Physiological Consequences of Upper Airway Obstruction in Sleep Apnea

OSA is diagnosed and managed by a metric called the apnea-hypopnea index (AHI). The AHI quantifies the number of respiratory events (apnea or hypopnea), disregarding important information on the characteristics and physiological consequences of respiratory events, including degrees of ventilatory deficit and associated hypoxemia, cardiac autonomic response, and cortical activity. The oversimplification of the disorder by the AHI is considered one of the reasons for divergent findings on the associations of OSA and cardiovascular disease (CVD) in observational and randomized controlled trial studies. Prospective observational cohort studies have demonstrated strong associations of OSA with several cardiovascular diseases, and randomized controlled trials of CPAP intervention have not been able to detect a benefit of CPAP to reduce the risk of CVD. Over the last several years, novel methodologies have been proposed to better quantify the magnitude of OSA-related breathing disturbance and its physiological consequences. As a result, stronger associations with cardiovascular and neurocognitive outcomes have been observed. In this review, we focus on the methods that capture polysomnographic heterogeneity of OSA.

Prevalence of temporomandibular disorders in adult obstructive sleep apnoea patients: A cross-sectional controlled study

BACKGROUND

Obstructive sleep apnoea (OSA) is characterised by partial or complete obstruction of the upper airways during sleep and it has been associated with temporomandibular disorders (TMDs) on the basis of several pathophysiological hypotheses.

OBJECTIVES

To assess the prevalence of TMDs in a population of patients affected by OSA compared to a control group of subjects not affected by OSA.

METHODS

A cross-sectional controlled study was conducted on a group subjects studied by polygraphy (PG) at the snoring section of the ENT department, Sant'Orsola-Malpighi Hospital - University of Bologna. Patients who received a diagnosis of OSA were included in the study group and subjects with a negative PG diagnosis for Sleep Disordered Breathing and PG respiratory pattern that did not suggest the occurrence of sleep disorders were enrolled in the control group. Both the subjects included in the study group and the control group underwent an examination following the Diagnostic Criteria for Temporomandibular Disorders Axis I and II.

RESULTS

Forty-three OSA patients (29 M, 16 F, mean age 52.26 ± 11.40) and 43 healthy controls (25 M, 18 F, mean age 49.95 ± 7.59) were included in the study. No significant differences were found between groups in demographic data. TMD prevalence and Axis II results did not differ between groups.

CONCLUSIONS

This paper does not highlight a higher prevalence of TMDs in adults with OSA compared to healthy controls. Further high-quality studies are needed to confirm the results and to give possible pathophysiological explanations, providing reliable evidence.

Immediate Physiological Responses to Inspiratory Flow Limited Events in Mild Obstructive Sleep Apnea

Rationale: Inspiratory flow limitation (IFL), characterized by flattening of individual breaths on the airflow/time tracing, is a noninvasive indicator of elevated upper airway resistance. An IFL "event" in isolation has not been defined, nor has the ability to reproducibly identify event occurrence been tested. IFL events and their association with immediate physiological responses-as well as the impact of characteristics such as age, sex, sleep stage, sleepiness, and event duration on their association with such outcomes-have not been studied. Symptomatic patients with a normal to mildly abnormal apnea-hypopnea index who have predominant IFL on their polysomnography may benefit from treatment. Objectives: To test the reproducibility of identifying IFL events and their termination and to determine the frequency of the immediate physiological response to their occurrence, including desaturation, electroencephalography (EEG) arousal, and increased heart rate (HR). Methods: Fifty-eight patients with obstructive sleep apnea (OSA) underwent full diagnostic polysomnography. IFL events and their termination were identified manually using predefined rules from the unscored nasal cannula flow channel alone and were evaluated for responses such as EEG arousal, oxygen desaturation of ⩾3%, and HR increase. Results: Interscorer reliability was acceptable, with an average percent agreement for occurrence of 82% ± 3%. Of all IFL events, 24% (regardless of the definition) were not associated with an EEG arousal, an increase in HR, or O₂ desaturation. Of all IFL events scored, 25% caused O₂ desaturation, 40% were associated with an EEG arousal, and 55% were associated with an increase in HR; 67% caused either an EEG arousal and/or an increase in HR. Responses were observed to occur either in isolation or in combination. IFL events that terminated with at least two non-IFL breaths, one of which had a 200% increase in amplitude, were significantly associated with O₂ desaturation, EEG arousal, and increase in HR compared with events that ended in one non-IFL breath. IFL events that had a >50% reduction in flow amplitude compared with baseline were significantly associated with O₂ desaturation compared with events that had a 30% reduction or less. Conclusions: Most IFL events resulted in immediate physiological responses, and no single consequence reliably occurred after every event. We propose a framework that can incorporate the scoring of IFL events into assessing the diagnosis and severity of OSA and suggest that no single consequence be used to define IFL as a respiratory event. The relationship of IFL events to OSA outcomes remains to be tested.

Quality of life in upper airway resistance syndrome

STUDY OBJECTIVES

to evaluate the health-related quality of life (HRQoL) in patients with upper airway respiratory syndrome (UARS) and obstructive sleep apnea (OSA) compared to the general population (GP) in Lima, Peru. To explore the variables associated with differences in HRQoL in UARS patients.

METHODS

retrospective study of medical and polysomnography (PSG) records from 2009-2014 in a referral sleep medicine center for patients aged 18-64 years. UARS was defined by PSG: apnea-hypopnea index (AHI) <5, oxygen saturation ≥92%, respiratory effort-related arousals (RERAs) index ≥5. HRQoL was assessed with the SF-36v1 questionnaire validated in Peru. GP HRQoL was obtained from a population-based survey. Linear and logistic regression analyses were conducted.

RESULTS

1329 PSG were reviewed and 888 selected. UARS and OSA were diagnosed in 93 and 795 participants, respectively. The GP cohort consisted of 641 participants. Total HRQoL mean scores (95% confidence interval) in UARS, OSA, and GP were 67.4 (63.7-71.1), 66.9 (65.4-68.4), and 82.9 (81.6-84.3), respectively. UARS and OSA patients had 5.5 times (CI 3.3-9.2) and 6.2 times (CI 4.6-8.4) greater probability of having a low total HRQoL score compared to the GP. In UARS patients, muscle pain, use of psychotropic medication, obesity, and depression were negatively correlated with the total HRQoL score.

