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Blood flow velocity, pulsatile in correspondence to cardiac events, in pulmonary arterioles of anesthetized bullfrogs could be measured on lung surfaces covered with a water-containing plastic disc by means of a laser Droppler microscope arranged in an oblique-backward mode.
A Doppler velocity meter for measuring blood flow velocity in the human aorta is described. Using pulsed ultrasound, this instrument allows the velocity to be measured at selected depths. The instrument has been tested in laboratory experiments, and appears to give accurate estimates of mean flow velocity for both steady and pulsatile flows. Flow velocities and estimates of stroke volume have been obtained from the ascending aorta in 18 patients. It is suggested that at present only relative values for flow and flow velocity can be measured. A method for obtaining absolute values for these parameters, based on scanning in the aortic arch, is proposed.
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The effect of inspiration on pulmonary vein blood flow velocity and forward pressure gradient from pulmonary vein to left atrium was studied in seven patients with chronic constrictive pericarditis, five of whom had clinically obvious pulsus paradoxus. Compared to patients without pericardial disease, where inspiration produced no change, patients with pericardial disease showed an inspiratory fall in the forward pressure gradient and forward blood flow velocity in the pulmonary veins on inspiration. The mechanism of pulsus paradoxus in these patients can be explained by incomplete transmission of the inspiratory fall of intrathoracic pressure to the left atrium.
By using thermistors for calorimetry to monitor blood flow velocity in the choroid of the anaesthetized rabbit, it was found that an elevation of intraocular pressure reduced the choroidal blood flow. The relationship between the ratio of perfusion pressure to intraocular tension (x) and the reciprocal value of the percentage of blood flow velocity (l/y) showed a curve convex towards the pressure axis. On a log-lin scale the graph was linear. A significant linear correlation with a coefficient of 0.965 was obtained. The regression equation was found to be log l/y = 0.48x-1.98 +/- 0.29. From the present experiments it is concluded that the vascular bed of the choroid in the rabbit is a passive one with no sign of autoregulation. The observations are discussed from the point of view of blood supply and possible damage to the optic disc.
A special 8-channel detector arrangement was used to determine atraumatically the mean blood flow velocities in the aorta and the large arteries of the lower extremities in man. Following intravenous injection of 99mTc-pertechnetate time-activity curves were recorded over defined measuring points over the arteries, from these the appearance times of the tracer determined, and the mean blood flow velocities calculated from the differences between appearance times (the minimal transit times) and the distances between measuring points. The simultaneous determination of the minimal transit times between the vena cava inferior and the root of the aorta, which correspond closely to the total cardiac transit times, permits recognition of cases in whom blood flow velocity is reduced as a result of cardiac disease.
A transcutaneous ultrasonic Doppler technique for measurement of aortic blood-flow velocities has been developed and compared to more established techniques in order to evaluate its potential usefulness. It is possible by this method to quantitate blood velocity in both the ascending aorta and the aortic arch with ease and reliability. Ultrasonic access to the aorta from the suprasternal notch proved adequate in more than 90 per cent of the normal subjects examined. If further clinical trials prove as encouraging, this technique may be of significant value for patient monitoring and cardiac diagnosis.
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An attempt was made to derive a useful noninvasive index to evalute a change in myocardial contractile state using transcutaneous Doppler flow-velocity curve from the carotid artery. In 5 mongrel dogs and in 43 patients with various heart disease, Doppler flow velocity curves were obtained from the ascending aorta intravascularly using a Doppler catheter and/or from carotid artery transcutaneously using a Doppler probe. The first derivative of left ventricular pressure (dp/dt) and electrocardiogram (ECG) were recorded simultaneously. The following 3 indices were measured from the Doppler flow-velocity curves: (1) macimum acceleration of blood flow (dv/dt), (2) time from onset of ejection to peak flow (time-to-peak), (3) time interval between the beginning of Q wave of ECG to the peak of Doppler flow velocity curve (ECG Q-Doppler peak). Among these 3 indices, only ECG Q-Doppler peak demonstrated a significant correlation between the values measured intravascularly and transcutaneously. Also, only ECG Q-Doppler peak showed significant correlation with maximum of dp/dt (max dp/dt). Since ECG Q-Doppler peak showed correlation with heart rate, the difference between observed and predicted ECG Q-Doppler peak (delta ECG Q-Doppler peak) was calculated to exclude the effect of heart rate. Predicted value of ECG Q-Doppler peak was calculated from the regression equation between heart rate and ECG Q-Doppler peak in the separate experiments. There was significant correlation between delta ECG Q-Doppler peak and max dp/dt. In 15 patients with coronary artery disease and in 16 healthy subjects, delta ECG Q-Doppler peak and the other noninvasive method (systolic time intervals) were measured. Delta ECG Q-Doppler peak showed better result in the separation of 2 groups than by systolic timeintervals. It was concluded that delta ECG Q-Doppler peak is a useful index to evaluate the myocardial contractile state since this index is readily obtained noninvasively.
The external diameter of the artery predominantly supplying the gracilis muscle was recorded by contact inductive transducer in anesthetized dogs. Blood flow from this artery was directed via an A--V shunt straight into the vein. An increase in blood flow from 4.9+/-0.7 to 45.5+/-6.6 ml/min with a latency of 11.3+/-1.3 sec evoked an increase of 12.6+/-1.3% in the diameter of this artery. Dilatation was independent of whether intravascular pressure at the recording site increased, decreased, or remained unchanged. The smooth arterial muscles seem to be able to "sense" the deformation and, as a result their arteries can automatically change their lumen in response to changes in blood flow velocity.
Numerous schemes have been used for measuring hemodynamic properties of deeply lying arteries; however, all have their limitations. This paper describes a new relatively nontraumatic intravenous approach that uses a catheter in connection with a pulsed ultrasonic Doppler velocity meter (PUDVM) and an echo track. The catheter was initially tested in a hydraulic model system for calibration of velocity and flow parameters. Lately, the catheter has permittted measurements of local instantaneous blood velocity, flow, and wall motion characteristics in adult Beagle dogs in the abdominal aorta and iliac artery. Evaluation studies have been conducted to compare the catheter-tip recordings with an independent method for measuring blood flow and wall motion. Coupling of this catheter-tip device with the PUDVM and echo track provides chronic measurements of hemodynamic parameters in these deep vessels which were virtually impossible to obtain previously. This technique may prove useful in monitoring vessel pathology longitudinally as well as in basic experimental situations requiring flow and arterial wall mechanical properties.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.