Brett Duce

Obstructive sleep apnea screening by integrating snore feature classes

Obstructive sleep apnea (OSA) is a serious sleep disorder with high community prevalence. More than 80% of OSA suffers remain undiagnosed. Polysomnography (PSG) is the current reference standard used for OSA diagnosis. It is expensive, inconvenient and demands the extensive involvement of a sleep technologist. At present, a low cost, unattended, convenient OSA screening technique is an urgent requirement. Snoring is always almost associated with OSA and is one of the earliest nocturnal symptoms. With the onset of sleep, the upper airway undergoes both functional and structural changes, leading to spatially and temporally distributed sites conducive to snore sound (SS) generation. The goal of this paper is to investigate the possibility of developing a snore based multi-feature class OSA screening tool by integrating snore features that capture functional, structural, and spatio-temporal dependences of SS. In this paper, we focused our attention to the features in voiced parts of a snore, where quasi-repetitive packets of energy are visible. Individual snore feature classes were then optimized using logistic regression for optimum OSA diagnostic performance. Consequently, all feature classes were integrated and optimized to obtain optimum OSA classification sensitivity and specificity. We also augmented snore features with neck circumference, which is a one-time measurement readily available at no extra cost. The performance of the proposed method was evaluated using snore recordings from 86 subjects (51 males and 35 females). Data from each subject consisted of 6-8 h long sound recordings, made concurrently with routine PSG in a clinical sleep laboratory. Clinical diagnosis supported by standard PSG was used as the reference diagnosis to compare our results against. Our proposed techniques resulted in a sensitivity of 93±9% with specificity 93±9% for females and sensitivity of 92±6% with specificity 93±7% for males at an AHI decision threshold of 15 events/h. These results indicate that our method holds the potential as a tool for population screening of OSA in an unattended environment.

The 2012 AASM Respiratory Event Criteria Increase the Incidence of Hypopneas in an Adult Sleep Center Population.

STUDY OBJECTIVES To investigate the effect of the 2012 American Academy of Sleep Medicine (AASM) respiratory event criteria on severity and prevalence of obstructive sleep apnea (OSA) relative to previous respiratory event criteria. METHODS A retrospective, randomized comparison was conducted in an Australian clinical sleep laboratory in a tertiary hospital. The polysomnograms (PSG) of 112 consecutive patients undertaking polysomnography (PSG) for suspected OSA were re-scored for respiratory events using either 2007 AASM recommended (AASM2007Rec), 2007 AASM alternate (AASM2007Alt), Chicago criteria (AASM1999), or 2012 AASM recommended (AASM2012) respiratory event criteria. RESULTS The median AHI using AASM2012 was approximately 90% greater than the AASM2007Rec AHI, approximately 25% greater than the AASM2007Alt AHI, and approximately 15% lower than the AASM1999 AHI. These changes increased OSA diagnoses by approximately 20% and 5% for AASM2007Rec and AASM2007Alt, respectively. Minimal changes in OSA diagnoses were observed between AASM1999 and AASM2012 criteria. To achieve the same OSA prevalence as AASM2012, the threshold for previous criteria would have to shift to 2.6/h, 3.6/h, and 7.3/h for AASM2007Rec, AASM2007Alt, and AASM1999, respectively. Differences between the AASM2007Rec and AASM2012 hypopnea indices (HI) were predominantly due to the change in desaturation levels required. Alterations to respiratory event duration rules had no effect on the HI. CONCLUSIONS This study demonstrates that implementation of the 2012 AASM respiratory event criteria will increase the AHI in patients undergoing PSG, and more patients are likely to be diagnosed with OSA. COMMENTARY A commentary on this article appears in this issue on page 1357.

Interhemispheric Asynchrony Correlates With Severity of Respiratory Disturbance Index in Patients With Sleep Apnea

Obstructive sleep apnea (OSA) hypopnea syndrome is a disorder characterized by airway obstructions during sleep; full obstructions are known as apnea and partial obstructions are called hypopnea. Sleep in OSA patients is significantly disturbed with frequent apnea/hypopnea and arousal events. We illustrate that these events lead to functional asymmetry of the brain as manifested by the interhemispheric asynchrony (IHA) computed using EEG recorded on the scalp. In this paper, based on the higher order spectra of IHA time series, we propose a new index [interhemispheric synchrony index (IHSI)], for characterizing brain asynchrony in OSA. The IHSI computation does not depend on subjective criteria and can be completely automated. The proposed method was evaluated on overnight EEG data from a clinical database of 36 subjects referred to a hospital sleep laboratory. Our results indicated that the IHSI could classify the patients into OSA/non-OSA classes with an accuracy of 91% (ρ = 0.0001), at the respiratory disturbance index threshold of 10, suggesting that the brain asynchrony carries vital information on OSA.

