Inspiratory flow limitation in a normal population of adults in São Paulo, Brazil

Flow Limitation Is Associated with Excessive Daytime Sleepiness in Individuals without Moderate or Severe Obstructive Sleep Apnea

Rationale: Moderate-severe obstructive sleep apnea (OSA) (apnea-hypopnea index [AHI], >15 events/h) disturbs sleep through frequent bouts of apnea and is associated with daytime sleepiness. However, many individuals without moderate-severe OSA (i.e., AHI <15 events/h) also report sleepiness. Objectives: To test the hypothesis that sleepiness in the AHI <15 events/h group is a consequence of substantial flow limitation in the absence of overt reductions in airflow (i.e., apnea/hypopnea). Methods: A total of 1,886 participants from the MESA sleep cohort were analyzed for frequency of flow limitation from polysomnogram-recorded nasal airflow signal. Excessive daytime sleepiness (EDS) was defined by an Epworth Sleepiness Scale score ⩾11. Covariate-adjusted logistic regression assessed the association between EDS (binary dependent variable) and frequency of flow limitation (continuous) in individuals with an AHI <15 events/h. Results: A total of 772 individuals with an AHI <15 events/h were included in the primary analysis. Flow limitation was associated with EDS (odds ratio, 2.04; 95% confidence interval, 1.17-3.54; per 2-standard deviation increase in flow limitation frequency) after adjusting for age, sex, body mass index, race/ethnicity, and sleep duration. This effect size did not appreciably change after also adjusting for AHI. Conclusions: In individuals with an AHI <15 events/h, increasing flow limitation frequency by 2 standard deviations is associated with a twofold increase in the risk of EDS. Future studies should investigate addressing flow limitation in low-AHI individuals as a potential mechanism for ameliorating sleepiness.

Increased Flow Limitation During Sleep Is Associated With Increased Psychomotor Vigilance Task Lapses in Individuals With Suspected OSA

BACKGROUND

Impaired daytime vigilance is an important consequence of OSA, but several studies have reported no association between objective measurements of vigilance and the apnea-hypopnea index (AHI). Notably, the AHI does not quantify the degree of flow limitation, that is, the extent to which ventilation fails to meet intended ventilation (ventilatory drive).

RESEARCH QUESTION

Is flow limitation during sleep associated with daytime vigilance in OSA?

STUDY DESIGN AND METHODS

Nine hundred ninety-eight participants with suspected OSA completed a 10-min psychomotor vigilance task (PVT) before same-night in-laboratory polysomnography. Flow limitation frequency (percent of flow-limited breaths) during sleep was quantified using airflow shapes (eg, fluttering and scooping) from nasal pressure airflow. Multivariable regression assessed the association between flow limitation frequency and the number of lapses (response times > 500 ms, primary outcome), adjusting for age, sex, BMI, total sleep time, depression, and smoking status.

RESULTS

Increased flow limitation frequency was associated with decreased vigilance: a 1-SD (35.3%) increase was associated with 2.1 additional PVT lapses (95% CI, 0.7-3.7; P = .003). This magnitude was similar to that for age, where a 1-SD increase (13.5 years) was associated with 1.9 additional lapses. Results were similar after adjusting for AHI, hypoxemia severity, and arousal severity. The AHI was not associated with PVT lapses (P = .20). In secondary exploratory analysis, flow limitation frequency was associated with mean response speed (P = .012), median response time (P = .029), fastest 10% response time (P = .041), slowest 10% response time (P = .018), and slowest 10% response speed (P = .005).

INTERPRETATION

Increased flow limitation during sleep was associated with decreased daytime vigilance in individuals with suspected OSA, independent of the AHI. Flow limitation may complement standard clinical metrics in identifying individuals whose vigilance impairment most likely is explained by OSA.

Ventilatory Burden as a Measure of Obstructive Sleep Apnea Severity Is Predictive of Cardiovascular and All-Cause Mortality

Rationale: The apnea-hypopnea index (AHI), used for the diagnosis of obstructive sleep apnea, captures only the frequency of respiratory events and has demonstrable limitations. Objectives: We propose a novel automated measure, termed "ventilatory burden" (VB), that represents the proportion of overnight breaths with less than 50% normalized amplitude, and we show its ability to overcome limitations of AHI. Methods: Data from two epidemiological cohorts (EPISONO [Sao Paolo Epidemiological Study] and SHHS [Sleep Heart Health Study]) and two retrospective clinical cohorts (DAYFUN; New York University Center for Brain Health) were used in this study to 1) derive the normative range of VB, 2) assess the relationship between degree of upper airway obstruction and VB, and 3) assess the relationship between VB and all-cause and cardiovascular disease (CVD) mortality with and without hypoxic burden that was derived using an in-house automated algorithm. Measurements and Main Results: The 95th percentiles of VB in asymptomatic healthy subjects across the EPISONO and the DAYFUN cohorts were 25.2% and 26.7%, respectively (median [interquartile range], VBEPISONO, 5.5 [3.5-9.7]%; VBDAYFUN, 9.8 [6.4-15.6]%). VB was associated with the degree of upper airway obstruction in a dose-response manner (VBuntreated, 31.6 [27.1]%; VBtreated, 7.2 [4.7]%; VBsuboptimally treated, 17.6 [18.7]%; VBoff-treatment, 41.6 [18.1]%) and exhibited low night-to-night variability (intraclass correlation coefficient [2,1], 0.89). VB was predictive of all-cause and CVD mortality in the SHHS cohort before and after adjusting for covariates including hypoxic burden. Although AHI was predictive of all-cause mortality, it was not associated with CVD mortality in the SHHS cohort. Conclusions: Automated VB can effectively assess obstructive sleep apnea severity, is predictive of all-cause and CVD mortality, and may be a viable alternative to the AHI.

