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Showing papers on "Pulsatile flow published in 1980"


Journal ArticleDOI
TL;DR: Pulsatile secretion of LH, in the rat at least, does not appear to be regulated sloely by the medial basal hypothalamus, and central noradrenergic, cholinergic, dopaminergic, and serotoninergic systems are involved in influencing episodic LH release.
Abstract: This review considers some of the neuroendocrine factors influencing pulsatile LH secretion. Such release is apparently due to the pulsatile discharge of LHRH from brain peptidergic neurons. This is a

155 citations


Journal ArticleDOI
TL;DR: Pressure and flow wave contour and impedance results were interpreted with the aid of a multibranched model of the systemic arterial tree, whose parameters could be manipulated to simulate different physiological and pathological conditions.
Abstract: This study seeks to explain mechanisms responsible for the contour of pressure and flow waves and the pattern of vascular impedance in human systemic arteries. Pulsatile pressure and flow were recorded from the ascending aorta of seven patients undergoing open heart surgery and from the ascending aorta and other arteries of 17 patients at diagnostic catheterization. Ascending aortic pressure/flow relationships in the seven surgical patients were expressed as input impedance to the systemic circulation. Pressure and flow wave contour and impedance results were interpreted with the aid of a multibranched model of the systemic arterial tree, whose parameters could be manipulated to simulate different physiological and pathological conditions. Our data and data previously published on pressure and flow waves and their relationship in human subjects could be explained on the basis of two reflecting sites in the systemic circulation-one representing the resultant of all arterial terminations in the upper part of the body, and the other, some 1.5 times further away, the resultant of all arterial terminations in the lower body. The concept of the arterial system as an asymmetric T tube with two discrete ends has been advanced previously to explain the main features of pressure and flow waves and their relationship in different experimental animals. This concept appears equally applicable to human subjects. Circ Res 46: 363-372, 1980

149 citations


Journal ArticleDOI
TL;DR: It is suggested that two pathways can stimulate the pulsatile mode of LH secretion independently of each other, one of these pathways involves the arcuate nuclei and possibly nearby structures, while the other appears to include extrahypothalamic structures and to enter the hypothalamus anteriorly.
Abstract: Various hypothalamic lesions were placed in long term ovariectomized rats, and their effects on pulsatile discharges of LH were noted in order to determine which neural regions are involved in the control of this mode of LH secretion. Complete hypothalamic deafferentiation did not affect pulsatile patterns of LH secretion unless the anterior portion of the cut also lesioned the anterior portion of the arcuate nuclei, in which case pulsatile LH discharges were completely blocked. Pulsatile LH secretion was not blocked by bilateral electrolytic lesions placed in ventromedial, paraventricular, or suprachiasmatic nuclei or anterior or posterior portions of the arcuate nuclei, although the nuclei were not completely destroyed by the lesions. When bilateral electrolytic lesions of the anterior portions of the arcuate nuclei were combined with anterior hypothalamic deafferentation, however, pulsatile discharges of LH were completely blocked. These results suggest that two pathways can stimulate the pulsatile mode of LH secretion independently of each other. One of these pathways involves the arcuate nuclei and possibly nearby structures, while the other appears to include extrahypothalamic structures and to enter the hypothalamus anteriorly.

80 citations


Journal ArticleDOI
TL;DR: A possible role of β-endorphin, in addition to Met 5 -enkephalin, in the control of LH release in male rats is suggested.

79 citations


Journal ArticleDOI
TL;DR: The experiments indicate that for comparative studies of platelet adhesion in steady flow at a physiological red cell concentration and a shear rate as observed in small arteries, it is preferable to apply subnormal platelet counts and perfusion times shorter than 5 min.

