title: Effects of CPAP on nitrate and norepinephrine levels in severe and mild-moderate sleep apnea.
abstract: BACKGROUND
  Reduced plasma nitrate (NO(x)) 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 NO(x) 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 NO(x) 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, NO(x) 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 NO(x) 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 NO(x) levels, 24-h U-NE level and BP in patients with severe OSA, but not in patients with mild-moderate OSA.
  
  
  BACKGROUND
  ClinicalTrials.gov: NCT01769807.
authors.affiliation: Serviço de Pneumologia II, Centro Hospitalar Lisboa Norte-Hospital Pulido Valente, Lisbon, Portugal. paulagpinto@gmail.com.
authors.forename: Paula
authors.initials: P
authors.lastname: Pinto
authors.forename: Cristina
authors.initials: C
authors.lastname: Bárbara
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Montserrat
authors.forename: Rita S
authors.initials: RS
authors.lastname: Patarrão
authors.forename: Maria P
authors.initials: MP
authors.lastname: Guarino
authors.forename: Miguel M
authors.initials: MM
authors.lastname: Carmo
authors.forename: Maria P
authors.initials: MP
authors.lastname: Macedo
authors.forename: Cristina
authors.initials: C
authors.lastname: Martinho
authors.forename: Rita
authors.initials: R
authors.lastname: Dias
authors.forename: Maria J M
authors.initials: MJ
authors.lastname: Gomes
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood / Q000652:urine; D018660:Blood Pressure Monitoring, Ambulatory; D045422:Continuous Positive Airway Pressure / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009566:Nitrates / Q000097:blood*; D009638:Norepinephrine / Q000652:urine*; D010100:Oxygen / Q000097:blood; D017286:Polysomnography; D011446:Prospective Studies; D012720:Severity of Illness Index; D012891:Sleep Apnea Syndromes / Q000378:metabolism* / Q000628:therapy*; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers; D009566:Nitrates; D010100:Oxygen; D009638:Norepinephrine