The Beginning of the AI-Enabled Preventative PAP Therapy Era: A First-in-Human Proof of Concept Interventional Study

Positive Airway Pressure (PAP) therapy is the most common and efficacious treatment for Obstructive Sleep Apnea (OSA). However, it suffers from poor patient adherence due to discomfort and may not fully alleviate all adverse consequences of OSA. Identifying abnormal respiratory events before they have occurred may allow for improved management of PAP levels, leading to improved adherence and better patient outcomes. Our previous work has resulted in the successful development of a Machine-Learning (ML) algorithm for the prediction of future apneic events using existing airflow and air pressure sensors available internally to PAP devices. Although researchers have studied the use of ML for the prediction of apneas, research to date has focused primarily on using external polysomnography sensors that add to patient discomfort and has not investigated the use of internal-to-PAP sensors such as air pressure and airflow to predict and prevent respiratory events. We hypothesized that by using our predictive software, OSA events could be proactively prevented while maintaining patients' sleep quality. An intervention protocol was developed and applied to all patients to prevent OSA events. Although the protocol's cool-down period limited the number of prevention attempts, analysis of 11 participants revealed that our system improved many sleep parameters, which included a statistically significant 31.6% reduction in Apnea-Hypopnea Index, while maintaining sleep quality. Most importantly, our findings indicate the feasibility of unobtrusive identification and unique prevention of each respiratory event as well as paving the path to future truly personalized PAP therapy by further training of ML models on individual patients.

The Effects of Changing Continuous Positive Airway Pressure Devices in Japanese Patients with Obstructive Sleep Apnea: A Case Series

Background The effects of continuous positive airway pressure (CPAP) devices on obstructive sleep apnea (OSA) in Japanese patients have not been reported. We assessed the effects of changing CPAP devices (from the Philips Respironics device to the ResMed device) on the control of OSA. Methods We retrospectively examined 13 patients with OSA who voluntarily changed from the Philips Respironics device to the ResMed device due to a Philips Respironics CPAP device recall. Data on the apnea-hypopnea index (AHI) were obtained from the CPAP devices for three months before and after changing the devices. Results The AHI obtained from the CPAP devices significantly decreased from 4.4 (3.1-10.7) events/h to 2.0 (0.8-3.6) events/h when patients changed devices (P=0.022). The AHI decreased to <5 events/h after changing devices in 4 patients, whereas it had been ≥5 events/h before changing devices in 6 patients. Conclusion Changing CPAP devices can decrease the AHI.

Assessment of pleural pressure during sleep in Marfan syndrome

STUDY OBJECTIVES

Patients with Marfan syndrome (MFS) have a high risk for aortic aneurysms. They are also susceptible to sleep-disordered breathing that may expose them to highly negative intrathoracic pressures known to increase aortic transmural pressure, which may accelerate aortic dilatation. Our objective was to quantify overnight intrathoracic pressure changes during sleep in snoring patients with MFS and the therapeutic effect of continuous positive airway pressure (CPAP).

METHODS

We used a questionnaire to identify self-reported snoring patients with MFS. In these patients, we monitored intrathoracic pressure using esophageal pressure (Pes) during overnight baseline and CPAP sleep studies. We defined a peak-inspiratory Pes (Pespeak-insp) < - 5 cm H2O as greater than normal and examined the distribution of Pespeak-insp during baseline and CPAP studies.

RESULTS

In our sample of 23 snorers with MFS, we found that 70% of sleep breaths exhibited Pespeak-insp < -5 cm H2O, with apnea/hypopneass accounting for only 12%, suggesting prevalent stable flow-limited breathing and snoring. In a subset (n = 12) with Pes monitoring during a CPAP night, CPAP lowered the mean proportion of breaths with Pespeak-insp < -5 cm H2O from 83.7% ± 14.9% to 3.6% ± 3.0% (P < .001). In addition, contemporaneous aortic root diameter was associated with the mean Pespeak-insp during inspiratory flow-limited breathing and apneas/hypopneas (β = -0.05, r = .675, P = .033).

CONCLUSIONS

The sleep state in MFS revealed prolonged exposure to exaggerated negative inspiratory Pes, which was reversible with CPAP. Since negative intrathoracic pressure can contribute to thoracic aortic stress and aortic dilatation, snoring may be a reversible risk factor for progression of aortic pathology in MFS.

CITATION

Sowho M, Jun J, Sgambati F, et al. Assessment of pleural pressure during sleep in Marfan syndrome. J Clin Sleep Med. 2022;18(6):1583-1592.

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.

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.

Snoring: a source of noise pollution and sleep apnea predictor

Snoring is a highly prevalent condition associated with obstructive sleep apnea (OSA) and sleep disturbance in bed partners. Objective measurements of snoring in the community, however, are limited. The present study was designed to measure sound levels produced by self-reported habitual snorers in a single night. Snorers were excluded if they reported nocturnal gasping or had severe obesity (BMI > 35 kg/m2). Sound was measured by a monitor mounted 65 cm over the head of the bed on an overnight sleep study. Snoring was defined as sound ≥40 dB(A) during flow limited inspirations. The apnea hypopnea index (AHI) and breath-by-breath peak decibel levels were measured. Snore breaths were tallied to determine the frequency and intensity of snoring. Regression models were used to determine the relationship between objective measures of snoring and OSA (AHI ≥ 5 events/h). The area under the curve (AUC) for the receiver operating characteristic (ROC) was used to predict OSA. Snoring intensity exceeded 45 dB(A) in 66% of the 162 participants studied, with 14% surpassing the 53 dB(A) threshold for noise pollution. Snoring intensity and frequency were independent predictors of OSA. AUCs for snoring intensity and frequency were 77% and 81%, respectively, and increased to 87% and 89%, respectively, with the addition of age and sex as predictors. Snoring represents a source of noise pollution in the bedroom and constitutes an important target for mitigating sound and its adverse effects on bed partners. Precise breath-by-breath identification and quantification of snoring also offers a way to risk stratify otherwise healthy snorers for OSA.

