ABSTRACT
I. Introduction Obstructive sleep apnea (OSA) is a common condition, being present in approximately 2% to 4% of the general middle-aged population (1). Repetitive collapse of the upper airway during sleep leads to ineffectual respiratory efforts and apnea, and causes abnormalities in sleep architecture and excessive daytime sleepiness. In recent years, there has been mounting evidence that OSA can also lead to serious cardiovascular consequences including hypertension, coronary artery disease, stroke, and congestive heart failure (CHF) (2-6). Central sleep apnea (CSA) differs from OSA in that central apneas are characterized by absent respiratory effort and result from instability in the chemoreflex control of breathing. Although rare in the general population, CSA is very common in the setting of heart failure (HF), being present in 30% to 40% of these patients in the two largest reported series (7,8).
