RESULTS

Forty-three eligible studies were reviewed with 39 included in the meta-analysis. OSA treatment led to large decreases in muscle sympathetic nerve activity (Hedges' g = -1.08; 95% CI -1.50, -0.65, n = 8) and moderate decreases in catecholamines (-0.60; -0.94, -0.27, n = 3) and radio nucleotide imaging (-0.61; -0.99, -0.24, n = 2). OSA therapy had no significant effect on baroreflex function (Hedges' g = 0.15; 95% CI -0.09, 0.39, n = 6) or heart rate variability (0.02; -0.32, 0.36, n = 14). There was a significant risk of bias due to studies being primarily non-randomized trials.

CONCLUSIONS

OSA therapy selectively improves autonomic function measures. The strongest evidence for the effect of OSA therapy on autonomic function was seen in reduced sympathetic activity as assessed by microneurography, but without increased improvement in parasympathetic function. OSA therapy may reduce the risk of cardiovascular disease in OSA through reduced sympathetic activity.

Continuous Positive Airway Pressure Treatment Decreases the Risk of Atrial Fibrillation Recurrence in Patients with Obstructive Sleep Apnea after Radiofrequency Ablation

This study aimed to determine the effect of continuous positive airway pressure (CPAP) therapy on patients with atrial fibrillation (AF) and obstructive sleep apnea (OSA) after radiofrequency ablation (RFCA).OSA predicts recurrence of AF in patients with AF and OSA after RFCA. However, the effect of CPAP therapy on recurrence of AF in these patients after RFCA is poorly known.All 122 patients who underwent RFCA from 2017 to 2020 were diagnosed OSA by polysomnography. A total of 62 patients were treated by CPAP, while the remaining 60 were not treated by CPAP. The recurrence of atrial tachyarrhythmia and use of antiarrhythmic drugs were compared between the two groups during a follow-up of 12 months. The outcome of these patients with OSA was compared to a group of 60 AF patients undergoing RFCA without OSA.Patients undergoing CPAP therapy had a higher AF-free survival rate compared to non-CPAP-treated patients (70.3% versus 31.5%; P = 0.02). LAD was associated with the risk of AF recurrence in patients with OSA (HR per mm increase: 1.0; 95% CI: 1.06-1.21; P = 0.01). The CPAP nonusers had more than two-fold increased risk of AF recurrence following pulmonary vein isolation (HR: 2.37; 95% CI: 1.21-4.96; P = 0.02).CPAP treatment highly increased arrhythmia-free survival in AF patients accompanied by OSA after RFCA and reduced recurrence of AF in these patients.

The differences between daytime and night-time heart rate variability may usefully predict the apnea-hypopnea index in patients with obstructive sleep apnea

STUDY OBJECTIVES

The association between daytime/night-time heart rate variability (HRV) and the apnea-hypopnea index (AHI) remains unclear. We sought a relationship between AHI and the daytime-to night-time HRV ratio as measured by 24-h Holter monitoring in patients with obstructive sleep apnea (OSA).

METHODS

We prospectively enrolled 66 patients who visited our sleep clinic complaining of habitual snoring or sleep apnea. All underwent 24-h Holter monitoring (to measure HRV) combined with full-night polysomnography (PSG). Sixty-two met our enrolment criteria. We evaluated the associations between HRV frequency domains and the PSG indices. We also considered medical histories and anthropometric data.

RESULTS

The night-time very low frequency (VLF), low frequency (LF), and high frequency (HF) HRVs were significantly higher than the daytime values. On correlation analysis, the day/night VLF (r = 0.550, p < 0.001), LF (r = 0.556, p < 0.001), and HF (r = 0.303, p = 0.017) HRVs were significantly related to the AHI. Of the day/night HRV ratios, the VLF (p for trend = 0.003) and LF (p for trend = 0.013) ratios decreased significantly by OSA severity. Multivariable analysis showed that the day/night VLF (β = 16.387, p < 0.001) and day/night LF (β = 25.248, p < 0.001) were independently (and significantly) associated with the AHI.

CONCLUSIONS

Twenty-four-hour Holter monitoring may usefully predict AHI. The day/night VLF and day/night LF ratios tended to decrease by OSA severity and were independently associated with the AHI.

Classification of Sleep Apnea Based on Sub-Band Decomposition of EEG Signals

To classify between normal and sleep apnea subjects based on sub-band decomposition of electroencephalogram (EEG) signals. This study comprised 159 subjects obtained from the ISRUC (Institute of System and Robotics—University of Coimbra), Sleep-EDF (European Data Format), and CAP (Cyclic Alternating Pattern) Sleep database, which consists of normal and sleep apnea subjects. The wavelet packet decomposition method was incorporated to categorize the EEG signals into five frequency bands, namely, alpha, beta, delta, gamma, and theta. Entropy and energy (non-linear) for all bands was calculated and as a result, 10 features were obtained for each EEG signal. The ratio of EEG bands included four parameters, including heart rate, brain perfusion, neural activity, and synchronization. In this study, a support vector machine with kernels and random forest classifiers was used for classification. The performance measures demonstrated that the improved results were obtained from the support vector machine classifier with a kernel polynomial order 2. The accuracy (90%), sensitivity (100%), and specificity (83%) with 14 features were estimated using the data obtained from ISRUC database. The proposed study is feasible and seems to be accurate in classifying the subjects with sleep apnea based on the extracted features from EEG signals using a support vector machine classifier.

