Reduction of nocturnal diuresis and natriuresis during treatment of obstructive sleep apnea (OSA) with nasal continuous positive air pressure (nCPAP) correlates to cGMP excretion.

In ten patients with severe obstructive sleep apnea (OSA) profound changes in renal function could be demonstrated at night during nCPAP therapy. Natriuresis and diuresis decreased by about 50% while creatinine excretion rate and urinary osmolality did not change. We found parallel changes in the excretion of ANP's second messenger cyclic guanosine monophosphate (cGMP) in a dose-response-related manner to natriuresis respectively diuresis. These data are in agreement with recently demonstrated decrease of nocturnal plasma levels of atrial natriuretic peptide (ANP) during nCPAP therapy in apneic patients. This may be an indicator for an increased cardiac volume load during obstructive apnea. The decrease of diuresis, natriuresis and cGMP excretion demonstrate the beneficial effects of nCPAP treatment on the cardiovascular system. Therefore measurements of cGMP excretion may be a useful parameter to assess the cardiovascular function of apneic patients before and during treatment.