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

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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 Pco, 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.