Shift working and cardiovascular health

Adequate sleep is an important component of cardiovascular health. Due to circadian misalignment and irregular shifts, inadequate sleep is common in shift workers. Adverse consequences include daytime sleepiness, decreased cognitive performance, increased sympathetic tone, inflammation, impaired glucose tolerance, and altered leptin and ghrelin levels. When circadian adjustment has not occurred, daytime sleepers often experience decreased sleep duration and increased wakefulness during displaced sleep; additionally, skipping sleep is common in shift workers, further contributing to sleep deprivation. Habitual decreased sleep duration and physiological changes contribute to obesity, diabetes, hypertension, and increased cardiovascular disease risk in shift workers. Shift workers with obstructive sleep apnea (OSA), the most common sleep-related breathing disorder, can experience more frequent sleep disruptions than non-shift workers with OSA. Furthermore, shift work-induced circadian misalignment may potentiate cardiometabolic risk in OSA patients through autonomic nervous system dysfunction and other mechanisms.

Association between autonomic function and obstructive sleep apnea: A systematic review

Obstructive sleep apnea (OSA) is an independent risk factor for hypertension and cardiovascular disease. Effects of OSA on the autonomic nervous system may mediate this association. We performed a systematic literature review to determine the profile of autonomic function associated with OSA. Three electronic databases were searched for studies of OSA patients aged ≥18 years in which autonomic function was assessed. Studies comparing patients with and without OSA, or examining the association of OSA severity with changes in autonomic function were included. Seventy-one studies met the inclusion criteria and autonomic function has been assessed using a range of techniques. The profile of autonomic function found in OSA include increased sympathetic activity, reduced parasympathetic activity and less consistently found low heart rate variability. Altered autonomic function in OSA may explain the pathophysiology of increased cardiovascular risk. Evidence from intervention studies is required to determine if treatment improves autonomic function associated with OSA.

Heart rate variability and obstructive sleep apnea: Current perspectives and novel technologies

Obstructive sleep apnea (OSA) is a highly prevalent condition, resulting in recurrent hypoxic events, sleep arousal, and daytime sleepiness. Patients with OSA are at an increased risk of cardiovascular morbidity and mortality. The mechanisms underlying the development of cardiovascular disease in OSA are multifactorial and cause a cascade of events. The primary contributing factor is sympathetic overactivity. Heart rate variability (HRV) can be used to evaluate shifts in the autonomic nervous system, during sleep and in response to treatment in patients with OSA. Newer technologies are aimed at improving HRV analysis to accelerate processing time, improve the diagnosis of OSA, and detection of cardiovascular risk. The present review will present contemporary understandings and uses for HRV, specifically in the realms of physiology, technology, and clinical management.

Assessment of Nocturnal Autonomic Cardiac Imbalance in Positional Obstructive Sleep Apnea. A Multiscale Nonlinear Approach

Positional obstructive sleep apnea (POSA) is a major phenotype of sleep apnea. Supine-predominant positional patients are frequently characterized by milder symptoms and less comorbidity due to a lower age, body mass index, and overall apnea-hypopnea index. However, the bradycardia-tachycardia pattern during apneic events is known to be more severe in the supine position, which could affect the cardiac regulation of positional patients. This study aims at characterizing nocturnal heart rate modulation in the presence of POSA in order to assess potential differences between positional and non-positional patients. Patients showing clinical symptoms of suffering from a sleep-related breathing disorder performed unsupervised portable polysomnography (PSG) and simultaneous nocturnal pulse oximetry (NPO) at home. Positional patients were identified according to the Amsterdam POSA classification (APOC) criteria. Pulse rate variability (PRV) recordings from the NPO readings were used to assess overnight cardiac modulation. Conventional cardiac indexes in the time and frequency domains were computed. Additionally, multiscale entropy (MSE) was used to investigate the nonlinear dynamics of the PRV recordings in POSA and non-POSA patients. A total of 129 patients (median age 56.0, interquartile range (IQR) 44.8-63.0 years, median body mass index (BMI) 27.7, IQR 26.0-31.3 kg/m2) were classified as POSA (37 APOC I, 77 APOC II, and 15 APOC III), while 104 subjects (median age 57.5, IQR 49.0-67.0 years, median BMI 29.8, IQR 26.6-34.7 kg/m2) comprised the non-POSA group. Overnight PRV recordings from positional patients showed significantly higher disorderliness than non-positional subjects in the smallest biological scales of the MSE profile (τ = 1: 0.25, IQR 0.20-0.31 vs. 0.22, IQR 0.18-0.27, p < 0.01) (τ = 2: 0.41, IQR 0.34-0.48 vs. 0.37, IQR 0.29-0.42, p < 0.01). According to our findings, nocturnal heart rate regulation is severely affected in POSA patients, suggesting increased cardiac imbalance due to predominant positional apneas.

