title: Comparison of critical closing pressures extracted from carotid tonometry and finger plethysmography.
abstract: BACKGROUND
  The reliability of critical closing pressure (CrCP) estimates derived from peripheral blood pressure (BP) measurements is unclear. We attempted to evaluate the influences of peripheral circulation on determining CrCP.
  
  
  METHODS
  Twenty-five young healthy volunteers were studied. BP waves were obtained with plethysmography (Portapres) and carotid applanatory tonometry, respectively, for analysis. Transcranial Doppler was used to monitor cerebral flow velocity. Using linear regression analysis, beat-to-beat CrCP was calculated at rest, during voluntary hyperventilation and during 5% CO2 inhalation.
  
  
  RESULTS
  Twenty of 25 participants demonstrating satisfactory tonometric tracings for both tests were included in the analysis. The systolic BP measured using plethysmography was higher than that derived from tonometry (139.4 +/- 24.7 vs. 105.5 +/- 29.6, p < 0.001). CrCP values derived from tonometry were all positive and higher than CrCP values derived from plethysmography (62.9 +/- 19.9 vs. 11.1 +/- 17.8, p < 0.001). The changes in CrCP induced by 5% CO2 inhalation and hyperventilation had a correlation between two BP monitoring methods (r = 0.52, p = 0.001).
  
  
  CONCLUSIONS
  Pressure waveform is an important determinant in calculating CrCP by linear regression analysis. The relative changes in CrCP induced by hemodynamic challenges remained a relevant indicator of cerebrovascular regulation regardless of the methods used for non-invasive BP recording.
authors.affiliation: Department of Internal Medicine, Veterans General Hospital-Taichung, Taiwan.
authors.forename: Hung-Yi
authors.initials: HY
authors.lastname: Hsu
authors.forename: A-Ching
authors.initials: AC
authors.lastname: Chao
authors.forename: Ying-Tsung
authors.initials: YT
authors.lastname: Chen
authors.forename: Wen-Jang
authors.initials: WJ
authors.lastname: Wong
authors.forename: Chang-Ming
authors.initials: CM
authors.lastname: Chern
authors.forename: Li-Chi
authors.initials: LC
authors.lastname: Hsu
authors.forename: Jon-Son
authors.initials: JS
authors.lastname: Kuo
authors.forename: Han-Hwa
authors.initials: HH
authors.lastname: Hu
mesh_terms: D000293:Adolescent; D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D002245:Carbon Dioxide / Q000378:metabolism; D002339:Carotid Arteries / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D005385:Fingers / Q000098:blood supply*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology; D016014:Linear Models; D008297:Male; D008365:Manometry; D009129:Muscle Tonus / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D009334:Neck Muscles / Q000502:physiology; D010991:Plethysmography; D012039:Regional Blood Flow / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D017585:Ultrasonography, Doppler, Transcranial
chemical_list: D002245:Carbon Dioxide