Sleep-Disordered Breathing-Do We Have to Change Gears in Heart Failure?

Monitoring of nocturnal central sleep apnea in Heart failure patients using noncontact respiratory differences

Monitoring of respiration patterns allows the early detection of various breathing disorders and may better identify those at risk for adverse acute outcomes in a variety of clinical settings. In this paper, we report on the use of SleepMinder (SM), a bedside non-contact Doppler-based biomotion recording sensor, to monitor remotely the nocturnal respiration patterns of 50 patients with systolic Heart failure (HF) while undergoing a lab based Polysomnography (PSG) test. A new respiration rate (RR) monitoring algorithm was developed based on the collected overnight radar signals. Two schemes of RR scoring were utilized: respiratory rate count (RRC) and instantaneous respiratory rates (IRR). Analysis of SM vs. PSG revealed that the mean/median IRR scored by SM is highly correlated with that scored on the nasal flow/effort signals from the corresponding PSG studies on all patients, with a significant correlation coefficient of 0.98 (average absolute difference of 0.31 breaths/min), and 0.97 (p<;0.01, average absolute difference of 0.38 breaths/min) for the median and mean of RR respectively. Our experimental results also show that the difference between the RR estimations from IRR and RRC schemes can be utilized to identify central sleep apnea (CSA)/Cheyne-Stokes respiration (CSR) sections without additional apnea detection modules. As a result, with a sensitivity and specificity of 71% and 88% respectively, and an accuracy of 86%, our CSA/CSR screener, plugged with our RR estimation, can play an important role in the remote management of HF patients.

Circulating exosomes in obstructive sleep apnea as phenotypic biomarkers and mechanistic messengers of end-organ morbidity

Obstructive sleep apnea (OSA), the most severe form of sleep disordered breathing, is characterized by intermittent hypoxia during sleep (IH), sleep fragmentation, and episodic hypercapnia. OSA is associated with increased risk for morbidity and mortality affecting cardiovascular, metabolic, and neurocognitive systems, and more recently with non-alcoholic fatty liver disease (NAFLD) and cancer-related deaths. Substantial variability in OSA outcomes suggests that genetically-determined and environmental and lifestyle factors affect the phenotypic susceptibility to OSA. Furthermore, OSA and obesity often co-exist and manifest activation of shared molecular end-organ injury mechanisms that if properly identified may represent potential therapeutic targets. A challenge in the development of non-invasive diagnostic assays in body fluids is the ability to identify clinically relevant biomarkers. Circulating extracellular vesicles (EVs) include a heterogeneous population of vesicular structures including exosomes, prostasomes, microvesicles (MVs), ectosomes and oncosomes, and are classified based on their size, shape and membrane surface composition. Of these, exosomes (30-100nm) are very small membrane vesicles derived from multi-vesicular bodies or from the plasma membrane and play important roles in mediating cell-cell communication via cargo that includes lipids, proteins, mRNAs, miRNAs and DNA. We have recently identified a unique cluster of exosomal miRNAs in both humans and rodents exposed to intermittent hypoxia as well as in patients with OSA with divergent morbid phenotypes. Here we summarize such recent findings, and will focus on exosomal miRNAs in both adult and children which mediate intercellular communication relevant to OSA and endothelial dysfunction, and their potential value as diagnostic and prognostic biomarkers.

Sleep apnea: State of the art

Many patient with, or at risk of, cardiovascular disease have sleep disordered breathing (SDB), which can be either obstructive (with intermittent collapse of the upper airway) or central (episodic loss of respiratory drive). SDB is associated with sleep disturbance, hypoxemia, hemodynamic changes, and sympathetic activation. Such patients have a worse prognosis than those without SDB. Mask-based therapies of positive airway pressure targeted at SDB can improve measures of sleep quality and partially normalize the sleep and respiratory physiology, but recent randomized trials of cardiovascular outcomes in SDB have either been neutral (obstructive sleep apnea) or suggested the possibility of harm, likely from increased sudden death, in central sleep apnea. Alternative methods for the treatment of SDB are being explored, including implantable technologies, but these have not been studied in adequately powered randomized controlled studies. International guidelines recommend screening for SDB, which can be done easily in clinical practice, as there may be a role for the treatment of patients with obstructive sleep apnea and daytime sleepiness, or resistant hypertension, or atrial fibrillation. Further randomised outcome studies are required to determine whether mask-based treatment for SDB is appropriate for patients with chronic systolic heart failure and obstructive sleep apnea; for those with heart failure with preserved ejection fraction; and for those with decompensated heart failure. The case is made that no longer can the surrogate endpoints of improvement in respiratory and sleep metrics be taken as adequate therapeutic outcome measures in patients with sleep apnea and cardiovascular disease.