Showing papers on "Pulsatile flow published in 1977"
••
TL;DR: The laser-Doppler method is a promising tool for rapid monitoring of dynamic changes in tissue perfusion and was found to vary in an approximately linear manner with skin blood flow.
Abstract: Laser light scattered from tissue in vivo is broadened in line width as a result of the Doppler shift produced by moving red cells in the microcirculation. A feasibility study was carried out to demonstrate use of this effect to measure and monitor tissue blood flow. Light from a helium-neon laser illuminated a 1-mm area of tissue (human skin or rat renal cortex), and the backscattered light was detected with a photomultiplier. The spectrum of the Doppler beat notes was analyzed directly with a digital spectrum analyzer, or processed by analog circuitry to yield a flow parameter based on the root-mean-square Doppler line width. This parameter was compared with 133Xe washout in the skin of volunteers subjected to UV-induced erythema and the skin of volunteers subjected to UV-induced erythema and was found to vary in an approximately linear manner with skin blood flow. The laser instrument provided continuous monitoring of blood flow fluctuations, including the pulsatile component. The instrument was used to monitor flow in the outer cortex of the rat kidney during administration of norepinephrine, angiotensin, hydralazine, dextran, dopamine, nitroprusside, and angiotensin blocked by saralasin. Dynamic and steady-state responses were consistent with known pharmacology and renal physiology, and with the assumption that vasoconstrictor angiotensin II receptors in the kidney are accessible to blood-borne inhibitors. The laser-Doppler method is a promising tool for rapid monitoring of dynamic changes in tissue perfusion.
477 citations
••
TL;DR: The technique can be used in clinical practice for studying the physiology and pathophysiology of cutaneous micro Circulation in man and may become an important diagnostic tool in diseases that involve disturbances of the microcirculation, such as diabetes, hypertension, and atherosclerosis.
Abstract: A noninvasive technique for studying blood flow dynamics in human skin capillaries is described A light microscope combined with a closed-circuit TV system was used to monitor and record capillary blood flow velocity on video tape Arterial pulsations were recorded plethysmographically and converted into video signals by modulating the position of a square, white area in the televised scene Twelve healthy subjects were studied The mean (+/- SD) resting capillary blood flow velocity was 065 +/- 03 mm/s at an average skin temperature of 304 +/- 23 degrees C Spontaneous fluctuations at a frequency of 6-10 cycles/min were observed in most subjects A well-pronounced flow pulsatile component could be demonstrated in all capillaries studied The technique can be used in clinical practice for studying the physiology and pathophysiology of cutaneous microcirculation in man It can be expected that the method may become an important diagnostic tool in diseases that involve disturbances of the microcirculation, such as diabetes, hypertension, and atherosclerosis
187 citations
••
TL;DR: The behaviour of human and frog red cells, platelets and rigid spheres were studied in the annular vortex formed in steady or pulsatile flow at the sudden concentric expansion of a 151 $\mu$ m into 504 $\mu $ m diameter glass tube.
Abstract: The behaviour of human and frog red cells, platelets and rigid spheres were studied in the annular vortex formed in steady or pulsatile flow at the sudden concentric expansion of a 151 $\mu$ m into 504 $\mu$ m diameter glass tube. During a single orbit the measured particle velocities and paths in steady flow were in good agreement with those calculated for the fluid, predicted by theory to circulate in closed orbits. Over longer periods, however, single blood cells and latex spheres $\mu$ m diameter migrated across the streamlines out of the vortex at a rate depending on the Reynolds number whereas spheres and aggregates of red cells > 30 $\mu$ m diameter remained in the vortex at all Reynolds numbers. Similar behaviour was noted in pulsatile flow when the vortex moved in phase with upstream fluid velocity and particles described spiral orbits of continually changing diameter. With red cell suspensions of 15-45% haematocrit in steady flow, migration of the corpuscles was also observed and resulted in the formation of a particle-free vortex. In pulsatile flow, cells were always present in the vortex, but their concentration which varied periodically was lower than that in the mainstream. The formation of aggregates of latex spheres and human platelets through collisions occurring in orbit, and their migration to the vortex centre was also observed.
