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Biomedical subjects

E R Greene

Publications and source records attributed to E R Greene.

At least 55 records · Page 3Linked to original sources
PubMed1984

A comparison of echo-Doppler and electromagnetic renal blood flow measurements.

The linearity and accuracy of noninvasive ultrasonic method of measuring beat-to-beat renal blood flow was evaluated by correlation with standard electromagnetic flowmetry. Using a combined real-time ultrasonic imager and pulsed Doppler velocimeter known as a duplex scanner (DS), lumen diameter (D) and average blood velocity (V) within the imaged renal artery were recorded. Renal blood flow ( QDS ) was calculated offline using a microprocessor from the equation QDS = (pi x D2 x V)/4. This noninvasive method had previously been validated in vitro using a controlled hydraulic system which modeled steady-state flow (QT) where QDS = 0.98 QT + 7.75, SEE = +/- 13.2, r = +0.98, P less than 0.001. In three anesthetized dogs, simultaneous QDS and electromagnetic flow ( QEMF ) measurements (range 44-484 ml x min-1) were made in the proximal left renal artery. Linear regression analysis gave QDS = 0.43 QEMF + 40.5, r = 0.78, SEE = 33.8 ml x min-1, P less than 0.01; QDS = 1.2 QEMF + 2.9, r = 0.86, SEE = 20.8 ml x min-1, P less than 0.01; QDS = 0.86 QEMF + 0.2, r = 0.93, SEE = 53.4 ml x min-1, P less than 0.01. These results suggest that noninvasive QDS measurements of renal blood flow are linear and reasonably accurate compared with invasive QEMF in dogs. The method may have utility in the noninvasive measurement of beat-to-beat blood flow in human renal arteries.

Animals↗
PubMed1984

Echo-Doppler angle determination for noninvasive transmitral blood velocity calculations in normal and porcine bioprosthetic mitral valves.

Doppler incident angle (DA) determination is a critical factor in the noninvasive attempt to measure transmitral blood velocity (TMBV) and to estimate volumetric flow. The error in TMBV varies with the cosine of DA. Using an echo-Doppler duplex scanner (DS), we studied transmitral flow velocities in 10 normal subjects (Group I) and 10 asymptomatic patients with procine mitral valve (PMV) bioprostheses. A 3-MHz scanhead with three medium focused rotating transducers was positioned at the left ventricular apex, and standard apical four-chamber views of the heart were obtained. The position of the Doppler sample volume (SV) was adjusted within the valve orifice until the maximal power of the Doppler audio spectra reflecting TMBV was recorded by a spectral analyzer. At this location of the SV, images were recorded and protractors were used to estimate DA. DA ranged from 10 to 40 degrees (x = 22.5 degrees +/- 10.8 degrees) in Group I and from 0 to 15 degrees (x = 4.5 degrees +/- 5.0 degrees) in Group II. Mean values of DA in Groups I and II were significantly different (p less than 0.01). We conclude: (1) in normal subjects, DA measured from the apex into the MV varies significantly and thus may compromise the accuracy of TMBV measurements; (2) the truncated funnel shape of the stent of the PMV bioprosthesis allows a DA less than 15 degrees and thus a smaller error in TMBV calculations.

Adult↗
PubMed1983

Noninvasive echo-Doppler duplex measurements of common femoral artery blood flow variables during supine exercise and post-occlusive reactive hyperemia.

Noninvasive dynamic measurements of common femoral artery blood flow (CFBF) and stroke volume (CFSV) during supine exercise (SE) and staged post-occlusive reactive hyperemia (PORH) in normal subjects using an echo-Doppler duplex scanner (DS) would provide baseline hemodynamic data in the study of the peripheral circulation in resting, stressed, and diseased conditions. Heart rate (HR), CFBF, and CFSV were determined at rest (R), after 5 minutes of SE on an ergometer (30 rpm) at 30, 60, 90-watt loads and after a 3-minute recovery. The same variables were also calculated after periods of 2-, 5-, and 10-minute thigh occlusions (greater than 240 mm Hg cuff pressure). Measurements of spatial average blood velocities and lumen diameters were used to calculate CFBF. Ankle pressure (AP) and brachial pressure (BP) were determined, and the ratio of systolic AP to systolic BP, the ankle index (AI), was calculated. As in vitro validation of the DS method was accomplished using a hydraulic model of CFBF (r = 0.98). Mean values for maximal CFBF following SE and PORH were 0.81 and 1.53 l/min, respectively. With SE, increases in CFBF and CFSV and decreases in AI were significantly (p less than .05) only at 60- and 90-watt loads. Increases in CFBF and CFSV and decreases in AP and AI were significantly different (p less than .05) from rest for the three occlusion durations and show a linear trend. This study suggests that the DS method can noninvasively and quantitatively measure CFBF and CFSV at rest following SE and during PORH.

Adult↗
PubMed1981

Hemodynamics after microsurgical anastomosis: the effects of topical lidocaine.

