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 investigators wanted to know the effect of CPAP on these biomarkers in mild-moderate OSA.

The investigators aimed 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.

The investigators 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.

Inclusion Criteria:

- Diagnosis of obstructive sleep apnea

Exclusion Criteria:

• current smoker
• respiratory disease
• cardiac disease (except for arterial hypertension)
• renal disorder
• hepatic disorder
• psychiatric disorder
• diabetes mellitus
• dyslipidemia
• rhinitis
• sinusitis
• acute illness
• daytime hypoxemia or hypercapnia
• therapy with oral nitrates
• therapy with angiotensin-converting enzyme inhibitors
• therapy with beta-blockers
• therapy with statins
• therapy with non-steroidal anti-inflammatory drugs
• presence of central respiratory events
• previous CPAP therapy
• previous uvulopalatopharyngoplasty