Morbid obesity influences the nocturnal electrocardiogram wave and interval durations among suspected sleep apnea patients.

BACKGROUND: Obesity is a global issue with a major impact on cardiovascular health. This study explores how obesity influences nocturnal cardiac electrophysiology in suspected obstructive sleep apnea (OSA) patients. METHODS: We randomly selected 12 patients from each of the five World Health Organization body mass index (BMI) classifications groups (ntotal = 60) while keeping the group's age and sex matched. We evaluated 1965 nocturnal electrocardiography (ECG) samples (10 s) using modified lead II recorded during normal saturation conditions. R-wave peaks were detected and confirmed using dedicated software, with the exclusion of ventricular extrasystoles and artifacts. The duration of waves and intervals was manually marked. The average electric potential graphs were computed for each segment. Thresholds for abnormal ECG waveforms were P-wave > 120 ms, PQ interval > 200 ms, QRS complex > 120 ms for, and QTc > 440 ms. RESULTS: Obesity was significantly (p < .05) associated with prolonged conduction times. Compared to the normal weight (18.5 ≤ BMI < 25) group, the morbidly obese patients (BMI ≥ 40) had a significantly longer P-wave duration (101.7 vs. 117.2 ms), PQ interval (175.8 vs. 198.0 ms), QRS interval (89.9 vs. 97.7 ms), and QTc interval (402.8 vs. 421.2 ms). We further examined ECG waveform prolongations related to BMI. Compared to other patient groups, the morbidly obese patients had the highest number of ECG segments with PQ interval (44% of the ECG samples), QRS duration (14%), and QTc duration (20%) above the normal limits. CONCLUSIONS: Morbid obesity predisposes patients to prolongation of cardiac conduction times. This might increase the risk of arrhythmias, stroke, and even sudden cardiac death.

Obstructive sleep apnea-related intermittent hypoxaemia is associated with impaired vigilance.

Obstructive sleep apnea (OSA)-related intermittent hypoxaemia is a potential risk factor for different OSA comorbidities, for example cardiovascular disease. However, conflicting results are found as to whether intermittent hypoxaemia is associated with impaired vigilance. Therefore, we aimed to investigate how desaturation characteristics differ between the non-impaired vigilance and impaired vigilance patient groups formed based on psychomotor vigilance task (PVT) performance and compared with traditional OSA severity parameters. The study population comprised 863 patients with suspected OSA who underwent a PVT test before polysomnography. The conventional OSA parameters, for example, the apnea-hypopnea index, oxygen desaturation index, and arousal index were computed. Furthermore, the median desaturation area, fall area, recovery area, and desaturation depth were computed with the pre-event baseline reference and with reference to the 100% oxygen saturation level. Patients were grouped into best- and worst-performing quartiles based on the number of lapses in PVT (Q1: PVT lapses <5 and Q4: PVT lapses >36). The association between parameters and impaired vigilance was evaluated by cumulative distribution functions (CDFs) and binomial logistic regression. Based on the CDFs, patients in Q4 had larger desaturation areas, recovery areas, and deeper desaturations when these were referenced to 100% saturation compared with Q1. The odds ratio (OR) of the median desaturation area (OR = 1.56), recovery area (OR = 1.71), and depth (OR = 1.65) were significantly elevated in Q4 in regression models. However, conventional OSA parameters were not significantly associated with impaired vigilance (ORs: 0.79-1.09). Considering desaturation parameters with a 100% SpO2 reference in the diagnosis of OSA could provide additional information on the severity of OSA and related daytime vigilance impairment.

QTc prolongation is associated with severe desaturations in stroke patients with sleep apnea.