CONCLUSIONS

the impact of OSA and UARS on HRQoL is similar between disease groups and markedly worse when compared to the GP. In patients with UARS, the presence of muscle pain, obesity, female sex, depression, or the use of psychotropic medication negatively impacted HRQoL.

Automatic detection of respiratory events during sleep from Polysomnography data using Layered Hidden Markov Model

OBJECTIVE

Sleep apnea is a serious respiratory disorder, which is associated with increased risk factors for cardiovascular disease. Many studies in recent years have been focused on automatic detection of sleep apnea from polysomnography (PSG) recordings, however, detection of subtle respiratory events named Respiratory Event Related Arousals (RERAs) that do not meet the criteria for apnea or hypopnea is still challenging. The objective of this study was to develop automatic detection of sleep apnea based on Hidden Markov Models (HMMs) which are probabilistic models with the ability to learn different dynamics of the real time-series such as clinical recordings.

APPROACH

In this study, a hierarchy of HMMs named Layered HMM was presented to detect respiratory events from PSG recordings. The recordings of 210 PSGs from Massachusetts General Hospital's database were used for this study. To develop detection algorithms, extracted feature signals from airflow, movements over the chest and abdomen, and oxygen saturation in blood (SaO2) were chosen as observations. The respiratory disturbance index (RDI) was estimated as the number of apneas, hypopneas, and RERAs per hour of sleep.

MAIN RESULTS

The best F1 score of the event by event detection algorithm was between 0.22±0.16 and 0.70±0.08 for different groups of sleep apnea severity. There was a strong correlation between the estimated and the PSG-derived RDI (R2=0.91, p<0.0001). The best recall of RERA detection was achieved 0.45±0.27.

SIGNIFICANCE

The results showed that the layered structure can improve the performance of the detection of respiratory events during sleep.

The efficacy of surgery for upper airway resistance syndrome: A systematic review, meta-analysis and case series

PURPOSE

Upper airway resistance syndrome (UARS) is a sleep related breathing disorder that was first described in 1993. This goal of this study is to determine the efficacy of surgical intervention for UARS.

MATERIALS AND METHODS

Systematic review of the literature and a case series of UARS patients at a large integrated healthcare system. Meta-analysis was performed.

RESULTS

For the systematic review, 971 abstracts were reviewed and 3 articles were included, yielding 49 subjects. All of the included studies were of level 3 or 4 evidence. Significant improvement in Epworth Sleepiness Scale (ESS) score was noted after surgery in two level 4 studies. No significant change in ESS was noted in one level 3 study. Our retrospective chart review of eleven UARS patients compared preoperative and postoperative ESS scores, as well as sleep study data. Patients underwent a variety of surgical procedures. Our findings show a significant improvement in mean ESS scores after surgery, from 11.0 (±3.5) to 7.0 (±4.8) with p = 0.01, though no difference in apnea hypopnea index (AHI) and respiratory disturbance index (RDI) were identified. Meta-analysis was performed on 2 studies from the systematic review and our cases series data. UARS surgery showed a mean change in ESS of -5.89 (95% CI, -8.29 to -3.50).

CONCLUSIONS

This systematic review, meta-analysis and retrospective case series indicate that surgery may improve ESS scores in patients with UARS. AHI and RDI are unlikely to be impacted by surgery.

Altered K-complex morphology during sustained inspiratory airflow limitation is associated with next-day lapses in vigilance in obstructive sleep apnea

STUDY OBJECTIVES

Determine if changes in K-complexes associated with sustained inspiratory airflow limitation (SIFL) during N2 sleep are associated with next-day vigilance and objective sleepiness.

METHODS

Data from thirty subjects with moderate-to-severe obstructive sleep apnea who completed three in-lab polysomnograms: diagnostic, on therapeutic continuous positive airway pressure (CPAP), and on suboptimal CPAP (4 cmH2O below optimal titrated CPAP level) were analyzed. Four 20-min psychomotor vigilance tests (PVT) were performed after each PSG, every 2 h. Changes in the proportion of spontaneous K-complexes and spectral characteristics surrounding K-complexes were evaluated for K-complexes associated with both delta (∆SWAK), alpha (∆αK) frequencies.

RESULTS

Suboptimal CPAP induced SIFL (14.7 (20.9) vs 2.9 (9.2); %total sleep time, p < 0.001) with a small increase in apnea-hypopnea index (AHI3A: 6.5 (7.7) vs 1.9 (2.3); p < 0.01) versus optimal CPAP. K-complex density (num./min of stage N2) was higher on suboptimal CPAP (0.97 ± 0.7 vs 0.65±0.5, #/min, mean ± SD, p < 0.01) above and beyond the effect of age, sex, AHI3A, and duration of SIFL. A decrease in ∆SWAK with suboptimal CPAP was associated with increased PVT lapses and explained 17% of additional variance in PVT lapses. Within-night during suboptimal CPAP K-complexes appeared to alternate between promoting sleep and as arousal surrogates. Electroencephalographic changes were not associated with objective sleepiness.

CONCLUSIONS

Sustained inspiratory airflow limitation is associated with altered K-complex morphology including the increased occurrence of K-complexes with bursts of alpha as arousal surrogates. These findings suggest that sustained inspiratory flow limitation may be associated with nonvisible sleep fragmentation and contribute to increased lapses in vigilance.

Frequency of flow limitation using airflow shape

STUDY OBJECTIVES

The presence of flow limitation during sleep is associated with adverse health consequences independent of obstructive sleep apnea (OSA) severity (apnea-hypopnea index, AHI), but remains extremely challenging to quantify. Here we present a unique library and an accompanying automated method that we apply to investigate flow limitation during sleep.