75 citations


Journal ArticleDOI
TL;DR: The preferential L→R diastolic flow from the descending aorta is related to existing analyses of the effects of geometry on the impedance of the systemic arterial system to raise questions about a potential interaction of this steal and necrotizing enterocolitis in infants with a large PDA.
Abstract: This paper considers the pulsatile pressure-flow relationships in patients with a patent ductus arteriosus (PDA). The emphasis is on the patterns that occurred with variable hemodynamic states, extending from the continuous left-to-right (L→R) PDA shunt with low pulmonary vascular resistance to the opposite extreme where the systemic circulation depended entirely on the right-to-left (R→L) PDA flow. Pressure gradients were determined from pressures measured simultaneously with matched catheter systems, and flow was evaluated by biplane cineangiography. In all of the hemodynamic states there was flow from the aorta to the pulmonary artery during diastole, even with aortic atresia. With bidirectional shunts, the R→L pressure gradient and flow occurred during the initial systolic rise of the pulse pressure in association with an earlier rise of the pulmonary artery pressure than the aortic pressure at the PDA site. With bidirectional shunts the L→R diastolic flow across the PDA originated preferentially from backflow in the descending thoracic aorta distal to the PDA. Because the aortic backflow appeared to be considerable and occurred over large distances in some patients, we suggest that this may result in a “diastolic steal” of blood from the abdominal organs to the pulmonary artery. The diastolic steal raises questions about a potential interaction of this steal and necrotizing enterocolitis in infants with a large PDA. Since the patterns found could not be explained using the concept of vascular resistance, especially the marked L→R PDA diastolic flow in aortic atresia, we relate the preferential L→R diastolic flow from the descending aorta to existing analyses of the effects of geometry on the impedance of the systemic arterial system.

70 citations


Journal ArticleDOI
TL;DR: While oscillatory measurements will be useful in assessing rheological parameters that may give insight into the fundamental aspects of flow of normal and pathological bloods, it is not clear that the elastic component of the complex viscosity of blood will be of significance in physiological pulsatile flow.
Abstract: The mechanisms of red cell aggregation and cell deformation can impart viscoelastic behavior to blood: at very high hematocrits, the cell deformation mechanism dominates; at physiological and low hematocrits, red cell aggregation dominates at low shear rates. At physiological hematocrits, the viscoelastic behavior may be linear at low shear rates, where the elastic component of the complex viscosity may be comparable in magnitude to the viscous component; in the higher shear rate region, where red cell aggregation is less extensive or absent, blood behavior is nonlinear, and the elastic component becomes less significant. The nonadditivity of steady and oscillatory flow data for prediction of pulsatile flow behavior is indicative of the importance of the mean shear rate and the kinetics of the red cell aggregation-disaggregation processes in governing pulsatile blood flow. While oscillatory measurements will be useful in assessing rheological parameters that may give insight into the fundamental aspects of flow of normal and pathological bloods, it is not clear that the elastic component of the complex viscosity of blood will be of significance in physiological pulsatile flow. Many interesting questions remain to be answered, such as the question raised by the finding that normal stress differences were not detectablemore » for blood under low shear rates. Judging from the number of papers presented at the Third International Congress of Biorheology, we can look forward to considerable activity in this area.« less

63 citations


01 Feb 1980
TL;DR: There is sufficient evidence to indicate that changes in the mechanical properties of the arterial tree influence the opposition to ventricular outflow.
Abstract: The load that the arterial system places upon the myocardium during ventricular ejection is of primary importance in the consideration of ventricular function. This dynamic load can be characterized by the total aortic input impedance spectrum obtained from Fourier analysis of pulsatile pressure and flow waves recorded in the ascending aorta. Certain indices derived from the impedance spectrum provide quantitative and qualitative information about this dynamic load in terms of peripheral arteriolar dimensions (resistance), aortic wall stiffness (compliance), and wave reflections (reflectance). Studies in isolated heart preparations and intact dogs have shown that increases in resistance (decrease in arteriolar caliber) or aortic stiffness (decrease in aortic compliance) independently influence an increase in peak left ventricular pressure and a decrease in stroke volume. An increase in wave reflections also has the potential to reduce stroke volume while increasing peak pressure. Recent human studies have shown that in heart failure patients the components of the dynamic vascular load are also elevated compared to subjects without heart failure. Infusion of the vasodilator sodium nitroprusside abruptly reduces these components of vascular load as ventricular stroke output is enhanced. Thus, there is sufficient evidence to indicate that changes in the mechanical properties of the arterial tree influence the opposition to ventricular outflow. Since these properties can be described by the aortic input impedance spectrum, this function can be used to define the external load imposed on the ventricle by the vascular system.

