A Breath-Holding Index Applied to the Internal Carotid Artery Siphon in Transcranial Doppler Studies

Abstract

BACKGROUND AND PURPOSE The breath-holding index (BHI) is a useful method to assess cerebrovascular reactivity. It is calculated based on the mean flow velocities of the middle cerebral artery (MCA) using transcranial Doppler (BHIMCA). Therefore, it is not feasible in patients with poor temporal windows. This study tested the feasibility of a BHI using the internal carotid artery (ICA) siphon flow velocity (BHIICA). METHODS Twenty-four patients (aged 38-79 years) with unilateral or bilateral stenosis of the cervical ICAs were prospectively recruited. The 48 examined bilateral ICAs were divided into three groups according to the stenosis degree: <50%, 50-99%, and occlusion. We investigated the reproducibility of both BHI methods (BHI(MCA)and BHIICA), the correlation between the two BHI methods, and the tendency for the BHIs to decrease with increasing degree of cervical ICA stenosis. RESULTS For the BHIMCA, we found a good reproducibility (intraclass correlation coefficient,r(I)( )> .9())and a significantly decreased BHI with increasing stenosis of the ICA (P= .001). For the BHIICA, good reproducibility was demonstrated (r(I) > or approximately equal to or the image of .9), but there was no significant decrease in the BHI related to the increasing degree of ICA stenosis (P= .952). Furthermore, the correlation between the two BHI methods was not robust (kappa coefficient, right .259; left .619). CONCLUSIONS Our study suggests that the BHI(ICA)is not a feasible alternative method to the BHIMCA.