Clinical Usefulness of New R-R Interval Analysis Using the Wearable Heart Rate Sensor WHS-1 to Identify Obstructive Sleep Apnea: OSA and RRI Analysis Using a Wearable Heartbeat Sensor

Obstructive sleep apnea (OSA) is highly associated with cardiovascular diseases, but most patients remain undiagnosed. Cyclic variation of heart rate (CVHR) occurs during the night, and R-R interval (RRI) analysis using a Holter electrocardiogram has been reported to be useful in screening for OSA. We investigated the usefulness of RRI analysis to identify OSA using the wearable heart rate sensor WHS-1 and newly developed algorithm. WHS-1 and polysomnography simultaneously applied to 30 cases of OSA. By using the RRI averages calculated for each time series, tachycardia with CVHR was identified. The ratio of integrated RRIs determined by integrated RRIs during CVHR and over all sleep time were calculated by our newly developed method. The patient was diagnosed as OSA according to the predetermined criteria. It correlated with the apnea hypopnea index and 3% oxygen desaturation index. In the multivariate analysis, it was extracted as a factor defining the apnea hypopnea index (r = 0.663, p = 0.003) and 3% oxygen saturation index (r = 0.637, p = 0.008). Twenty-five patients could be identified as OSA. We developed the RRI analysis using the wearable heart rate sensor WHS-1 and a new algorithm, which may become an expeditious and cost-effective screening tool for identifying OSA.

Optimal Continuous Positive Airway Pressure Treatment of Obstructive Sleep Apnea Reduces Daytime Resting Heart Rate in Prediabetes: A Randomized Controlled Study

Background It has been widely recognized that obstructive sleep apnea (OSA) is linked to cardiovascular disease. Yet, randomized controlled studies failed to demonstrate a clear cardiovascular benefit from OSA treatment, mainly because of poor adherence to continuous positive airway pressure (CPAP). To date, no prior study has assessed the effect of CPAP treatment on daytime resting heart rate, a strong predictor of adverse cardiovascular outcomes and mortality. Methods and Results We conducted a randomized controlled study in 39 participants with OSA and prediabetes, who received either in-laboratory all-night (ie, optimal) CPAP or an oral placebo for 2 weeks. During daytime, participants continued daily activities outside the laboratory. Resting heart rate was continuously assessed over 19 consecutive days and nights using an ambulatory device consisting of a single-lead ECG and triaxis accelerometer. Compared with placebo, CPAP reduced daytime resting heart rate (treatment difference, -4.1 beats/min; 95% CI, -6.5 to -1.7 beats/min; P=0.002). The magnitude of reduction in daytime resting heart rate after treatment significantly correlated with the magnitude of decrease in plasma norepinephrine, a marker of sympathetic activity (r=0.44; P=0.02), and the magnitude of decrease in OSA severity (ie, apnea-hypopnea index [r=0.48; P=0.005], oxygen desaturation index [r=0.50; P=0.003], and microarousal index [r=0.57; P<0.001]). Conclusions This proof-of-concept randomized controlled study demonstrates, for the first time, that CPAP treatment, when optimally used at night, reduces resting heart rate during the day, and therefore has positive cardiovascular carry over effects. These findings suggest that better identification and treatment of OSA may have important clinical implications for cardiovascular disease prevention. Registration URL: https:/// www.clini​caltr​ials.gov; Unique identifier: NCT01156116.

Sleep apnea: Tracking effects of a first session of CPAP therapy by means of Granger causality

Connectivity between physiological networks is an issue of particular importance for understanding the complex interaction brain-heart. In the present study, this interaction was analyzed in polysomnography recordings of 28 patients diagnosed with obstructive sleep apnea (OSA) and compared with a group of 10 control subjects. Electroencephalography and electrocardiography signals from these polysomnography time series were characterized employing Granger causality computation to measure the directed connectivity among five brain waves and three spectral subbands of heart rate variability. Polysomnography data from OSA patients were recorded before and during a first session of continuous positive air pressure (CPAP) therapy in a split-night study. Results showed that CPAP therapy allowed the recovery of inner brain connectivities, mainly in subsystems involving the theta wave. In addition, differences between control and OSA patients were established in connections that involve lower frequency ranges of heart rate variability. This information can be potentially useful in the initial diagnosis of OSA, and determine the role of cardiac activity in sleep dynamics based on the use of three subbands of heart rate variability.

Effectiveness of sleep surgery versus a mandibular advancement device for obstructive sleep apnea in terms of nocturnal cardiac autonomic activity

PURPOSE

Sleep surgery and mandibular advancement devices (MAD) are treatments for obstructive sleep apnea (OSA), but their comparative efficacy remains unclear. We compared their efficacy using various parameters.

METHODS

Subjects treated for OSA with sleep surgery or MAD (n = 30/group)-matched for sex, body mass index (BMI), and baseline apnea-hypopnea index (AHI)-were enrolled. The efficacy of these treatments according to polysomnographic parameters, sleep quality questionnaires, and heart rate variability (HRV) time- and frequency-domain parameters were compared between pre-treatment and 3-month post-treatment.

RESULTS

Polysomnographic and sleep quality questionnaire parameters improved significantly in both groups. In time-domain HRV analysis, average normal-to-normal intervals increased significantly in the surgery (942.2 ± 140.8 to 994.6 ± 143.1, P = 0.008) and MAD (901.1 ± 131.7 to 953.7 ± 123.1, P = 0.002) groups. Low frequency (LF) decreased significantly in the surgery group (P = 0.012); high frequency (HF) remained unchanged in both groups. The LF/HF ratio decreased in both groups (2.9 ± 1.8 to 2.3 ± 1.7, P = 0.017, vs. 3.0 ± 1.8 to 2.4 ± 1.4, P = 0.025). Normalized high frequency increased significantly in both groups (31.0 ± 13.2 to 36.8 ± 13.7, P = 0.009, vs. 29.1 ± 10.7 to 33.7 ± 12.5, P = 0.024), in contrast to normalized low frequency. However, no HRV parameter changes differed significantly between the groups after adjusting for age, BMI, and AHI.

