Improvement in sleep apnea during nocturnal peritoneal dialysis is associated with reduced airway congestion and better uremic clearance.

BACKGROUND AND OBJECTIVES Among peritoneal dialysis (PD) patients, nocturnal PD (NPD) is known to improve sleep apnea compared with continuous ambulatory peritoneal dialysis (CAPD), but the contributing factors are unclear. DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS Thirty-eight incident ESRD patients underwent overnight polysomnography (PSG) during NPD and CAPD. Bioelectrical impedance analysis, magnetic resonance imaging of the upper airway, and urea kinetics (Kt/V) during sleep were measured on both occasions. RESULTS The prevalence of severe sleep apnea (apnea-hypopnea index, AHI > or = 15/h) was 21.1% during NPD, and 42.1% during CAPD. Mean AHI increased from 9.6 +/- 2.7/h during NPD to 21.5 +/- 4.2/h during CAPD. Both obstructive and central apnea worsened after conversion to CAPD. NPD achieved greater reductions in total body water, hydration fraction, and net ultrafiltration than CAPD during sleep. Overnight peritoneal Kt/V and creatinine clearance were lower after conversion. Both peritoneal Kt/V and peritoneal creatinine clearance correlated with AHI, as did their changes after conversion. Volumetric magnetic resonance imaging revealed reduced pharyngeal volumes and cross-sectional area, and tongue enlargement after conversion. CONCLUSIONS Improvement in sleep apnea during NPD versus CAPD is associated with better fluid and uremic clearance and reduced upper airway congestion during sleep.