Dirk Pevernagie

REM sleep-related brady-arrhythmia syndrome

Rapid eye movement (REM) sleep-related brady-arrhytmia syndrome is a cardiac rhythm disorder characterised by asystoles lasting several seconds during REM sleep in otherwise healthy individuals. In contrast to arrhythmias associated with obstructive sleep apnea, REM sleep-related sinus arrests and atrioventricular (AV) blocks are not associated with episodes of apnea or hypopnea. In literature, only few cases have been published, suggesting that the prevalence of this nighttime rhythm disorder is very rare. In this paper, we report two new cases of REM sleep-related sinus arrests and one case of REM sleep-related total AV block. To explore the underlying mechanism, an analysis of heart rate variability was performed. In a matched control population, we observed a significant lower low-to-high frequency (LF/HF) ratio in slow wave sleep as compared to REM sleep (2.04u2009±u20091.2 vs 4.55u2009±u20091.82, respectively [Mann–Whitney U test pu2009<u20090.01]), demonstrating a global increase in sympathetic activity during REM. When using the same technique in two of three patients with REM-related arrhythmias, the shift to an increased LF/HF ratio from slow wave sleep to REM sleep tended to be lower. This may reflect an increased vagal activity (HF component) during REM sleep in these subjects. We, therefore, hypothesise that, in our patients with REM sleep-related arrhythmias, the overall dominance of sympathetic activity during REM is present but to a lesser extent and temporarily switches into vagal dominance when the bursts of REMs occur. As it was still unclear whether these REM sleep-related asystoles needed to be paced, we compared our treatment and these of previously reported cases with the current American College of Cardiology/American Heart Association guidelines for implantation of cardiac pacemakers.

Comfort and pressure profiles of two auto-adjustable positive airway pressure devices: a technical report

STUDY OBJECTIVESnThe purpose of this study was to compare comfort parameters and pressure profiles of the AutoSet (Resmed) and the SOMNOsmart (Weinmann), two auto-adjustable positive airway pressure (APAP) devices.nnnSETTINGnThe sleep disorders center of a university hospital.nnnDESIGNnA single-blind randomized trial protocol was applied. A split night procedure allowed each patient to be treated in a crossover fashion with both APAP devices during one overnight study.nnnPATIENTS AND METHODSnFifty consecutive obstructive sleep apnea (OSA) patients were recruited. Each patient filled out an evaluation form for both devices after the study night. Visual analogue scales were used to score four comfort measures. Three CPAP outcomes generated by the devices (P50, P95 and Pmax) were assessed, compared with each other and correlated with the individually predicted CPAP (Ppred).nnnRESULTSnForty-five males and 5 females, mean age 53.0 years, body mass index 31.0, were included. The mean apnea-hypopnea index was 58.7, the mean arousal index was 54.3. Mean CPAP-compliance before the titration study was 4.9 h per night. Comparison of the two devices regarding the effect on the subjective sleep quality parameters showed no differences. The AutoSet pressure outcomes correlated significantly better with Ppred in comparison with the SOMNOsmart. The P50 and P95 but not the Pmax values were significantly lower in the SOMNOsmart as compared with the AutoSet (P50: 5.1+/-1.3 vs 7.1 +/- 1.9 mbar, P<0.0001; P95: 7.8+/-3.0 vs 9.6+/-1.9 mbar, P<0.0005; Pmax: 10.0+/-3.4 vs 10.8+/-1.8 mbar, NS).nnnCONCLUSIONnWhile the subjective tolerance of the two APAP machines was comparable, these devices were characterized by different pressure profiles. The pressure parameters of the AutoSet correlated better with Ppred than those of the SOMNOsmart.

Titration Efficacy of Two Auto-Adjustable Continuous Positive Airway Pressure Devices Using Different Flow Limitation-Based Algorithms

Background: Auto-adjustable continuous positive airway pressure devices are widely used in titration procedures to determine therapeutic pressure levels in obstructive sleep apnea patients. However, differences in operational characteristics may influence the effect on the apnea-hypopnea index (AHI). Objectives: We compared the titration performance of two devices based on detection of inspiratory flow limitation, i.e. the Respironics REMstar Auto™ (RR) and the ResMed Spirit™ (RS). Methods: Fifty obstructive sleep apnea patients were recruited for a double-blind randomized crossover trial. Both devices were employed overnight by means of split-night polysomnography. The primary outcome was the AHI. Secondary outcome measures were the snoring index, pressure profiles and subjective appraisal of sleep quality assessed the morning after the sleep study. The Wilcoxon signed rank test for matched pairs was applied to assess differences between treatment conditions. Results: No significant differences were found in sleep parameters, subjective sleep quality and snoring index. The use of the RR was associated with a significantly lower AHI in comparison with the RS [mean (SD) 6.9 (11.6)/h vs. 9.4 (9.2)/h, p = 0.004]. This result was obtained at significantly lower pressure levels [P95 9.2 (2.3) cm H2O vs. 10.2 (1.5) cm H2O, p = 0.001]. Conclusion: While the RR provided a lower AHI than the RS at lower pressure levels, it could not be assessed whether this difference was relevant for clinical outcomes. However, this face-to-face comparison of Auto-adjustable continuous positive airway pressure devices seems useful for the assessment of titration efficacy.