CONCLUSION

Sleep surgery and MAD are equally effective treatments for OSA according to cardiac autonomic activity.

Nocturnal heart rate variability may be useful for determining the efficacy of mandibular advancement devices for obstructive sleep apnea

A mandibular advancement device (MAD) is recommended as an alternative therapy for obstructive sleep apnea (OSA), which effectively reduces the collapsibility of the upper airway during sleep by advancing the mandible. However, the effects of MAD therapy on cardiac autonomic modulation remain unclear. We evaluated the effects of MAD on nocturnal heart rate variability (HRV) in OSA. Anthropometric data, questionnaire results, and HRV parameters (evaluated using time domain and frequency domain methods) of 58 adult patients with OSA treated with MAD therapy were retrospectively reviewed. All patients underwent polysomnography at baseline and 3-month follow-up. The average normal-to-normal (NN) interval, standard deviation of the NN interval, low-frequency power in normalized units (LFnu), and high-frequency power in normalized units (HFnu) showed significant changes with MAD therapy. Based on the criteria for success (decrease in the apnea-hypopnea index by >50% and value <20/h), 34 and 24 patients were classified into the response and nonresponse groups, respectively. No differences in baseline characteristics were detected between groups, except for higher body mass index and lower minimal oxygen saturation in the nonresponse group. A subgroup analysis indicated that the average NN interval and HFnu significantly increased, and that Total power (TP), very low frequency, low frequency(LF), low frequency/high frequency and LFnu significantly decreased compared to baseline in the response group; however, no HRV changes were found in the nonresponse group. After adjusting for age, sex, and body mass index, the response group showed significant changes from baseline in TP and LF compared to the nonresponse group. Therefore, HRV may be useful for determining the efficacy of MAD therapy in OSA.

Changes in heart rate variability (HRV) in patients with severe and moderate obstructive sleep apnea before and after acute CPAP therapy during nocturnal polysomnography

INTRODUCTION

Obstructive sleep apnea is an important risk factor for cardiovascular disease. Noninvasive positive pressure ventilation is the standard treatment of this disease, and it can reduce mortality in patients. Dysfunction of the autonomic system is one of the reasons for an increased risk of cardiovascular disease in these patients. The purpose of the present study was to investigate the effect of positive airway pressure (PAP) therapy on heart rate variability (HRV) indices.

METHODS

The study population was comprised of 55 patients, who underwent nocturnal polysomnography for the diagnosis of obstructive sleep apnea and PAP titration on the same night. The levels of continuous positive airway pressure (CPAP) and bilevel positive airway pressure were adjusted to relieve obstructive sleep apnea, hypopnea, and desaturation. The patients' heart changes and cardiac characteristics were recorded before and after the start of routine CPAP therapy. Finally, the cases' sleep and polysomnography tests were analyzed and interpreted in collaboration with a sleep specialist and their cardiac changes with the aid of a cardiologist before and after treatment with CPAP.

RESULTS

The participants were 55 patients at a mean age of 57.04±12.9 years. There were 34 (61.8%) male and 21 (38.2%) female cases. PAP therapy on the same night resulted in a decreased standard deviation of the N-N interval index (p=0.036) and a low-frequency index (p=0.021), as well as increased high-frequency index (p<0.001) and low frequency / high frequency ratios (p=0.008).

CONCLUSION

Our findings indicate a relative improvement in the activity of the autonomic system in patients with obstructive sleep apnea after 1 night of PAP therapy. Overwhelming evidence suggests that improvement in the sympathetic balance can reduce the risk of cardiovascular disease in patients.

Obstructive sleep apnea screening by heart rate variability-based apnea/normal respiration discriminant model

OBJECTIVE

Obstructive sleep apnea (OSA) is a common sleep disorder; however, most patients are undiagnosed and untreated because it is difficult for patients themselves to notice OSA in daily living. Polysomnography (PSG), which is the gold standard test for sleep disorder diagnosis, cannot be performed in many hospitals. This fact motivates us to develop a simple system for screening OSA at home.

APPROACH

The autonomic nervous system changes during apnea, and such changes affect heart rate variability (HRV). This work develops a new apnea screening method based on HRV analysis and machine learning technologies. An apnea/normal respiration (A/N) discriminant model is built for respiration condition estimation for every heart rate measurement, and an apnea/sleep ratio is introduced for final diagnosis. A random forest is adopted for the A/N discriminant model construction, which is trained with the PhysioNet apnea-ECG database.

MAIN RESULTS

The screening performance of the proposed method was evaluated by applying it to clinical PSG data. Sensitivity and specificity achieved 76% and 92%, respectively, which are comparable to existing portable sleep monitoring devices used in sleep laboratories.

SIGNIFICANCE

Since the proposed OSA screening method can be used more easily than existing devices, it will contribute to OSA treatment.

