Comparison of critical closing pressures extracted from carotid tonometry and finger plethysmography.
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.
Hsu
Hung-Yi
HY
Department of Internal Medicine, Veterans General Hospital-Taichung, Taiwan.
Chao
A-Ching
AC
Chen
Ying-Tsung
YT
Wong
Wen-Jang
WJ
Chern
Chang-Ming
CM
Hsu
Li-Chi
LC
Kuo
Jon-Son
JS
Hu
Han-Hwa
HH
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
D002245:Carbon Dioxide