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Rationale: Obstructive sleep apnea (OSA) severity is typically assessed by the apnea-hypopnea index (AHI), a frequency-based metric that allocates equal weight to all respiratory events. However, more severe events may have a greater physiologic impact. Objectives: The purpose of this study was to determine whether the degree of event-related hypoxemia would be associated with the postevent physiologic response. Methods: Patients with OSA (AHI, ⩾5/h) from the multicenter Canadian Sleep and Circadian Network cohort were studied. Using mixed-effect linear regression, we examined associations between event-related hypoxic burden (HB ev ) assessed by the area under the event-related oxygen saturation recording with heart rate changes (ΔHR ev ), vasoconstriction (vasoconstriction burden [VCB ev ] assessed with photoplethysmography), and electroencephalographic responses (power ratio before and after events). Results: Polysomnographic recordings from 658 patients (median [interquartile range] age, 55.00 [45.00, 64.00] yr; AHI, 27.15 [14.90, 64.05] events/h; 42% female) were included in the analyses. HB ev was associated with an increase in all physiologic responses after controlling for age, sex, body mass index, sleep stage, total sleep time, and study centers; for example, 1 standard deviation increase in HB ev was associated with 0.21 [95% confidence interval, 0.2, 0.22], 0.08 [0.08, 0.09], and 0.22 [0.21, 0.23] standard deviation increases in ΔHR ev , VCB ev , and β-power ratio, respectively. Conclusions: Increased event-related hypoxic burden was associated with greater responses across a broad range of physiologic signals. Future metrics that incorporate information about the variability of these physiologic responses may have promise in providing a more nuanced assessment of OSA severity.

Rationale: Obstructive sleep apnea (OSA) is associated with an increased risk of mild cognitive impairment (MCI) within the general population. However, MCI risk in sleep-clinic populations of patients with OSA is poorly characterized. Objectives: To determine the prevalence of MCI in a sleep-clinic population of patients with OSA and which patients are at the greatest risk for this complication. Methods: Adults ( n  = 1,084) referred to three academic sleep centers for suspected OSA who had home sleep apnea testing or in-laboratory polysomnography were recruited. Patients completed sleep and medical history questionnaires, the Montreal Cognitive Assessment Test (MoCA) of global cognition, the Rey Auditory Verbal Learning Test of memory, and the Wechsler Adult Intelligence Scale-Fourth Edition Digit-Symbol Coding (DSC) subtest of information processing speed. Results: A MoCA score <26 (range 0-30) was operationally defined as MCI. MCI was present in 47.9% of our entire patient cohort, increasing to >55.3% in patients with moderate and severe OSA. Patients with a MoCA <26 were predominantly older males with more severe OSA, hypoxemia, and vascular comorbidities. Moderate and severe OSA were independently associated with >70% higher odds for MCI compared with patients with no OSA ( P  = 0.003). Memory and information processing speed was lower than age-matched normal values ( P  < 0.001), with lower MoCA and DSC scores associated with a higher oxygen desaturation index and nocturnal hypoxemia. Conclusions: Cognitive impairment is highly prevalent in patients referred to sleep clinics for suspected OSA, occurring predominantly in older males with moderate to severe OSA and concurrent vascular comorbidities. Moderate to severe OSA is an independent risk factor for MCI.

Rationale: Lack of timely access to diagnosis and treatment of sleep-disordered breathing (SDB) has sparked interest in using nonphysician providers. Previous studies of these alternative care providers (ACPs) excluded patients with more complicated forms of SDB and did not directly explore the impacts of a model incorporating ACPs on healthcare system performance, such as wait times. Objectives: To evaluate the use of ACPs in the management of patients with severe SDB from a clinical and system perspective. Methods: In this noninferiority study, patients with severe SDB ( N  = 156) were enrolled from October 2014 to July 2016 and randomized to either sleep physician management or management by ACP with same-day sleep physician review. Severe SDB was defined as one of 1 ) respiratory event index greater than 30/h, 2 ) mean nocturnal oxygen saturation less than 85%, and 3 ) arterial carbon dioxide greater than 45 mm Hg with respiratory event index greater than 15/h. The primary outcome was nightly positive airway pressure adherence at 3 months, using a noninferiority margin of 1 hour. Secondary outcomes included sleepiness, quality of life, patient satisfaction, wait times for diagnosis and treatment initiation, and demand for further testing and clinical assessment. Outcomes were evaluated using modified intention-to-treat and per-protocol analyses. Results: Care delivery using ACPs was indeterminate compared with sleep physician care with respect to treatment adherence, because the 95% confidence interval included the noninferiority margin of 1 hour (mean difference, -0.5 [-1.49 to 0.49] h). Patients in the ACP arm reported greater improvements in sleepiness and quality of life; wait times were shorter for initial assessment (28%) and treatment initiation (18%). There was no difference in demand for sleep testing or clinical follow-up. Per-protocol analysis revealed similar results. Conclusions: Management of severe SDB using ACPs was indeterminate compared with sleep physician care. The small decrease in adherence in the ACP arm was balanced by benefits in patient-reported outcomes and reduction in wait times. In systems with unacceptably long wait times for SDB diagnosis and treatment, a small decrease in treatment adherence, as was observed in this study, may be an acceptable trade-off to improve access to care for patients with severe SDB.Clinical trial registered with www.clinicaltrials.gov (NCT02191085).

Rationale: Hypoxemia in obese patients is likely to be associated with a high prevalence of sleep-disordered breathing. Supplemental oxygen is commonly used to treat chronic hypoxemia but carries some risk in obese individuals due to unrecognized comorbid obstructive sleep apnea (OSA) and obesity hypoventilation syndrome (OHS)., Objectives: The first step in the estimation of this risk is to determine the prevalence of OSA and OHS in obese individuals with chronic, awake hypoxemia., Methods: A single-center retrospective cohort study was performed to assess the prevalence and severity of OSA and OHS among obese individuals with hypoxemia. One hundred eighty-four individuals underwent arterial blood gas testing and polysomnography. One hundred fifty-eight of these individuals also had spirometry., Measurements and Main Results: The prevalence of OSA was 80%, and the prevalence of OHS was 51%. Chronic obstructive pulmonary disease (COPD) was confirmed by spirometry in 49% of the cohort, and OSA was found in 69% of those individuals. The severity of hypoxemia in this cohort was not statistically related to COPD, OSA, or OHS., Conclusions: OSA and OHS are highly prevalent in obese patients with chronic awake hypoxemia, and OSA frequently coexists with COPD. Evaluation of chronic, awake hypoxemia solely based on arterial blood gas measurements and pulmonary function testing is not sufficient to identify OSA and OHS. Further diagnostic sleep testing should be performed to identify those who could benefit from alternative therapies and to avoid potential harm from treatment with supplemental oxygen alone.