METHODS

A library of 117,871 breaths (N=40 participants) were visually classified (certain flow limitation, possible flow limitation, normal) using airflow shape and physiological signals (ventilatory drive per intra-esophageal diaphragm EMG). An ordinal regression model was developed to quantify flow limitation certainty using flow-shape features (e.g. flattening, scooping); breath-by-breath agreement (Cohen's ƙ) and overnight flow limitation frequency (R 2, %breaths in certain or possible categories during sleep) were compared against visual scoring. Subsequent application examined flow limitation frequency during arousals and stable breathing, and associations with ventilatory drive.

RESULTS

The model (23 features) assessed flow limitation with good agreement (breath-by-breath ƙ=0.572, p<0.001) and minimal error (overnight flow limitation frequency R 2=0.86, error=7.2%). Flow limitation frequency was largely independent of AHI (R 2=0.16) and varied widely within individuals with OSA (74[32-95]%breaths, mean[range], AHI>15/hr, N=22). Flow limitation was unexpectedly frequent but variable during arousals (40[5-85]%breaths) and stable breathing (58[12-91]%breaths), and was associated with elevated ventilatory drive (R 2=0.26-0.29; R 2<0.01 AHI v. drive).

CONCLUSIONS

Our method enables quantification of flow limitation frequency, a key aspect of obstructive sleep-disordered breathing that is independent of the AHI and often unavailable. Flow limitation frequency varies widely between individuals, is prevalent during arousals and stable breathing, and reveals elevated ventilatory drive.

Use of the WatchPAT to detect occult residual sleep-disordered breathing in patients on CPAP for obstructive sleep apnea

STUDY OBJECTIVES

To determine the accuracy of the apnea-hypopnea index (AHI) as measured by continuous positive airway pressure (CPAP) machines by simultaneously employing a home sleep apnea testing device (WatchPAT 200, Itamar Medical, Israel [WPAT]) in patients suspected of having residual sleep-disordered breathing (SDB).

METHODS

Patients with new, recurrent, or worsening signs, symptoms, or comorbidities associated with obstructive sleep apnea underwent home sleep apnea testing using WPAT while simultaneously using CPAP at their usual prescribed settings. CPAP AHI and WPAT AHI, respiratory disturbance index, and oximetry readings were then compared.

RESULTS

We identified an elevated AHI with WPAT testing in nearly half of patients with clinically suspected residual SDB and a normal CPAP AHI. WPAT detected additional respiratory events as well, including rapid eye movement-related apneas, respiratory effort-related arousals, and hypoxemia.

CONCLUSIONS

WPAT AHI was significantly higher than simultaneous CPAP AHI in nearly half of those patients with clinically suspected residual SDB being treated with CPAP. Additional respiratory disturbances, including rapid eye movement-related respiratory events, respiratory effort-related arousals, and hypoxemia, were elucidated only with the use of the WPAT. Residual SDB may have potential clinical consequences, including reduced CPAP adherence, ongoing hypersomnolence, and other health-related sequelae. Simultaneous WPAT testing of patients with a normal CPAP AHI may represent a valuable tool to detect clinically suspected residual SDB or to ensure adequate treatment in high-risk patients with obstructive sleep apnea in general.

Dissociation between objectively quantified snoring and sleep quality

BACKGROUND

The impact of simple snoring on sleep structure and sleepiness has not been well described. In several studies, self-reported snoring was associated with increased daytime sleepiness. However, most studies did not distinguish patients with simple snoring from those with coexisting obstructive sleep apnea (OSA) using objective measures. We therefore evaluated the relationship between objectively measured snoring and both sleep structure and daytime sleepiness in patients with no or mild OSA.

METHODS

Subjects referred for suspected sleep disorders underwent polysomnography (PSG) during which breath sounds were recorded by a microphone. Those with an apnea-hypopnea index (AHI) <15/h were analyzed. Individual snores were identified by a computer algorithm, from which the snore index (SI) was calculated as the number of snores/h of sleep. Sleep stages and arousals were quantified. Daytime sleepiness was evaluated using the Epworth Sleepiness Scale (ESS) score.

RESULTS

74 (35 males) subjects were included (age, mean ± SD: 46.4 ± 15.3 years and body mass index: 29.8 ± 7.0 kg/m²). The mean SI was 266 ± 243 snores/h. Subjects were categorized according to their SI into 3 tertiles: SI < 100, between 100-350, and >350. No sleep structure indeces, arousals, or ESS score differed among SI tertiles (p > 0.13). There was no correlation between SI and any of these variables (p > 0.29). In contrast, the AHI was significantly related to frequency of arousals (r = 0.23, p = 0.048).

CONCLUSIONS

These findings suggest that simple snoring assessed objectively is not related to indices of sleep structure or subjective sleepiness.

Continuous positive airway pressure versus standard care for the treatment of people with mild obstructive sleep apnoea (MERGE): a multicentre, randomised controlled trial

BACKGROUND

The evidence base for the treatment of mild obstructive sleep apnoea is limited and definitions of disease severity vary. The MERGE trial investigated the clinical effectiveness of continuous positive airway pressure in patients with mild obstructive sleep apnoea.

METHODS

MERGE, a multicentre, parallel, randomised controlled trial enrolled patients (≥18 years to ≤80 years) with mild obstructive sleep apnoea (apnoea-hypopnoea index [AHI] ≥5 to ≤15 events per h using either AASM 2007 or AASM 2012 scoring criteria) from 11 UK sleep centres. Participants were assigned (1:1) to either 3 months of continuous positive airway pressure plus standard care (sleep counselling), or standard care alone, by computer-generated randomisation; neither participants nor researchers were blinded. The primary outcome was a change in the score on the Short Form-36 questionnaire vitality scale in the intention-to-treat population of patients with mild obstructive sleep apnoea diagnosed using the American Academy of Sleep Medicine 2012 scoring criteria. The study is registered with ClinicalTrials.gov, NCT02699463.

