Loop Gain in the Reversion of OSA Treated by Either CPAP or Cardiac Valve Replacement

Sleep apnea including obstructive sleep apnea (OSA) and central sleep apnea (CSA), are common in patients with cardiovascular disease. The prevalence of OSA is 2%-4% in general population and 16%-47% in surgical-heart failure patients. The previous studies found that the sleep apnea types shifted from OSA to CSA after continuous positive airway pressure (CPAP) treatment or from CSA to OSA after heart surgery (cardiac valve replacement/ repair or heart transplantation) without the mechanism illuminated clearly. The recent studies found that the loop gain (LG) could predict the effect of upper airway surgery and CPAP treatment on the reversion of OSA. However, in patients with valvular heart disease, whether LG and related parameters can predict the therapeutic efficacy of CPAP or cardiac valve replacement is not expounded clearly. The investigators' previous study found that there were different outcomes of sleep apnea after cardiac valve replacement: elimination or consistent. But the corresponding non-anatomic mechanisms was not clear. The investigators' preliminary experiment showed that the LG and related parameters were not improved while OSA improved by CPAP treatment; however, the recovery of OSA after cardiac valve replacement was closed related to the improvement of LG and related parameters. The investigators speculated that, 1. LG and related parameters could predict OSA outcome of CPAP treatment or cardiac valve replacement. 2. non-anatomic mechanisms including LG and associated parameters, contributed to CPAP treatment and cardiac valve replacement were different. In this study, the investigators aimed to explore the relationship between LG and, outcomes of OSA and the regarding non-anatomic mechanisms in patient with heart valve disease.