48 citations


Journal ArticleDOI
TL;DR: The computational method developed by Ling and Atabek (1972) is extended to include effects of viscoelasticity of arterial walls and stability of the computations is considered.

47 citations


Journal Article
TL;DR: Systemic vascular resistance fell dramatically during cardiopulmonary bypass but rapidly rose after bypass with a reciprocal change in cardiac index, and there was no difference between pulsatile and nonpulsatile cases.
Abstract: In a randomized trial of pulsatile vs nonpulsatile cardiopulmonary bypass for coronary artery surgery, we studied hemodynamic and hormonal responses. Anesthesia did not produce a response but, from the time of the incision, cortisol and antidiuretic hormone levels and plasma renin activity all increased. Cortisol levels continued to rise after surgery, whereas the other began to fall. Systemic vascular resistance fell dramatically during cardiopulmonary bypass but rapidly rose after bypass with a reciprocal change in cardiac index. We did not see the changes ascribed to nonpulsatile bypass by others. There ws no difference between our pulsatile and nonpulsatile cases. High-flow cardiopulmonary bypass, vasodilating inhalation anesthesia and continuation of Inderal therapy may account for our results.

45 citations


Journal ArticleDOI
TL;DR: A mathematical model for pulsatile flow in a partially occluded tube has applications in studying the effects of blood flow characteristics on atherosclerotic development and shows fairly good agreement with the available experimental results.
Abstract: A mathematical model for pulsatile flow in a partially occluded tube is presented. The problem has applications in studying the effects of blood flow characteristics on atherosclerotic development. The model brings out the importance of the pulsatility of blood flow on separation and the stress distribution. The results obtained show fairly good agreement with the available experimental results.

Journal ArticleDOI
TL;DR: Depression in myocardial function was detectable within 1 minute after initiation of propranolol and persisted when negative chronotropic effects were eliminated by atrial pacing, and the multisensor catheter technique allows rapid and safe detection of changes in cardiovascular function during proPRanolol administration in conscious man.
Abstract: A catheter-tip velocity transducer with two high-fidelity pressure manometers was used to evaluate the left ventricular (LV) hemodynamic effects of intravenous propranolol (10 mg). Nine patients without clinical evidence of heart failure were studied. Pulsatile ascending aortic blood flow velocity and pressure and LV pressure were measured continuously during drug administration. Beat-to-beat changes in stroke volume index, stroke work index, LV end-diastolic pressure, maximum blood flow velocity and acceleration, and maximum LV dP/dt were determined. Propranolol produced a decrease in maximum blood flow velocity (from 58 +/- 4.7 to 42 +/- 5.1 cm/sec, p less than 0.002), and acceleration (from 1181 +/- 130 to 847 +/- 117 cm/sec2, p less than 0.002, max dP/dt (from 1361 +/- 70 to 1146 +/- 63 mm Hg/sec, p less than 0.002), stroke volume index (from 47 +/- 3.0 to 38 +/- 3.2 ml/m2, p less than 0.002) and total stroke work index (from 702 +/- 33 to 603 +/- 44 mJ/m2 p less than 0.04), with little change in mean aortic pressure, peak systolic pressure and LV end-diastolic pressure. Depression in myocardial function was detectable within 1 minute after initiation of propranolol and persisted when negative chronotropic effects were eliminated by atrial pacing. The multisensor catheter technique allows rapid and safe detection of changes in cardiovascular function during propranolol administration in conscious man.