122 citations
••
TL;DR: The rheologic effects of multiple “non-obstructive” plaques in main coronary arteries of man were examined by numerically solving the fluid dynamic equations of motion for pulsatile viscous flow of blood through an arterial section using the actual variation of flow rate during the cardiac cycle.
122 citations
••
TL;DR: Hemodynamic alterations of magnitudes documented in this study assume clinical importance and the assumption that a solitary critical stenosis must exist before significant hemodynamic changes occur is no longer tenable.
Abstract: Diminished poststenotic pressure and flow accompanied experimental application of multiple subcritical arterial stenoses in series. Effects of additional stenoses, causing equivalent constrictions, were cumulative in a nonlinear fashion. Seven-hundred-twenty measurements were performed using 10 cm ileofemoral canine arterial segments in vitro and in vivo with pulsatile and nonpulsatile blood flow. Pressures and flow volumes utilized for testing were within normal physiologic ranges. Data analysis included correlations of experimental observations with predictions generated from a theoretic hydraulic model. Kinetic energy losses with multiple subcritical stenoses were associated with decreased pressure and flow. Poststenotic pressure decreased as much as 51% in some experiments. Diminutions in flow paralleled pressure changes. Measured pressure changes were nonlinear and followed mathematic predictions of appreciable but lesser effects of added stenoses. Hemodynamic alterations of magnitudes documented in this study assume clinical importance. The assumption that a solitary critical stenosis must exist before significant hemodynamic changes occur is no longer tenable.
68 citations
••
TL;DR: In vivo measurements with oxygen microelectrodes in animals are needed to learn more about variations of oxygen transport in plaque regions, in particular on the back side of plaques where hypoxia may occur.
61 citations
•
TL;DR: There is a definite mechanical lesion associated with pulsatile preservation, which can be minimized by utilizing low perfusion pressures and solutions of high colloid osmotic pressure and which has the potential of producing a picture resembling hyperacute rejection following transplantation.
46 citations
••
44 citations
••
TL;DR: The PAD is a simple and reliable device for intraoperative counterpulsation and for the creation of pulsatile cardiopulmonary bypass and may decrease both the incidence of perioperative myocardial infarction and the need for postoperative intraaortic balloon pumping.
43 citations
•
TL;DR: A case of persistent sciatic artery aneurysm in a 65-year-old woman was treated by exclusion and reconstruction with a saphenous vein graft and arteriography is the most important diagnostic aide.
43 citations
••
•
TL;DR: Data indicate that fibrillation-induced regional myocardial ischemia distal to a critical stenosis can be prevented by maintaining pulsatile perfusion during cardiopulmonary bypass.
Abstract: In a previous study from this laboratory, regional myocardial ischemia developed distal to a critical coronary stenosis in the fibrillating heart on cardiopulmonary bypass when myocardial perfusion was non-pulsatile To assess the effect of pulsatile perfusion on the development of the fibrillation-induced ischemia, 10 dogs were placed on total cardiopulmonary bypass with the heart in the vented fibrillating state A critical stenosis was applied to the left anterior descending artery (LAD) Pulsatile perfusion with a pulse pressure of 35 mm Hg and a pulse rate of 100/min was produced by a new method developed in this laboratory During the 2 hours of bypass, ischemia in the LAD-supplied myocardium was assessed by changes in intramyocardial oxygen (PmO2) and carbon dioxide (PmCO2) tensions and by regional arterial-coronary venous lactate difference With linear perfusion, regional ischemia in the LAD myocardium had been evidenced by a low PmO2 (8 +/- 3 mm Hg), a high PmCO2 (170 +/- 25 mm Hg) and regional lactate production (92 +/- 42 mg/100 ml) In contrast with pulsatile perfusion intramyocardial gas tensions remained stable during the 2 hours on bypass (PmO2 = 21 +/- 3 mm Hg, PmCO2 = 65 +/- 5 mm Hg, P less than 005 vs linear flow study) and lactate consumption was demonstrated (+177 +/- 29 mg/100 ml, P less than 0001 vs linear flow group) With linear perfusion, myocardial blood flow to the LAD area had decreased 56 +/- 8% in the subendocardial layer and 46 +/- 7% in the subepicardial layer In the dogs receiving pulsatile flow during bypass, regional LAD blood flow remained unchanged over the 2-hour bypass period and was significantly higher than the flow with linear flow (P less than 005) These data indicate that fibrillation-induced regional myocardial ischemia distal to a critical stenosis can be prevented by maintaining pulsatile perfusion during cardiopulmonary bypass
••
TL;DR: It is concluded, from both experimental results and from the theoretical calculations, that the total effect of a series of noncritical stenoses may become critical and produce symptoms of arterial insufficiency.