Acute effects of continuous positive airway pressure in patients with obstructive sleep apnea

Objectives. To enhance the initial compliance of continuous positive airway pressure (CPAP) in the patient with obstructive sleep apnea (OSA), we investigate the acute effects of one-night CPAP on morning blood pressure (BP) and, if any exist, to determine which factors predict BP-lowering effects of one-night CPAP in OSA subgroups stratified by the presence or absence of uncontrolled hypertension. Design. Newly diagnosed OSA patients (a respiratory distress index (RDI) ≥ 15) without a history of hypertension were stratified by the presence or absence of morning hypertension. Comparisons were made of morning BP, overnight change in mean BP (MBP), and circadian BP pattern (R_M/E, the ratio of morning to evening MBP) between two time points of diagnostic and CPAP titrations in each subgroup. In the subgroup with a significantly reduced morning BP, predictors of changes in morning MBP were determined by multiple linear regression analyses. Results. The prevalence of morning hypertension was 48.8%. One-night CPAP reduced BP immediately only in patients with morning hypertension. By contrast, patients without morning hypertension did not experience any BP-lowering effects. In the subgroup with morning hypertension, baseline morning MBP, female sex, and R_M/E were independently associated with reduced morning MBP, and R_M/E was the most important predictor. Conclusions. These results confirm the acute effects of one-night CPAP on lowering BP in OSA patients with morning hypertension. An unfavorable circadian BP pattern is the most important predictor.

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.

The effects of nasal continuous positive airway pressure and high flow nasal cannula on heart rate variability in extremely preterm infants after extubation: A randomized crossover trial

BACKGROUND

NCPAP and High flow nasal cannula (HFNC) are common modes of non-invasive respiratory support used after extubation. Heart rate variability (HRV) has been demonstrated as a marker of well-being in neonates and differences in HRV were described in preterm infants receiving respiratory care. The objective was to investigate the effects of NCPAP and HFNC on HRV after extubation.

METHODS

Randomized crossover trial in infants with birth weight (BW) ≤1250 g after undergoing their first elective extubation. ECG recordings were performed during 45 min while on HFNC and nasal continuous positive airway pressure (NCPAP). Time domain, non-linear, and frequency domain parameters were calculated and compared during HFNC and NCPAP using paired nonparametric tests. A secondary analysis was performed in the subgroup of infants that were successfully extubated.

RESULTS

Thirty infants with median [range] gestational age of 27 weeks [24.1-29.3] and BW of 930 g [610-1220] were studied at 5 days [1-39] of age. No differences in HRV parameters were observed between HFNC and NCPAP. In the secondary analysis, infants successfully extubated (n = 27) had a significantly higher HRV during HFNC for some time domain parameters. For instance, the standard deviation of the RR intervals (SDRR) was more likely to be higher during HFNC compared to NCPAP (HFNC: 18/27 vs NCPAP: 9/27, P = 0.017) .

CONCLUSION

During the first hours after extubation, no differences in HRV were detected between HFNC and NCPAP in the overall cohort. However, a significantly higher HRV was noted during HFNC in the subgroup of infants successfully extubated.

Continuous Positive Airway Pressure Therapy Improves Heterogeneity of R-R intervals in a Patient with Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea (OSA) is associated with the occurrence of various kinds of bradyarrhythmia and tachyarrhythmia. The activation of the autonomic nerve system is an important causative factor of the pathogenesis of the arrhythmia in OSA patients. Previous studies have shown that the R-R interval is an effective parameter for evaluating autonomic nerve activities. However, whether or not OSA can induce variations in the R-R interval and whether or not continuous positive airway pressure (CPAP) therapy can improve these variations in OSA patients are unclear. The present study explored whether or not CPAP therapy could improve the regularity of the R-R interval.

The Association Between Obstructive Sleep Apnea and Arrhythmias

Obstructive sleep apnea (OSA) is caused by intermittent episodes of partial or complete closure of the upper airway, leading to apneic episodes while the patient is asleep. Atrial fibrillation (AF) leads to more than 750,000 hospitalizations per year and accounts for an estimated 130,000 deaths each year. The death rate from AF as the primary or a contributing cause of death has been rising for more than two decades. The material reviewed in this paper focuses on the association between OSA and arrhythmias. It goes into the details of the epidemiology, pathophysiology, and types of arrhythmias and the therapies seen in association with OSA.

Heart rate variability in adults with obstructive sleep apnea: a systematic review

Obstructive Sleep Apnea is a common respiratory disorder characterized by recurrent nocturnal episodes of normal breathing interruption due to upper airway total or partial collapse. Obstructive sleep apnea and cardiovascular diseases has similar risk factors, but the first is also a predisposing factor for cardiovascular pathologies independently of individuals demographic characteristics or risk markers. Heart rate variability is a non-invasive method to evaluate the regulation of autonomic nervous system and its a promising marker for health and disease, such as cardiovascular and respiratory diseases. The aim was to review whether heart rate variability is altered in patients with obstructive sleep apnea. We searched in five databases, including BIREME, Cochrane, Scholar Google, MEDLINE/PubMed and Periodics CAPES, and reference lists were also searched. Only cross-sectional studies comparing the heart rate variability of obstructive sleep patients with controls were included. Two authors independently extracted data and assessed trial quality. Twelve studies (513 participants with obstructive sleep apnea and 340 controls) met the inclusion criteria. This review evidence that adults with obstructive sleep apnea may demonstrate diminished vagal tone and higher sympathetic responsiveness.