FINDINGS

Between Nov 28, 2016 and Feb 12, 2019, 301 patients were recruited and randomised. 233 had mild obstructive sleep apnoea using AASM 2012 criteria and were included in the intention-to-treat analysis: 115 were allocated to receive continuous positive airway pressure and 118 to receive standard care. 209 (90%) of these participants completed the trial. The vitality score significantly increased with a treatment effect of a mean of 10·0 points (95% CI 7·2-12·8; p<0·0001) after 3 months of continuous positive airway pressure, compared with standard care alone (9·2 points [6·8 to 11·6] vs -0·8 points [-3·2 to 1·5]). Using the ANCOVA last-observation-carried-forward analysis, a more conservative estimate, the vitality score also significantly increased with a treatment effect of a mean of 7·5 points (95% CI 5·3 to 9·6; p<0·0001) after 3 months of continuous positive airway pressure, compared with standard care alone (7·5 points [6·0 to 9·0] vs 0·0 points [-1·5 to 1·5]). Three serious adverse events occurred (one allocated to the continuous positive airway pressure group) and all were unrelated to the intervention.

INTERPRETATION

3 months of treatment with continuous positive airway pressure improved the quality of life in patients with mild obstructive sleep apnoea. These results highlight the need for health-care professionals and providers to consider treatment for patients with mild obstructive sleep apnoea.

FUNDING

ResMed Ltd.

[Sleep-related breathing disorders in adults: diagnosis, consequences and comorbidities]

Obstructive sleep apnea/hypopnea syndrome (OSAHS) is a collapse of the upper airways leading to a decrease (hypopneas) or interruption of air flow (apneas). Since its identification, only forty years ago, definitions, diagnostic techniques have evolved, the consequences of this syndrome have been widely studied but establishing it as an independent cardiovascular (CV) risk factor has come up against the existence of many confounding factors, such as obesity, high blood pressure (hypertension)… Paraclinical diagnosis is based on the results of poly(somno)graphy. Recommendations on measurement techniques and scoring are regularly published, evolving in parallel with technological progress, with the aim of standardizing and ensuring the reliability of the diagnosis. At the same time, large cohort studies were set up in the 1990s, allowing for transversal and longitudinal follow-up of thousands of patients. Finally, the pathophysiological mechanisms of the consequences of SAHOS were explored. OSA has been shown to be responsible for a particularly high accidental risk due to sleep fragmentation induced by abnormal respiratory events. It has been possible to establish an independent statistical relationship between SAHOS and CV diseases, metabolic disorders and more recently cancer, mainly explained by intermittent hypoxia. OSAHOS is a frequent disease, diagnosed on the basis of clinical signs and poly(somno)graphy, now established as an independent risk factor for morbidity and mortality (accidental and CV).

High-Resolution Pulse Oximetry and Titration of a Mandibular Advancement Device for Obstructive Sleep Apnea

Background: To determine whether utilizing high-resolution pulse oximetry is a viable method for evaluating the successful titration of oral appliances for the treatment of obstructive sleep apnea (OSA) patients.

Methods: Of 136 consecutive potentially eligible OSA patients, 133 were fitted with mandibular advancement devices (MADs), and 101 completed all phases of treatment. The vertical and horizontal dimensions of the appliances were adjusted based on three-nights with a high-resolution pulse oximeter during sleep and associated software after each adjustment.

Results: Significant improvements in OSA severity were apparent in patients at all disease severity levels. High-resolution pulse oximetry provided reliable guidance in the titration process of mandibular advancement therapy. In 67 subjects (66.3%), a respiratory event index of <5 events/hour was achieved.

Conclusions: OSA can be effectively treated with a MAD at any severity level, and high-resolution pulse oximetry provides critical information to guide oral appliance titration.

Quantifying the magnitude of pharyngeal obstruction during sleep using airflow shape

Rationale and objectives

Non-invasive quantification of the severity of pharyngeal airflow obstruction would enable recognition of obstructiveversuscentral manifestation of sleep apnoea, and identification of symptomatic individuals with severe airflow obstruction despite a low apnoea–hypopnoea index (AHI). Here we provide a novel method that uses simple airflow-versus-time (“shape”) features from individual breaths on an overnight sleep study to automatically and non-invasively quantify the severity of airflow obstruction without oesophageal catheterisation.

Methods

41 individuals with suspected/diagnosed obstructive sleep apnoea (AHI range 0–91 events·h−1) underwent overnight polysomnography with gold-standard measures of airflow (oronasal pneumotach: “flow”) and ventilatory drive (calibrated intraoesophageal diaphragm electromyogram: “drive”). Obstruction severity was defined as a continuous variable (flow:drive ratio). Multivariable regression used airflow shape features (inspiratory/expiratory timing, flatness, scooping, fluttering) to estimate flow:drive ratio in 136 264 breaths (performance based on leave-one-patient-out cross-validation). Analysis was repeated using simultaneous nasal pressure recordings in a subset (n=17).

Results

Gold-standard obstruction severity (flow:drive ratio) varied widely across individuals independently of AHI. A multivariable model (25 features) estimated obstruction severity breath-by-breath (R2=0.58versusgold-standard, p<0.00001; mean absolute error 22%) and the median obstruction severity across individual patients (R2=0.69, p<0.00001; error 10%). Similar performance was achieved using nasal pressure.

Conclusions

The severity of pharyngeal obstruction can be quantified non-invasively using readily available airflow shape information. Our work overcomes a major hurdle necessary for the recognition and phenotyping of patients with obstructive sleep disordered breathing.

Sleep-disordered breathing and stroke: chicken or egg?

The bidirectional interaction between sleep-disordered breathing (SDB) and stroke has been the subject of many studies. On the one hand, different forms of SDB, and especially obstructive sleep apnea, increase the risk of stroke either directly or indirectly by influencing other known cardiovascular risk factors such as arterial hypertension and arrhythmias. On the other hand, stroke itself can cause either de novo appearance of SDB, aggravate a pre-existing SDB, or trigger a transition from one type of pathological SDB pattern into another. In this review, we discuss some aspects of this "chicken or egg" relationship.

Prevalence and Clinical Significance of Respiratory Effort-Related Arousals in the General Population

STUDY OBJECTIVES

To determine the prevalence and clinical associations of respiratory effort-related arousals (RERA) in a general population sample.