••
TL;DR: An ultrasonic transit-time micrometer has been developed to measure pulsatile changes in arterial diameter with sufficient accuracy to verify haemodynamic theories and yields results within the range of predicted values from pulsatile flow theory.
Abstract: An ultrasonic transit-time micrometer has been developed to measure pulsatile changes in arterial diameter with sufficient accuracy to verify haemodynamic theories. The instrument samples up to four distances at repetition frequencies above 1 kHz and is calibrated by a separate determination of the velocity of ultrasound in blood. New methods of transmitter pulse triggering and received pulse amplification and detection, and construction and testing of small arterial transducers, are described. The system will resolve distance changes smaller than 1 μm and will run continuously for long periods without temperature drift. Trials by measurement of the dynamic distension of a long water-filled rubber tube and comparison with the manometrically measured phase velocity showed that the technique yields results within the range of predicted values from pulsatile flow theory.
••
••
TL;DR: A high incidence of elevated amylase values following bypass with either modality is documents and evidence for possible improved visceral circulation with pulsatile extracorporeal bypass during routine cardiac operations is provided.
••
TL;DR: Flow was pulsatile in all areas of the arterial system investigated, i.e., the aorta, the cephalic arterial sinus and pedal arteries, and it was suggested that the action of theAortic bulb maintained aortic flow during ventricular diastole.
Abstract: In the pink abalone, Haliotis corrugata, pulsatile flow and pulsatile pressure were measured at 15°C by electromagnetic and Doppler ultrasonic flowmeters and strain gauge manometers. Flow was pulsatile in all areas of the arterial system investigated, i.e., the aorta, the cephalic arterial sinus and pedal arteries. Flow rates of approximately 2.9 ml/min were measured in the aorta of animals after surgical implantation of electromagnetic flowprobes. The events of the cardiac cycle are correlated with aortic blood flow. Simultaneous recording of pressure and flow suggested that the action of the aortic bulb maintained aortic flow during ventricular diastole.
••
TL;DR: A mathematical model is used to investigate hemodynamic characteristics during the incipient period of the aortic flow and demonstrates that four types of discharge coefficients are needed for the hydrodynamic evaluation of pulsatile flow through both natural and prosthetic heart valves.
••
TL;DR: The results indicate that estrogen is an effective feedback signal inhibiting pulsatile release of LH in the rat and that progesterone alone has little, if any, influence in this regard.
Abstract: The effects of chronic and acute systemic administration of estradiol-17beta and progesterone on the pulsatile release of luteinizing hormone (LH) were studied in ovariectomized rats. When estradiol-17beta was injected iv plasma concentrations of LH gradually declined though the pulsatile pattern of release was not completely blocked. The administration of estradiol-17beta by sc Silastic capsules lowered plasma LH concentrations for the first 6 hours though periodic increases were still observed. These pulsatile discharges were virtually completely suppressed by LH concentrations and the pattern of LH release were not affected by daily sc injection. There was no apparent synergistic effect of progesterone when administered in combination with estradiol-17beta. The findings show that estrogen effectively exerts a negative feedback effect on the pulsatile release of LH in the rat and that progesterone has little if any effect in this regard.
•
23 May 1977
TL;DR: In this paper, a blood flow meter responsive only to the pulsatile component of blood flow is combined with apparatus for converting normal blood flow in a limb to fully pulsated flow to provide accurate zero baseline and total flow information.
