Central and Peripheral 24-h Blood Pressure Before and After 3 Month of CPAP Treatment in Obstructive Sleep Apnea

The purpose of this study is to investigate the effect of 3 months of continuous positive airway pressure (CPAP) treatment of obstructive sleep apnea (OSA) in moderate to severe cases in patients with chronic kidney disease. The effect is evaluated on blood pressure levels, particularly nocturnal blood pressure, both central and peripheral, and renal function, including the kidneys treatment of salt and water. Hypothesis: 1. Central 24-h blood pressure measuring is a reveals fluctuations in blood pressure during the day more accurately than peripheral 24-h blood pressure measuring because the measurement is painless and does not interfere with the patient activities during the daytime or nighttime sleep. 2. Central blood pressure is elevated in patients with OSA and falls during treatment with CPAP. 3. The renal tubular function relating to the treatment of water and sodium is abnormal in patients with OSA with increased tubular absorption of water via the U-aquaporin 2 (u-AQP2) and of sodium by epithelial sodium channel (ENAC) and is normalized during treatment with CPAP. 4 Quality of life is improved during treatment with CPAP.