Duplex scanning of the internal carotid artery: An assessment of cerebral blood flow

Abstract

Duplex ultrasound scanning (B‐mode imaging and pulsed Doppler shift analysis) was used to measure internal carotid artery blood flow (ICBF) in 20 volunteers. The effect of changes in end tidal CO₂ on cerebral blood flow was measured. When corrected to a P_co, of 40 torr (5.32 kPa) internal carotid artery blood flow was 286 ± 16 ml min⁻¹ (mean ± s.e.m.). Specific CO₂ reactivity (the change in flow per torr change in CO₂) was 8·16±0·69 ml min⁻¹ torr⁻¹ which was equivalent to 2·0 ± 0·1 per cent of the flow at 40 torr per torr change in CO₂ (percentage CO₂ reactivity). The mean value and the CO₂ reactivity compare favourably with previously reported measurements by other techniques. These data suggest that the non‐invasive measurement of internal carotid artery blood flow by Doppler ultrasound scanning is an assessment of cerebral blood flow that can be used to study both normal and pathological changes within the cerebral circulation.