Effects of nasal continuous positive airway pressure (NCPAP) on nocturnal renal function in obstructive sleep apnea syndrome (OSAS)

Nocturnal renal function was examined in 8 patients with obstructive sleep apnea syndrome (OSAS) and the effects of nasal CPAP (NCPAP) on renal function were also studied. Nocturia was observed more than twice in all cases when no treatment was performed, but it disappeared after initiation of NCPAP. Fractional nocturnal urine volume and creatinine clearance decreased significantly from 1.36 +/- 0.15 ml/min to 0.75 +/- 0.20 ml/min (p less than 0.01) and from 116.8 +/- 46.5 ml/min to 101.1 +/- 33.0 ml/min (p less than 0.05), respectively, after initiation of NCPAP. Although the serum Na and creatinine did not change following NCPAP, the urine Na and creatinine changed significantly after NCPAP therapy. The serum renin, aldosterone, and ADH did not change after NCPAP therapy. The significant positive correlation (p less than 0.05) between the fractional nocturnal urine volume and DI, and also significant inverse correlation (p less than 0.05) between the fractional urine volume and %FRC were observed. These results suggest that the abnormal renal function seen in cases of OSAS is related to the hypoxemia during sleep. It was concluded that the nocturnal renal function in cases of OSAS was different from those in normal controls and NCPAP therapy induced the recovery of these abnormalities.