BACKGROUND: Obstructive sleep apnea (OSA) is associated with vascular diseases from which stroke and sudden cardiac death are the most significant ones. It is known that disturbances of the autonomic nervous system and electrocardiographic changes are seen in patients with a previous cerebrovascular event. However, the pathophysiological cascade between breathing cessations, autonomic regulation, and cardiovascular events is not fully understood. METHODS: We aimed to investigate the acute effect of desaturation on repolarisation in OSA patients with a previous stroke. We retrospectively analysed heart-rate corrected QT (QTc) intervals before, within, and after 975 desaturations in OSA patients with a stroke history and at least moderate sleep apnea (apnea-hypopnea index ≥ 15 events/h, n = 18). For the control population (n = 18), QTc intervals related to 1070 desaturation were analysed. Desaturations were assigned to groups according to their length and duration. Groupwise comparisons and regression analyses were further executed to investigate the influence of desaturation features on repolarization. RESULTS: In the stroke population the QTc prolonged at least 11 ms during 27.1% of desaturations, and over 20 ms during 12.2% of desaturations. QTc was significantly prolonged during longer (> 30 s, p < 0.04) and deeper (> 7%, p < 0.03) desaturations. Less severe desaturations didn't influence QTc. In median, QTc prolonged 7.5 ms during > 45 s desaturations and 7.4 ms during > 9% deep desaturations. In the control population, QTc prolongation was observed but to a significantly lesser extent than in stroke patients. In addition, desaturation duration was found to be an independent predictor of QTc prolongation (ß = 0.08, p < 0.001) among all study patients. CONCLUSIONS: We demonstrated that longer (> 30 s) and deeper (> 7%) desaturations prolong QTc in patients with stroke history. A significant proportion of desaturations produced clinically relevant QTc prolongation. As it is known that a long QTc interval is associated with lethal arrhythmias, this finding might in part explain the pathophysiological sequelae of cardiovascular mortality in OSA patients with a history of stroke.

Comparison of the effect of weight change, simulated computational continuous positive airway pressure treatment and positional therapy on severity of sleep apnea.

Weight loss, continuous positive airway pressure (CPAP) and positional therapy (PT) are important treatments in obstructive sleep apnea (OSA). Although all of these reduce the apnea-hypopnea index (AHI) effectively, the benefits of these treatments have not been thoroughly investigated in a patient-specific manner. Therefore, clinicians do not have objective means to choose an optimal treatment for each patient. We aim to provide clinicians the possibility for treatment optimization in a patient-specific manner by introducing a computational simulation approach. The effect of actual weight change, computationally simulated CPAP treatment and PT and their combinations on the AHI were compared in 54 OSA patients divided into three equally sized groups (weight loss > 7%, weight loss 0%-7%, and weight gain) after a 5-year follow-up with lifestyle intervention. Weight loss reduced the AHI by 43.5% (p < .05) and 18%, simulated CPAP treatment with 3.3-hr adherence by 42.4% (p < .05) and 35.5% (p < .05), and simulated PT by 13.5% (p < .05) and 30.7% (p < .05) in > 7% and 0%-7% weight loss groups, respectively. Simulated CPAP treatment and PT were able to compensate for the increase in the AHI caused by weight gain. A developed simulation approach could help clinicians to estimate treatment success in advance in order to prescribe the most optimal patient-specific treatment to reduce OSA-related health risks.

Longer duration electroencephalogram arousals have a better relationship with impaired vigilance and health status in obstructive sleep apnoea.

PURPOSE: Obstructive sleep apnoea (OSA) is a prevalent sleep disorder with significant health consequences. Sleep fragmentation is a feature of OSA and is often determined by the arousal index (ArI), a metric based on the electroencephalograph (EEG). The ArI has a weak correlation with neurocognitive outcomes in OSA patients. In this study, we examine whether changing from the current minimum EEG arousal duration of 3 s improves the association between sleep fragmentation and neurocognitive outcomes. METHODS: In a retrospective study, we selected OSA patients without any other comorbidities that are associated with neurocognitive impairment. The OSA patients were clustered into two groups based on their psychomotor vigilance task (PVT) performance to represent impaired and unimpaired neurocognition. RESULTS: While no differences were found in demographics or usual sleep study statistics, the impaired group had a greater number of EEG arousals greater than 5 s (P = 0.034), 7 s (P = 0.041), and 15 s (P = 0.036) in duration. There were no differences in the number of EEG arousals associated with sleep-disordered breathing events. These differences also corresponded with quality of life outcomes between the two groups. An ArI with a duration of 5 s or greater had the best combination of sensitivity (70.0%) and specificity (66.7%) compared with the usual 3 s duration (sensitivity and specificity of 70.0% and 53.3%, respectively). CONCLUSION: A re-examination of the EEG arousal scoring rules, and their duration, may help with allocation of health resources to OSA patients most in need.