METHODS

A total of 2,162 participants (51.2% women, 58.5 ± 11.0 years old, body mass index [BMI] 25.6 ± 4.2 kg/m²) of a general population-based cohort (HypnoLaus, Switzerland) underwent full polysomnography at home. Each subject with a RERA index ≥ 5 events/h was compared with an age-, sex- and apnea-hypopnea index (AHI)-matched control without RERA.

RESULTS

A RERA index ≥ 5 events/h was present in 84 participants (3.8%; 95% confidence interval: 3.2-4.8%). In 17 participants (0.8%; 95% confidence interval: 0.5-1.3%), RERAs were the predominant sleep breathing disorder and only one of them complained of excessive daytime sleepiness. Compared to matched controls, subjects with a RERA index ≥ 5 events/h were similar in terms of BMI (26.5 ± 3.5 versus 26.3 ± 4.8 kg/m², P = .73), neck circumference (38.5 ± 3.3 versus 37.6 ± 3.7 cm, P = .10) and Epworth Sleepiness Scale score (6.7 ± 3.7 versus 6.0 ± 3.7, P = .22). Also, no differences were found for hypertension (21.4% versus 27.4%, P = .47), diabetes (7.1% versus 7.1%, P = 1.00), or metabolic syndrome (31.0% versus 23.8%, P = .39).

CONCLUSIONS

In a middle-aged population-based cohort, the prevalence of a RERA index ≥ 5 events/h was low (3.8%) and was not associated with negative clinical outcomes when using the currently recommended scoring criteria of the American Academy of Sleep Medicine.

Electrocardiographic variables in children with syndromic craniosynostosis and primary snoring to mild obstructive sleep apnea: significance of identifying respiratory arrhythmia during sleep

BACKGROUND

In the spectrum of children with symptomatic sleep disordered breathing (SDB), some individuals - such as those with upper airway resistance syndrome (UARS) - do not have abnormalities on polysomnography (PSG). In this study we have assessed whether assessment of respiratory arrhythmia (RA) and heart rate variability (HRV) analysis helps in management of children with syndromic craniosynostosis and none-to-mild obstructive sleep apnea (OSA).

METHODS

Prospective cohort study in children aged 1-18 years old with syndromic craniosynostosis. Children were selected for HRV analysis from the ECG if their obstructive apnea-hypopnea index (oAHI) was between zero and five per hour (ie, oAHI ≤5/hour). Subjects were divided into groups based on the presence or absence of respiratory arrhythmia (with or without RA respectively) using the electrocardiogram (ECG). The main analysis included studying the relationship between RA and HRV, symptoms, interventions, and sleep architecture.

RESULTS

We identified 42 patients with, at worst, mild OSA. We found higher parasympathetic control and higher total power in children with RA during the non-rapid eye movement (non-REM) sleep. Children with RA also have a relatively higher percentage of paradoxical breathing during non-REM sleep (P = 0.042). Intracranial hypertension was distributed equally between groups. Last, RA patients showed increased parasympathetic activity that further increased in non-REM sleep.

CONCLUSION

In syndromic craniosynostosis cases with SDB and PSG showing oAHI ≤5/hour, the presence of RA may indicate subsequent need for treatment interventions, and a trend toward higher occurrence of clinical symptoms. ECG analyses of HRV variables in subjects with RA demonstrate increased parasympathetic activity and total power. Such findings may add to the diagnosis of apparently asymptomatic children.

An Official American Thoracic Society Workshop Report: Noninvasive Identification of Inspiratory Flow Limitation in Sleep Studies

This report summarizes the proceedings of the American Thoracic Society Workshop on the Noninvasive Identification of Inspiratory Flow Limitation in Sleep Studies held on May 16, 2015, in Denver, Colorado. The goal of the workshop was to discuss methods for standardizing the scoring of flow limitation from nasal cannula pressure tracings. The workshop began with presentations on the physiology underlying flow limitation, existing methods of scoring flow limitation, the effects of signal acquisition and filtering on flow shapes, and a review of the literature examining the adverse outcomes related to flow limitation. After these presentations, the results from online scoring exercises, which were crowdsourced to workshop participants in advance of the workshop, were reviewed and discussed. Break-out sessions were then held to discuss potential algorithms for scoring flow limitation. Based on these discussions, subsequent online scoring exercises, and webinars after the workshop, a consensus-based set of recommendations for a scoring algorithm for flow limitation was developed. Key conclusions from the workshop were: (1) a standardized and automated approach to scoring flow limitation is needed to provide a metric of nonepisodic elevated upper airway resistance, which can then be related to clinical outcomes in large cohorts and patient groups; (2) at this time, the most feasible method for standardization is by proposing a consensus-based framework, which includes scoring rules, developed by experts (3) hardware and software settings of acquisition devices, including filter settings, affect the shape of the flow curve, and should be clearly specified; and (4) a priority for future research is the generation of an open-source, expert-derived training set to encourage and support validation of automated flow limitation scoring algorithms.

Phenotyping the pathophysiology of obstructive sleep apnea using polygraphy/polysomnography: a review of the literature

Continuous positive airway pressure (CPAP) is the first-line treatment for the majority of patients affected by obstructive sleep apnea syndrome (OSA). However, long-term compliance with CPAP therapy may result limited and alternatives to CPAP therapy are required to address the increasing need to provide tailored therapeutic options. Understanding the pathophysiological traits (PTs) of OSA patients [upper airway (UA) anatomical collapsibility, loop gain (LG), arousal threshold (AT), and UA gain (UAG)] lies at the heart of the customized OSA treatment. However, sleep research laboratories capable to phenotype OSA patients are sparse and the diagnostic procedures time-consuming, costly, and requiring significant expertise. The question arises whether the use of routine clinical polysomnography or nocturnal portable multi-channel monitoring (PSG/PM) can provide sufficient information to characterize the above traits. The aim of the present review is to deduce if the information obtainable from the clinical PSG/PM analysis, independently of the scope and context of the original studies, is clinically useful to define qualitatively the PTs of individual OSA patients. In summary, it is possible to identify four patterns using PSG/PM that are consistent with an altered UA collapsibility, three that are consistent with altered LG, two with altered AT, and three consistent with flow limitation/UA muscle response. Furthermore, some PSG/PM indexes and patterns, useful for the suitable management of OSA patient, have been discussed. The delivery of this clinical approach to phenotype pathophysiological traits will allow patients to benefit in a wider range of sleep services by facilitating tailored therapeutic options.