Tidal volume and stroke volume changes caused by respiratory events during sleep and their relationship with OSA severity: a pilot study

PURPOSE

Breath-by-breath tidal volume (TV) and beat-by-beat stroke volume (SV) were continuously measured in patients with OSA undergoing polysomnography (PSG). The objectives were to (1) determine the changes in TV/SV in response to respiratory events and (2) assess the relationship between these changes and the disease severity.

METHODS

From the PSG data of nine patients with OSA, six different types of respiratory events were identified, i.e., flow limitation (FL), respiratory effort related arousal (RERA), hypopnea with arousal only (Ha), hypopnea with desaturation only (Hd), hypopnea with arousal and desaturation (Had), and apnea. The measured TV and SV values during and after each respiratory event were compared with the pre-event baseline values.

RESULTS

The mean TV/SV reductions during all hypopneas and apneas were 38.1%/4.2% and 70.5%/8.8%, respectively. Among three different hypopnea types, the reductions in TV during Hd and Had were significantly greater than those during Ha. The TV reductions during Ha and FL were similar. After RERA, Ha, Had, and apnea, there was an overshoot in TV and SV values, whereas there was no overshoot after FL and Hd. During RERA, there was no reduction in TV/SV.

CONCLUSIONS

The changes in TV during and after each type of respiratory event were significantly different in most cases. The changes in SV between hypopnea and apnea were different with statistical significance. The AHI does not properly account for the ventilation losses caused by respiratory events. Thus, TV measurements might be useful in the future in assessing the OSA severity in conjunction with the AHI.

Pulse transit time in pregnancy: a new way to diagnose and classify sleep disordered breathing?

STUDY OBJECTIVES

There are significant discrepancies between the prevalence of snoring and that of objectively defined sleep disordered breathing among pregnant women, suggesting subtle airflow limitations that may not be captured by conventional scoring. This study examined the performance of pulse transit time, an indirect measure of arterial stiffness and sympathetic activation, in pregnancy.

METHODS

Pregnant women with obesity and snoring and a group of controls without symptoms of sleep disordered breathing were recruited in the first trimester. Women underwent a level III in-laboratory sleep monitoring study including an electrocardiogram and pulse oximetry, and pulse transit time was measured. Sleep disordered breathing was defined as an apnea-hypopnea index at least five events per hour of sleep. Statistical analysis was performed using Spearman correlation, Fisher's exact t-test, and univariate analysis.

RESULTS

Of the 222 women, 38 met criteria for sleep disordered breathing. Pulse transit time drops were very prevalent (95% of participants with snoring had > 5 drops per hour). Median apnea-hypopnea index was 0.7 (interquartile range [IQR]: 2.6) events per hour whereas median pulse transit time drop index was 20.70 (IQR: 35.90) events per hour. Pulse transit time index was significantly higher in snorers with apnea-hypopnea index less than five events per hours and participants with apnea-hypopnea index greater than five events per hour compared to controls. Examination of random epochs with pulse transit time drops showed that 95% of pulse transit time drops were associated with airflow limitation.

CONCLUSIONS

Pulse transit time ascertains frequent events of sympathetic activation in at-risk women with and without sleep disordered breathing beyond conventional apneas and hypopneas. Pulse transit time may be an important addition to the identification of clinically significant sleep disordered breathing in pregnant women, and may identify more sleep disordered breathing than apnea-hypopnea index.

Apraxia in children and adults with obstructive sleep apnea syndrome

Study Objectives

Early in life impairment of orofacial growth leads to sleep-disordered breathing (SDB). Normal lingual gnosis and praxis are part of this early development related to the normal sensorimotor development of the tongue and surrounding oral musculature. The aim of this retrospective study was to explore if lingual praxia is impaired in both SDB children and adults and if there is an association to craniofacial morphology.

Methods

The ability to perform simple tongue maneuvers was investigated in 100 prepubertal SDB children and 150 SDB adults (shown with polysomnography). All individuals had a clinical investigation by specialists to assess any orofacial growth impairment and the elements potentially behind this impairment. In a subgroup of individuals both able and unable to perform the maneuvers, we also performed a blind recognition of forms placed in the mouth.

Results

A subgroup of pediatric and adult SDB patients presented evidence not only of orofacial growth impairment, but also apraxia independent of age and severity of OSA.

Conclusions

By 3 years of age, children should be able to perform requested tongue maneuvers and have oral form recognition. Abnormal gnosis–praxis was noted, independent of age in SDB children and adults, demonstrating that an abnormal functioning of the tongue in the oral cavity during early development can be detected. Both children and adults with SDB may present similar absences of normal oral development very early in life and a similar presentation of apraxia, suggesting that the distinction of SDB in children versus adults may not be relevant.

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, Orofacial Growth, and Prevention of Obstructive Sleep Apnea

Abnormal breathing during sleep is related to intrinsic and extrinsic factors that are present early in life. Investigation of fetal development and early-in-life orofacial growth allows recognition of risk factors that lead to change in upper airway patency, which leads to abnormal upper airway resistance, abnormal inspiratory efforts, and further increase in resistance and progressive narrowing of the collapsible upper airway. Such evolution can be recognized by appropriate clinical evaluation, specific polysomnographic patterns, and orofacial imaging. Recognition of the problems should lead to appropriate treatments and prevention of obstructive sleep apnea and its comorbidities.

