“…Most studies recruited outpatients from heart failure clinics, but some included hospitalized patients and the severity of heart failure, assessed either by echocardiography or clinically, varied widely. The apnea-hypopnea index (AHI) that defined sleep apnea ranged from 15 to 5 cycles per hour and, accordingly, the prevalence varied from 47 to 82% and from 21 to 66% for sleep-disordered breathing and CSR in patients with CHF, respectively [2,3,11,12,13,14,15,16,17,18,19,20,21] (fig. 2).…”