Polysomnographic risk factors for vigilance-related cognitive decline and obstructive sleep apnea.

PURPOSE: Cognitive decline (CD) and obstructive sleep apnea (OSA) are often comorbid. Some modifiable risk factors (RF) for CD are also associated with OSA. Diagnostic polysomnography (PSG) measures these RF and may identify at risk patients prior to the onset of CD. We aim to determine whether there are severe RF associated with established CD and an increasing severity of OSA that could identify patients at risk for CD for medical intervention. METHODS: We gathered information from subjects having type 1 PSG for suspected OSA. The psychomotor vigilance task (PVT) measured established CD (group 0 and group1). We compared levels of severe RF in group 0 and group 1 with a larger group (group 2) without the PVT. We used severe standardized values of excessive daytime sleepiness (Epworth Sleepiness Score [ESS]), overnight change of systolic blood pressure (ΔSBP), change of oxygen desaturation (ΔSpO2), and sleep arousal (ArI) as RF. We compared the severe levels of ESS, ΔSBP, ΔSpO2, and ArI by group and OSA severity. RESULTS: A total of 136 patients underwent diagnostic PSG. PVT parameters were available for 43 subjects. The severity of the RF was consistent with risk for CD (ΔSBP 22.0 ± 5.6, ESS 18.2 ± 2.2, ArI 58.8 ± 18.7, ΔSpO2 61.7 ± 21.9). The levels of RF increased with increasing severity of OSA. There were significant between-group differences for severe ΔSpO2 (p = 0.004) and ΔSpO2 + ArI (p = 0.019). CONCLUSION: The levels of RF increase with increasing OSA severity. Subjects with severe RF ΔSpO2 and ΔSpO2 + ArI are likely to have PVT-determined CD. Risk factor analysis may screen for CD.

Severe desaturations increase psychomotor vigilance task-based median reaction time and number of lapses in obstructive sleep apnoea patients.

Current diagnostic parameters estimating obstructive sleep apnoea (OSA) severity have a poor connection to the psychomotor vigilance of OSA patients. Thus, we aimed to investigate how the severity of apnoeas, hypopnoeas and intermittent hypoxaemia is associated with impaired vigilance.We retrospectively examined type I polysomnography data and corresponding psychomotor vigilance tasks (PVTs) of 743 consecutive OSA patients (apnoea-hypopnoea index (AHI) ≥5 events·h-1). Conventional diagnostic parameters (e.g. AHI and oxygen desaturation index (ODI)) and novel parameters (e.g. desaturation severity and obstruction severity) incorporating duration of apnoeas and hypopnoeas as well as depth and duration of desaturations were assessed. Patients were grouped into quartiles based on PVT outcome variables. The odds of belonging to the worst-performing quartile were assessed. Analyses were performed for all PVT outcome variables using binomial logistic regression.A relative 10% increase in median depth of desaturations elevated the odds (ORrange 1.20-1.37, p<0.05) of prolonged mean and median reaction times as well as increased lapse count. Similarly, an increase in desaturation severity (ORrange 1.26-1.52, p<0.05) associated with prolonged median reaction time. Female sex (ORrange 2.21-6.02, p<0.01), Epworth Sleepiness Scale score (ORrange 1.05-1.07, p<0.01) and older age (ORrange 1.01-1.05, p<0.05) were significant risk factors in all analyses. In contrast, increases in conventional AHI, ODI and arousal index were not associated with deteriorated PVT performance.These results show that our novel parameters describing the severity of intermittent hypoxaemia are significantly associated with increased risk of impaired PVT performance, whereas conventional OSA severity and sleep fragmentation metrics are not. These results underline the importance of developing the assessment of OSA severity beyond the AHI.

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 H2 O; oronasal, 11.7 cm H2 O; 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 H2 O 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.

Apnoea and hypopnoea scoring for people with spinal cord injury: new thresholds for sleep disordered breathing diagnosis and severity classification.

