Efficacy of CPAP Treatment on Blood Pressure of Resistant Hypertension Patients With Obstructive Sleep Apnea Syndrome

• clinic and ambulatory blood pressures [ Time Frame: 6 months ] [ Designated as safety issue: No ]
  Clinic and ambulatory blood pressures (during 24-hour ambulatory blood pressure monitoring, which included both daytime and nighttime blood pressures, as well as the nocturnal dipping pattern).
  
  

• Microalbuminuria [ Time Frame: 6 months ] [ Designated as safety issue: No ]
  Urinary albumin excretion rate on 24-hour urine collection
  
  
• Aldosterone excess measurements [ Time Frame: 6 months ] [ Designated as safety issue: No ]
  Serum aldosterone concentration, plasma renin activity, aldosterone-to-renin ratio and 24-hour urinary aldosterone excretion.
  
  
• Arterial stiffness [ Time Frame: 6 months ] [ Designated as safety issue: No ]
  Carotid-femoral pulse wave velocity and aortic pulse wave contour analysis (which include aortic systolic and pulse pressure and augmentation index)
  
  
• Autonomic system measurements [ Time Frame: 6 months ] [ Designated as safety issue: No ]
  Measures of autonomic system balance derived from 24-hour Holter monitoring, which includes heart rate variability on time and frequency domains.
  
  
• Cardiorespiratory fitness [ Time Frame: 6 months ] [ Designated as safety issue: No ]
  Cardiorespiratory fitness by 6 min walking test with maximum oxigen consumption measurement and by complete ergospirometric treadmill test.
  
  

Obstructive sleep apnea syndromes (OSAS) have been demonstrated to be highly prevalent in patients with resistant hypertension (defined as uncontrolled clinic BP despite being on anti-hypertensive treatment with at least 3 drugs in optimal doses and including a diuretic). Nevertheless, the effect of treating OSAS with Continuous Positive Airway Pressure (CPAP) device on clinic and ambulatory BPs in patients with resistant hypertension is largely unknown. Hence, the primary aim of this randomized clinical trial is to evaluate the effect of CPAP on BP levels in resistant hypertensive patients with moderate-severe OSAS (defined as an apnea-hypopnea index [AHI] greater than 15 on a full polysomnographic examination). Two-hundred patients will be randomly allocated either to treatment with CPAP device plus their usual anti-hypertensive treatment or to continue their usual treatment alone for 6 months. Clinic and 24-hour ambulatory BP monitoring, laboratory evaluation (including microalbuminuria and aldosterone-to-renin ratio), 24-hour Holter monitoring, ergospirometric treadmill test, and carotid-femoral pulse wave velocity measurement will be performed before and after the 6-month treatment, with the observers blinded to the allocation group.