The AASM Recommended and Acceptable EEG Montages are Comparable for the Staging of Sleep and Scoring of EEG Arousals

STUDY OBJECTIVE To examine the measurement differences in sleep and EEG arousal statistics between the American Academy of Sleep Medicine (AASM) recommended EEG montage (F4-M1, C4-M1, O2-M1) and acceptable EEG montage (Fz-Cz, C4-M1, Oz-Cz). DESIGN Prospective, blinded, randomized comparison. SETTING Australian clinical sleep laboratory in a tertiary hospital. PATIENTS OR PARTICIPANTS 50 consecutive patients undertaking polysomnography (PSG) for the clinical suspicion of sleep disordered breathing. INTERVENTIONS N/A. MEASUREMENTS AND RESULTS Patient EEGs were recorded using both the AASM recommended and acceptable EEG montages during the PSG. Two scorers were used to examine the difference in PSG statistics using the two EEG montages. The scorers analyzed the 50 studies using the two EEG montages. Ten of the studies were scored twice for each montage by each scorer to calculate intra-scorer and inter-scorer agreement. No statistically significant differences were observed between the PSG statistics of the recommended and acceptable EEG montages. The recommended EEG montage had greater inter-scorer agreement but no difference in intra-scorer agreement. CONCLUSIONS This study demonstrates that the two EEG montages endorsed by the AASM Manual produce similar sleep and EEG arousal statistics.

The AASM 2012 recommended hypopnea criteria increase the incidence of obstructive sleep apnea but not the proportion of positional obstructive sleep apnea

OBJECTIVE/BACKGROUND This study compared the effects of using the 2007 and 2012 American Academy of Sleep Medicine (AASM) recommended hypopnea criteria on the proportion of positional obstructive sleep apnea (pOSA). The effect of modifying the minimum recording time in each sleeping position on the proportion of pOSA was also investigated. PATIENTS/METHODS 207 of 303 consecutive patients (91 of 207 were female) participated in polysomnography (PSG) for the suspicion of OSA met the inclusion criteria for this retrospective investigation. PSGs were scored for both the 2007 AASM recommended hypopnea criteria (AASM2007Rec) and the 2012 AASM recommended hypopnea criteria (AASM2012Rec). For each hypopnea criteria OSA patients were grouped as positional [either supine predominant OSA (spOSA) or supine independent OSA (siOSA)] or non-positional. Outcome measures such as SF-36, FOSQ, PVT, and DASS-21 were compared between groups. RESULTS The AASM2012Rec increased the incidence of OSA compared to AASM2007Rec (84% vs 49% respectively). AASM2012Rec increased the number of patients with supine predominant OSA (spOSA) and supine independent OSA (siOSA) but did not change the proportion (spOSA: 61% AASM2012Rec vs 61% AASM2007Rec, siOSA: 32% AASM2012Rec vs 36% AASM2007Rec). OSA patients diagnosed by AASM2007Rec criteria had similar outcome measures to those diagnosed by the AASM2012Rec criteria. The AASM2012Rec increased the proportion of female OSA patients with spOSA and siOSA. A minimum recording time of 60 minutes in each position decreased the proportion of spOSA, but not siOSA patients when compared to a minimum time of 15 minutes. CONCLUSIONS This study demonstrates that, compared to AASM2007Rec, AASM2012Rec almost doubles the incidence of OSA but does not alter the proportion of OSA patients with pOSA. The proportion of female OSA patients with pOSA however, increases as a result of AASM2012Rec. Furthermore, the use of different minimum recording times in each sleeping position can alter the proportion of spOSA.

Amsterdam positional OSA classification: the AASM 2012 recommended hypopnoea criteria increases the number of positional therapy candidates

PurposeThis study examined the effect of hypopnoea criteria on the prevalence of positional obstructive sleep apnoea (pOSA) identified under the Amsterdam Positional OSA Classification (APOC) system.MethodsThree hundred three consecutive patients undertaking polysomnography (PSG) for the suspicion of OSA were included in this retrospective investigation. PSGs were scored using both the 2007 American Academy of Sleep Medicine (AASM) recommended hypopnoea criteria (AASM2007Rec) and the 2012 AASM recommended hypopnoea criteria (AASM2012Rec). For each hypopnoea criteria, OSA patients were grouped according to the APOC categories (I, II or II) or else deemed non-APOC if they did not meet the APOC criteria. Outcome measures, such as Functional Outcomes of Sleep Questionnaire (FOSQ), MOS 36-item short-form health survey (SF-36) and psychomotor vigilance task (PVT), were also compared between the groups.ResultsThe AASM2012Rec increased the prevalence of OSA compared to AASM2007Rec. The AASM2012Rec trebled the number of APOC I patients compared to AASM2007Rec (297% increase) as well as increased the proportion of females in the APOC I group. AASM2012Rec did not change the number of APOC II and APOC III patients. In fact, the same patients were present in these categories irrespective of hypopnoea criteria. The proportion of non-APOC patients proportionally decreased with the AASM2012Rec criteria. There were no differences in outcome measures between the AASM2012Rec and AASM2007Rec groups.ConclusionsThis study demonstrates that, compared to AASM2007Rec, AASM2012Rec increases the prevalence of who could be successfully treated with positional therapy. The proportion of females with pOSA also increases as a consequence of AASM2012Rec.

