Atrial natriuretic peptide levels and pulmonary artery pressure awake, at exercise and asleep in obstructive sleep apnoea syndrome

Elevated nocturnal plasma atrial natriuretic peptide (ANP) levels were foun d in patients with obstructive sleep apnoea (OSA). The purpose of our study was to examine the secretion of ANP during the night and to measure change s in oxygen saturation, pulmonary artery pressure and intrathoracic pressur e swings in patients with OSA. Moreover, we analysed the secretion of ANP a nd the pulmonary artery pressure in different behavioural states, e.g, awak e, at exercise and asleep. Consecutive apnoeas in non-rapid eye movement (N REM) sleep at the beginning, middle and end of the sleep study were analyse d in six patients with obstructive sleep apnoea. In addition, we measured t he plasma levels of ANP. The apnoea duration was significantly longer (P< 0 .05) at the middle of the sleep study than at the beginning or end. Corresp ondingly, the end-apnoeic oxygen saturation and end-apnoeic oesophageal pre ssure were both significantly lower (P< 0.05) in the middle of the sleep st udy than at the beginning or end. No significant differences were found in the end-apnoeic systolic transmural pulmonary artery pressure (P-PATM) and the levels of ANP. Evaluation of the ANP levels during different behavioura l states revealed that the asleep levels were slightly, but not significant ly, higher than the awake levels (0.235+/-0.088 vs. 0.207+/-0.057 nmol/L). However, the highest levels were found during exercise (0.334+/-0.170 nmol/ L) with a significant difference compared with the awake and asleep levels. These data suggest that volume effects may be a potent factor in liberatin g ANP during exercise, but the role of OSA in ANP secretion when asleep is questionable.