Abstract: A blood flowmeter responsive only to the pulsatile component of blood flow is combined with apparatus for converting normal blood flow in a limb to fully pulsated flow to provide accurate zero baseline and total flow information. Preferably, the arterial flow in a limb is fully pulsatized by inflating a pressure cuff, which surrounds the limb on the distal side of a flow sensor location, to a pressure at or slightly above the local diastolic pressure. Arterial flow in the limb is thereby occluded during the diastolic and post-diastolic period of each heart cycle, preventing any flow that otherwise typically occurs during this period. The resulting pulsatile flow during the higher pressure systolic period will increase to compensate for any lost residual forward flow during the post-diastolic period; so that the total net forward flow with the cuff pressurized is approximately the same as the total net forward flow without the cuff pressurized. The altered flow is totally pulsatile, however. Subtraction of the integrated flow measured without cuff pressure from the integrated flow measured with the cuff pressurized yields a value approximately equal to any residual diastolic flow, which otherwise could not be measured by certain non-invasive magnetic flowmeters.
••
TL;DR: Signal processing of the kind applied here provides meaningful data in pulsatile turbulent flows and appears to be new in experimental investigations of cardiovascular flows.
••
TL;DR: In this paper, a linearized Navier-Stokes equation was proposed to investigate the time-dependent flow structure and the wall shear stress near the stagnation point, which is very close to the exact solution first derived numerically by Hiemenz.
Abstract: A linearized Navier-Stokes equation governing the two-dimensional viscous incompressible flow impinging on an infinite flat plate is suggested to investigate the time-dependent flow structure and the wall shear stress near the stagnation point. It can be shown that this equation yields a simple analytical solution for the steady Hiemenz flow, which is very close to the exact solution first derived numerically by Hiemenz. Therefore, it is expected that for unsteady Hiemenz flows this equation describes the flow structure as well. Perturbed solutions for a pulsatile Hiemenz flow directed normally and obliquely to the plane wall are calculated in analytical forms when the amplitude of pulsation is small, and show some essential features of the pulsatile flow near the stagnation point.
••
TL;DR: The results show that the pulsatile error portion of the total error of the indicator dilution methods can be kept <1% with certain conditions which are determined in the paper.
Abstract: For the calculation of blood volumes by indicator-dilution techniques, the assumption of a steady blood flow is usually made, neglecting the pulsatile character of the flow. A theoretical and experimental analysis of the error reveals whether this assumption leads to a considerable loss of accuracy or not. These studies neglect the effects of recirculation, indicator loss and poor mixing. The results show that the pulsatile error portion of the total error of the indicator dilution methods can be kept <1% with certain conditions which are determined in the paper.
••
TL;DR: The numerical results suggest that stasis may not be as significant a factor in atherogenesis as may have been thought, at least for the area ratio considered here.
•
18 Jan 1977
TL;DR: In this article, a pulsatile flow pumping unit adapted to serve as a total cardiac replacement device, a cardiac assist pump for orthotopic placement, for extracorporeal application in conjunction with a membrane oxygenator for cardiopulmonary support during surgery or critical illnesses, and for filling and emptying of an aortic diastolic augmentation balloon for cardiac assist is provided.
Abstract: A pulsatile flow pumping unit adapted to serve as a total cardiac replacement device, a cardiac assist pump for orthotopic placement, for extracorporeal application in conjunction with a membrane oxygenator for cardiopulmonary support during surgery or critical illnesses, for pulsatile flow coronary artery perfusion, and for filling and emptying of an aortic diastolic augmentation balloon for cardiac assist is provided. The pumping unit features simplicity of construction, comparative economy and reliability by utilizing a minimum number of working parts including a large diameter slitted rotary driver and cam operated follower means which avoids close machining tolerances and attendant high cost of manufacturing. The device automatically adjusts its rate of pumping in accordance with both preload (filling pressure) and afterload (pulmonic and systemic pressure) and in addition modifies its stroke volume in a downward direction when confronted with high afterload. The automatic adjustment of the device during operation depending on several variables is accomplished without electronic control or monitoring.