STUDY DESIGN: Descriptive study. OBJECTIVES: To determine the effect of respiratory event rule-set changes on the apnoea hypopnoea index, and diagnostic and severity thresholds in people with acute and chronic spinal cord injury. SETTING: Eleven acute spinal cord injury inpatient hospitals across Australia, New Zealand, Canada and England; community dwelling chronic spinal cord injury patients in their own homes. METHODS: Polysomnography of people with acute (n = 24) and chronic (n = 78) tetraplegia were reanalysed from 1999 American Academy of Sleep Medicine (AASM) respiratory scoring, to 2007 AASM 'alternative' and 2012 AASM respectively. Equivalent cut points for published 1999 AASM sleep disordered breathing severity ranges were calculated using receiver operator curves, and results presented alongside analyses from the able-bodied. RESULTS: In people with tetraplegia, shift from 1999 AASM to 2007 AASM 'alternative' resulted in a 22% lower apnoea hypopnoea index, and to 2012 AASM a 17% lower index. In people with tetraplegia, equivalent cut-points for 1999 AASM severities of 5,15 and 30 were calculated at 2.4, 8.1 and 16.3 for 2007 AASM 'alternative' and 3.2, 10.0 and 21.2 for 2012 AASM. CONCLUSION: Interpreting research, prevalence and clinical polysomnography results conducted over different periods requires knowledge of the relationship between different rule-sets, and appropriate thresholds for diagnosis of disease. SPONSORSHIP: This project was proudly supported by the Traffic Accident Commission (Program grant) and the National Health and Medical Research Council (PhD stipend 616605).

The prevalence of REM-related obstructive sleep apnoea is reduced by the AASM 2012 hypopnoea criteria.

PURPOSE: The variations in reported prevalence of rapid eye movement-related obstructive sleep apnoea (REM-OSA) have been attributed to different definitions, although the effect of hypopnoea criteria has not been previously investigated. METHODS: Within this retrospective study, 134 of 382 consecutive patients undertaking polysomnography (PSG) for the suspicion of OSA met the inclusion criteria. PSGs were scored using both the 2007 AASM recommended hypopnoea criteria (AASM2007Rec) and the 2012 AASM recommended hypopnoea criteria (AASM2012Rec). For each hypopnoea criteria, REM-OSA patients were grouped as REM-related [either as REM-predominant OSA (rpOSA) or REM-isolated OSA (riOSA)] or non-stage-specific OSA (nssOSA). Outcome measures (SF-36, FOSQ and DASS-21) were also compared between groups. RESULTS: Incorporation of the AASM2012Rec criteria compared to the AASM2007Rec criteria increased the apnoea-hypopnoea index (AHI) for NREM and REM sleep but decreased the AHIREM/AHINREM ratio from 1.9 to 1.3 (p < 0.001). It also decreased the prevalence of riOSA [15.7 vs 2.2% (p < 0.001) for AASM2007Rec and AASM2012Rec, respectively]. The prevalence of rpOSA remained the same for each hypopnoea criteria although the prevalence of nssOSA increased with the AASM2012Rec hypopnoea criteria [53.0 vs 66.4% (p < 0.006) for AASM2007Rec and AASM2012Rec, respectively]. There were no differences in clinical symptoms between the groups, irrespective of hypopnoea criteria used. CONCLUSIONS: This study demonstrates that in comparison with AASM2007Rec, the AASM2012Rec hypopnoea criteria reduce the prevalence of riOSA but not rpOSA by reducing the ratio of REM respiratory events and NREM respiratory events.

Severity of desaturation events differs between hypopnea and obstructive apnea events and is modulated by their duration in obstructive sleep apnea.

