Can cerebrovascular reactivity be assessed without measuring blood pressure in patients with carotid artery disease?  .
OBJECTIVE
Conventional methods of assessing cerebrovascular reactivity (CVR) omit the influence of blood pressure (BP). This study demonstrates the significant influence of BP during the assessment of CVR in patients with carotid artery disease.


METHODS
In 56 subjects the CVR was bilaterally assessed by measurement of cerebral blood flow velocity change in response to inhalation of 5% CO2 in air while BP was continuously monitored. Three methods of calculating the CVR were used: the conventional ratio between relative cerebral blood flow velocity and end-tidal CO2, simple linear regression, and multiple linear regression analysis (MLRA). The clinical significance of the difference in CVR indices was evaluated. The Bland-Altman test was applied to quantify the comparability and bias between measurements. The magnitude and significance of a change in BP during the CVR assessment were calculated in conjunction with an estimate of the velocity change attributed to the BP. The statistical significance of the data segment length on the variability and magnitude of the CVR index was computed.


RESULTS
The value of the CVR index was reduced by 20% and 6% in comparison to the conventional ratio approach when MLRA and linear regression were applied, respectively. With the use of MLRA, in 96% of cases the value of the BP coefficient was statistically significant, and in four patients the increase in velocity was primarily attributed to the increase in BP.


CONCLUSIONS
The influence of BP is significant and requires consideration when the CVR index is calculated in patients with carotid artery disease.
Dumville
J
J
Division of Medical Physics, Faculty of Medicine, University of Leicester, United Kingdom. jd23@le.ac.uk
Panerai
R B
RB
Lennard
N S
NS
Naylor
A R
AR
Evans
D H
DH
D000368:Aged; D001783:Blood Flow Velocity / Q000187:drug effects / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D002245:Carbon Dioxide / Q000008:administration & dosage / Q000494:pharmacology; D002319:Cardiovascular System / Q000503:physiopathology; D002340:Carotid Artery Diseases / Q000503:physiopathology*; D002536:Cerebral Arteries / Q000187:drug effects / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000187:drug effects / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology; D016014:Linear Models; D008875:Middle Aged; D010313:Partial Pressure; D013990:Tidal Volume; D013997:Time Factors
D002245:Carbon Dioxide