Journal ArticleDOI
TL;DR: Patients undergoing hypothermic cardiopulmonary bypass were perfused with the standard flow delivered by a roller pump and pulsatile flow induced by a "pulsatile assist device" and the temperature gradient between core tissues and muscle was not influenced by the type of flow used during rewarming.

Journal ArticleDOI
TL;DR: It was found that after volume expansion the characteristic impedance of the proximal aorta, Zc, was decreased and after hemorrhage Zc was increased, and it was concluded that changes in Zc seen with volume expansion or hemorrhage are caused mainly by changes in aortic smooth muscle activity.
Abstract: Experiments on 12 anesthetized dogs were performed to study the effects of changes in blood volume on the pulsatile hemodynamics of the arterial system as seen from its input. Pressure and flow were measured in the ascending aorta under control conditions, after volume expansion with dextran 70 (+30% of estimated blood volume), and after hemorrhage (-15% of estimated blood volume). The input inpedance of the arterial system was calculated for each condition. It was found that after volume expansion the characteristic impedance of the proximal aorta, Zc, was decreased by 26.6 +/- 5.1% (SE) (P less than 0.01). After hemorrhage Zc was increased by 30.4 +/- 3.4% (P less than 0.01). Since it is well known that Zc is a very weak function of the mean arterial pressure, it is concluded that the changes in Zc seen with volume expansion or hemorrhage are caused mainly by changes in aortic smooth muscle activity. This conclusion is also supported by direct measurements of aortic pressure diameter relationships in earlier work from our lab.

Journal ArticleDOI
TL;DR: Amplitude of pulsatile release of LH was examined in OVX rats of ages 3-4, 9-11, and 17-18, months, serially bled via chronic jugular catheters and suggested that a common, central mechanism may be responsible for both theChanges in reproductive pattern and the changes in pulsatileRelease of LH which accompany aging in the rat.
Abstract: SummaryAmplitude of pulsatile release of LH was examined in OVX rats of ages 3-4, 9-11, and 17-18, months, serially bled via chronic jugular catheters. At the time of ovariectomy, rats showed normally cycling (NC), irregularly cycling (IC), or constant estrus (CE) ovarian activity. Amplitude of pulsatile release of LH was significantly reduced in CE rats as compared to all other groups. Further, LH pulse amplitude appeared to be more closely associated with reproductive state at the time of ovariectomy than with the age of the animal. Thus, LH pulse amplitude was greatest in NC rats, intermediate in IC rats, and lowest in CE rats, regardless of age. These data suggest that a common, central mechanism may be responsible for both the changes in reproductive pattern and the changes in pulsatile release of LH which accompany aging in the rat.

Journal ArticleDOI
01 Mar 1980-Steroids
TL;DR: Results confirm that corticosterone release is pulsatile, as has been reported previously, but with a much faster time course and a pulse frequency close to one pulse per minute.

Patent
25 Feb 1980
TL;DR: A pulsatile blood pump comprising a disposable power bladder of flexible and anticoagulative material which is provided with a suction port with an inlet check valve and a delivery port with a outlet check valve to constitute a blood pump unit and hermetically sealed container for receiving said blood pump units is described in this article.
Abstract: A pulsatile blood pump comprising a disposable power bladder of flexible and anticoagulative material which is provided with a suction port with an inlet check valve and a delivery port with an outlet check valve to constitute a blood pump unit and hermetically sealed container for receiving said blood pump unit, said container being connected to a pulsating mechanism and filled with a pressure transmissive fluid which is subjected to a pulsatile pressure generated by the pulsating mechanism to vary the volume of the power bladder for pulsatile blood delivery.


Journal ArticleDOI
TL;DR: The data indicate that any differences between the two techniques must be explained by a mechanism other than increased total cortical blood flow or by redistribution of cortical flow.

