title: Cerebral autoregulation in patients with obstructive sleep apnea syndrome during wakefulness.
abstract: OBJECTIVE
  Obstructive sleep apnea syndrome (OSAS) is an independent risk factor for stroke. Impairment of cerebral autoregulation may play a potential role in the pre-disposition to stroke of OSAS patients. In this study, we aimed to assess dynamic cerebral autoregulation (DCA) during wakefulness in OSAS patients and a group of matched controls.
  
  
  METHODS
  Patients and controls were examined in the morning after an overnight complete polysomnography. Mean cerebral blood flow velocity (CBFV) in the middle cerebral artery and mean arterial blood pressure (ABP) were continuously recorded using transcranial Doppler and Finapres. DCA was assessed using the Mx autoregulatory index. Mx is a moving correlation coefficient between mean CBFV and mean ABP. More positive value of Mx indicates worse autoregulation.
  
  
  RESULTS
  Eleven OSAS patients (mean age +/- SD; 52.6 +/- 7.9) and 9 controls (mean age +/- SD; 49.1 +/- 5.3) were enrolled. The mean apnea-hypopnea index (AHI) in the OSAS group was of 22.7 +/- 11.6. No significant difference was found between the two groups as for age, body mass index, mean ABP and endtidal CO(2) pressure. Cerebral autoregulation was impaired in OSAS patients compared with controls (Mx index: 0.414 +/- 0.138 vs. 0.233 +/- 0.100; P = 0.009). The severity of autoregulation impairment correlated to the severity of the sleep respiratory disturbance measured by the AHI (P = 0.003).
  
  
  CONCLUSIONS
  Cerebral autoregulation is impaired in patients with OSAS during wakefulness. Impairment of cerebral autoregulation is correlated with the severity of OSAS.
authors.affiliation: Service de Neurologie Vasculaire, Hôpital Rangueil, INSERM U858- Team 09, Toulouse, France. nasr.n@chu-toulouse.fr
authors.forename: N
authors.initials: N
authors.lastname: Nasr
authors.forename: A Pavy-Le
authors.initials: AP
authors.lastname: Traon
authors.forename: M
authors.initials: M
authors.lastname: Czosnyka
authors.forename: M
authors.initials: M
authors.lastname: Tiberge
authors.forename: E
authors.initials: E
authors.lastname: Schmidt
authors.forename: V
authors.initials: V
authors.lastname: Larrue
mesh_terms: D001783:Blood Flow Velocity; D001794:Blood Pressure; D002245:Carbon Dioxide / Q000378:metabolism; D002560:Cerebrovascular Circulation / Q000502:physiology; D054022:Cerebrum / Q000098:blood supply / Q000503:physiopathology*; D005260:Female; D006706:Homeostasis; D006801:Humans; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000503:physiopathology; D017286:Polysomnography; D011312:Pressure; D012039:Regional Blood Flow; D012044:Regression Analysis; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*; D014851:Wakefulness / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide