Bitter T, et al. - Researchers investigated if initial diagnostic polysomnography (PSG) in patients with heart failure with reduced ejection fraction (HFREF) and obstructive sleep apnea (OSA) can detect unmasking of central sleep apnea during continuous positive airway pressure (CPAP) initiation. They analyzed obstructive apneas during diagnostic PSG for cycle length (CL), ventilation length (VL), apnea length (AL), time to peak ventilation (TTPV), and circulatory delay (CD). Findings showed that in initial diagnostic PSG, longer CL, VL, TTPV, and CD from obstructive events could identify OSA/central sleep apnea in HFREF. The presence of an increased loop gain (LG) appeared to be the underlying mechanism.