Interpretation of sleep studies for patients with sleep-disordered breathing: What the anesthesiologist needs to know

There is increased interest in the perioperative management of patients with sleep-disordered breathing (SDB). Anesthesiologists must distill information from clinical reports to make key decisions for optimizing perioperative care. A patient with SDB may present with a sleep study report at the time of surgery. Knowledge of the essential components of such a report can help the anesthesiologist evaluate the patient and optimize the perioperative management. In this narrative review, we describe how level I (i.e., laboratory-based) polysomnography (PSG) data are collected and scored using the recommended scoring guidelines, as well as the basic information and salient features of a typical PSG report relevant to the anesthesiologist. In addition, we briefly review the indications for sleep studies, including the types of laboratory-based studies, as well as the role and limitations of portable monitors (level II-IV studies) and examples of PSG reports in the clinical context.

Patterns of Upper Airway Obstruction on Drug-Induced Sleep Endoscopy in Patients with Sleep-Disordered Breathing with AHI <5

Objective

To describe the patterns of upper airway obstruction in patients with sleep-disordered breathing with apnea-hypopnea index (AHI) <5 using drug-induced sleep endoscopy (DISE).

Study Design

Retrospective study.

Setting

Tertiary care center.

Subjects and Methods

Inclusion of patients with sleep-disordered breathing with AHI <5 on polysomnography who underwent DISE. Patients <18 years of age were excluded. DISE findings were reported with the VOTEL classification system: the level of collapse was described as occurring at the velum, oropharynx, tongue base, epiglottis, and the lingual tonsils. The degree of collapse was reported as complete, partial, or none. The pattern of the obstruction was described as anteroposterior, lateral, or concentric when applicable.

Results

A total of 54 patients with sleep-disordered breathing with AHI <5 underwent DISE. Ages ranged from 19 to 65 years. DISE was performed alone in 7% (n = 4) of patients and in conjunction with surgery in 93% (n = 50) of patients. The velum was the most frequent site of upper airway obstruction (85%, n = 46), followed by base of tongue (63%, n = 34), epiglottis (39%, n = 21), lingual tonsils (35%, n = 19), and oropharynx (31%, n = 17). Eighty-three percent (n = 45) of patients had multiple levels of upper airway obstruction, and 15% (n = 8) had a single level of upper airway obstruction.

Conclusion

Patients with sleep-disordered breathing with AHI <5 have significant upper airway obstruction as seen on DISE. DISE findings indicate that a majority of these patients have multiple levels of upper airway obstruction, which can lead to significant symptoms.

Sex differences in sleep disordered breathing in adults

The prevalence of sleep disordered breathing is greater in men compared to women. This disparity could be due to sex differences in the diagnosis and presentation of sleep apnea, and the pathophysiological mechanisms that instigate this disorder. Women tend to report more non-typical symptoms of sleep apnea compared to men, and the presentation of apneic events are more prevalent in rapid compared to non-rapid eye movement sleep. In addition, there is evidence of sex differences in upper airway structure and mechanics and in neural mechanisms that impact on the control of breathing. The purpose of this review is to summarize the literature that addresses sex differences in sleep-disordered breathing, and to discuss the influence that upper airway mechanics, chemoreflex properties, and sex hormones have in modulating breathing during sleep in men and women.

Effectiveness of Oral Appliances in Obstructive Sleep Apnea with Respiratory Arousals

STUDY OBJECTIVES

To compare adherence and treatment effects with an oral appliance (OA) in patients with different types of obstructive sleep apnea (OSA): those with mainly respiratory arousals ("arousers"), and those with oxygen desaturations ("desaturaters") at polysomnography (PSG).

METHODS

A prospective intervention study on 72 "tired snorers" with "normal" home sleep study (HSS), but later diagnosed as OSA with PSG, who accepted OA treatment. They were offered evaluation with a follow-up PSG and questionnaires, including the Epworth Sleepiness Scale (ESS), general health (GH), satisfaction, and side effects.

RESULTS

Sixty-six patients, 33 arousers and 33 desaturaters, were adapted to OA. The 1-year adherence rate was significantly higher among arousers (85%) than desaturaters (55%) (p = 0.034). Thirty-six of 66 patients underwent follow-up PSG; the apnea-hypopnea index was significantly reduced in 22 arousers from a median of 14 to 3 (p < 0.001), and in 14 desaturaters from 18 to 7 (p = 0.002; no significant group difference). ESS and GH showed no significant improvements in either group, although sleepy "arousers" (ESS ≥ 10) significantly improved their ESS. In total, 77% reported side effects, while 63% were still satisfied with the OA treatment. Gender analysis showed a significant dominance of females classified as "arousers" (p = 0.025).

CONCLUSIONS

OSA patients with mainly arousals at PSG showed higher adherence to OA treatment, compared to patients with desaturations. Both groups responded similarly to treatment: improved nocturnal respiration, but only a small reduction of symptoms. We suggest that "tired snorers" with "normal HSS" should be offered PSG, and if OSA, also OA treatment.

Impact of obstructive sleep apnoea on insulin resistance in nonobese and obese children

Obstructive sleep apnoea (OSA) has been inconsistently associated with insulin resistance and adverse metabolic states. We aimed to assess independent contributions of OSA to insulin resistance and dyslipidaemia in a large paediatric cohort.

Habitually snoring children underwent overnight polysomnography, anthropometric measurements and fasting laboratory evaluations. Primary outcome measures included insulin, glucose, homeostasis model of insulin resistance, lipoproteins and sleep disturbance measures.

Among 459 children aged 5–12 years, obesity was the primary driver of most associations between OSA and metabolic measures, but sleep duration was inversely associated with glucose levels, with N3 and rapid eye movement (REM) sleep being negatively associated and sleep fragmentation positively associated with insulin resistance measures. In children with mild OSA, the presence of obesity increased the odds for insulin resistance, while higher apnoea/hypopnoea index values emerged among obese children who were more insulin-resistant.