The hemodynamics in the femoral arteries of 30 rats were measured with a 20-MHz pulsed Doppler velocity meter (PUDVM) in an attempt to define the changes resulting from anastomosis and to assess the effects of 1% lidocaine on those changes. Control values were obtained, the arteries were severed and anastomosed, and either physiologic saline or 1% lidocaine was applied topically to the vessels in a randomized blind study. Velocity measurements, derivations of vessel lumen diameters, and calculations of blood flow then were made with the velocity meter at intervals of 1,2,3,5, and 10 minutes after the addition of the experimental fluid. The measurements obtained indicated that calculated blood flow through the anastomoses was reduced 36% at the 10-minute interval in the group treated with physiologic saline but only 5% in the group treated with 1% lidocaine. These results demonstrate that microsurgical anastomosis adversely effects normal hemodynamic variables, but these effects are minimized by the application of a bolus of 1% lidocaine, a topical vasodilator. These results also suggest that the 20-MHz PUDVM has sufficient resolution and sensitivity to provide the measurements of blood velocity necessary for reproducible calculations of blood flow distal to a microsurgical anastomosis in small vessels.

Animals↗
PubMed1981

A method for the calculation of blood flow in human digital arteries.

The assessment of digital artery blood flow in human beings would ideally be noninvasive and accurate. The transcutaneous use of a high-resolution 20 MHz ultrasonic pulsed Doppler provides information about average blood velocities, vessel lumen diameters, and velocity profiles in small vessels. These data are used in calculations which quantitate blood flow in human digital arteries.

Angiography↗
PubMed1981

Noninvasive characterization of renal artery blood flow.

Noninvasive characterization of renal artery blood flow variables in the human has not been reported. Using a unique dual-frequency real-time two-dimensional echo Doppler (Duplex scanner) that was calibrated in vitro, we characterized renal artery blood flow patterns in 16 normal subjects (6 females). Calculated mean values of systolic diameter (Ds), maximal spatial average blood velocity (Vmsa), and volume flow rate (Q) were as follows: 4.5 +/- 0.6 mm right, 4.4 +/- 0.6 mm left; 67.6 +/- 9.4 cm . sec-1 right, 69.6 +/- 12.0 cm . sec-1 left; and 403 +/- 127 ml . min-1 right, 395 +/- 98 ml . min-1 left; respectively. Direct linear regression correlation of body surface area (BSA) with Ds and Q were statistically significant (P less than 0.01, r = 0.70; and P less than 0.01, r = 0.72, respectively). In a blind prospective series, six of seven angiographically normal renal arteries were noninvasively identified by normal geometry and blood velocity patterns. One angiographically normal artery was incorrectly classified as mildly stenotic. Eleven angiographically documented abnormal renal arteries were noninvasively identified by their abnormal blood flow patterns and/or geometry. This study suggests that dual-frequency Duplex scanning with careful sample volume control and Doppler audio spectra/blood velocity waveform analysis can be used to characterize blood flow variables in normal and diseased human renal arteries.

Blood Flow Velocity↗
PubMed1981

Beat-by-beat stroke volume assessment by pulsed Doppler in upright and supine exercise.

A 3.0 MHz pulsed Doppler echocardiography was used to estimate instantaneous stroke volume (SV) and cardiac output (Q) in eight men during steady-state supine (S) and upright (U) exercise at 300 kpm/min. The mean transients in heart rate (HR), SV, and Q for the first 20 s of exercise in each posture were then determined. Center-line blood velocities were obtained in the ascending aorta with the transducer positioned manually in the suprasternal notch. Mean supine values for SV and Q at rest and exercise were 111 ml and 6.4 1/min and 112 ml and 9.71/min, respectively. The corresponding results for U were 76 ml and 5.61/min and 92 ml and 8.41/min, respectively. These values compare favorably with previous studies utilizing invasive procedures. The transient response of Q following the onset of exercise in U was about twice as fast as in S because of the rapid and almost immediate upsurge in SV. In S, only HR served to augment Q, as SV initially fell. The faster rise in aortic flow in U with exercise represented an additional volume (184 ml) of blood passing through the aorta compared with S in the first 20s. This must be related to the rapid mobilization of pooled venous blood from the leg veins during U.

Adult↗
PubMed1981

Noninvasive pulsed Doppler blood velocity measurements and calculated flow in human digital arteries.

Few quantitative studies of blood velocities and calculated flow measurements in the human digital arteries have been reported due to resolution limitations of existing Doppler instruments. Under carefully controlled conditions, we transcutaneously measured blood flow velocities in the ten digital arteries in the right hand of five male adults (BSA 1.83-2.19m2) with a high resolution 20MHz pulsed Doppler instrument which was calibrated in vitro. A 1.0mm2 ultrasonic transducer was mounted on a 16 gage needle in a stereotaxic apparatus at a known Doppler angle to the vessel flow axis. The sample volume (SV) was adjustable in both range (1 - 13 mm) and length (0.3 - 4.0 mm). In order to obtain a more uniform acoustic field in the SV, the transmitted pulse was attenuated exponentially at a rate consistent with acoustic attenuation in blood. This permitted measurement of velocity profiles and spatially averaged velocities along the sound beam. Deconvoluted calculations of vessel internal diameter (D) and volume flow rates (Q) were made in the 10 different digital vessels. Velocity waveforms were triphasic with positive diastolic flow. In the digital vessels, the average D varied from 0.78 +/- 0.11 to 1.04 +/- 0.05 mm and the average Q from 2.03 +/- 0.92 to 3.71 +/- 0.69 ml/min. For each vessel, Q correlated with body surface area r = 0.80 to 0.91 (p less than .05) with a coefficient of variance calculated from the normalized flow rate (Q/BSA) ranging from 10% to 38%. Flows in parallel vessels of the middle digits were not significantly different. These studies suggest that noninvasive, spatially averaged blood velocity and calculated flow measurements, which are accurate and reproducible, can be made in human digital arteries.

Adult↗