Journal Article
TL;DR: The laser Doppler system has been established as a useful tool for eliciting the properties of simulated cardiovascular flows, and thus for comparative studies of flow properties of prosthetic valves, despite the volume and complexity of the data required.
Abstract: The laser Doppler system has been established as a useful tool for eliciting the properties of simulated cardiovascular flows, and thus for comparative studies of flow properties of prosthetic valves. Significant differences among valve types and between models of one type have been documented. The complex variations of velocity profiles with time show that comparisons must be made for unsteady pulsatile rather than steady flow, despite the volume and complexity of the data required. Future studies will include methods of compacting the data presentation and improving the details of the experimental stimulation.

Journal ArticleDOI
TL;DR: The phenomenon of "cardiogenic gas mixing" in the airways in vivo is a result of a direct action of the heart on the lungs rather than arterial pulsations, suggesting a beneficial effect of flow- and pressure pulsations.
Abstract: The importance of the perfusion pattern for the oxygen transfer has been examined in isolated rabbit lungs perfused with plasma at constant volume inflow. The lungs were ventilated with constant tidal volume and constant end-expiratory pressure. Following a standardized rise in FIO2 the rate of rise in pulmonary venous PO2 (delta PO2/delta t) was measured during alternately pulsatile and non-pulsatile perfusion in normal lungs and in lungs made edematous by elevation of left atrial pressure. In normal lungs there was no difference in delta PO2/delta t when the two modes of perfusion were compared. In edematous lungs delta PO/delta t was statistically higher during pulsatile perfusion, indicating a beneficial effect of flow- and pressure pulsations, e.g. a better distribution of V/Q ratios throughout the lungs. In a separate series of expts. the advancement of a high O2 front through the airways was measured, and the two perfusion patterns compared. Since no difference was found, we suggest that the phenomenon of "cardiogenic gas mixing" in the airways in vivo is a result of a direct action of the heart on the lungs rather than arterial pulsations.

Journal ArticleDOI
TL;DR: In rabbits, collagen synthesis was studied in five different regions of the vasuclar tree and the findings suggest a link between mechanical stretching and cellular metabolic function and have significance as to the relationship of pulsatile flow to normal vascular and organ physiology.
Abstract: In rabbits, collagen synthesis was studied in five different regions of the vasuclar tree which are subjected to different degrees of pulsatile distention, i.e., cyclic stretching, and mean pressure. The vessels with greatest pulsatile distention had the highest specific activity of hydroxyproline in collagen after incubation with 14C-proline and the inferior vena cava with low pressure and negligible pulsatile distention had the lowest specific activity. The findings suggest a link between mechanical stretching and cellular metabolic function and have significance as to the relationship of pulsatile flow to normal vascular and organ physiology.



Journal ArticleDOI
TL;DR: This study examined the possible involvement of dopamine (DA) and/or serotonin (5-HT) in regulating basal pulsatile LH release, and in mediating perisuprachiasmatic (peri-SCN)-induced suppression of p.
Abstract: This study examined the possible involvement of dopamine (DA) and/or serotonin (5-HT) in regulating basal pulsatile LH release, and in mediating perisuprachiasmatic (peri-SCN)-induced suppression of p

Journal ArticleDOI
TL;DR: It is concluded that, in the capillaries of resting sartorius muscle in frogs, two types of velocity variations occur: pulsatile variations caused by the pumping action of the heart, and superimposed nonperiodic fluctuations.

