man grasping at his chestSleep-disordered breathing (SDB) is common in patients with heart failure (HF), and hypoxia and hypercapnia stimulate autonomic reflex responses. During an apneic episode, hypoxia and hypercapnia occur, triggering these involuntary reflex responses.  These can include muscle sympathetic nerve activity (MSNA) and ventilation. In patients with heart failure (HF), stimulation causes an increase in ventilation, MSNA, and vasoconstriction. Patients with HF and SDB have more severe muscle vasoconstriction during hypoxia and hypercapnia than HF patients without SDB. It remains unknown whether SDB directly contributes to increased HF morbidity and mortality, or whether it just marks HF severity.  In this study, you will read that HF patients with SDB have more pronounced skeletal muscle vasoconstriction than HF patients without SDB (during peripheral and central chemoreceptors stimulation). Please click here to read the full article about the SDB and heart failure connection.