The exclusive presence of interactions between OSA and obesity in the degree of insulin resistance is coupled with synergistic contributions by sleep fragmentation to insulin resistance in the context of obesity. Insufficient N3 or REM sleep may also contribute to higher glycaemia independently of obesity. Studies are needed to better delineate the roles of puberty and sleep fragmentation in insulin resistance and the metabolic syndrome.

Myofunctional therapy applied to upper airway resistance syndrome: a case report

The literature presents publications on the treatment of patients with obstructive sleep apnea syndrome (OSAS) by myofunctional therapy, but there are no reports of this approach to patients with upper airway resistance syndrome (UARS). The objective was to verify the effect of myofunctional therapy in a case of UARS in relation to morphological and functional aspects of the stomatognathic system, anthropometric data, and quality of sleep. Patient, aged 61 years, diagnosed with UARS, underwent 12 sessions of myofunctional therapy for 3 months with exercises aimed at the suprahyoid, the tongue, and the soft palate muscles. Evaluations were performed before the start of the therapeutic process, right after the end, as well as 1, 2, 4, and 10 months after the completion of the treatment, considering: tonicity and mobility of the suprahyoid muscles, the tongue, and the soft palate; modified Mallampati grade; neck circumference; body mass index; and parameters of sleep quality. After the therapeutic process, there was a decrease in scores related to the tonus of the suprahyoid muscles, mobility, and tonus of the tongue and of the soft palate. The Mallampati grade was IV in the initial evaluation, and III in subsequent assessment. There was a reduction of 2 cm in neck circumference and BMI remained similar over time. In analyzing the three parameters of sleep quality, improvement was observed in all evaluations after discharge. Therefore, the effect of myofunctional therapy in a case of UARS was positive for all parameters.

The role of flow limitation as an important diagnostic tool and clinical finding in mild sleep-disordered breathing

Obstructive sleep apnea (OSA) is defined by quantifying apneas and hypopneas along with symptoms suggesting sleep disruption. Subtler forms of sleep-disordered breathing can be missed when this criteria is used. Newer technologies allow for non-invasive detection of flow limitation, however consensus classification is needed. Subjects with flow limitation demonstrate electroencephalogram changes and clinical symptoms indicating sleep fragmentation. Flow limitation may be increased in special populations and treatment with nasal continuous positive airway pressure (CPAP) has been shown to improve outcomes. Titrating CPAP to eliminate flow limitation may be associated with improved clinical outcomes compared to treating apneas and hypopneas.

Treatment of upper airway resistance syndrome in adults: Where do we stand?

OBJECTIVE

To evaluate the available literature regarding Upper Airway Resistance Syndrome (UARS) treatment.

METHODS

Keywords "Upper Airway Resistance Syndrome," "Sleep-related Breathing Disorder treatment," "Obstructive Sleep Apnea treatment" and "flow limitation and sleep" were used in main databases.

RESULTS

We found 27 articles describing UARS treatment. Nasal continuous positive airway pressure (CPAP) has been the mainstay therapy prescribed but with limited effectiveness. Studies about surgical treatments had methodological limitations. Oral appliances seem to be effective but their efficacy is not yet established.

CONCLUSION

Randomized controlled trials with larger numbers of patients and long-term follow-up are important to establish UARS treatment options.

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.

Lack of Impact of Mild Obstructive Sleep Apnea on Sleepiness, Mood and Quality of Life

BACKGROUND AND OBJECTIVES

Obstructive sleep apnea (OSA) is associated with sleepiness, depression and reduced quality of life. However, it is unclear whether mild OSA has these negative impacts. Using data from the Apnea Positive Pressure Long-term Efficacy Study (APPLES), this study determined whether participants with mild OSA had greater sleepiness, more depressive symptoms and poorer quality of life in comparison to those without OSA.

METHODS

239 individuals evaluated for participation in APPLES with a baseline apnea hypopnea index (AHI) < 15 /hour were assigned to 1 of 2 groups: No OSA (N=40, AHI < 5 /hour) or Mild OSA (N=199, 5 to <15 /hour) based on their screening polysomnogram. Scores on their Epworth Sleepiness Scale (ESS), Stanford Sleepiness Scale (SSS), Hamilton Rating Scale for Depression (HAM-D), Profile of Mood States (POMS) and Sleep Apnea Quality of Life Index (SAQLI) were compared between groups.

RESULTS

There were no significant differences between the No OSA and Mild OSA groups on any of the 5 measures: ESS (No OSA, 9.8 ± 3.5 vs Mild OSA, 10.6 ± 4.3, p=0.26), SSS,(2.8 ± 0.9 vs. 2.9 ± 1.0, p=0.52), HAM-D (4.6 ± 3.0 vs. 4.9 ± 4.7, p=0.27), POMS (33.5 ± 22.3 vs. 28.7 ± 22.0, p=0.70), SAQLI (4.5 ± 0.8 vs. 4.7 ± 0.7, p=0.39).

CONCLUSION

Individuals with mild OSA in this cohort do not have worse sleepiness, mood or quality of life in comparison to those without OSA.

Chronic upper airway obstruction induces abnormal sleep/wake dynamics in juvenile rats

OBJECTIVES

Conventional scoring of sleep provides little information about the process of transitioning between vigilance-states. We used the state space technique to explore whether rats with chronic upper airway obstruction (UAO) have abnormal sleep/wake states, faster movements between states, or abnormal transitions between states.

DESIGN

The tracheae of 22-day-old Sprague-Dawley rats were surgically narrowed to increase upper airway resistance with no evidence for frank obstructed apneas or hypopneas; 24-h electroencephalography of sleep/wake recordings of UAO and sham-control animals was analyzed using state space technique. This non-categorical approach allows quantitative and unbiased examination of vigilance-states and state transitions. Measurements were performed 2 weeks post-surgery at baseline and following administration of ritanserin (5-HT2 receptor antagonist) the next day to stimulate sleep.

