Sleep Apnea, CentralCheyne-Stokes RespirationSleep Apnea SyndromesPolysomnographySleep Apnea, ObstructiveSleepContinuous Positive Airway PressureRespirationHeart FailureHypocapniaPositive-Pressure RespirationCarbon DioxideOxygen Inhalation TherapySleep, REMHypercapniaSleep DisordersSeverity of Illness IndexOxygenCell RespirationStroke VolumeSnoringTreatment OutcomeFollow-Up StudiesProspective Studies