••
01 Apr 1977
TL;DR: An in vitro flow visualization study has been carried out on a range of aortic and mitral valve prostheses mounted in rigid, transparent models of the aorta and left ventricle, finding the aorted ball valve was found to produce less flow disturbance than either tilting disc valve or the porcine bioprosthesis.
Abstract: An in vitro flow visualization study has been carried out on a range of aortic and mitral valve prostheses mounted in rigid, transparent models of the aorta and left ventricle, The valves were subjected to pulsatile flow and the flow patterns produced by each valve were visualized by injecting multi-dye streams into the valve orifice, or by observing illuminated particles suspended in the flow. The patterns were recorded by still photography and high speed cinematography.In the mitral region each tilting disc valve produced a large vortex which dominated the ventricular cavity. By contrast disc and ball valves each produced an annular vortex, and the bioprosthesis produced a central flow. In the aortic region the flow patterns produced by a tilting disc valve depended on the orientation of the valve in the aorta. The aortic ball valve was found to produce less flow disturbance than either tilting disc valve or the porcine bioprosthesis.
••
TL;DR: The data suggest caution in the expectation that pulsatile perfusion will reverse the coronary flow and myocardial oxygen consumption changes seen with fibrillation.
••
TL;DR: This paper studies similarity solutions for pulsatile flow in a tube with wall injection and suction by solving the Navier-Stokes equations for steady flow and finding the exact numerical solutions compare well with the asymptotic solutions.
Abstract: This paper studies similarity solutions for pulsatile flow in a tube with wall injection and suction. The Navier-Stokes equations are reduced to a system of three ordinary differential equations. Two of the equations represent the effects of suction and injection on the steady flow while the third represents the effects of suction and injection on pulsatile flow. Since the equations for steady flow have been studied previously, the analysis centers on the third equation. This equation is solved numerically and by the method of matched asymptotic expansions. The exact numerical solutions compare well with the asymptotic solutions. The effects of suction and injection on pulsatile flow are the following: a) Small values of suction can cause a resonance-like effect for low frequency pulsatile flow. b) The annular effect still occurs but for large injection or suction the frequency at which this effect becomes dominant depends on the cross-flow Reynolds number. c) The maximum shear stress at the wall is decreased by injection, but may be increased or decreased by suction.
••
TL;DR: Pulsatile discharges of LH in long-term OVX rats occur throughout the 24-h day, and mean, peak, and nadir plasma LH concentrations for each group did not differ between sampling periods.
Abstract: Blood samples were taken every 5 min for a 2-h period commencing at 09.00 h or 313.00 h from long-term ovariectomized (OVX) rats under regular lighting conditions (lights on 05.00–19.00 h), and commencing at 09.30 h or 14.00 h from long-term OVX rats under reversed lighting conditions (lights on 18.00–08.00 h), the latter equivalent to starting sampling at 20.30 h or 01.00 h under regular lighting. Five rats were used in each group, and luteinizing hormone (LH) was measured in duplicate aliquots of each sample by radioimmunoassay. Pulsatile increases in plasma LH concentrations were observed in all 20 animals, and mean, peak, and nadir plasma LH concentrations for each group did not differ between sampling periods. Similarly, the time of day did not affect the frequency at which pulsatile discharges of LH occurred. These data suggest that pulsatile discharges of LH in long-term OVX rats occur throughout the 24-h day.
•
05 Jul 1977
TL;DR: A medical electronic diagnostic device particularly suitable for determining and displaying segmental pulsatile flow of a patient is described in this paper. But it is not suitable for the measurement of the pulsatile component of the total blood flow.
Abstract: A medical electronic diagnostic device particularly suitable for determining and displaying segmental pulsatile flow of a patient. Means are provided for stabilization of a calibrated segmental volume time curve relative to a baseline, so as to eliminate the effect of patient movement during testing, as well as miscellaneous electrical noise. The disclosed device is capable, in addition to displaying a pulse volume curve, of measuring and recording the pulsatile component of the total blood flow.