PURPOSE: Frequency of apnea and hypopnea events is used to estimate the severity of obstructive sleep apnea (OSA). However, comprehensive information on whether apneas and hypopneas cause an equal biological effect is not available. The purpose of the present work was to evaluate the effect of the breathing cessation event type (i.e., obstructive apnea or hypopnea) and duration on the severity of related SpO2 desaturation events. METHODS: Type 1 polysomnographies of 395 patients (220 males and 175 females) examined for suspected OSA were analyzed. Desaturation severity related to hypopnea and obstructive apnea events were compared and comparison was controlled for gender, sleep stage, sleeping position, age, and body mass index. Hypopneas and obstructive apneas were further divided into eight different durational categories and related desaturation event characteristics were compared between the categories. RESULTS: SpO2 desaturation events caused by obstructive apneas were statistically significantly (p ≤ 0.004) longer, greater in area, and deeper compared to the SpO2 desaturations caused by hypopneas. The increase in the duration of hypopnea and obstructive apnea events led to increase in the duration and area of related SpO2 desaturations. The increase in the obstructive apnea event duration also led to increase in the depth of related desaturation event. CONCLUSIONS: Obstructive apneas led to more severe SpO2 desaturation compared to hypopneas. Increased event duration led to increase in the severity of the related SpO2 desaturation. In addition to considering event duration, obstructive apneas should have more weight than hypopneas when estimating severity of OSA and associated long-term cardiovascular risk.

Severity of individual obstruction events is gender dependent in sleep apnea.

PURPOSE: In obstructive sleep apnea (OSA), severity of individual obstruction events is connected to increased mortality rate and it can be significantly different in patients with similar apnea-hypopnea index (AHI). However, possible gender-dependent variation in severity of obstruction events in different OSA categories is unknown. We investigated whether the severity of obstruction events differs between genders with similar AHI and if this difference varies between OSA categories. METHODS: Polygraphic recordings of 2057 consecutive patients with suspected OSA were reanalyzed and those with AHI ≥5/h were included for further analysis (n male = 893 and n female = 197). Statistical significance of differences in AHI, apnea index, hypopnea index, oxygen desaturation index, obstruction severity parameter, and severity of individual obstruction events between genders were evaluated using the Mann-Whitney U (MWU) test as well as the general linear model (GLM) univariate analysis adjusted for age, BMI, smoking, daytime sleepiness, snoring, and heart failure. RESULTS: Apneas were 16.9 and 19.6% longer (MWU p ≤ 0.015, GLM p ≤ 0.036) and desaturation areas were 15.4 and 23.7% larger (MWU p ≤ 0.024, GLM p ≤ 0.053) in males compared to females with moderate and severe OSA, respectively. In contrast, hypopneas were 9.1% shorter (MWU p = 0.001, GLM p ≤ 0.001) and desaturation areas were 6.0% smaller (MWU p = 0.114, GLM p = 0.025) in men with mild OSA. The apnea index was 433.3 and 313.1% higher (MWU p ≤ 0.001, GLM p ≤ 0.043) and the hypopnea index was 12.2 and 17.8% lower (MWU p ≤ 0.001, GLM p = 0.002, p = 0.083) in males with mild and moderate OSA, respectively. CONCLUSION: As severity of individual obstruction events was significantly different in males and females, the overall severity of OSA may not be similar despite the similarity in AHI.

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

PURPOSE: This 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. METHODS: Three 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. RESULTS: The 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. CONCLUSIONS: This 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.

Factors associated with noninvasive ventilation usage in patients with hypoventilation disorders.

Study Objectives: The objective of this study was to investigate the association between demographic, clinical, and interface factors and noninvasive ventilation (NIV) usage. Methods: A retrospective cohort analysis of 478 patients prescribed NIV from 2013 to 2021 was performed. Demographic factors, clinical indications for NIV, and interface factors were collected, and linear regression was conducted to evaluate the association between these variables and NIV usage (hour/night). Results: The average usage of the cohort was 6.5 hour/night ±â€…4.6, with an average age of 57 years ±â€…16 and body mass index (BMI) of 40.5kg/m2 ±â€…14.7. The cohort was mostly male (n = 290, 60.6%). The most common indications for NIV prescription were high-pressure requirement for obstructive sleep apnea (HPR, n = 190, 39.7%), neuromuscular disease (NMD, n = 140, 29.3%), and obesity hypoventilation syndrome (OHS, n = 111, 23.2%). A diagnosis of NMD was a significant predictor of higher NIV usage (8.0 ±â€…6.1 hour/night) in multivariate analysis (p = .036). The HPR subcohort had the lowest usage of all indications. Age and BMI did not predict usage. A nasal interface (p < .01) and lower expiratory positive airway pressure (EPAP) setting (p < .001) were associated with increased NIV usage. Conclusions: This study highlights the multifaceted nature of NIV usage. Where demographic factors were not consistent predictors of usage, interface, and clinical indication were associated with usage. These findings highlight that the HPR users are a group at risk of low usage.