MEASUREMENTS AND RESULTS

UAO rats spent less time in deep (delta-rich) slow wave sleep (SWS) and near transition zones between states. State transitions from light SWS to wake and vice versa and microarousals were more frequent and rapid in UAO rats, indicating that obstructed animals have more regions where vigilance-states are unstable. Ritanserin consolidated sleep in both groups by decreasing the number of microarousals and trajectories between wake and light SWS, and increasing deep SWS in UAO.

CONCLUSIONS

State space technique enables visualization of vigilance-state transitions and velocities that were not evident by traditional scoring methods. This analysis provides new quantitative assessment of abnormal vigilance-state dynamics in UAO in the absence of frank obstructed apneas or hypopneas.

Simple snoring: not quite so simple after all?

Simple snoring (SS), in the absence of obstructive sleep apnoea (OSA), is a common problem, yet our understanding of its causes and consequences is incomplete. Our understanding is blurred by the lack of consistency in the definition of snoring, methods of assessment, and degree of concomitant complaints. Further, it remains contentious whether SS is independently associated with daytime sleepiness, or adverse health outcomes including cardiovascular disease and metabolic syndrome. Regardless of this lack of clarity, it is likely that SS exists on one end of a continuum, with OSA at its polar end. This possibility highlights the necessity of considering an otherwise 'annoying' complaint, as a serious risk factor for the development and progression of sleep apnoea, and consequent poor health outcomes. In this review, we: 1) highlight variation in prevalence estimates of snoring; 2) review the literature surrounding the distinctions between SS, upper airway resistance syndrome (UARS) and OSA; 3) present the risk factors for SS, in as far as it is distinguishable from UARS and OSA; and 4) describe common correlates of snoring, including cardiovascular disease, metabolic syndrome, and daytime sleepiness.

Polysomnographic investigation of sleep and respiratory parameters in women with temporomandibular pain disorders

STUDY OBJECTIVES

Temporomandibular pain disorders (TMD) and myofascial pain were linked to increased prevalence of insomnia and obstructive sleep apnea (OSA) on clinical grounds. However, the literature lacks an accurate polysomnographic (PSG) characterization of sleep abnormalities associated with TMD, given that prior studies included small or uncontrolled samples of TMD patients. The present investigation aims to objectively evaluate measures of sleep and respiratory disturbance in a large representative sample of TMD cases in comparison with matched controls.

METHODS

Sleep, respiration, and limb movements were measured using a 2-night attended PSG protocol in 170 women-124 TMD cases with myofascial pain and 46 demographically matched controls. The second night data were compared between the groups using ANCOVAs. In TMD cases, the relationship between pain ratings and sleep parameters was analyzed using multiple regressions.

RESULTS

In comparison to healthy controls, TMD cased evidenced a significant increase in stage N1 sleep (12.2% ± 7.6% vs. 9.2% ± 5.0%, p = 0.03), which was only mild relative to normative values. TMD cases also demonstrated mild but significant elevations in arousals associated with all types of respiratory events (6.0/h ± 6.1 vs. 3.5/h ± 3.3 p = 0.02) and in respiratory effort related arousals (RERAs, 4.3/h ± 4.3 vs. 2.6/h ± 2.7, p = 0.02). Myofascial pain predicted a lower sleep efficiency (p = 0.01), more frequent awakenings (p = 0.04), and higher RERA index (p = 0.04) among TMD cases.

CONCLUSIONS

Myofascial pain in TMD is associated with mild elevation in sleep fragmentation and increased frequency of RERA events. Further research is required to evaluate the clinical significance of these findings.

Diagnostic and management approach to common sleep disorders during pregnancy

The significance for maternal and fetal health of gestational obstructive sleep apnea, primary insomnia, restless legs syndrome, and narcolepsy are summarized. The pathophysiology, signs, symptoms, and basic Sleep Medicine concepts that assist the obstetrician in suspecting these 4 conditions are described. Where appropriate, initial management options are also outlined. Referral guidelines to a Sleep Medicine specialist are included when further diagnostic, severity assessment, and management suggestions are needed.

Pediatric obstructive sleep apnea syndrome

Pediatric obstructive sleep apnea syndrome (OSAS) is a common health problem diagnosed and managed by various medical specialists, including family practice physicians, pediatricians, pulmonologists, and general and pediatric otolaryngologists. If left untreated, the sequelae can be severe. Over the last decade, significant advancements have been made in the evidence-based management of pediatric OSAS. This article focuses on the current understanding of this disease, its management, and related clinical practice guidelines.

How does obstructive sleep apnoea evolve in syndromic craniosynostosis? A prospective cohort study

OBJECTIVE

To describe the course of obstructive sleep apnoea syndrome (OSAS) in children with syndromic craniosynostosis.

DESIGN

Prospective cohort study.

SETTING

Dutch Craniofacial Centre from January 2007 to January 2012.

PATIENTS

A total of 97 children with syndromic craniosynostosis underwent level III sleep study. Patients generally undergo cranial vault remodelling during their first year of life, but OSAS treatment only on indication.

MAIN OUTCOME MEASURES

Obstructive apnoea-hypopnoea index, the central apnoea index and haemoglobin oxygenation-desaturation index derived from consecutive sleep studies.

RESULTS

The overall prevalence of OSAS in syndromic craniosynostosis was 68% as defined by level III sleep study. Twenty-three patients were treated for OSAS. Longitudinal profiles were computed for 80 untreated patients using 241 sleep studies. A mixed effects model showed higher values for the patients with midface hypoplasia as compared to those without midface hypoplasia (Omnibus likelihood ratio test=7.9). In paired measurements, the obstructive apnoea-hypopnoea index (Z=-3.4) significantly decreased over time, especially in the first years of life (Z=-3.3), but not in patients with midface hypoplasia (Z=-1.5). No patient developed severe OSAS during follow-up if it was not yet diagnosed during the first sleep study.

CONCLUSIONS

OSAS is highly prevalent in syndromic craniosynostosis. There is some natural improvement, mainly during the first 3 years of life and least in children with Apert or Crouzon/Pfeiffer syndrome. In the absence of other co-morbid risk factors, it is highly unlikely that if severe OSAS is not present early in life it will develop during childhood. Ongoing clinical surveillance is of great importance and continuous monitoring for the development of other co-morbid risk factors for OSAS should be warranted.