Moderate correlation between breath-holding and CO(2)  inhalation/hyperventilation methods for transcranial doppler evaluation of cerebral vasoreactivity.
BACKGROUND
Both CO(2) inhalation followed by hyperventilation and breath-holding have been utilized to measure cerebral vasomotor reactivity (VMR) but their correlation has been poorly studied and understood.


METHODS
A retrospective study was conducted in 143 subjects (62.6 ± 15.8 years old, 64% men) with transcranial Doppler ultrasonography measurement of mean flow velocity (MFV) at baseline, after 30 seconds of breath-holding, and after CO(2) inhalation followed by hyperventilation, in the left and right middle cerebral artery. Breath-holding index (BHI) was calculated as the percentage of MFV increase from baseline per second of apnea. CO(2) inhalation/hyperventilation index (CO(2) /HV) was calculated as the percentage of MFV difference between CO(2) inhalation and hyperventilation.


RESULTS
There were 75 carotid arteries with >70% stenosis or occlusion, and 18 middle cerebral arteries with >50% stenosis or occlusion. The mean BHI was 0.93 ± 0.7 and 0.89 ± 0.6, whereas the mean CO(2) /HV was 61 ± 26% and 60 ± 26%, respectively, on the right and left sides. The correlation between BHI and CO(2) /HV was moderate on the right (r = 0.33; p < 0.01) and left sides (r = 0.38; p < 0.01). Multivariate linear regression analysis indicated that age (p = 0.01) and history of stroke (p = 0.007) were associated independently with an impaired VMR on the right as measured by CO(2) /HV. No predictors for impaired VMR by CO(2) /HV on the left and by BHI on either side were found.


CONCLUSIONS
CO(2) /HV and BHI are only moderately correlated. Further studies are necessary to determine which method more accurately predicts clinical morbidity. © 2012 Wiley Periodicals, Inc. J Clin Ultrasound 2012; Published online in Wiley Online Library.
Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
Diogo C
DC
Haussen
Michael
M
Katsnelson
Abiezer
A
Rodriguez
Nelly
N
Campo
Iszet
I
Campo-Bustillo
Jose G
JG
Romano
Sebastian
S
Koch
D001783:Blood Flow Velocity; D062485:Breath Holding; D002245:Carbon Dioxide; D002560:Cerebrovascular Circulation; D002561:Cerebrovascular Disorders / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005260:Female; D006439:Hemodynamics; D006801:Humans; D006985:Hyperventilation; D001239:Inhalation / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging; D012189:Retrospective Studies; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods*
D002245:Carbon Dioxide