One-minute heart rate variability - an adjunct for airway obstruction identification

Heart rate variability (HRV) reflects cardiac and autonomic nervous system activity. It is usually measured over a relatively prolonged period and presented using multiple parameters. Here, we studied rapid HRV changes during airway obstruction using a short (1 min) sampling window. Forty healthy volunteers underwent a trial of obstructed breathing. Heart rate was recorded during three consecutive sets comprised of 1-min control followed by 1 min of obstructed breathing, with 1 min of rest between sets. Time and frequency domain analysis were used to compare HRV during control versus obstructed breathing. Compared with control, HRV intensely increased during obstructed breathing: R-R intervals (time between consecutive R waves) standard deviation increased from 65 to 108 msec (P < 0.0001), root mean square of successive R-R interval from 61 to 82 msec (P = 0.001), number of pairs of successive R-R intervals that differ by more than 50 msec (NN50) from 16.5 to 25.3 events (P < 0.0001), and proportion of NN50 divided by total number of R-R intervals from 26.6 to 35.1% (P = 0.001). Low frequency power increased by more than fourfold (P < 0.0001), allowing 90% sensitivity and 75% specificity for identifying airway obstruction (ROC area 0.88, P < 0.0001). We observed a rapid intense increase in HRV during obstructed breathing, significant enough to detect during a short 1-min sampling window. These findings suggest that HRV may be useful for rapid detection of airway obstruction, especially in situations where end-tidal CO2 monitoring is not optimal, such as during partial airway obstruction.

Hypoglossal Nerve Stimulation and Heart Rate Variability: Analysis of STAR Trial Responders

OBJECTIVE

Hypoglossal nerve stimulation represents a novel therapy for the treatment of moderate-severe obstructive sleep apnea; nonetheless, its cardiovascular effects are not known. We examine the effects of hypoglossal nerve stimulation on heart rate variability, a measure of autonomic function.

STUDY DESIGN

Substudy of the STAR trial (Stimulation Therapy for Apnea Reduction): a multicenter prospective single-group cohort.

SETTING

Academic and private practice centers in the United States and Europe.

SUBJECTS AND METHODS

A subset of responder participants (n = 46) from the STAR trial was randomized to therapy withdrawal or therapy maintenance 12 months after surgery. Heart rate variability analysis included standard deviation of the R-R interval (SDNN), low-frequency power of the R-R interval, and high-frequency power of the R-R interval. Analysis was performed by sleep with 5-minute sliding window epochs during baseline, 12 months, and the maintenance/withdrawal period.

RESULTS

A significant improvement from baseline to 12 months in heart rate variability was seen for SDNN and low frequency across all sleep stages. SDNN analysis demonstrated no change in the wake period (mean ± SD: 0.042 ± 0.01 vs 0.077 ± 0.07, P = .19). Reduction in SDNN was correlated to improvement in apnea-hypopnea index ( r = 0.39, P = .03). In the therapy withdrawal group, no significant changes in SDNN were seen for N1/N2, N3, or rapid eye movement sleep.

CONCLUSION

Hypoglossal nerve stimulation therapy appears to reduce heart rate variability during sleep. This reduction was not affected by a 1-week withdrawal period. Larger prospective studies are required to better understand the effect of hypoglossal nerve stimulation on autonomic dysfunction in obstructive sleep apnea.

Clues to the Pathophysiology of Sudden Cardiac Death in Obstructive Sleep Apnea

BACKGROUND

Risk assessment of sudden cardiac death (SCD) is multifactorial and complex, especially among individuals without established cardiovascular disease. There are insufficiently investigated conditions that can affect arrhythmogenesis. One such condition is obstructive sleep apnea (OSA) syndrome, which is not on the list of risk factors of the Russian National Society of Arrhythmology.

OBJECTIVE

The aim of this review article is to discuss clues to the pathophysiology of SCD in OSA subjects.

METHODS

We searched the literature for data reporting the impact of apnea on arrhythmogenesis. The preferred languages were English and Russian. The most important clinical reports, as well as biochemistry and pathophysiology guides, were selected for inclusion in the review.

RESULTS

It was clearly observed in the searched literature that OSA is the crucial aspect of arrhythmogenesis. Among the clues are intermittent nocturnal hypoxia, reactive oxygen species, cardiomyocyte metabolism disturbances, myocardial electric heterogeneity, and intrathoracic pressure changes.

CONCLUSION

This review emphasizes the importance of the inclusion of OSA in the list of risk factors of the Russian National Society of Arrhythmology.

Sympathetic Overactivity Based on Heart-Rate Variability in Patients with Obstructive Sleep Apnea and Cerebral Small-Vessel Disease

Background and Purpose

Obstructive sleep apnea (OSA) is associated with cerebral white-matter changes (WMC), but the underlying mechanisms are not completely understood. Our aim was to identify the cardiovascular autonomic characteristics during sleep that are associated with cerebral WMC in OSA patients.

Methods

We recruited subjects from our sleep-center database who underwent both polysomnography and brain MRI within a 1-year period. Sixty patients who had OSA with WMC (OSA+WMC), 44 patients who had OSA without WMC (OSA−WMC), and 31 control subjects who had neither OSA nor WMC were analyzed. Linear and nonlinear indices of heart-rate variability (HRV) were analyzed in each group according to different sleep stages and also over the entire sleeping period.

Results

Among the nonlinear HRV indices, the Poincaré ratio (SD12) during the entire sleep period was significantly increased in the OSA+WMC group, even after age adjustment. Meanwhile, detrended fluctuation analysis 1 during non-rapid-eye-movement sleep tended to be lowest in the OSA+WMC group. These indices were altered regardless of the presence of hypertension or diabetes. In the subgroup analysis of middle-aged OSA patients, approximate entropy during rapid-eye-movement sleep was significantly lower in OSA+WMC patients than in OSA−WMC patients. Overall, the nonlinear HRV indices suggest that sympathetic activity was higher in the OSA+WMC group than in the OSA−WMC and control groups.

