title: [Normal values of cerebral vasomotor reactivity using the Breath-Holding Test].
abstract: BACKGROUND
  Cerebral circulation has its own mechanism for regulating blood flow so that a constant supply can be maintained despite the variations that take place in systemic variables. This mechanism is called cerebral vasomotor reactivity (CVR) and it can be measured using a number of different tests. Transcranial Doppler ultrasonography (TDU) is one of them. To measure cerebral vasomotor reactivity by means of TDU, intravenous infusion of acetazolamide, inhalation of CO2 or voluntary breath-holding can be employed to stimulate vasodilatation. This last method is called the Breath-Holding Test and can be offered as a percentage increase in flow velocity (PIV) weighted by the time the breath is held -what is then known as the Breath-Holding Index (BHI). Given the growing interest in CVR in vascular pathology of the brain, we have calculated the normal values for the breath-holding test in our area.
  
  
  METHODS
  The sample used in the study was made up of subjects of both sexes over the age of 18. Patients with a history of strokes, chest diseases, cervical or intracranial vascular stenoses, haematological disorders and clinical pictures suggesting sleep apnea were excluded. CVR was measured using TDU and the breath-holding test in the middle cerebral artery and the basilar artery, by means of the percentage increase of flow velocity, which was weighted by breath-holding time.
  
  
  RESULTS
  The mean BHI value was 1.45 +/- 0.50 in the middle cerebral artery, and 1.52 +/- 0.60 in the basilar artery, the respective PIV values being 31.6 +/- 12.3% in the middle cerebral artery and 32.8 +/- 15.1% in the basilar artery. The CVR determined by this test was similar in the two arteries. Significant differences were found among age groups but not between sexes.
  
  
  CONCLUSIONS
  The Breath-Holding Test is a simple method for measuring CVR. In this article we report the normal values for our area. Although differences were obtained according to age groups, none were found according to sex or between the middle cerebral and the basilar arteries. These findings can be used as a reference in ultrasonography laboratories in our country.
authors.affiliation: Servicio de Neurología, Hospital Virgen de la Salud, Toledo, Spain. pjimenez1010@yahoo.es
authors.forename: P E
authors.initials: PE
authors.lastname: Jiménez-Caballero
authors.forename: T
authors.initials: T
authors.lastname: Segura
mesh_terms: D000328:Adult; D000368:Aged; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009460:Neurologic Examination / Q000379:methods; D012016:Reference Values; D012119:Respiration; D014666:Vasomotor System / Q000502:physiology*