Upper airway resistance syndrome 2018: non-hypoxic sleep-disordered breathing

INTRODUCTION

Upper airway resistance syndrome (UARS) as obstructive sleep apnea syndrome (OSAS) has been described as abnormal breathing during sleep, based on the recording technologies and knowledge of the time. These terms have advanced the field, but are they still useful? Area Covered: Historically, the definition of UARS syndrome was aimed at recognizing pathology not covered by 'OSAS' and to prompt specialists to go further than the obvious. It aimed at pushing specialists to recognize pathologies earlier and to elicit research in the developmental features of sleep-disordered-breathing (SDB). The technology used to monitor SDB changed over-time, allowing recognition of SDB differently but not necessarily better. Expert Commentary: Currently, we have a better understanding of the development of SDB, and its evolution with aging, leading to co-morbid-OSA. However, the real issue is to recognize the problems much earlier, and to understand what can be done to prevent its development. The notions of OSA, UARS, apnea hypopnea index are only historical. There is enough knowledge to date to go beyond these definitions, to recognize problems differently and to lead to the prevention of the factors leading to SDB. The recognition of non-hypoxic sleep-disordered breathing is a step in this direction.

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.

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.

Long-Term Oral Appliance Therapy Improves Daytime Function and Mood in Upper Airway Resistance Syndrome Patients

Objectives

To evaluate the long-term effects of an oral appliance on clinical symptoms, respiratory sleep parameters, sleep quality, and sustained attention in patients with upper airway resistance syndrome (UARS) were compared with placebo.

Methods

This study was a randomized placebo-controlled clinical trial. Thirty UARS patients were randomized in two groups: placebo and mandibular advancement device (MAD) groups. UARS criteria were presence of sleepiness (Epworth Sleepiness Scale ≥ 10) and/or fatigue (Modified Fatigue Impact Scale ≥ 38) associated with an apnea/hypopnea index ≤ 5 and a respiratory disturbance index (RDI) > 5 events/hour of sleep, and/or flow limitation in more than 30% of total sleep time. All patients completed the Pittsburgh Sleep Quality Index (PSQI), the Functional Outcomes of Sleep Questionnaire, the Beck Anxiety and Depression Inventories, underwent full-night polysomnography, multiple sleep latency test, and Psychomotor Vigilance Test (PVT). Evaluations were performed before and after 1.5 years of treatment.

Results

RDI, number of respiratory effort-related arousal, percentage of total sleep time with flow limitation, and arousal index significantly decreased after 1.5 years of MAD treatment. PSQI total score improved, severity of depression symptoms decreased, and mean reaction time in the PVT, based on the first measurement taken at 8:00 am, significantly decreased (p = .03) at the end of the protocol.

Conclusions

The MAD was effective in decreasing respiratory events in UARS patients. For UARS, 1.5 years of oral appliance therapy also improved sleep quality and sustained attention, and decreased the severity of depression symptoms.

Clinical Trial

Efficacy of Oral Appliance for Upper Airway Resistance Syndrome: Randomized, Parallel, Placebo-Controlled Study, NCT02636621.

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

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

Weighted Polynomial Approximation for Automated Detection of Inspiratory Flow Limitation

Inspiratory flow limitation (IFL) is a critical symptom of sleep breathing disorders. A characteristic flattened flow-time curve indicates the presence of highest resistance flow limitation. This study involved investigating a real-time algorithm for detecting IFL during sleep. Three categories of inspiratory flow shape were collected from previous studies for use as a development set. Of these, 16 cases were labeled as non-IFL and 78 as IFL which were further categorized into minor level (20 cases) and severe level (58 cases) of obstruction. In this study, algorithms using polynomial functions were proposed for extracting the features of IFL. Methods using first- to third-order polynomial approximations were applied to calculate the fitting curve to obtain the mean absolute error. The proposed algorithm is described by the weighted third-order (w.3rd-order) polynomial function. For validation, a total of 1,093 inspiratory breaths were acquired as a test set. The accuracy levels of the classifications produced by the presented feature detection methods were analyzed, and the performance levels were compared using a misclassification cobweb. According to the results, the algorithm using the w.3rd-order polynomial approximation achieved an accuracy of 94.14% for IFL classification. We concluded that this algorithm achieved effective automatic IFL detection during sleep.

The Efficacy of Low-Level Continuous Positive Airway Pressure for the Treatment of Snoring

STUDY OBJECTIVES

To assess effects of low-level continuous positive airway pressure (CPAP) on snoring in habitual snorers without obstructive sleep apnea (OSA).

METHODS

A multicenter prospective in-laboratory reversal crossover intervention trial was conducted between September 2013 and August 2014. Habitual snorers were included if they snored (inspiratory sound pressure level ≥ 40 dBA) for ≥ 30% all sleep breaths on a baseline sleep study (Night 1), and if significant OSA and daytime somnolence were absent. Included participants then underwent a CPAP titration study at 2, 4, or 6 cm H₂O (Night 2) to examine snoring responses to step-increases in nasal pressure, a treatment night at optimal pressure (Night 3), followed by baseline night (Night 4). At each pressure, snoring intensity was measured on each breath. Snoring frequency was quantified as a percentage of sleep breaths at thresholds of 40, 45, 50, and 55 dBA. Sleep architecture and OSA severity were characterized using standard measurements.

RESULTS

On baseline sleep studies, participants demonstrated snoring at ≥ 40 dBA on 53 ± 3% and ≥ 45 dBA on 35 ± 4% of breaths. Snoring frequency decreased progressively as nasal pressure increased from 0 to 4 cm H₂O at each threshold, and plateaued thereafter. CPAP decreased snoring frequency by 67% and 85% at 40 and 45 dBA, respectively. Intervention did not alter sleep architecture and sleep apnea decreased minimally.

CONCLUSIONS

Low-level CPAP below the range required to treat OSA diminished nocturnal snoring, and produced uniform reduction in nightly noise production below the World Health Organization's limit of 45 dBA.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, identifier: NCT01949584.

Continuous positive airway pressure therapy in obstuctive sleep apnea: benefits and alternatives

INTRODUCTION

Obstructive sleep apnea (OSA) is a highly prevalent condition affecting persons of all age with an increasing public health burden. It is implicated in cardiovascular disease, metabolic syndrome, neurocognitive impairment, reductions in quality of life, and increased motor vehicle accidents. The goals of OSA treatment are to improve sleep and daytime symptoms, and minimize cardiovascular risks.Areas covered: Continuous positive airway pressure (CPAP) is considered the gold standard therapy that delivers pressurized air into the upper airway to relieve obstruction during sleep. Although CPAP is an effective modality of treatment for OSA, adherence to therapy is highly variable. This article highlights the benefits of CPAP therapy, along with alternative treatment options including oral appliance, implantable and wearable devices, and surgery. Expert commentary: CPAP therapy is the gold standard treatment option and should continue to be offered to those who suffer from OSA. Alternative options are available for those who are unable to adhere to CPAP or choose an alternative treatment modality. The most interesting advances have been incorporating orthodontic procedures in conjunction with myofunctional therapy in prepubertal children, raising the possibility of OSA prevention by initiating treatment early in life.

Cross-Sectional Comparison of Sleep-Disordered Breathing in Native Peruvian Highlanders and Lowlanders

Pham, Luu V., Christopher Meinzen, Rafael S. Arias, Noah G. Schwartz, Adi Rattner, Catherine H. Miele, Philip L. Smith, Hartmut Schneider, J. Jaime Miranda, Robert H. Gilman, Vsevolod Y. Polotsky, William Checkley, and Alan R. Schwartz. Cross-sectional comparison of sleep-disordered breathing in native Peruvian highlanders and lowlanders. High Alt Med Biol. 18:11-19, 2017.

BACKGROUND

Altitude can accentuate sleep disordered breathing (SDB), which has been linked to cardiovascular and metabolic diseases. SDB in highlanders has not been characterized in large controlled studies. The purpose of this study was to compare SDB prevalence and severity in highlanders and lowlanders.

METHODS

170 age-, body-mass-index- (BMI), and sex-matched pairs (age 58.2 ± 12.4 years, BMI 27.2 ± 3.5 kg/m2, and 86 men and 84 women) of the CRONICAS Cohort Study were recruited at a sea-level (Lima) and a high-altitude (Puno, 3825 m) setting in Peru. Participants underwent simultaneous nocturnal polygraphy and actigraphy to characterize breathing patterns, movement arousals, and sleep/wake state. We compared SDB prevalence, type, and severity between highlanders and lowlanders as measured by apnea-hypopnea index (AHI) and pulse oximetry (SPO2) during sleep.

RESULTS

Sleep apnea prevalence was greater in highlanders than in lowlanders (77% vs. 54%, p < 0.001). Compared with lowlanders, highlanders had twofold elevations in AHI due to increases in central rather than obstructive apneas. In highlanders compared with lowlanders, SPO2 was lower during wakefulness and decreased further during sleep (p < 0.001). Hypoxemia during wakefulness predicted sleep apnea in highlanders, and it appears to mediate the effects of altitude on sleep apnea prevalence. Surprisingly, hypoxemia was also quite prevalent in lowlanders, and it was also associated with increased odds of sleep apnea.

CONCLUSIONS

High altitude and hypoxemia at both high and low altitude were associated with increased SDB prevalence and severity. Our findings suggest that a large proportion of highlanders remain at risk for SDB sequelae.

Pulse transit time changes in subjects exhibiting sleep disordered breathing

INTRODUCTION

Pulse Transit Time (PTT) represents a non-invasive marker of sleep fragmentation in OSAS. Little is known regarding PTT in sleepy subjects exhibiting nocturnal Inspiratory Flow Limitation (IFL) in the absence of apneas or desaturation.

MATERIALS AND METHODS

The IFL cohort was gender and age matched to subjects with OSAS and a cohort where Sleep Disordered Breathing (SBD)/IFL was absent ("Non Flow Limited" or NFL cohort); PTT Arousal index (PTT Ar) defined by number of PTT arousals per hour.

RESULTS

20 subjects meeting criteria for the IFL cohort were aged and gender matched with OSAS and "NFL" subjects. Females comprised 65% of the IFL cohort; the mean BMI of the IFL cohort was significantly higher than the NFL cohort (34.25 v 28.90; p = 0.016) but not when compared to the OSAS cohort (34.25 v 36.31; p = 0.30). The PTT Ar in the IFL cohort (33.67 h) was significantly higher than the NFL cohort (23.89 h) but significantly lower than the OSAS cohort (55.21 h; F = 8.76; p < 0.001). PTT Ar was found to positively correlate with AHI (CC = 0.46; p < 0.001), ODI (CC = 0.47; p < 0.001) and RDI (CC = 0.49; p < 0.001). Within the IFL cohort, PTT Ar positively correlated with age (CC = 0.501; p = 0.024) but not gender and BMI.

CONCLUSION

The PTT Arousal Index increased proportionately with severity of SDB with significantly higher markers of arousal in sleepy subjects exhibiting nocturnal IFL when compared to controls. Subjects exhibiting IFL were predominantly female with an elevated BMI. IFL may thus represent a significant pathogenic entity in the development of daytime sleepiness.

Prolonged partial upper airway obstruction during sleep - an underdiagnosed phenotype of sleep-disordered breathing

Obstructive sleep apnea syndrome (OSAS) is a well-recognized disorder conventionally diagnosed with an elevated apnea-hypopnea index. Prolonged partial upper airway obstruction is a common phenotype of sleep-disordered breathing (SDB), which however is still largely underreported. The major reasons for this are that cyclic breathing pattern coupled with arousals and arterial oxyhemoglobin saturation are easy to detect and considered more important than prolonged episodes of increased respiratory effort with increased levels of carbon dioxide in the absence of cycling breathing pattern and repetitive arousals. There is also a growing body of evidence that prolonged partial obstruction is a clinically significant form of SDB, which is associated with symptoms and co-morbidities which may partially differ from those associated with OSAS. Partial upper airway obstruction is most prevalent in women, and it is treatable with the nasal continuous positive pressure device with good adherence to therapy. This review describes the characteristics of prolonged partial upper airway obstruction during sleep in terms of diagnostics, pathophysiology, clinical presentation, and comorbidity to improve recognition of this phenotype and its timely and appropriate treatment.