Prospective crossover trial of positional and CPAP therapy for the treatment of mild-to-moderate positional obstructive sleep apnea.

STUDY OBJECTIVES: To evaluate efficacy of vibrotactile positional therapy (PT) compared to standard CPAP therapy in mild-to-moderate positional obstructive sleep apnea (pOSA). METHODS: Prospective crossover randomized controlled trial of adult patients with treatment-naïve, symptomatic, mild-to-moderate pOSA - defined as ≥5 total apnea-hypopnea index (AHI) <30 with supine-to-non-supine (s:ns)AHI ratio ≥2. Participants were randomized to in-laboratory treatment initiation polysomnography with either PT or CPAP on sequential nights before an eight-week trial of each therapy. The primary endpoint was symptomatic improvement (Epworth Sleepiness Scale; ΔESS). Secondary endpoints included patient preference, usage, sleep architecture and quality of life (QoL) measures. RESULTS: 52 participants were enrolled and completed both arms of the study. Participants were symptomatic with median ESS 12 (IQR 10-14). Treatment resulted in a significant (p<0.001) symptomatic improvement with both PT and CPAP (ΔESS 4; IQR 6-11) without a significant difference between treatment arms (p=0.782). PT was effective at restricting supine sleep and demonstrated improved sleep efficiency compared with CPAP, although no better than baseline. Both therapies were effective at reducing AHI, although CPAP demonstrated superior AHI reduction. There were otherwise no clinically significant differences in sleep architecture, usage, or secondary outcomes including overall patient preference. CONCLUSIONS: In this cohort, treatment with PT or CPAP resulted in clinically significant symptomatic improvement (ΔESS) that was not significantly different between treatment arms. No real difference was seen in other secondary outcome measures. This study provides further evidence to support the use of PT as an alternative first-line therapy with CPAP in appropriately selected patients with pOSA. CLINICAL TRIAL REGISTRATION: Registry: Australian New Zealand Clinic Trials Registry; Name: Prospective crossover trial of Positional and Continuous positive airway pressure Therapy for the treatment of mild-to-moderate positional obstructive sleep apnoea; Identifier: ACTRN12619000475145; URL: https://anzctr.org.au/Trial/Registration/TrialReview.aspx?id=377221&isReview=true.

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.

Australasian Sleep Association 2024 guidelines for sleep studies in adults.

Executive summary: This document is a consensus statement of a subcommittee of experienced sleep physicians and scientists, tasked to review the literature and formulate recommendations on the indications, performance, and reporting of sleep studies, to update clinical practice from the 2017 Australasian Sleep Association (ASA) guidelines for sleep studies in adults (Douglas JA, Chai-Coetzer CL, McEvoy D, et al. Guidelines for sleep studies in adults - a position statement of the Australasian Sleep Association. Sleep Med. 2017;36(Suppl 1):S2-S22. doi:10.1016/j.sleep.2017.03.019). This document moves the focus beyond important discussions outlined in the 2017 guidelines, particularly surrounding the sensitivity and specificity of validated questionnaires and home sleep studies. The 2024 guide outlines the performance of the broad range of sleep testing available for the investigations of sleep disorders in adults including indications, strengths, limitations, and reporting standards.

Respiratory event index underestimates severity of sleep apnea compared to apnea-hypopnea index.

