Objective: To investigate the effect of treatment with continuous positive airway pressure (CPAP) on nocturnal polyuria in patients with obstructive sleep apnea syndrome (OSAS).
Methods: 15 patients with obstructive sleep apnea syndrome were included. The number of nocturia, the nocturia output, the osmotic pressure of nocturia and the nocturia excretion of Na(+) were recorded. Plasma levels of atrial natriuretic peptide (ANP) in night were measured in 8 patients. After treatment with CPAP, all the criteria were repeated.
Results: (1) The number of nocturia decreased significantly after treatment with CPAP (P < 0.01); (2) The difference between nocturia output pre-and post treatment was significant (P < 0.01); (3) The osmotic pressure of nocturia rose from (381 +/- 96) mmol/L to (570 +/- 169) mmol/L (P < 0.05); (4) The nocturia excretion of Na(+) dropped from (1.16 +/- 0.35) mmol/h to (0.63 +/- 0.13) mmol/h (P < 0.01); (5) Plasma levels of ANP in night decreased from (146 +/- 14) ng/L to (106 +/- 10) ng/L (P < 0.01); (6) After treatment with CPAP, the reduction of ANP is correlated with the reduction of the nocturia output, the addition of the osmotic pressure of nocturia and the reduction of the nocturia excretion of Na(+). The correlation coefficients were 0.82, 0.84, 0.81 respectively.
Conclusion: Treatment with CPAP can reduce the number of nocturia, the nocturia output and the nocturia excretion of Na(+), increase the osmotic pressure of nocturia. The changes probably relate to the reduction of plasma level of ANP.