A frequent phenotype for paediatric sleep apnoea: short lingual frenulum

A short lingual frenulum has been associated with difficulties in sucking, swallowing and speech. The oral dysfunction induced by a short lingual frenulum can lead to oral-facial dysmorphosis, which decreases the size of upper airway support. Such progressive change increases the risk of upper airway collapsibility during sleep.

Clinical investigation of the oral cavity was conducted as a part of a clinical evaluation of children suspected of having sleep disordered breathing (SDB) based on complaints, symptoms and signs. Systematic polysomnographic evaluation followed the clinical examination. A retrospective analysis of 150 successively seen children suspected of having SDB was performed, in addition to a comparison of the findings between children with and without short lingual frenula.

Among the children, two groups of obstructive sleep apnoea syndrome (OSAS) were found: 1) absence of adenotonsils enlargement and short frenula (n=63); and 2) normal frenula and enlarged adenotonsils (n=87). Children in the first group had significantly more abnormal oral anatomy findings, and a positive family of short frenulum and SDB was documented in at least one direct family member in 60 cases.

A short lingual frenulum left untreated at birth is associated with OSAS at later age, and a systematic screening for the syndrome should be conducted when this anatomical abnormality is recognised.

A short lingual frenulum left untreated at birth is associated with obstructive sleep apnoea syndrome at a later agehttp://ow.ly/6kMQ30163nG

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

Purpose

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

Methods

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

Results

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

Conclusions

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

Effects of Oropharyngeal Exercises on Snoring: A Randomized Trial

BACKGROUND

Snoring is extremely common in the general population and may indicate OSA. However, snoring is not objectively measured during polysomnography, and no standard treatment is available for primary snoring or when snoring is associated with mild forms of OSA. This study determined the effects of oropharyngeal exercises on snoring in minimally symptomatic patients with a primary complaint of snoring and diagnosis of primary snoring or mild to moderate OSA.

METHODS

Patients were randomized for 3 months of treatment with nasal dilator strips plus respiratory exercises (control) or daily oropharyngeal exercises (therapy). Patients were evaluated at study entry and end by sleep questionnaires (Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index) and full polysomnography with objective measurements of snoring.

RESULTS

We studied 39 patients (age, 46 ± 13 years; BMI, 28.2 ± 3.1 kg/m2; apnea-hypopnea index (AHI), 15.3 ± 9.3 events/h; Epworth Sleepiness Scale, 9.2 ± 4.9; Pittsburgh Sleep Quality Index, 6.4 ± 3.3). Control (n = 20) and therapy (n = 19) groups were similar at study entry. One patient from each group dropped out. Intention-to-treat analysis was used. No significant changes occurred in the control group. In contrast, patients randomized to therapy experienced a significant decrease in the snore index (snores > 36 dB/h), 99.5 (49.6-221.3) vs 48.2 (25.5-219.2); P = .017 and total snore index (total power of snore/h), 60.4 (21.8-220.6) vs 31.0 (10.1-146.5); P = .033.

CONCLUSIONS

Oropharyngeal exercises are effective in reducing objectively measured snoring and are a possible treatment of a large population suffering from snoring.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01636856; URL: www.clinicaltrials.gov.

Polysomnographic Markers in Children With Cystic Fibrosis Lung Disease

BACKGROUND AND OBJECTIVES

Children with cystic fibrosis (CF) often report poor sleep, increased daytime sleepiness, and fatigue. The purpose of this study was to identify respiratory patterns over the spectrum of disease severity in children with CF. The overall hypothesis for the current study is that children with CF compared with snoring control subjects demonstrate gas exchange abnormalities and increased respiratory loads during sleep that are not reported or recognized by conventional polysomnography (PSG).

METHODS

Analysis of breathing patterns and gas exchange on PSG was performed in children with CF and healthy controls matched by age and BMI. For all CF and control subjects, the indication for PSG was evaluation for obstructive sleep apnea based on a history of snoring.

RESULTS

Children with CF, compared with age- and BMI-matched snoring controls, demonstrated lower oxyhemoglobin saturation (95% ± 1.6% vs 98% ± 0.6%, P = .005), higher respiratory rate (19.5 ± 4.9 vs 16.5 ± 1.2 breaths per minute, P = .03), and a higher proportion of inspiratory flow limitation (44.1% ± 24.7% vs 12.1% ± 13.5%, P = .007) during non-rapid eye movement sleep. The respiratory disturbance index did not differ between CF and snoring control groups (1.5 ± 2.7 vs 0.6 ± 0.6 events per hour, P = .11).

CONCLUSIONS

Children with CF exhibited abnormalities in gas exchange and increased respiratory load during sleep compared with normal age- and BMI-matched snoring controls. Because these abnormalities were independent of weight and lung function, sleep state may serve as an opportunity for early detection of breathing abnormalities and possibly CF lung disease progression.

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.

Missing teeth and pediatric obstructive sleep apnea

BACKGROUND

Missing teeth in early childhood can result in abnormal facial morphology with narrow upper airway. The potential association between dental agenesis or early dental extractions and the presence of obstructive sleep apnea (OSA) was investigated.

METHODS

We reviewed clinical data, results of polysomnographic sleep studies, and orthodontic imaging studies of children with dental agenesis (n = 32) or early extraction of permanent teeth (n = 11) seen during the past 5 years and compared their findings to those of age-, gender-, and body mass index-matched children with normal teeth development but tonsilloadenoid (T&A) hypertrophy and symptoms of OSA (n = 64).