Conclusions

Our findings suggest that dysregulation of HRV, especially overactivation of sympathetic tone, could be a pathophysiologic mechanism underlying the development of WMC in OSA patients.

Sudden Unexpected Death During Sleep in Familial Dysautonomia: A Case-Control Study

Study Objectives

Sudden unexpected death during sleep (SUDS) is the most common cause of death in patients with familial dysautonomia (FD), an autosomal recessive disease characterized by sensory and autonomic dysfunction. It remains unknown what causes SUDS in these patients and who is at highest risk. We tested the hypothesis that SUDS in FD is linked to sleep-disordered breathing.

Methods

We retrospectively identified patients with FD who died suddenly and unexpectedly during sleep and had undergone polysomnography within the 18-month period before death. For each case, we sampled one age-matched surviving subject with FD that had also undergone polysomnography within the 18-month period before study. Data on polysomnography, EKG, ambulatory blood pressure monitoring, arterial blood gases, blood count, and metabolic panel were analyzed.

Results

Thirty-two deceased cases and 31 surviving controls were included. Autopsy was available in six cases. Compared with controls, participants with SUDS were more likely to be receiving treatment with fludrocortisone (odds ratio [OR]; 95% confidence interval) (OR 29.7; 4.1-213.4), have untreated obstructive sleep apnea (OR 17.4; 1.5-193), and plasma potassium levels <4 mEq/L (OR 19.5; 2.36-161) but less likely to use noninvasive ventilation at night (OR 0.19; 0.06-0.61).

Conclusions

Initiation of noninvasive ventilation when required and discontinuation of fludrocortisone treatment may reduce the high incidence rate of SUDS in patients with FD. Our findings contribute to the understanding of the link between autonomic, cardiovascular, and respiratory risk factors in SUDS.

The effect of continuous positive airway pressure on heart rate variability during the night in patients with chronic heart failure and central sleep apnoea

Continuous positive airway pressure (CPAP) improves autonomic activity in patients with chronic heart failure (CHF) and central sleep apnoea (CSA), but its effect on heart rate variability (HRV) during therapy has not been reported. We hypothesized that CPAP may decrease HRV, despite its beneficial effects on sympathetic overactivation, due to the expected stabilization of breathing. Sixty-seven CHF patients underwent polysomnography (PSG). Ten of them presented with CSA (age 66.1±8.5 years, apnoea-hypopnea index [AHI]=57.6±23.3, central AHI [cAHI]=41.6±24.6 [mean±SD]) and were subjected to a second PSG with manual CPAP titration. Beat-to-beat heart intervals for a 6-hour period of sleep were extracted from each recording and HRV was analysed. CPAP significantly reduced AHI (AHI=23.1±18.3 P=.004). Standard deviation of normal-normal interbeat interval (SDNN) (61.5±29.0 vs 49.5±19.3 ms, P=.021), root mean square of successive differences (RMSSD) (21.8±9.2 vs 16.4±7.1 ms, P=.042), total power (lnTP=7.8±1.1 vs 7.4±0.8 ms² , P=.037), low frequency power (lnLF=5.5±1.5 vs 5.0±1.4 ms² , P=.003) and high frequency power (lnHF=4.6±1.0 vs 4.0±1.0 ms² , P=.024) were decreased. There was a strong correlation between the decrease in AHI and the decrease in lnHF (Spearman's ρ=.782). CPAP leads to a decrease in spectral and time domain parameters of HRV during therapy in CHF patients with CSA. These changes are best explained by the effect which CPAP-influenced breathing pattern and lowered AHI exert on HRV.

Neurologic Diseases and Sleep

Sleep disorders and neurologic illness are common and burdensome in their own right; when combined, they can have tremendous negative impact at an individual level as well as societally. The socioeconomic burden of sleep disorders and neurologic illness can be identified, but the real cost of these conditions lies far beyond the financial realm. There is an urgent need for comprehensive care and support systems to help with the burden of disease. Further research in improving patient outcomes in those who suffer with these conditions will help patients and their families, and society in general.

Obstructive sleep apnea and arrhythmia: A systemic review

There is a growing consensus in the scientific community that suggests a strong association between obstructive sleep apnea (OSA) and cardiovascular (CVD) conditions and events, including coronary artery disease, hypertension, arrhythmia, heart failure, and sudden cardiac death. We reviewed evidence on the relationship between OSA and arrhythmia. Our conclusion, based on our review of the literature, is that the evidence supports a strong link between OSA and cardiovascular mortality, which warrants treating OSA. Continuous positive airway pressure (CPAP) appears to reduce the CVD consequences of OSA. Future research is expected to clarify the benefits and optimal application of these treatment approaches.

Heart Rate Variability as a Method for Assessment of the Autonomic Nervous System and the Adaptations to Different Physiological and Pathological Conditions

The autonomic nervous system controls the smooth muscles of the internal organs, the cardiovascular system and the secretory function of the glands and plays a major role in the processes of adaptation. Heart rate variability is a non-invasive and easily applicable method for the assessment of its activity. The following review describes the origin, parameters and characteristics of this method and its potential for evaluation of the changes of the autonomic nervous system activity in different physiological and pathological conditions such as exogenous hypoxia, physical exercise and sleep. The application of heart rate variability in daily clinical practice would be beneficial for the diagnostics, the outcome prognosis and the assessment of the effect of treatment in various diseases.