A new measure to quantify sleepiness using higher order statistical analysis of EEG

Chronic sleepiness is a common symptom in the sleep disorders, such as, Obstructive Sleep Apnea, Periodic leg movement syndrome, narcolepsy etc. It affects 5% of the adult population and is associated with significant morbidity and increased risk to individual and society. MSLT and MWT are the existing tests for measuring sleepiness. Sleep Latency (SL) is the main measures of sleepiness computed in these tests. Existing method of SL computation relies on the visual extraction of specific features in multi-channel electrophysiological data (EEG, EOG, and EMG) using the R&K criteria (1968). This process is cumbersome, time consuming, and prone to inter and intra-scorer variability. In this paper we propose a fully automated, objective sleepiness analysis technique based on the single channel of EEG. The method uses a one-dimensional slice of the EEG Bisprectrum representing a nonlinear transformation of the underlying EEG generator to compute a novel index called Sleepiness Index. The SL is then computed from the SI. A strong correlation (r = 3D0.93, ρ = 3D0.0001) was found between technician scored SL and that computed via SI. The proposed Sleepiness Index can provide an elegant solution to the problems surrounding manual scoring and objective sleepiness.

Differences in arousal probability and duration after apnea and hypopnea events in adult OSA patients

OBJECTIVE In obstructive sleep apnea (OSA), breathing cessations are often followed by arousals, leading to sleep fragmentation and thus impaired sleep quality. Arousals and fragmented sleep are also related to detrimental cardiovascular events. The key index for OSA diagnosis (i.e. the apnea-hypopnea index) attributes equal diagnostic value to apneas and hypopneas, despite the fact that the associated arousals and desaturations may be very different. Thus, considering the severity of the consequences of apneas and hypopneas could enhance the estimation of OSA severity. In this study, we investigate whether the probability and duration of apnea- and hypopnea-related arousals differ and whether the differences in desaturation severity following apneas and hypopneas are dependent on sleep stage. APPROACH Polysomnographic recordings of 348 consecutive OSA patients were included for analysis. The severity of arousals and desaturations associated with hypopneas within different sleep stages was compared to that of arousals and desaturations associated with apneas. In addition, the probability of arousals related to apneas and hypopneas was evaluated within OSA severity categories. MAIN RESULTS Apneas caused arousals less frequently than hypopneas in N1, N2, and N3 sleep in all OSA severity categories. However, the arousals caused by apneas were longer (p  <  0.001) and the desaturations related to apneas were more severe (p  <  0.001) than those related to hypopneas in N1, N2, and rapid eye movement sleep even after adjustment for respiratory event durations. SIGNIFICANCE Desaturations and arousals related to apneas are more severe than those related to hypopneas. Therefore, apneas followed by arousal or desaturation should have a different diagnostic value than hypopneas when assessing OSA severity and related risk for cardiovascular consequences.

A randomised crossover trial comparing nasal masks with oronasal masks: No differences in therapeutic pressures or residual apnea-hypopnea indices

In treating obstructive sleep apnea (OSA), the use of oronasal masks with continuous positive airway pressure (CPAP) has been reported to increase pressure levels and reduce compliance. These reports come mostly from large observational studies. In this study, we examined the impact that oronasal masks have on 95th centile pressures, the residual apnea‐hypopnea index (AHI) and compliance compared with nasal masks. A randomised crossover design was implemented. Participants already established on CPAP were randomly allocated to a nasal mask or oronasal mask with auto‐titrating positive airway pressure (APAP) for 2 weeks. Participants then crossed over to use the alternate mask for another 2 weeks. Seventy‐one participants were recruited but only 60 completed the trial. There were no differences in median 95th centile pressure (nasal, 11.5 cm H2O; oronasal, 11.7 cm H2O; p = 0.115), median residual AHI (nasal, 4.9 events/hr; oronasal, 5.3 events/hr; p = 0.234) or median compliance (nasal, 7.3 hr/night; oronasal, 7.3 hr/night; p = 0.961). Only four patients had 95th centile pressures that were at least 1.5 cm H2O greater with oronasal masks. Oronasal masks do not systematically increase therapeutic CPAP requirements. Rather, a small subset of patients display significant differences in CPAP levels.