REPEATABILITY OF TRANSCRANIAL DOPPLER MEASUREMENTS OF ARTERIAL BLOOD-FLOW VELOCITIES IN HEALTHY-SUBJECTS

1. Transcranial Doppler measurements of the mean blood flow velocity a nd the resistance index in the middle cerebral artery are used to asse ss cerebral haemodynamics. The prerequisite for the use of these param eters in clinical pharmacology studies is an evaluation of their repea tability and spontaneous variation with time. 2. Repeatability of tran scranial Doppler measurements of mean blood flow velocity and resistan ce index was investigated in healthy subjects by calculation of the re peatability coefficient as defined by the British Standards Institutio n. Intra-observer repeatability (comparison of two successive determin ations by one observer, n=30 subjects), between-observer repeatability (comparison of two successive measurements each performed by a differ ent observer, n=30) and long-term repeatability (comparison of two det erminations performed at the same hour with a 1 week interval by one o bserver, n=14) were assessed. In addition, the spontaneous evolution w ith time of mean blood flow velocity and resistance index was determin ed over an 8 h period (n=14). 3. Repeatability coefficients for intra- observer repeatability, between-observer repeatability and long-term r epeatability were 4.83, 4.59 and 3.32 cm/s for mean blood flow velocit y (normal value = 61.2+/-10.2 cm/s) and 2.62, 3.12 and 3.49% for resis tance index, respectively (normal value = 53.6+/-5.9%), indicating tha t transcranial Doppler measurements are repeatable enough to be used o ver periods of time of up to 1 week in clinical pharmacology studies. 4. Finally, a time effect was detected for mean blood flow velocity, i ndicating that this parameter undergoes diurnal variation.