Background: Reduced plasma nitrate (NOx) levels and increased urinary norepinephrine (U-NE) levels have been described in severe obstructive sleep apnea (OSA), and are reverted by continuous positive airway pressure (CPAP). The effect of CPAP on these biomarkers in mild-moderate OSA is not well understood. The aim of this study was to compare NOx and U-NE levels and blood pressure (BP) between male patients with mild-moderate and severe OSA and determine the impact of 1 month of CPAP therapy on these parameters. Methods: We undertook a prospective study of 67 consecutive OSA patients (36 mild-moderate, 31 severe). Measurements of plasma NOx at 11 pm, 4 am and 7 am, 24-h U-NE and ambulatory BP were obtained at baseline and after 1 month of CPAP. Results: At baseline, NOx levels showed a significant decrease during the night in both groups (p < 0.001). U-NE level and BP were significantly higher in the severe OSA group. After 1 month of CPAP, there was a significant increase in NOx levels and a reduction in U-NE level and BP only in patients with severe OSA. Conclusions: One month of CPAP results in significant improvements in NOx levels, 24-h U-NE level and BP in patients with severe OSA, but not in patients with mild-moderate OSA.
Pinto, P., Bárbara, C., Montserrat, J. M., Patarrão, R., Guarino, M. P., Carmo, M. M., Macedo, M. P., Martinho, C., & Gomes, M. J. M. (2013). Effects of CPAP on nitrate and norepinephrine levels in severe and mild-moderate sleep apnea. BMC Pulmonary Medicine, 13(NA), 13-13. https://doi.org/10.1186/1471-2466-13-13