Measurement of instantaneous blood-flow velocity in the human aorta using pulsed Doppler ultrasound.

The reproducibility and ease of use of a pulsed Doppler system has been investigated in 27 normal subjects. Measurements were performed in the ascending aorta and the aortic arch in the sitting and supine position. Good quality recordings were obtained in over 90% of the subjects. Maximum velocities of 120 and 108 cm . s-1 were found in the supine position of the ascending aorta in males and females respectively, while the corresponding acceleration were 2254 and 2148 cm . s-2. When moving from the sitting to the supine position, changes in integral under the mean and maximum velocity curve, which is supposed to be proportioned to stroke volume, were approximately 30% both in the ascending aorta and in the aorta arch. Making certain assumptions about dimensions of the aorta, reasonable values for cardiac output could be calculated in all subjects. The reproducibility of the measurements was tested by making ten repeat measurements in five subjects. The mean variation coefficient was between 6 and 11% for all measured variables. It is concluded that blood-flow velocity can be measured in the ascending aorta and the aortic arch using pulsed ultrasound and that the method has a reproducibility which permits measurements of changes in the flow and flow velocity of over 10%.