RESULTS

The 31 children with dental agenesis and 11 children with early dental extractions had at least 2 permanent teeth missing. All children with missing teeth (n = 43) had clinical complaints and signs evoking OSA. There was a significant difference in mean apnea-hypopnea indices (AHI) in the three dental agenesis, dental extraction, and T&A studied groups (p < 0.001), with mean abnormal AHI lowest in the pediatric dental agenesis group. In the children with missing teeth (n = 43), aging was associated with the presence of a higher AHI (R (2) = 0.71, p < 0.0001).

CONCLUSION

Alveolar bone growth is dependent on the presence of the teeth that it supports. The dental agenesis in the studied children was not part of a syndrome and was an isolated finding. Our children with permanent teeth missing due to congenital agenesis or permanent teeth extraction had a smaller oral cavity, known to predispose to the collapse of the upper airway during sleep, and presented with OSA recognized at a later age. Due to the low-grade initial symptomatology, sleep-disordered breathing may be left untreated for a prolonged period with progressive worsening of symptoms over time.

Relationship between Oral Flow Patterns, Nasal Obstruction, and Respiratory Events during Sleep

STUDY OBJECTIVES

Sleep breathing patterns are altered by nasal obstruction and respiratory events. This study aimed to describe the relationships between specific sleep oral flow (OF) patterns, nasal airway obstruction, and respiratory events.

METHODS

Nasal flow and OF were measured simultaneously by polysomnography in 85 adults during sleep. OF was measured 2 cm in front of the lips using a pressure sensor.

RESULTS

OF could be classified into three patterns: postrespiratory event OF (postevent OF), during-respiratory event OF (during-event OF), and spontaneous arousal-related OF (SpAr-related OF). Postevent OFs begin at the end of airflow reduction, are preceded by respiratory arousal, and are accompanied by postapneic hyperventilation; during-event OFs occur during nasal flow reduction; and SpAr-related OFs to OF begin during stable breathing, and are preceded by spontaneous arousal but are rarely accompanied by apnea/hypopnea. Multivariate regression showed that nasal obstruction was predictive of SpAr-related OF. The relative frequency of SpAr-related OF events was negatively correlated with the apnea-hypopnea index. The fraction of SpAr-related OF duration relative to total OF duration was significantly greater in patients with nasal obstruction than in those without.

CONCLUSION

SpAr-related OF was associated with nasal obstruction, but not respiratory events. This pattern thus functions as a "nasal obstruction bypass", mainly in normal subjects and patients with mild sleep disordered breathing (SDB). By contrast, the other two types were related to respiratory events and were typical patterns seen in patients with moderate and severe SDB.

Sleep and Respiration in 100 Healthy Caucasian Sleepers--A Polysomnographic Study According to American Academy of Sleep Medicine Standards

STUDY OBJECTIVES

Despite differences between American Academy of Sleep Medicine (AASM) and Rechtschaffen and Kales scoring criteria, normative values following the current AASM criteria are lacking. We investigated sleep and respiratory variables in healthy adults over the lifespan, and established polysomnographic normative values according to current standards.

DESIGN

Prospective polysomnographic investigation.

SETTING

Academic referral hospital sleep laboratory.

PARTICIPANTS

One hundred healthy sleepers aged 19-77 y were selected from a representative population sample by a two-step screening.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

All subjects underwent one full-night polysomnography. Sleep and arousals were scored according to AASM standards. Respiration was scored according to AASM 2007 and 2012 criteria in order to compare both methods. Percentile curves showed age-related differences in sleep architecture: a decrease was found for sleep efficiency [≤ 30 y: 87.0 (71.9-94.1)% versus > 60 y: 79.7 (44.5-90.9)%], total sleep time [≤ 30 y: 413.5 (345.6-451.9) min versus > 60 y: 378.3 (216.0-440.0) min], the percentages of N3 [≤ 30 y 20.7 (15.2-37.5)% versus > 60 y: 14.9 (2.4-35.6)%] and rapid eye movement sleep [≤ 30 y 15.5 (7.5-23.6)% versus. > 60 y: 10.3 (1.9-21.9)%], whereas the percentage of wake time after sleep onset increased with age [≤ 30 y 6.0 (1.9-22.8)% versus > 60 y: 15.2 (6.3-48.7)%]. The apnea-hypopnea index (AHI) was higher when applying the AASM 2012 criteria [AHI AASM 2007 0.7 (0.0-21.5)/h versus 2012: 1.7 (0.0-25)/h; P < 0.001]. Eight percent of subjects had an AHI > 15/h.

CONCLUSIONS

This study provides normative data on sleep macrostructure, microstructure, and respiration in adults following AASM standards. Furthermore, we demonstrated that respiration scoring according to AASM 2012 results in higher AHIs, and challenge the use of age-independent respiratory cutoff values.

Mouth breathing, "nasal disuse," and pediatric sleep-disordered breathing

BACKGROUND

Adenotonsillectomy (T&A) may not completely eliminate sleep-disordered breathing (SDB), and residual SDB can result in progressive worsening of abnormal breathing during sleep. Persistence of mouth breathing post-T&As plays a role in progressive worsening through an increase of upper airway resistance during sleep with secondary impact on orofacial growth.

METHODS

Retrospective study on non-overweight and non-syndromic prepubertal children with SDB treated by T&A with pre- and post-surgery clinical and polysomnographic (PSG) evaluations including systematic monitoring of mouth breathing (initial cohort). All children with mouth breathing were then referred for myofunctional treatment (MFT), with clinical follow-up 6 months later and PSG 1 year post-surgery. Only a limited subgroup followed the recommendations to undergo MFT with subsequent PSG (follow-up subgroup).

