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Open Access Research article

Effects of CPAP on nitrate and norepinephrine levels in severe and mild-moderate sleep apnea

Paula Pinto123*, Cristina Bárbara123, Joseph M Montserrat4, Rita S Patarrão2, Maria P Guarino2, Miguel M Carmo2, Maria P Macedo2, Cristina Martinho1, Rita Dias1 and Maria JM Gomes23

Author Affiliations

1 Serviço de Pneumologia II, Centro Hospitalar Lisboa Norte-Hospital Pulido Valente, Lisbon, Portugal

2 Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal

3 Centro de Estudos de Doenças Crónicas, Lisbon, Portugal

4 Hospital Clinic. CIBERES. IDIBAPS, Barcelona, Spain

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BMC Pulmonary Medicine 2013, 13:13  doi:10.1186/1471-2466-13-13

Published: 13 March 2013



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.


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.


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.


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.

Trial registration http://NCT01769807 webcite