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

Abstract

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 ). 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 (BHIMCA and BHIICA ), the correlation between the two BHI methods, and the tendency for the BHIs to decrease with increasing degree of cervical ICA stenosis. For the BHIMCA , we found a good reproducibility (intraclass correlation coefficient, rI > .9) and a significantly decreased BHI with increasing stenosis of the ICA (P = .001). For the BHIICA , good reproducibility was demonstrated (rI > or ≒ .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). Our study suggests that the BHIICA is not a feasible alternative method to the BHIMCA.