Polygraphy (PG) is often used to diagnose obstructive sleep apnea (OSA). However, it does not use electroencephalography, and therefore cannot estimate sleep time or score arousals and related hypopneas. Consequently, the PG-derived respiratory event index (REI) differs from the polysomnography (PSG)-derived apnea-hypopnea index (AHI). In this study, we comprehensively analyzed the differences between AHI and REI. Conventional AHI and REI were calculated based on total sleep time (TST) and total analyzed time (TAT), respectively, from two different PSG datasets (n = 1561). Moreover, TAT-based AHI (AHITAT) and TST-based REI (REITST) were calculated. These indices were compared keeping AHI as the gold standard. The REI, AHITAT, and REITST were significantly lower than AHI (p < 0.0001, p ≤ 0.002, and p ≤ 0.01, respectively). The total classification accuracy of OSA severity based on REI was 42.1% and 72.8% for two datasets. Based on AHITAT, the accuracies were 68.4% and 85.9%, and based on REITST, they were 65.9% and 88.5% compared to AHI. AHI was most correlated with REITST (r = 0.98 and r = 0.99 for the datasets) and least with REI (r = 0.92 and r = 0.97). Compared to AHI, REI had the largest mean absolute errors (13.9 and 6.7) and REITST the lowest (5.9 and 1.9). REI had the lowest sensitivities (42.1% and 72.8%) and specificities (80.7% and 90.9%) in both datasets. Based on these present results, REI underestimates AHI. Furthermore, these results indicate that arousal-related hypopneas are an important measure for accurately classifying OSA severity.

Arousal burden is highest in supine sleeping position and during light sleep.

STUDY OBJECTIVES: Arousal burden (AB) is defined as the cumulative duration of arousals during sleep divided by the total sleep time. However, in-depth analysis of AB related to sleep characteristics is lacking. Based on previous studies addressing the arousal index (ArI), we hypothesized that the AB would peak in the supine sleeping position and during non-rapid eye movement stage 1 (N1) and show high variability between scorers. METHODS: Nine expert scorers analyzed polysomnography recordings of 50 participants, the majority with an increased risk for obstructive sleep apnea. AB was calculated in different sleeping positions and sleep stages. A generalized estimating equation was utilized to test the association between AB and sleeping positions, sleep stages, and scorers. The correlation between AB and ArI was tested with Spearman's rank-order correlation. RESULTS: AB significantly differed between sleeping positions (p<0.001). The median AB in the supine sleeping position was 47-62% higher than in the left and right position. The AB significantly differed between the sleep stages (p<0.001); the median AB was more than 200% higher during N1 than during other sleep stages. In addition, the AB differed significantly between scorers (p<0.001) and correlated strongly with ArI (r=0.935, p<0.001). CONCLUSIONS: AB depends on the sleeping position, sleep stage, and scorer as hypothesized. AB behaved similarly as the ArI, but the high variability in the ABs between scorers indicates a potential limitation caused by subjective manual scoring. Thus, the development of more accurate techniques for scoring arousals is required before AB can be reliably utilized.

Power spectral analysis of the sleep electroencephalogram in positional obstructive sleep apnea.

OBJECTIVE/BACKGROUND: Previous studies have shown that obstructive sleep apnoea (OSA) is associated with reduced delta EEG and increased beta EEG power and increased EEG slowing ratio. There are however no studies that explore differences in sleep EEG between positional obstructive sleep apnoea (pOSA) and non-positional obstructive sleep apnoea (non-pOSA) patients. PATIENTS/METHODS: 556 of 1036 consecutive patients (246 of 556 were female) undertaking polysomnography (PSG) for the suspicion of OSA met the inclusion criteria for this study. We calculated power spectra of each sleep epoch using Welch's method with ten, 4-s overlapping windows. Outcome measures such as Epworth Sleepiness Scale, SF-36 Quality of Life, Functional Outcomes of Sleep Questionnaire and Pyschomotor Vigilance Task were compared between the groups. RESULTS: Patients with pOSA had greater delta EEG power in NREM and greater N3 proportions compared to their non-pOSA counterparts. There were no differences in theta (4-8Hz), alpha (8-12Hz), sigma (12-15Hz) or beta (15-25Hz) EEG power or EEG slowing ratio between the two groups. There were also no differences in the outcome measures between these two groups. The division of pOSA into spOSA and siOSA groups showed better sleep parameters in siOSA but with no difference in sleep power spectra. CONCLUSIONS: This study partially supports our hypothesis in showing that pOSA, compared to non-pOSA, is associated with increased delta EEG power but did not show any variation to beta EEG power or EEG slowing ratio. This limited improvement in sleep quality did not translate to measurable changes to outcomes, suggesting beta EEG power or EEG slowing ratio may be key factors.