Journal Article
W. Saggau, Bacá I, Ros E, Storch Hh, W. Schmitz 
01 Feb 1980-Herz
TL;DR: In 20 patients who underwent open-heart surgery, the plasma concentrations of glucose, insulin, glucagon, growth hormone, free hemoglobin, and cholinesterase were measured before, during and after pulsatile and continuous perfusion.
Abstract: In 20 patients who underwent open-heart surgery, the plasma concentrations of glucose, insulin, glucagon, growth hormone, free hemoglobin, and cholinesterase were measured before, during and after pulsatile and continuous perfusion. Pulsatile flow was achieved by modification of a roller pump to effect rapid acceleration and slowing. The driving motor was interfaced with a control module to enable ECG-triggered perfusion. In addition to the clinical studies, investigations were performed in 9 dogs to assess the effects of pulsatile and continuous perfusion on liver and pancreas flow during total bypass. During pulsatile perfusion there was a significant increase in insulin which, however, was clearly diminished in relation to glucose levels. The response of the beta-cells was markedly more compromised after continuous than pulsatile perfusion. The secondary postoperative increase in insulin can be accounted for by intravenous administration of glucose and, particularly, after pulsatile perfusion, indicates an almost completely normal response of pancreatic beta-cells. As opposed to the effects of continuous perfusion, the low glucose, glucagon, and growth hormone levels, the insulin increase during and after pulsatile perfusion as well as normal cholinesterase values observed in association with pulsatile perfusion appear to be the result of improved pancreatic and hepatic function. This contention is supported by the experimental finding of significantly increased pancreas and liver perfusion during pulsatile perfusion.

Journal ArticleDOI
TL;DR: A method has been defined which is suitable for continuous estimation of limb blood flow in newborn babies under intensive care and it is believed that this simple technique will help the development of full understanding of the circulatory changes associated with events in the neonatal period.
Abstract: This study aims to define a method for acquiring limb flood flow data from newborn babies on a continuous basis which would be suitable for automatic processing. Pulsatile electrical impedance and strain gauge signals were analyzed in 3 different ways. The results were compared with estimates of flow derived from venous occlusion plethysmography with a mercury-in-rubber strain gauge. Measurements were made from 33 babies. The impedance technique was easier to perform than the strain gauge technique. The reproducibility of the various estimates of flow is shown in Table 3. The beat-to-beat reproducibility of simultaneous pulsatile mesurements and of repeated measurements on different subjects was greater from the impedance recordings than from the strain gauge recordings. The results of linear regression analyses between the different flow estimates are shown in Table 4. The best correlation with flow measured using venous occlusion plethysmography was with flow calculated from the impedance pulse height, F(Zmax) (r = 0.76; n = 30; P < 0.001). The regression line between these 2 variables was not statistically significantly different from the line of identity, (P < 0.98), and the intercept is close to zero. The measurement of the impedance pulse height, delta Zmax, and the subsequent calculation of F(Zmax) could be automated and provide continuous beat-to-beat blood flow estimations.

Journal ArticleDOI
TL;DR: The results are consistent with the view that pulsatile LHRH release is responsible for the pulsatile nature of plasma LH in OVX rats and do not support the concepts of a short-loop Feedback of LH or an ultra-short-loop feedback of L HRH on LH secretion at least on an acute basis.
Abstract: Experiments were conducted in vivo to investigate further if the control of the pulsatile plasma LH phenomenon in ovariectomized (OVX) rats is located in the brain or in the adenohypophysis. Luteinizing hormone releasing hormone (LHRH) was infused at a constant rate (2--100 ng/h) through an indwelling venous cannula in unanesthetized, unrestrained OVX rats. Blood samples were collected at 5-min intervals through a second venous cannula prior to and during LHRH infusion for subsequent radioimmunoassay of plasma LH. LHRH infusion at 12.5, 50 and 100 ng/h did not interfere with the magnitude or the periodicity of LH pulses in plasma but the range within which plasma LH fluctuated was elevated. Phenobarbital (75 mg/kg BW; i.p.) blocked the pulsatile plasma LH and maintained the plasma LH nearly constant at reduced levels. Pulse i.v. injections of LHRH but not constant rate i.v. infusions restored pulsatile LH patterns in phenobarbital-treated OVX rats. The results are consistent with the view that pulsatile LHRH release is responsible for the pulsatile nature of plasma LH in OVX rats. The results do not support the concepts of a short-loop feedback of LH or an ultra-short-loop feedback of LHRH on LH secretion at least on an acute basis.

Journal ArticleDOI
TL;DR: The degree of hemolysis occurring during cardiopulmonary bypass was evaluated in two groups of patients undergoing pulsatile and nonpulsatile perfusion, and a newly developed method of creating pulsatile flow was developed.