RESULTS

Sixty-four prepubertal children meeting inclusion criteria for the initial cohort were investigated. There was significant symptomatic improvement in all children post-T&A, but 26 children had residual SDB with an AHI > 1.5 events/hour and 35 children (including the previous 26) had evidence of "mouth breathing" during sleep as defined [minimum of 44 % and a maximum of 100 % of total sleep time, mean 69 ± 11 % "mouth breather" subgroup and mean 4 ± 3.9 %, range 0 and 10.3 % "non-mouth breathers"]. Eighteen children (follow-up cohort), all in the "mouth breathing" group, were investigated at 1 year follow-up with only nine having undergone 6 months of MFT. The non- MFT subjects were significantly worse than the MFT-treated cohort. MFT led to normalization of clinical and PSG findings.

CONCLUSION

Assessment of mouth breathing during sleep should be systematically performed post-T&A and the persistence of mouth breathing should be treated with MFT.

New insights on the pathophysiology of inspiratory flow limitation during sleep

INTRODUCTION

Inspiratory flow limitation (IFL) is defined as a "flattened shape" of inspiratory airflow contour detected by nasal cannula pressure during sleep and can indicate increased upper airway resistance especially in mild sleep-related breathing disorders (SRBD). The objective of this study was to investigate the association between upper airway abnormalities and IFL in patients with mild SRBD.

METHODS

This study was derived from a general population study consisting of selected individuals with apnea-hypopnea index (AHI) below 5 events/h of sleep, ("no obstructive sleep apnea" group) and individuals with AHI between 5 and 15 events/h ("mild obstructive sleep apnea" group). A total of 754 individuals were divided into four groups: group 1: AHI <5/h and <30 % of total sleep time (TST) with IFL (515 individuals), group 2: AHI <5/h and >30 % of TST with IFL (46 individuals), group 3: AHI: 5-15/h and <30 % of TST with IFL (168 individuals), and group 4: AHI: 5-15/h and >30 % of TST with IFL (25 individuals).

RESULTS

Individuals with complains of oral breathing demonstrated a risk 2.7-fold larger of being group 4 compared with group 3. Abnormal nasal structure increased the chances of being in group 4 3.2-fold in comparison to group 1. Individuals with voluminous lateral wall demonstrated a risk 4.2-fold larger of being group 4 compared with group 3.

CONCLUSION

More than 30 % of TST with IFL detected in sleep studies was associated with nasal and palatal anatomical abnormalities in mild SRBD patients.

Airflow limitations in pregnant women suspected of sleep-disordered breathing

BACKGROUND AND AIM

Pregnancy physiology may predispose women to the development of airflow limitations during sleep. The goal of this study was to evaluate whether pregnant women suspected of sleep-disordered breathing (SDB) are more likely to have airflow limitations compared to non-pregnant controls.

METHODS

We recruited pregnant women referred for polysomnography for a diagnosis of SDB. Non-pregnant female controls matched for age, body mass index (BMI), and apnoea-hypopnoea index (AHI) were identified from a database. We examined airflow tracings for changes in amplitude and shape. We classified airflow limitation by (a) amplitude criteria defined as decreased airflow of > or =10 s without desaturation or arousal (FL 10), or decreased airflow of any duration combined with either 1-2% desaturation or arousal, (FL 1-2%); and (b) shape criteria defined as the presence of flattening or oscillations of the inspiratory flow curve.

RESULTS

We identified 25 case-control pairs. Mean BMI was 44.0±6.9 in cases and 44.1±7.3 in controls. Using shape criteria, pregnant women had significantly more flow-limited breaths throughout total sleep time (32.4±35.8 vs. 9.4±17.9, p<0.0001) and in each stage of sleep (p<0.0001) than non-pregnant controls. In a subgroup analysis, pregnant women without a diagnosis of obstructive sleep apnoea (OSA) who had an AHI <5 had similar findings (p<0.0001). There was no difference in airflow limitation by amplitude criteria between pregnant women and controls (p=0.22).

CONCLUSIONS

Pregnant women suspected of OSA have more frequent shape-defined airflow limitations than non-pregnant controls, even when they do not meet polysomnographic OSA criteria.

Multinight recording and analysis of continuous positive airway pressure airflow in the home for titration and management of sleep disordered breathing

OBJECTIVES

The authors examined magnitude/variability of residual sleep disordered breathing (SDB) at pressures around the therapeutic continuous positive airway pressure (CPAP), and described a multinight approach to CPAP titration/retitration consisting of recording airflow and summarizing SDB over multiple nights at multiple pressures and choosing an optimal pressure from these summarized data.

DESIGN

Prospective, single-center nonblinded study.

PATIENTS

Ten female/18 male patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) (respiratory disturbance index [RDI] 67/h), 17 newly-initiated, 11 chronic CPAP users.

INTERVENTIONS

A custom CPAP device (Fisher & Paykel Healthcare) recording airflow and pre-programmed to vary CPAP between 2-3 cm H2O below and 1-2 cm H2O above prescription pressure as determined by a full laboratory titration.

RESULTS

Airflow and pressure continuously recorded for multiple nights (15.9 ± 5.1 nights) at four to seven different pressures in each patient. SDB events manually scored from the airflow as apnea (airflow reduction > 90%), hypopnea (airflow reduction > 30% lasting 10 to 120 sec with inspira-tory flow limitation [IFL]) and runs of sustained IFL > 2 min identified. RDI = (apnea + hypopnea)/total sleep time calculated for each night and an obstruction index, including sustained IFL, also was calculated. PressureMultinight was obtained for each patient from multiple nights of data using two mathematical techniques. Night-to-night variability of SDB indices was low in some patients and significant in others. PressureMultinight could be determined in 17 of 28 patients and was similar to the in-laboratory pressure.

CONCLUSIONS

This study showed that recording multiple nights of CPAP airflow in the home and analyzing these data for residual SDB provided useful information, including the possibility of determining a therapeutic prescription for fixed CPAP in most patients and identification of others with significant physiologic variability of SDB.