No abstract

Our results demonstrated that the severity of OSA is independently related to atherosclerosis and that the severity of OSA-related hypoxemia is more important than the frequency of obstructive events.

Obstructive sleep apnea syndrome (OSAS) is a major public health problem with a prevalence estimated at approximately 4% of adults in both Western and Asian countries. 1,2 Nasal continuous positive airway pressure (CPAP) therapy for OSAS has been the most effective and widely used treatment. [3][4][5] However, approximately 25% to 50% of patients with OSA will either refuse to try or will not tolerate CPAP therapy. 6 Furthermore, some patients do not respond to CPAP treatment, either without symptom improvements or without reductions in overall respiratory events. Finally, central apneas can emerge with initiation of CPAP therapy, a condition that has been called "complex sleep apnea." 7 Taken together, these facts indicate signifi cant variability of the OSAS phenotype.Background: Mixed apneas share both central and obstructive components and are often treated as if they are obstructive events. The hypothesis is that patients with obstructive sleep apnea syndrome (OSAS) who exhibit a majority of mixed apneas will differ in ventilatory control from those with predominantly obstructive apneas during wakefulness; moreover, this difference could affect nasal continuous positive airway pressure (CPAP) adherence. Methods: In a retrospectively derived case-control study, 5 min of respiratory inductance plethysmography signals during wakefulness prior to sleep onset were extracted from a diagnostic polysomnogram in these groups: (1) mixed apnea-dominant OSAS (mix-OSAS) (n 5 36), (2) obstructive apnea-dominant OSAS (pure-OSAS) (n 5 20), (3) central apnea-dominant sleep apnea syndrome (pure-CSAS) (n 5 6), and (4) control subjects (n 5 10). Breathing patterning was compared between the groups using the coeffi cient of variation (CV) for breath-to-breath inspiration time (T I ), expiration time (T E ), T I 1 T E (Ttot), and tidal volume, and an information theory-based metric of signal pattern variability (sample entropy). Subsequent CPAP adherence over 12 months was determined in OSAS groups. Results: Breath-to-breath CV parameters and sample entropy in the mix-OSAS group were significantly greater as compared with the pure-OSAS and control groups. In a subanalysis, CV and sample entropy were similar in the mix-OSAS and the pure-CSAS groups. CPAP adherence was signifi cantly poorer in mix-OSAS compared with pure-OSAS. Conclusions: During wakefulness, both breath patterning and sample entropy in mix-OSAS are similar to pure-CSAS and more variable than in pure-OSAS. In addition, CPAP adherence was decreased in patients with mix-OSAS, which may be related to basic differences in respiratory control.CHEST 2011; 140(1):54-61

A simple screening method for sleep-disordered breathing (SDB) is desirable for primary care practices. In the present study, a simple monitor, which utilises a new type of flow sensor and a novel algorithm, was prospectively validated.Home recording for 2 nights with the monitor only, followed by in-laboratory recording with the monitor together with polysomnography, were carried out in consecutive patients (n5100) suspected of SDB. A subjective sleep log was also recorded. The signal was analysed using power spectral analysis, which yielded the flow respiratory disturbance index (flow-RDI).There was no recording failure at home. The reproducibility of the flow-RDI between the 2 nights at home was high (intraclass correlation coefficient50.92). The sensitivity and specificity of the in-laboratory flow-RDI to diagnose SDB were 0.96 and 0.82, 0.91 and 0.82, and 0.89 and 0.96, for apnoea/hypopnoea index (AHI) o5, o15 and o30 events?h -1 , respectively. The diagnostic ability in low-severity subgroups (female, normal weight, AHI ,15 events?h -1 ) was almost comparable to that in the entire group. Excluding subjective waking time on the sleep log from the recording time had no significant effect on the flow-RDI. The single-channel monitor is considered feasible for ambulatory sleep disordered breathing monitoring because of its easy applicability, high reproducibility and relatively high agreement with polysomnography results.

Study Objectives: Obstructive sleep apnea (OSA) can be severe and present in higher numbers during rapid eye movement (REM) than nonrapid eye movement (NREM) sleep; however, OSA occurs in NREM sleep and can be predominant. In general, ventilation decreases an average 10% to 15% during transition from wakefulness to sleep, and there is variability in just how much ventilation decreases. As dynamic changes in ventilation contribute to irregular breathing and breathing during NREM sleep is mainly under chemical control, our hypothesis is that patients with a more pronounced reduction in ventilation during the transition from wakefulness to NREM sleep will have NREM-predominant rather than REM-predominant OSA. Methods: A retrospective analysis of 451 consecutive patients (apnea-hypopnea index [AHI] > 5) undergoing diagnostic polysomnography was performed, and breath-tobreath analysis of the respiratory cycle duration, tidal volume, and estimated minute ventilation before and after sleep onset were examined. Values were calculated using respiratory inductance plethysmography. The correlation between the percent change in estimated minute ventilation during wakesleep transitions and the percentage of apnea-hypopneas in NREM sleep (%AHI in NREM; defi ned as (AHI-NREM) / [(AHI-NREM) + (AHI-REM)] × 100) was the primary outcome. Results: The decrease in estimated minute ventilation during wake-sleep transitions was 15.0 ± 16.6% (mean ± standard deviation), due to a decrease in relative tidal volume. This decrease in estimated minute ventilation was signifi cantly correlated with %AHI in NREM (r = −0.222, p < 0.01). 1,2 In general, upper airway obstruction and hypopnea is in REM sleep when upper airway muscle tonus is decreased as compared to nonrapid eye movement (NREM) sleep. However, OSA occurring predominantly in NREM sleep or equally in a numeric manner in both REM and NREM sleep is also encountered in clinical practice; neither prevalence nor mechanisms driving the relative distribution of REM and NREM events have been considered in any detail. In NREM sleep, detailed physiologic studies detect dynamic changes in ventilatory control during state transitions, which are considered to induce irregular breathing, and lead to obstructive apnea and/or hypopnea. [3][4][5][6][7] Detailed studies in REM sleep are absent, leaving an opportunity for the clinical polysomnogram to inform not only REM-predominant OSA but the possibility of NREM predominant OSA as well. ConclusionsVentilation decreases an average of 10% to 15% during the transition from wakefulness to sleep due mainly to a decrease in tidal volume; however, the literature reports substantial