1. Central Sleep Apneas Sung Chul Hwang, M.D. Dept. of Pulmonary and Critical Care Medicine Ajou University School of Medicine

2. Central Sleep Apneas Central apneas reflect unstable breathing control Decreased resp. drive : Hypoventilation during sleep --> Hypercapneic CSA Increased resp. drive : Hyperventilation during wake and sleep --> Hypocapneic CSA

3. Mechanisms Result of abolished ventilatory motor out- put Hypocapnea during NREM sleep is the major cause of reduced ventilatory motor out put

4. Pathogenesis Instability often occurs at sleep onset : PaCO2 during awake is less than required for rhythm generation in sleep Enhanced by chronic hyperventilation during wakefulness and hypocapnea below threshold Hypoxia, Aggravation of cardiorespiratory disease, Hyperventilation, Pulmonary congestion Circulatory slowing due to cardiac failure lead to ventilatory instability

5. Clinical Features CSA is an alveolar hypoventilation syndrome Daytime hypercapnea and hypoxemia Recurrent resp. failure, polycythemia, Pul. hypertension, Rt. heart Failure Poor sleep, morning headaches, daytime fatigue, somnolence, nocturnal awakenings, etc

6. Diagnosis Clinical features Definitive Dx : Polysomnography Measurement of transcutaneous PaCO2 Defect in Resp. control or NM function : elevated Ps CO2 that tend to increased during night esp. REM sleep

7. Treatment Nocturnal O2 to correct Hypoxemia Acetazolamide -> Acidosis -> increase ventilation Nasal CPAP : increasePaCO2 as the added expiratory mechanical load Nasal CPAP is particularly effective in CSA secondary to CHF in improving sleep quality and daytime cardiac condition