The sympathetic nervous system and catecholamines metabolism in obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is the most common sleep disorder of breathing in middle-aged and overweight subjects. It features recurrent episodes of upper airway total (apnoea) o partial (hypopnea) collapse during sleep, which are associated with a reduction in blood oxygen saturation and with arousal from sleep to re-establish airway patency. An association of OSA with dysregulation of the autonomous nervous system (ANS) and altered catecholamines (CAs) metabolism has been contended for years. However, the pathophysiology mechanisms underlying these alterations remain to be fully clarified. Nonetheless, these alterations are deemed to play a key pathogenic role in the established association of OSA with several conditions besides arterial hypertension (HT), including coronary artery disease, stroke, and, more in general, with increased risk of cardiovascular (CV) events. Hence, in this review we will analyse the relationship between the sleep disturbances associated with OSA and the altered function of the ANS, including CAs metabolism.

Normalizing sleep quality disturbed by psychiatric polypharmacy: a single patient open trial (SPOT)

There is a growing interest in personalized and preventive medicine initiatives that leverage serious patient engagement, such as those initiated and pursued among participants in the quantified-self movement. However, many of the self-assessments that result are not rooted in good scientific practices, such as exploiting controls, dose escalation strategies, multiple endpoint monitoring, etc. Areas where individual monitoring and health assessments have great potential involve sleep and behavior, as there are a number of very problematic sleep and behavior-related conditions that are hard to treat without personalization. For example, winter depression or seasonal affective disorder (SAD) is a serious, recurrent, atypical depressive disorder impacting millions each year. In order to prevent yearly recurrence antidepressant drugs are used to prophylactically treat SAD. In turn, these antidepressant drugs can affect sleep patterns, further exacerbating the condition. Because of this, possibly unique combinatorial or ‘polypharmaceutical’ interventions involving sleep aids may be prescribed. However, little research into the effects of such polypharmacy on the long-term sleep quality of treated individuals has been pursued. Employing wireless monitoring in a patient-centered study we sought to gain insight into the influence of polypharmacy on sleep patterns and the optimal course of therapy for an individual being treated for SAD with duloxetine (Cymbalta) and temazepam. We analyzed continuous-time sleep data while dosages and combinations of these agents were varied. We found that the administration of Cymbalta led to an exacerbation of the subject’s symptoms in a statistically significant way. We argue that such analyses may be necessary to effectively treat individuals with similar overall clinical manifestations and diagnosis, despite their having a unique set of symptoms, genetic profiles and exposure histories. We also consider the limitations of our study and areas for further research.

Impaired sustained attention and lapses are present in patients with mild obstructive sleep apnea

BACKGROUND

Severe obstructive sleep apnea (OSA) directly affects the quality of life, mood, and sustained attention of individuals, but it has not yet been established in the literature, if these changes also affect patients with mild OSA. The purpose of this study was to investigate such negative effects on the parameters described above.

METHODS

A controlled study was held at the Universidade Federal de Sao Paulo, Department of Psychobiology. Thirty-nine mild OSA patients and 25 controls were included. Volunteers could be of both genders with body mass index (BMI) ≤35 kg/m(2) and age between 18 and 65 years. Both groups were subjected to full-night polysomnography (PSG), the subjective assessment of mood (Beck Inventory of Anxiety and Depression), Functional Outcomes of Sleep Questionnaire (FOSQ), and the psychomotor vigilance task (PVT) five times during the day. We considered mild OSA patients those with apnea-hypopnea index (AHI) score between 5 and 15. The control group included subjects with AHI scores <5, respiratory disturbance index (RDI) scores ≤5, arousal index values ≤15, and Epworth Sleepiness Scale (ESS) values ≤9.

RESULTS

Mild OSA patients were older and more obese than the controls. After adjusting for age, BMI, and schooling years, there was an increased number of total lapses (3.90 ± 4.16 and 2.43 ± 5.55, p = 0.004).

CONCLUSIONS

Patients with mild OSA showed increased sustained attention lapses compared with normal subjects.

AD, Costa FSM, Bianchi AM. Are Complexity Metrics Reliable in Assessing HRV Control in Obese Patients During Sleep?

Obesity is associated with cardiovascular mortality. Linear methods, including time domain and frequency domain analysis, are normally applied on the heart rate variability (HRV) signal to investigate autonomic cardiovascular control, whose imbalance might promote cardiovascular disease in these patients. However, given the cardiac activity non-linearities, non-linear methods might provide better insight. HRV complexity was hereby analyzed during wakefulness and different sleep stages in healthy and obese subjects. Given the short duration of each sleep stage, complexity measures, normally extracted from long-period signals, needed be calculated on short-term signals. Sample entropy, Lempel-Ziv complexity and detrended fluctuation analysis were evaluated and results showed no significant differences among the values calculated over ten-minute signals and longer durations, confirming the reliability of such analysis when performed on short-term signals. Complexity parameters were extracted from ten-minute signal portions selected during wakefulness and different sleep stages on HRV signals obtained from eighteen obese patients and twenty controls. The obese group presented significantly reduced complexity during light and deep sleep, suggesting a deficiency in the control mechanisms integration during these sleep stages. To our knowledge, this study reports for the first time on how the HRV complexity changes in obesity during wakefulness and sleep. Further investigation is needed to quantify altered HRV impact on cardiovascular mortality in obesity.

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.